{"gene":"LDHC","run_date":"2026-06-10T02:59:49","timeline":{"discoveries":[{"year":2008,"finding":"Targeted disruption of Ldhc in mice severely impaired male fertility. LDHC homotetramer (LDH-C4) accounts for the majority of LDH enzymatic activity in sperm. Ldhc-null sperm showed more rapid ATP depletion, loss of motility, failure to acquire hyperactivated motility, inability to penetrate the zona pellucida in vitro, and failure to undergo capacitation-associated phosphorylation events.","method":"Gene knockout (targeted disruption), sperm motility assay, ATP measurement, in vitro fertilization assay, capacitation phosphorylation assay","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean KO with multiple defined cellular and biochemical phenotypes; replicated in subsequent studies","pmids":["18367675"],"is_preprint":false},{"year":2013,"finding":"In the absence of glucose, Ldhc-null sperm can produce ATP via oxidative phosphorylation, but when glucose is present, oxidative phosphorylation is suppressed and sperm rely on aerobic glycolysis (Crabtree effect). LDHC is required to maintain glycolytic flux and ATP production specifically in the presence of glucose.","method":"Ldhc knockout mouse model (C57BL/6 and 129S6 backgrounds), oxygen consumption measurement, ATP quantification, motility analysis under defined energy substrate conditions","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — two genetic backgrounds with multiple orthogonal metabolic readouts; replicates and extends PMID 18367675","pmids":["23486916"],"is_preprint":false},{"year":2013,"finding":"Human LDHA introduced as a transgene into Ldhc-null mice rescued sperm motility, protein tyrosine phosphorylation (capacitation marker), and fertility, demonstrating that LDHC does not possess unique catalytic properties essential for fertility and that cytosolic LDH activity per se is sufficient. However, ATP and lactate levels in rescued sperm did not significantly differ from Ldhc-null sperm, suggesting localization of LDH to the sperm cytosol (rather than specific enzymatic properties of LDHC) is the main determinant of rescue.","method":"Transgenic rescue experiment (LDHA transgene in Ldhc-/- background), sperm motility assay, tyrosine phosphorylation assay, fertility testing, ATP/lactate measurement","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Strong — transgenic rescue with multiple functional readouts and mechanistic interpretation; single lab but orthogonal methods","pmids":["23467744"],"is_preprint":false},{"year":1998,"finding":"A 100 bp genomic fragment overlapping the LDHC transcription start site is sufficient to drive testis-specific expression in transgenic mice, with expression restricted to leptotene/pachytene primary spermatocytes.","method":"Transgenic mice carrying lacZ reporter driven by 100 bp LDHC promoter fragment; in vitro transcription assay with 60 bp promoter","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Strong — in vivo transgenic confirmation of in vitro transcription assay; two orthogonal methods in one study","pmids":["9813024"],"is_preprint":false},{"year":2001,"finding":"NF-I/CTF family proteins bind to a palindromic element in the Ldhc promoter and repress its activity in somatic (non-germ) cells. Mutation of the NF-I binding site in the palindrome increased promoter activity ~4-fold in mouse L cells; overexpression of NF-IA, -B, -C, or -X decreased wild-type promoter activity 20–50% but had no effect when the NF-I binding element was mutated.","method":"Gel retardation assay, transient transfection reporter assay in mouse L cells, NF-I overexpression, site-directed mutagenesis of promoter","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (EMSA, mutagenesis, overexpression) in a single study; single lab","pmids":["11447215"],"is_preprint":false},{"year":2012,"finding":"Transcription factor MYBL1 (A-MYB) stimulates Ldhc expression in spermatocytes via the CRE site in the Ldhc core promoter. MYBL1 transactivation domain (TAD) interacts with the KIX domain of CBP, and TAD and DNA-binding domain of MYBL1 each interact with the CREB N-terminal domain. LDHC expression is lost in 21-day testes of MYBL1 mutant mice. MYBL1 activates Ldhc through CRE elements rather than canonical Myb-binding sites.","method":"MYBL1 mutant mouse analysis, reporter assays in GC1-spg cells, EMSA, co-immunoprecipitation/interaction domain mapping between MYBL1-TAD and CBP-KIX/CREB","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 / Moderate — multiple methods including mutant mouse, reporter assay, domain interaction mapping; single lab","pmids":["21998171"],"is_preprint":false},{"year":1997,"finding":"DNase I footprinting in isolated mouse pachytene spermatocytes identified a single protected region over the GC-box (Sp1-binding site) in the LDH/C proximal promoter. Functional studies showed that enhancer-assisted Sp1-mediated transactivation drives LDH/C promoter activity; mutation of the GC-box abolished activity.","method":"PCR-based in vivo DNase I footprinting in isolated pachytene spermatocytes, CAT reporter assays with wild-type and mutated promoter constructs in germ cell and somatic cell lines","journal":"Nucleic acids research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vivo footprinting combined with functional reporter mutagenesis; single lab","pmids":["9153323"],"is_preprint":false},{"year":1998,"finding":"EMSA studies identified at least one germ-cell-specific nuclear transcription factor (distinct from Sp1) that binds the GC-box motif of the LDH/C proximal promoter, with methylation interference identifying a unique 5'G residue within the GC-box as critical for this binding. Somatic cells (HeLa) have at least six different DNA-protein complexes at this element, only one of which involves Sp1.","method":"EMSA with nuclear extracts from primary germ cells and HeLa cells, supershift analysis with Sp1 antibody, methylation interference analysis, GC-box mutagenesis","journal":"The Journal of experimental zoology","confidence":"Medium","confidence_rationale":"Tier 3 / Moderate — multiple EMSA approaches with mutagenesis; single lab, in vitro binding only","pmids":["9723175"],"is_preprint":false},{"year":1995,"finding":"The human LDH-C promoter contains a CpG-rich region of ~230 bp that is heavily methylated at nine sites in somatic cells but specifically hypomethylated at those same sites in expressing tissues (testis). A methylated promoter forms a specific complex in vitro with a methyl-DNA binding protein, linking promoter hypermethylation to LDHC silencing in non-expressing tissues.","method":"Endonuclease sensitivity coupled with PCR (methylation mapping), in vitro protein-DNA complex formation with methyl-DNA binding protein","journal":"Developmental genetics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (restriction enzyme/PCR methylation mapping and in vitro binding assay); single lab","pmids":["7736669"],"is_preprint":false},{"year":1995,"finding":"The 3'-UTR of primate (baboon, human) but not rodent Ldhc mRNA contains AU-rich elements that destabilize the transcript. Baboon Ldhc mRNA is labile in a cell-free system while mouse mRNA is highly stable. Removal of the human Ldhc 3'-UTR stabilizes the mRNA; mutation of AU-rich motifs also results in stabilization. Steady-state primate Ldhc mRNA levels are 8–12-fold lower than mouse.","method":"Cell-free mRNA stability assay, deletion and point mutagenesis of 3'-UTR AU-rich elements, steady-state mRNA quantification in germ cell line","journal":"Molecular endocrinology","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution of mRNA stability with mutagenesis; multiple approaches in one study; single lab","pmids":["8614414"],"is_preprint":false},{"year":2022,"finding":"During porcine testis development, the LDHC promoter is heavily methylated in pre-pubertal testes and demethylated post-pubertally. Artificial demethylation with 5-Aza-CdR induced LDHC expression in immature Sertoli cells. Transcription factor SP1 was recruited to bind hypomethylated DMRs in the LDHC promoter, upregulating LDHC expression. LDHC overexpression in mature Sertoli cells significantly increases lactate secretion.","method":"MeDIP-seq, 5-Aza-CdR demethylation experiment, ChIP (SP1 binding to LDHC promoter DMR), LDHC overexpression with lactate secretion measurement","journal":"Genomics","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple methods (MeDIP-seq, demethylation experiment, ChIP, functional overexpression); single lab","pmids":["36041633"],"is_preprint":false},{"year":2023,"finding":"Tanshinone IIA (Tan IIA) covalently binds to LDHC and inhibits its enzymatic activity, as identified by activity-based protein profiling (ABPP) combined with LC-MS/MS. LDHC inhibition by Tan IIA reduces ROS accumulation in osteoclasts, suppressing osteoclast-specific marker expression and osteoclast differentiation.","method":"Activity-based protein profiling (ABPP) + LC-MS/MS identification of covalent binding, enzymatic activity assay, ROS measurement, osteoclast differentiation assay","journal":"Chinese medicine","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — ABPP chemical proteomics with enzymatic activity validation and functional readout; single lab","pmids":["37189204"],"is_preprint":false},{"year":2020,"finding":"LDHC overexpression in lung adenocarcinoma (LUAD) cells increased lactate and ATP production, enhanced cell migration and invasion, and accelerated xenograft tumor growth. LDHC overexpression elevated phosphorylation of AKT and GSK-3β; PI3K inhibition reversed these effects, reducing proliferation, migration, invasion, and EMT-related protein changes.","method":"LDHC overexpression/knockdown in LUAD cell lines, in vitro invasion/migration assays, xenograft tumor model, PI3K inhibitor treatment, Western blot for p-AKT/p-GSK3β and EMT markers","journal":"Experimental cell research","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple in vitro and in vivo functional assays with pathway pharmacological validation; single lab","pmids":["33301764"],"is_preprint":false},{"year":2024,"finding":"LDHC silencing in basal-like breast cancer cells (MDA-MB-468, BT-549) compromised cell survival in conjunction with downregulation of STAT3 signaling, whereas LDHC silencing in Her2-enriched breast cancer cells (HCC-1954) enhanced STAT3 activation and promoted survival. STAT3 inhibition reversed the pro-survival effect of LDHC silencing in Her2-enriched cells, establishing a LDHC-STAT3 signaling axis.","method":"siRNA knockdown, transcriptomic analysis, cell viability assay, STAT3 inhibitor treatment, Western blot","journal":"Cancers","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — knockdown plus pharmacological inhibition with transcriptomic and functional readouts; single lab","pmids":["39001513"],"is_preprint":false},{"year":2025,"finding":"LDHC silencing in breast cancer cells enhanced early T cell activation and cytolytic activity. Mechanistically, LDHC knockdown increased pro-inflammatory cytokine secretion (IFN-γ, GM-CSF, MCP-1, CXCL1), decreased immunosuppressive factors (IL-6, Gal-9), and reduced tumor cell surface PD-L1 expression. In cancer cell–T cell co-cultures, LDHC knockdown reduced immune checkpoint molecule expression (PD-1, CTLA-4, TIGIT, TIM3, VISTA) on CD8+ T cells.","method":"siRNA knockdown, multiplex cytokine assay, flow cytometry for immune checkpoints and surface markers, IFN-γ ELISpot, 7-AAD cytotoxicity assay in cancer cell–T cell co-cultures","journal":"Cell communication and signaling","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — multiple orthogonal methods (cytokine assay, flow cytometry, ELISpot) in monoculture and co-culture; single lab","pmids":["40108668"],"is_preprint":false},{"year":2022,"finding":"Human LDHC knocked into the mouse Ldhc locus (replacing mouse LDHC) fully rescued sperm motility and male fertility. An LDH inhibitor more specific for human LDHC than mouse LDHC reduced in vitro fertilization rates in hLDHC knock-in mice but not wild-type mice, validating hLDHC as a pharmacologically distinct contraceptive target.","method":"CRISPR/Cas9 humanized knock-in mouse, CASA sperm motility analysis, IVF with LDH inhibitor treatment","journal":"Andrology","confidence":"High","confidence_rationale":"Tier 2 / Strong — humanized knock-in genetic model with pharmacological validation using species-selective inhibitor; multiple functional readouts","pmids":["36464740"],"is_preprint":false},{"year":2025,"finding":"In stallion spermatozoa, LDHC localizes to the cytosol and the motile cilium (flagellum), while LDHA is cytosolic and LDHB is mitochondrial. Functional inhibition of LDHC with a specific inhibitor impaired sperm function, consistent with LDHC playing an essential role in aerobic glycolysis and NAD+ regeneration within the flagellum.","method":"Proteomics/metabolomics of sperm metabolic proteome, cellular fractionation/localization, specific LDHC inhibitor functional assay, sperm motility and viability assays","journal":"Reproduction (Cambridge, England)","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — localization by proteomics combined with functional inhibitor experiment; single lab","pmids":["40299647"],"is_preprint":false}],"current_model":"LDHC is a testis-specific LDH isozyme that forms homotetramers (LDH-C4) localized to the sperm flagellum/cytosol, where it catalyzes the reversible interconversion of pyruvate and lactate, maintaining glycolytic flux and NAD+ regeneration required for ATP production, sperm motility, capacitation, and male fertility; its testis-specific expression is controlled at multiple levels including promoter activation via Sp1/MYBL1-CRE-CBP interactions, repression by NF-I proteins in somatic cells, promoter DNA methylation status, and post-transcriptional destabilization via 3'-UTR AU-rich elements in primates; in cancer contexts, aberrant LDHC expression activates PI3K/AKT/GSK-3β and modulates STAT3 signaling and immune checkpoint expression."},"narrative":{"mechanistic_narrative":"LDHC is a testis-specific lactate dehydrogenase isozyme that, as the homotetramer LDH-C4, provides the majority of LDH activity in sperm and is essential for male fertility [PMID:18367675]. Functioning in the sperm cytosol and flagellum, it sustains glycolytic flux and ATP production: Ldhc-null sperm deplete ATP rapidly, lose motility, fail to hyperactivate, cannot undergo capacitation-associated tyrosine phosphorylation, and cannot penetrate the zona pellucida [PMID:18367675]. LDHC is specifically required to maintain aerobic glycolysis in the presence of glucose, when oxidative phosphorylation is suppressed (Crabtree effect) [PMID:23486916]. Its essential contribution is the cytosolic LDH catalytic activity itself rather than unique enzymatic properties, since a cytosolic human LDHA transgene restores motility, capacitation phosphorylation, and fertility in Ldhc-null mice [PMID:23467744], and a humanized human-LDHC knock-in fully rescues fertility while conferring sensitivity to a human-LDHC-selective inhibitor, defining LDHC as a contraceptive target [PMID:36464740]. Testis-restricted expression is set by layered control: a minimal promoter directs spermatocyte-specific transcription [PMID:9813024] activated through an Sp1-bound GC-box [PMID:9153323] and through MYBL1 acting at a CRE site via interactions with CBP-KIX and CREB [PMID:21998171], while NF-I proteins repress the promoter in somatic cells [PMID:11447215]; promoter CpG methylation silences the gene outside the testis and demethylation permits Sp1 recruitment and expression [PMID:7736669, PMID:36041633]. In primates, AU-rich elements in the 3'-UTR destabilize the transcript, accounting for lower expression than in rodents [PMID:8614414]. Aberrantly expressed LDHC drives oncogenic phenotypes, enhancing lactate/ATP production, migration, invasion, and tumor growth via PI3K/AKT/GSK-3β signaling [PMID:33301764], modulating STAT3 signaling in a context-dependent manner [PMID:39001513], and shaping anti-tumor immunity through effects on cytokine secretion, PD-L1, and T-cell checkpoint expression [PMID:40108668].","teleology":[{"year":1995,"claim":"Established that species-specific post-transcriptional control limits LDHC abundance, explaining why primates express far less LDHC mRNA than rodents.","evidence":"Cell-free mRNA stability assays and 3'-UTR AU-rich element mutagenesis in baboon, human, and mouse transcripts","pmids":["8614414"],"confidence":"High","gaps":["Trans-acting destabilizing factors binding the AU-rich elements not identified","Physiological consequence of lower primate LDHC levels not addressed"]},{"year":1995,"claim":"Linked tissue-restricted LDHC expression to promoter DNA methylation, showing the CpG-rich promoter is methylated and silent in somatic tissue but hypomethylated in testis.","evidence":"Methylation mapping by restriction/PCR and in vitro methyl-DNA binding protein complex formation on the human LDH-C promoter","pmids":["7736669"],"confidence":"Medium","gaps":["Identity of the methyl-DNA binding protein not established","Causality between methylation and silencing not tested in vivo"]},{"year":1997,"claim":"Identified the proximal GC-box as a functional control element and implicated Sp1-mediated transactivation in driving promoter activity in spermatocytes.","evidence":"In vivo DNase I footprinting in pachytene spermatocytes plus CAT reporter mutagenesis","pmids":["9153323"],"confidence":"Medium","gaps":["Did not resolve whether Sp1 or a germ-cell factor occupies the site in vivo"]},{"year":1998,"claim":"Defined the minimal cis-regulatory element sufficient for germ-cell-specific transcription, narrowing testis-specificity to ~100 bp around the start site.","evidence":"lacZ transgenic mice and in vitro transcription with a 60 bp promoter fragment","pmids":["9813024"],"confidence":"High","gaps":["Full set of trans factors binding the minimal promoter not enumerated"]},{"year":1998,"claim":"Showed the GC-box is bound by a germ-cell-specific factor distinct from Sp1, refining the regulatory logic beyond canonical Sp1 occupancy.","evidence":"EMSA, Sp1 supershift, and methylation interference with germ cell and HeLa nuclear extracts","pmids":["9723175"],"confidence":"Medium","gaps":["Germ-cell-specific factor not molecularly identified","In vitro binding only, no in vivo confirmation"]},{"year":2001,"claim":"Provided a mechanism for silencing in non-germ cells by showing NF-I proteins bind a promoter palindrome and repress transcription.","evidence":"EMSA, reporter assays, NF-I overexpression, and binding-site mutagenesis in mouse L cells","pmids":["11447215"],"confidence":"High","gaps":["Repression demonstrated in a somatic cell line, not in germ-cell differentiation context"]},{"year":2008,"claim":"Demonstrated that LDHC is required for male fertility, defining its cellular role in sperm energetics, motility, capacitation, and zona penetration.","evidence":"Targeted Ldhc knockout mice with sperm motility, ATP, capacitation phosphorylation, and IVF assays","pmids":["18367675"],"confidence":"High","gaps":["Did not resolve which downstream energetic step limits motility"]},{"year":2012,"claim":"Identified MYBL1 as a positive transcriptional activator acting through the CRE site, mechanistically connecting it to CBP and CREB.","evidence":"MYBL1 mutant mice, reporter assays in GC1-spg cells, EMSA, and TAD-CBP-KIX/CREB interaction domain mapping","pmids":["21998171"],"confidence":"High","gaps":["How MYBL1, Sp1, and the germ-cell factor are coordinated at the promoter not integrated"]},{"year":2013,"claim":"Clarified that LDHC is essential specifically under glycolytic conditions, since null sperm compensate by oxidative phosphorylation only when glucose is absent.","evidence":"Ldhc knockout across two strains with oxygen consumption, ATP, and motility under defined substrates","pmids":["23486916"],"confidence":"High","gaps":["Molecular basis of the glucose-dependent Crabtree suppression in sperm not defined"]},{"year":2013,"claim":"Showed LDHC's role reflects cytosolic LDH catalytic activity rather than unique isozyme properties, since cytosolic LDHA rescues fertility.","evidence":"Human LDHA transgenic rescue in Ldhc-null mice with motility, phosphorylation, fertility, and metabolite readouts","pmids":["23467744"],"confidence":"High","gaps":["Why rescued sperm function despite unchanged ATP/lactate levels not fully explained"]},{"year":2020,"claim":"Extended LDHC biology to cancer, showing ectopic LDHC drives migration, invasion, and tumor growth via PI3K/AKT/GSK-3β.","evidence":"LDHC overexpression/knockdown in LUAD cells, xenografts, and PI3K inhibitor rescue with Western blot","pmids":["33301764"],"confidence":"Medium","gaps":["Direct link between LDHC catalytic output and AKT activation not established","Single tumor type"]},{"year":2022,"claim":"Confirmed methylation-gated expression in a developmental context and identified SP1 recruitment to demethylated promoter regions controlling LDHC and lactate output.","evidence":"MeDIP-seq, 5-Aza-CdR demethylation, SP1 ChIP, and overexpression with lactate measurement in porcine Sertoli cells","pmids":["36041633"],"confidence":"Medium","gaps":["Causality of demethylation versus SP1 binding ordering not resolved"]},{"year":2022,"claim":"Validated human LDHC as a species-selective contraceptive target by humanizing the mouse locus and showing inhibitor sensitivity.","evidence":"CRISPR/Cas9 humanized knock-in mice, CASA motility, and IVF with a human-LDHC-selective inhibitor","pmids":["36464740"],"confidence":"High","gaps":["In vivo contraceptive efficacy of the inhibitor not tested"]},{"year":2024,"claim":"Defined a context-dependent LDHC-STAT3 axis with opposite survival effects across breast cancer subtypes.","evidence":"siRNA knockdown, transcriptomics, viability assays, and STAT3 inhibition in basal-like and Her2-enriched cells","pmids":["39001513"],"confidence":"Medium","gaps":["Molecular basis of subtype-specific opposite outcomes unclear","Whether LDHC catalysis or moonlighting drives STAT3 effects not separated"]},{"year":2025,"claim":"Linked tumor LDHC to immune evasion, showing knockdown enhances T-cell activation and reduces PD-L1 and checkpoint expression.","evidence":"siRNA knockdown, multiplex cytokine assays, flow cytometry, ELISpot, and cytotoxicity in cancer-T cell co-cultures","pmids":["40108668"],"confidence":"Medium","gaps":["Mechanism connecting LDHC to PD-L1 and cytokine changes not defined"]},{"year":2025,"claim":"Confirmed flagellar/cytosolic localization of LDHC across species and its functional requirement for sperm energetics.","evidence":"Sperm proteome/metabolome profiling, fractionation, and specific LDHC inhibitor functional assays in stallion sperm","pmids":["40299647"],"confidence":"Medium","gaps":["Mechanism of flagellar targeting not addressed"]},{"year":null,"claim":"How LDHC's catalytic lactate/NAD+ chemistry mechanistically connects to its oncogenic signaling (PI3K/AKT, STAT3) and immunomodulatory effects remains unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No demonstration that enzymatic activity is required for cancer signaling effects","No structural model of LDHC distinguishing it from somatic LDH isozymes in the corpus"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016491","term_label":"oxidoreductase activity","supporting_discovery_ids":[0,1,2,11,16]},{"term_id":"GO:0140098","term_label":"catalytic activity, acting on RNA","supporting_discovery_ids":[0,2,11]}],"localization":[{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[2,16]},{"term_id":"GO:0005929","term_label":"cilium","supporting_discovery_ids":[16]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2,10,12]},{"term_id":"R-HSA-1474165","term_label":"Reproduction","supporting_discovery_ids":[0,1,2,15]},{"term_id":"R-HSA-74160","term_label":"Gene expression (Transcription)","supporting_discovery_ids":[3,4,5,6,8,10]}],"complexes":["LDH-C4 homotetramer"],"partners":["MYBL1","CREB","CBP","SP1"],"other_free_text":[]}},"prefetch_data":{"uniprot":{"accession":"P07864","full_name":"L-lactate dehydrogenase C chain","aliases":["Cancer/testis antigen 32","CT32","LDH testis subunit","LDH-X"],"length_aa":332,"mass_kda":36.3,"function":"Possible role in sperm motility","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/P07864/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/LDHC","classification":"Not Classified","n_dependent_lines":0,"n_total_lines":1208,"dependency_fraction":0.0},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[{"gene":"LDHA","stoichiometry":0.2},{"gene":"LDHB","stoichiometry":0.2},{"gene":"SSB","stoichiometry":0.2}],"url":"https://opencell.sf.czbiohub.org/search/LDHC","total_profiled":1310},"omim":[{"mim_id":"619999","title":"N-ALPHA-ACETYLTRANSFERASE 40, NatD CATALYTIC SUBUNIT; NAA40","url":"https://www.omim.org/entry/619999"},{"mim_id":"619059","title":"MITOCHONDRIAL COMPLEX IV DEFICIENCY, NUCLEAR TYPE 15; MC4DN15","url":"https://www.omim.org/entry/619059"},{"mim_id":"618928","title":"LACTATE DEHYDROGENASE A-LIKE PROTEIN 6A; LDHAL6A","url":"https://www.omim.org/entry/618928"},{"mim_id":"610985","title":"UBIQUITIN E2 VARIANT AND LACTATE/MALATE DEHYDROGENASE DOMAINS-CONTAINING PROTEIN; UEVLD","url":"https://www.omim.org/entry/610985"},{"mim_id":"150150","title":"LACTATE DEHYDROGENASE C; LDHC","url":"https://www.omim.org/entry/150150"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"Supported","locations":[{"location":"Cytosol","reliability":"Supported"},{"location":"Mid piece","reliability":"Additional"},{"location":"Principal piece","reliability":"Additional"},{"location":"End piece","reliability":"Additional"}],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"testis","ntpm":247.8}],"url":"https://www.proteinatlas.org/search/LDHC"},"hgnc":{"alias_symbol":["CT32"],"prev_symbol":[]},"alphafold":{"accession":"P07864","domains":[{"cath_id":"3.90.110.10","chopping":"162-327","consensus_level":"high","plddt":97.1849,"start":162,"end":327}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/P07864","model_url":"https://alphafold.ebi.ac.uk/files/AF-P07864-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-P07864-F1-predicted_aligned_error_v6.png","plddt_mean":96.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=LDHC","jax_strain_url":"https://www.jax.org/strain/search?query=LDHC"},"sequence":{"accession":"P07864","fasta_url":"https://rest.uniprot.org/uniprotkb/P07864.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/P07864/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/P07864"}},"corpus_meta":[{"pmid":"18367675","id":"PMC_18367675","title":"Expression of the gene for mouse lactate dehydrogenase C (Ldhc) is required for male fertility.","date":"2008","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/18367675","citation_count":175,"is_preprint":false},{"pmid":"19875487","id":"PMC_19875487","title":"LDHC: the ultimate testis-specific gene.","date":"2009","source":"Journal of andrology","url":"https://pubmed.ncbi.nlm.nih.gov/19875487","citation_count":114,"is_preprint":false},{"pmid":"23486916","id":"PMC_23486916","title":"Glycolysis and mitochondrial respiration in mouse LDHC-null sperm.","date":"2013","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/23486916","citation_count":71,"is_preprint":false},{"pmid":"9813024","id":"PMC_9813024","title":"Transgenic mice demonstrate a testis-specific promoter for lactate dehydrogenase, LDHC.","date":"1998","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/9813024","citation_count":56,"is_preprint":false},{"pmid":"33301764","id":"PMC_33301764","title":"Cancer/testis antigen LDHC promotes proliferation and metastasis by activating the PI3K/Akt/GSK-3β-signaling pathway and the in lung adenocarcinoma.","date":"2020","source":"Experimental cell research","url":"https://pubmed.ncbi.nlm.nih.gov/33301764","citation_count":46,"is_preprint":false},{"pmid":"3180843","id":"PMC_3180843","title":"Mapping of human lactate dehydrogenase-A, -B, and -C genes and their related sequences: the gene for LDHC is located with that for LDHA on chromosome 11.","date":"1988","source":"Cytogenetics and cell genetics","url":"https://pubmed.ncbi.nlm.nih.gov/3180843","citation_count":43,"is_preprint":false},{"pmid":"2844458","id":"PMC_2844458","title":"Locus determining the human sperm-specific lactate dehydrogenase, LDHC, is syntenic with LDHA.","date":"1987","source":"Developmental genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2844458","citation_count":32,"is_preprint":false},{"pmid":"31932876","id":"PMC_31932876","title":"Identification of two HLA-A*0201 immunogenic epitopes of lactate dehydrogenase C (LDHC): potential novel targets for cancer immunotherapy.","date":"2020","source":"Cancer immunology, immunotherapy : CII","url":"https://pubmed.ncbi.nlm.nih.gov/31932876","citation_count":27,"is_preprint":false},{"pmid":"23467744","id":"PMC_23467744","title":"Human lactate dehydrogenase A (LDHA) rescues mouse Ldhc-null sperm function.","date":"2013","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/23467744","citation_count":23,"is_preprint":false},{"pmid":"37189204","id":"PMC_37189204","title":"Tanshinone IIA inhibits osteoclastogenesis in rheumatoid arthritis via LDHC-regulated ROS generation.","date":"2023","source":"Chinese medicine","url":"https://pubmed.ncbi.nlm.nih.gov/37189204","citation_count":17,"is_preprint":false},{"pmid":"7736669","id":"PMC_7736669","title":"The CpG-rich promoter of human LDH-C is differentially methylated in expressing and nonexpressing tissues.","date":"1995","source":"Developmental genetics","url":"https://pubmed.ncbi.nlm.nih.gov/7736669","citation_count":17,"is_preprint":false},{"pmid":"21998171","id":"PMC_21998171","title":"A-MYB (MYBL1) stimulates murine testis-specific Ldhc expression via the cAMP-responsive element (CRE) site.","date":"2012","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/21998171","citation_count":16,"is_preprint":false},{"pmid":"2596827","id":"PMC_2596827","title":"Regional localization of the sperm-specific lactate dehydrogenase, LDHC, gene on human chromosome 11.","date":"1989","source":"Annals of human genetics","url":"https://pubmed.ncbi.nlm.nih.gov/2596827","citation_count":16,"is_preprint":false},{"pmid":"9892725","id":"PMC_9892725","title":"cDNA copies of the testis-specific lactate dehydrogenase (LDH-C) mRNA are present in spermatogenic cells in mice, but processed pseudogenes are not derived from mRNAs that are expressed in haploid and late meiotic spermatogenic cells.","date":"1999","source":"Mammalian genome : official journal of the International Mammalian Genome Society","url":"https://pubmed.ncbi.nlm.nih.gov/9892725","citation_count":15,"is_preprint":false},{"pmid":"40108668","id":"PMC_40108668","title":"Immunomodulatory effects of tumor Lactate Dehydrogenase C (LDHC) in breast cancer.","date":"2025","source":"Cell communication and signaling : CCS","url":"https://pubmed.ncbi.nlm.nih.gov/40108668","citation_count":14,"is_preprint":false},{"pmid":"9153323","id":"PMC_9153323","title":"Molecular and functional characterization of the promoter region of the mouse LDH/C gene: enhancer-assisted, Sp1-mediated transcriptional activation.","date":"1997","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/9153323","citation_count":14,"is_preprint":false},{"pmid":"11447215","id":"PMC_11447215","title":"ldhc expression in non-germ cell nuclei is repressed by NF-I binding.","date":"2001","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11447215","citation_count":12,"is_preprint":false},{"pmid":"27490559","id":"PMC_27490559","title":"Effect of Hypoxia on Ldh-c Expression in Somatic Cells of Plateau Pika.","date":"2016","source":"International journal of environmental research and public health","url":"https://pubmed.ncbi.nlm.nih.gov/27490559","citation_count":12,"is_preprint":false},{"pmid":"8614414","id":"PMC_8614414","title":"Posttranscriptional regulation of primate Ldhc mRNA by its AUUUA-like elements.","date":"1995","source":"Molecular endocrinology (Baltimore, Md.)","url":"https://pubmed.ncbi.nlm.nih.gov/8614414","citation_count":11,"is_preprint":false},{"pmid":"36041633","id":"PMC_36041633","title":"MeDIP-seq and RNA-seq analysis during porcine testis development reveals functional DMR at the promoter of LDHC.","date":"2022","source":"Genomics","url":"https://pubmed.ncbi.nlm.nih.gov/36041633","citation_count":6,"is_preprint":false},{"pmid":"22373157","id":"PMC_22373157","title":"LDH-C can be differentially expressed during fermentation of CHO cells.","date":"2011","source":"BMC proceedings","url":"https://pubmed.ncbi.nlm.nih.gov/22373157","citation_count":6,"is_preprint":false},{"pmid":"36464740","id":"PMC_36464740","title":"Generation of humanized LDHC knock-in mice as a tool to assess human LDHC-targeting contraceptive drugs.","date":"2022","source":"Andrology","url":"https://pubmed.ncbi.nlm.nih.gov/36464740","citation_count":5,"is_preprint":false},{"pmid":"28916706","id":"PMC_28916706","title":"The expression of Ldh-c in the skeletal muscle of plateau pika (Ochotona curzoniae) enhances adaptation to a hypoxic environment.","date":"2017","source":"Biology open","url":"https://pubmed.ncbi.nlm.nih.gov/28916706","citation_count":4,"is_preprint":false},{"pmid":"40299647","id":"PMC_40299647","title":"Stallion spermatozoa express LDH isoforms A, B, and C, with LDHC playing a crucial role in sustaining sperm viability.","date":"2025","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/40299647","citation_count":3,"is_preprint":false},{"pmid":"39001513","id":"PMC_39001513","title":"The LDHC-STAT3 Signaling Network Is a Key Regulator of Basal-like Breast Cancer Cell Survival.","date":"2024","source":"Cancers","url":"https://pubmed.ncbi.nlm.nih.gov/39001513","citation_count":3,"is_preprint":false},{"pmid":"9723175","id":"PMC_9723175","title":"Cell-type-specific transcription factor interactions with cis-elements present in the mouse LDH/C proximal promoter region.","date":"1998","source":"The Journal of experimental zoology","url":"https://pubmed.ncbi.nlm.nih.gov/9723175","citation_count":3,"is_preprint":false},{"pmid":"41339282","id":"PMC_41339282","title":"Lactylation Genes LDHA and LDHC Alleviate Osteoarthritis by Reducing Specific B-Cell Expression: Mechanistic Exploration and Experimental Validation.","date":"2025","source":"Journal of cellular and molecular medicine","url":"https://pubmed.ncbi.nlm.nih.gov/41339282","citation_count":2,"is_preprint":false},{"pmid":"26109304","id":"PMC_26109304","title":"[The expression of the sperm-specific lactate dehydrogenase gene Ldh-c in plateau pika (Ochotona curzoniae) cardiac muscle and its effect on the anaerobic glycolysis].","date":"2015","source":"Sheng li xue bao : [Acta physiologica Sinica]","url":"https://pubmed.ncbi.nlm.nih.gov/26109304","citation_count":2,"is_preprint":false},{"pmid":"40270965","id":"PMC_40270965","title":"Identification of new HLA-A*0201-restricted cytotoxic T lymphocyte epitopes from LDHC in lung adenocarcinoma.","date":"2025","source":"Frontiers in immunology","url":"https://pubmed.ncbi.nlm.nih.gov/40270965","citation_count":1,"is_preprint":false},{"pmid":"41153772","id":"PMC_41153772","title":"Machine Learning-Based Validation of LDHC and SLC35G2 Methylation as Epigenetic Biomarkers for Food Allergy.","date":"2025","source":"Biomedicines","url":"https://pubmed.ncbi.nlm.nih.gov/41153772","citation_count":0,"is_preprint":false},{"pmid":"41879946","id":"PMC_41879946","title":"Comparative study on the functions of LDHA and LDHC in triple-negative breast cancer.","date":"2026","source":"Discover oncology","url":"https://pubmed.ncbi.nlm.nih.gov/41879946","citation_count":0,"is_preprint":false},{"pmid":"41599186","id":"PMC_41599186","title":"Cell-Penetrating Peptide-Mediated siRNA Targeting of LDHC Suppresses Tumor Growth in a Triple-Negative Breast Cancer Zebrafish Xenograft Model.","date":"2026","source":"Pharmaceutics","url":"https://pubmed.ncbi.nlm.nih.gov/41599186","citation_count":0,"is_preprint":false},{"pmid":null,"id":"bio_10.1101_2025.03.11.641612","title":"Anti-tumor effects of a novel cell penetrating peptide-based therapeutic approach to target Lactate Dehydrogenase C (LDHC) in triple negative breast cancer","date":"2025-03-13","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.11.641612","citation_count":0,"is_preprint":true},{"pmid":null,"id":"bio_10.1101_2025.03.19.25324051","title":"Multi-level Regulatory Roles of Lactate Metabolism Gene Network in Oral Cancer: Machine Learning Insights","date":"2025-03-20","source":"bioRxiv","url":"https://doi.org/10.1101/2025.03.19.25324051","citation_count":0,"is_preprint":true}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":18966,"output_tokens":4582,"usd":0.062814,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12682,"output_tokens":4491,"usd":0.087843,"stage2_stop_reason":"end_turn"},"total_usd":0.150657,"stage1_batch_id":"msgbatch_01BbTCMyrRPyhtEq6b1MdwCN","stage2_batch_id":"msgbatch_011dEed5bbxYvTAaQWKJevxu","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2008,\n      \"finding\": \"Targeted disruption of Ldhc in mice severely impaired male fertility. LDHC homotetramer (LDH-C4) accounts for the majority of LDH enzymatic activity in sperm. Ldhc-null sperm showed more rapid ATP depletion, loss of motility, failure to acquire hyperactivated motility, inability to penetrate the zona pellucida in vitro, and failure to undergo capacitation-associated phosphorylation events.\",\n      \"method\": \"Gene knockout (targeted disruption), sperm motility assay, ATP measurement, in vitro fertilization assay, capacitation phosphorylation assay\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean KO with multiple defined cellular and biochemical phenotypes; replicated in subsequent studies\",\n      \"pmids\": [\"18367675\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"In the absence of glucose, Ldhc-null sperm can produce ATP via oxidative phosphorylation, but when glucose is present, oxidative phosphorylation is suppressed and sperm rely on aerobic glycolysis (Crabtree effect). LDHC is required to maintain glycolytic flux and ATP production specifically in the presence of glucose.\",\n      \"method\": \"Ldhc knockout mouse model (C57BL/6 and 129S6 backgrounds), oxygen consumption measurement, ATP quantification, motility analysis under defined energy substrate conditions\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — two genetic backgrounds with multiple orthogonal metabolic readouts; replicates and extends PMID 18367675\",\n      \"pmids\": [\"23486916\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Human LDHA introduced as a transgene into Ldhc-null mice rescued sperm motility, protein tyrosine phosphorylation (capacitation marker), and fertility, demonstrating that LDHC does not possess unique catalytic properties essential for fertility and that cytosolic LDH activity per se is sufficient. However, ATP and lactate levels in rescued sperm did not significantly differ from Ldhc-null sperm, suggesting localization of LDH to the sperm cytosol (rather than specific enzymatic properties of LDHC) is the main determinant of rescue.\",\n      \"method\": \"Transgenic rescue experiment (LDHA transgene in Ldhc-/- background), sperm motility assay, tyrosine phosphorylation assay, fertility testing, ATP/lactate measurement\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — transgenic rescue with multiple functional readouts and mechanistic interpretation; single lab but orthogonal methods\",\n      \"pmids\": [\"23467744\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"A 100 bp genomic fragment overlapping the LDHC transcription start site is sufficient to drive testis-specific expression in transgenic mice, with expression restricted to leptotene/pachytene primary spermatocytes.\",\n      \"method\": \"Transgenic mice carrying lacZ reporter driven by 100 bp LDHC promoter fragment; in vitro transcription assay with 60 bp promoter\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — in vivo transgenic confirmation of in vitro transcription assay; two orthogonal methods in one study\",\n      \"pmids\": [\"9813024\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"NF-I/CTF family proteins bind to a palindromic element in the Ldhc promoter and repress its activity in somatic (non-germ) cells. Mutation of the NF-I binding site in the palindrome increased promoter activity ~4-fold in mouse L cells; overexpression of NF-IA, -B, -C, or -X decreased wild-type promoter activity 20–50% but had no effect when the NF-I binding element was mutated.\",\n      \"method\": \"Gel retardation assay, transient transfection reporter assay in mouse L cells, NF-I overexpression, site-directed mutagenesis of promoter\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (EMSA, mutagenesis, overexpression) in a single study; single lab\",\n      \"pmids\": [\"11447215\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Transcription factor MYBL1 (A-MYB) stimulates Ldhc expression in spermatocytes via the CRE site in the Ldhc core promoter. MYBL1 transactivation domain (TAD) interacts with the KIX domain of CBP, and TAD and DNA-binding domain of MYBL1 each interact with the CREB N-terminal domain. LDHC expression is lost in 21-day testes of MYBL1 mutant mice. MYBL1 activates Ldhc through CRE elements rather than canonical Myb-binding sites.\",\n      \"method\": \"MYBL1 mutant mouse analysis, reporter assays in GC1-spg cells, EMSA, co-immunoprecipitation/interaction domain mapping between MYBL1-TAD and CBP-KIX/CREB\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods including mutant mouse, reporter assay, domain interaction mapping; single lab\",\n      \"pmids\": [\"21998171\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1997,\n      \"finding\": \"DNase I footprinting in isolated mouse pachytene spermatocytes identified a single protected region over the GC-box (Sp1-binding site) in the LDH/C proximal promoter. Functional studies showed that enhancer-assisted Sp1-mediated transactivation drives LDH/C promoter activity; mutation of the GC-box abolished activity.\",\n      \"method\": \"PCR-based in vivo DNase I footprinting in isolated pachytene spermatocytes, CAT reporter assays with wild-type and mutated promoter constructs in germ cell and somatic cell lines\",\n      \"journal\": \"Nucleic acids research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vivo footprinting combined with functional reporter mutagenesis; single lab\",\n      \"pmids\": [\"9153323\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1998,\n      \"finding\": \"EMSA studies identified at least one germ-cell-specific nuclear transcription factor (distinct from Sp1) that binds the GC-box motif of the LDH/C proximal promoter, with methylation interference identifying a unique 5'G residue within the GC-box as critical for this binding. Somatic cells (HeLa) have at least six different DNA-protein complexes at this element, only one of which involves Sp1.\",\n      \"method\": \"EMSA with nuclear extracts from primary germ cells and HeLa cells, supershift analysis with Sp1 antibody, methylation interference analysis, GC-box mutagenesis\",\n      \"journal\": \"The Journal of experimental zoology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 / Moderate — multiple EMSA approaches with mutagenesis; single lab, in vitro binding only\",\n      \"pmids\": [\"9723175\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The human LDH-C promoter contains a CpG-rich region of ~230 bp that is heavily methylated at nine sites in somatic cells but specifically hypomethylated at those same sites in expressing tissues (testis). A methylated promoter forms a specific complex in vitro with a methyl-DNA binding protein, linking promoter hypermethylation to LDHC silencing in non-expressing tissues.\",\n      \"method\": \"Endonuclease sensitivity coupled with PCR (methylation mapping), in vitro protein-DNA complex formation with methyl-DNA binding protein\",\n      \"journal\": \"Developmental genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (restriction enzyme/PCR methylation mapping and in vitro binding assay); single lab\",\n      \"pmids\": [\"7736669\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 1995,\n      \"finding\": \"The 3'-UTR of primate (baboon, human) but not rodent Ldhc mRNA contains AU-rich elements that destabilize the transcript. Baboon Ldhc mRNA is labile in a cell-free system while mouse mRNA is highly stable. Removal of the human Ldhc 3'-UTR stabilizes the mRNA; mutation of AU-rich motifs also results in stabilization. Steady-state primate Ldhc mRNA levels are 8–12-fold lower than mouse.\",\n      \"method\": \"Cell-free mRNA stability assay, deletion and point mutagenesis of 3'-UTR AU-rich elements, steady-state mRNA quantification in germ cell line\",\n      \"journal\": \"Molecular endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution of mRNA stability with mutagenesis; multiple approaches in one study; single lab\",\n      \"pmids\": [\"8614414\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"During porcine testis development, the LDHC promoter is heavily methylated in pre-pubertal testes and demethylated post-pubertally. Artificial demethylation with 5-Aza-CdR induced LDHC expression in immature Sertoli cells. Transcription factor SP1 was recruited to bind hypomethylated DMRs in the LDHC promoter, upregulating LDHC expression. LDHC overexpression in mature Sertoli cells significantly increases lactate secretion.\",\n      \"method\": \"MeDIP-seq, 5-Aza-CdR demethylation experiment, ChIP (SP1 binding to LDHC promoter DMR), LDHC overexpression with lactate secretion measurement\",\n      \"journal\": \"Genomics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple methods (MeDIP-seq, demethylation experiment, ChIP, functional overexpression); single lab\",\n      \"pmids\": [\"36041633\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Tanshinone IIA (Tan IIA) covalently binds to LDHC and inhibits its enzymatic activity, as identified by activity-based protein profiling (ABPP) combined with LC-MS/MS. LDHC inhibition by Tan IIA reduces ROS accumulation in osteoclasts, suppressing osteoclast-specific marker expression and osteoclast differentiation.\",\n      \"method\": \"Activity-based protein profiling (ABPP) + LC-MS/MS identification of covalent binding, enzymatic activity assay, ROS measurement, osteoclast differentiation assay\",\n      \"journal\": \"Chinese medicine\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — ABPP chemical proteomics with enzymatic activity validation and functional readout; single lab\",\n      \"pmids\": [\"37189204\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"LDHC overexpression in lung adenocarcinoma (LUAD) cells increased lactate and ATP production, enhanced cell migration and invasion, and accelerated xenograft tumor growth. LDHC overexpression elevated phosphorylation of AKT and GSK-3β; PI3K inhibition reversed these effects, reducing proliferation, migration, invasion, and EMT-related protein changes.\",\n      \"method\": \"LDHC overexpression/knockdown in LUAD cell lines, in vitro invasion/migration assays, xenograft tumor model, PI3K inhibitor treatment, Western blot for p-AKT/p-GSK3β and EMT markers\",\n      \"journal\": \"Experimental cell research\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple in vitro and in vivo functional assays with pathway pharmacological validation; single lab\",\n      \"pmids\": [\"33301764\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"LDHC silencing in basal-like breast cancer cells (MDA-MB-468, BT-549) compromised cell survival in conjunction with downregulation of STAT3 signaling, whereas LDHC silencing in Her2-enriched breast cancer cells (HCC-1954) enhanced STAT3 activation and promoted survival. STAT3 inhibition reversed the pro-survival effect of LDHC silencing in Her2-enriched cells, establishing a LDHC-STAT3 signaling axis.\",\n      \"method\": \"siRNA knockdown, transcriptomic analysis, cell viability assay, STAT3 inhibitor treatment, Western blot\",\n      \"journal\": \"Cancers\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — knockdown plus pharmacological inhibition with transcriptomic and functional readouts; single lab\",\n      \"pmids\": [\"39001513\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"LDHC silencing in breast cancer cells enhanced early T cell activation and cytolytic activity. Mechanistically, LDHC knockdown increased pro-inflammatory cytokine secretion (IFN-γ, GM-CSF, MCP-1, CXCL1), decreased immunosuppressive factors (IL-6, Gal-9), and reduced tumor cell surface PD-L1 expression. In cancer cell–T cell co-cultures, LDHC knockdown reduced immune checkpoint molecule expression (PD-1, CTLA-4, TIGIT, TIM3, VISTA) on CD8+ T cells.\",\n      \"method\": \"siRNA knockdown, multiplex cytokine assay, flow cytometry for immune checkpoints and surface markers, IFN-γ ELISpot, 7-AAD cytotoxicity assay in cancer cell–T cell co-cultures\",\n      \"journal\": \"Cell communication and signaling\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — multiple orthogonal methods (cytokine assay, flow cytometry, ELISpot) in monoculture and co-culture; single lab\",\n      \"pmids\": [\"40108668\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Human LDHC knocked into the mouse Ldhc locus (replacing mouse LDHC) fully rescued sperm motility and male fertility. An LDH inhibitor more specific for human LDHC than mouse LDHC reduced in vitro fertilization rates in hLDHC knock-in mice but not wild-type mice, validating hLDHC as a pharmacologically distinct contraceptive target.\",\n      \"method\": \"CRISPR/Cas9 humanized knock-in mouse, CASA sperm motility analysis, IVF with LDH inhibitor treatment\",\n      \"journal\": \"Andrology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — humanized knock-in genetic model with pharmacological validation using species-selective inhibitor; multiple functional readouts\",\n      \"pmids\": [\"36464740\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In stallion spermatozoa, LDHC localizes to the cytosol and the motile cilium (flagellum), while LDHA is cytosolic and LDHB is mitochondrial. Functional inhibition of LDHC with a specific inhibitor impaired sperm function, consistent with LDHC playing an essential role in aerobic glycolysis and NAD+ regeneration within the flagellum.\",\n      \"method\": \"Proteomics/metabolomics of sperm metabolic proteome, cellular fractionation/localization, specific LDHC inhibitor functional assay, sperm motility and viability assays\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — localization by proteomics combined with functional inhibitor experiment; single lab\",\n      \"pmids\": [\"40299647\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"LDHC is a testis-specific LDH isozyme that forms homotetramers (LDH-C4) localized to the sperm flagellum/cytosol, where it catalyzes the reversible interconversion of pyruvate and lactate, maintaining glycolytic flux and NAD+ regeneration required for ATP production, sperm motility, capacitation, and male fertility; its testis-specific expression is controlled at multiple levels including promoter activation via Sp1/MYBL1-CRE-CBP interactions, repression by NF-I proteins in somatic cells, promoter DNA methylation status, and post-transcriptional destabilization via 3'-UTR AU-rich elements in primates; in cancer contexts, aberrant LDHC expression activates PI3K/AKT/GSK-3β and modulates STAT3 signaling and immune checkpoint expression.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"LDHC is a testis-specific lactate dehydrogenase isozyme that, as the homotetramer LDH-C4, provides the majority of LDH activity in sperm and is essential for male fertility [#0]. Functioning in the sperm cytosol and flagellum, it sustains glycolytic flux and ATP production: Ldhc-null sperm deplete ATP rapidly, lose motility, fail to hyperactivate, cannot undergo capacitation-associated tyrosine phosphorylation, and cannot penetrate the zona pellucida [#0]. LDHC is specifically required to maintain aerobic glycolysis in the presence of glucose, when oxidative phosphorylation is suppressed (Crabtree effect) [#1]. Its essential contribution is the cytosolic LDH catalytic activity itself rather than unique enzymatic properties, since a cytosolic human LDHA transgene restores motility, capacitation phosphorylation, and fertility in Ldhc-null mice [#2], and a humanized human-LDHC knock-in fully rescues fertility while conferring sensitivity to a human-LDHC-selective inhibitor, defining LDHC as a contraceptive target [#15]. Testis-restricted expression is set by layered control: a minimal promoter directs spermatocyte-specific transcription [#3] activated through an Sp1-bound GC-box [#6] and through MYBL1 acting at a CRE site via interactions with CBP-KIX and CREB [#5], while NF-I proteins repress the promoter in somatic cells [#4]; promoter CpG methylation silences the gene outside the testis and demethylation permits Sp1 recruitment and expression [#8, #10]. In primates, AU-rich elements in the 3'-UTR destabilize the transcript, accounting for lower expression than in rodents [#9]. Aberrantly expressed LDHC drives oncogenic phenotypes, enhancing lactate/ATP production, migration, invasion, and tumor growth via PI3K/AKT/GSK-3\\u03b2 signaling [#12], modulating STAT3 signaling in a context-dependent manner [#13], and shaping anti-tumor immunity through effects on cytokine secretion, PD-L1, and T-cell checkpoint expression [#14].\",\n  \"teleology\": [\n    {\n      \"year\": 1995,\n      \"claim\": \"Established that species-specific post-transcriptional control limits LDHC abundance, explaining why primates express far less LDHC mRNA than rodents.\",\n      \"evidence\": \"Cell-free mRNA stability assays and 3'-UTR AU-rich element mutagenesis in baboon, human, and mouse transcripts\",\n      \"pmids\": [\"8614414\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Trans-acting destabilizing factors binding the AU-rich elements not identified\", \"Physiological consequence of lower primate LDHC levels not addressed\"]\n    },\n    {\n      \"year\": 1995,\n      \"claim\": \"Linked tissue-restricted LDHC expression to promoter DNA methylation, showing the CpG-rich promoter is methylated and silent in somatic tissue but hypomethylated in testis.\",\n      \"evidence\": \"Methylation mapping by restriction/PCR and in vitro methyl-DNA binding protein complex formation on the human LDH-C promoter\",\n      \"pmids\": [\"7736669\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of the methyl-DNA binding protein not established\", \"Causality between methylation and silencing not tested in vivo\"]\n    },\n    {\n      \"year\": 1997,\n      \"claim\": \"Identified the proximal GC-box as a functional control element and implicated Sp1-mediated transactivation in driving promoter activity in spermatocytes.\",\n      \"evidence\": \"In vivo DNase I footprinting in pachytene spermatocytes plus CAT reporter mutagenesis\",\n      \"pmids\": [\"9153323\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Did not resolve whether Sp1 or a germ-cell factor occupies the site in vivo\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Defined the minimal cis-regulatory element sufficient for germ-cell-specific transcription, narrowing testis-specificity to ~100 bp around the start site.\",\n      \"evidence\": \"lacZ transgenic mice and in vitro transcription with a 60 bp promoter fragment\",\n      \"pmids\": [\"9813024\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full set of trans factors binding the minimal promoter not enumerated\"]\n    },\n    {\n      \"year\": 1998,\n      \"claim\": \"Showed the GC-box is bound by a germ-cell-specific factor distinct from Sp1, refining the regulatory logic beyond canonical Sp1 occupancy.\",\n      \"evidence\": \"EMSA, Sp1 supershift, and methylation interference with germ cell and HeLa nuclear extracts\",\n      \"pmids\": [\"9723175\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Germ-cell-specific factor not molecularly identified\", \"In vitro binding only, no in vivo confirmation\"]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"Provided a mechanism for silencing in non-germ cells by showing NF-I proteins bind a promoter palindrome and repress transcription.\",\n      \"evidence\": \"EMSA, reporter assays, NF-I overexpression, and binding-site mutagenesis in mouse L cells\",\n      \"pmids\": [\"11447215\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Repression demonstrated in a somatic cell line, not in germ-cell differentiation context\"]\n    },\n    {\n      \"year\": 2008,\n      \"claim\": \"Demonstrated that LDHC is required for male fertility, defining its cellular role in sperm energetics, motility, capacitation, and zona penetration.\",\n      \"evidence\": \"Targeted Ldhc knockout mice with sperm motility, ATP, capacitation phosphorylation, and IVF assays\",\n      \"pmids\": [\"18367675\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Did not resolve which downstream energetic step limits motility\"]\n    },\n    {\n      \"year\": 2012,\n      \"claim\": \"Identified MYBL1 as a positive transcriptional activator acting through the CRE site, mechanistically connecting it to CBP and CREB.\",\n      \"evidence\": \"MYBL1 mutant mice, reporter assays in GC1-spg cells, EMSA, and TAD-CBP-KIX/CREB interaction domain mapping\",\n      \"pmids\": [\"21998171\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How MYBL1, Sp1, and the germ-cell factor are coordinated at the promoter not integrated\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Clarified that LDHC is essential specifically under glycolytic conditions, since null sperm compensate by oxidative phosphorylation only when glucose is absent.\",\n      \"evidence\": \"Ldhc knockout across two strains with oxygen consumption, ATP, and motility under defined substrates\",\n      \"pmids\": [\"23486916\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Molecular basis of the glucose-dependent Crabtree suppression in sperm not defined\"]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Showed LDHC's role reflects cytosolic LDH catalytic activity rather than unique isozyme properties, since cytosolic LDHA rescues fertility.\",\n      \"evidence\": \"Human LDHA transgenic rescue in Ldhc-null mice with motility, phosphorylation, fertility, and metabolite readouts\",\n      \"pmids\": [\"23467744\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Why rescued sperm function despite unchanged ATP/lactate levels not fully explained\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Extended LDHC biology to cancer, showing ectopic LDHC drives migration, invasion, and tumor growth via PI3K/AKT/GSK-3\\u03b2.\",\n      \"evidence\": \"LDHC overexpression/knockdown in LUAD cells, xenografts, and PI3K inhibitor rescue with Western blot\",\n      \"pmids\": [\"33301764\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct link between LDHC catalytic output and AKT activation not established\", \"Single tumor type\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Confirmed methylation-gated expression in a developmental context and identified SP1 recruitment to demethylated promoter regions controlling LDHC and lactate output.\",\n      \"evidence\": \"MeDIP-seq, 5-Aza-CdR demethylation, SP1 ChIP, and overexpression with lactate measurement in porcine Sertoli cells\",\n      \"pmids\": [\"36041633\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Causality of demethylation versus SP1 binding ordering not resolved\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Validated human LDHC as a species-selective contraceptive target by humanizing the mouse locus and showing inhibitor sensitivity.\",\n      \"evidence\": \"CRISPR/Cas9 humanized knock-in mice, CASA motility, and IVF with a human-LDHC-selective inhibitor\",\n      \"pmids\": [\"36464740\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"In vivo contraceptive efficacy of the inhibitor not tested\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"Defined a context-dependent LDHC-STAT3 axis with opposite survival effects across breast cancer subtypes.\",\n      \"evidence\": \"siRNA knockdown, transcriptomics, viability assays, and STAT3 inhibition in basal-like and Her2-enriched cells\",\n      \"pmids\": [\"39001513\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular basis of subtype-specific opposite outcomes unclear\", \"Whether LDHC catalysis or moonlighting drives STAT3 effects not separated\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Linked tumor LDHC to immune evasion, showing knockdown enhances T-cell activation and reduces PD-L1 and checkpoint expression.\",\n      \"evidence\": \"siRNA knockdown, multiplex cytokine assays, flow cytometry, ELISpot, and cytotoxicity in cancer-T cell co-cultures\",\n      \"pmids\": [\"40108668\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism connecting LDHC to PD-L1 and cytokine changes not defined\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Confirmed flagellar/cytosolic localization of LDHC across species and its functional requirement for sperm energetics.\",\n      \"evidence\": \"Sperm proteome/metabolome profiling, fractionation, and specific LDHC inhibitor functional assays in stallion sperm\",\n      \"pmids\": [\"40299647\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of flagellar targeting not addressed\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How LDHC's catalytic lactate/NAD+ chemistry mechanistically connects to its oncogenic signaling (PI3K/AKT, STAT3) and immunomodulatory effects remains unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No demonstration that enzymatic activity is required for cancer signaling effects\", \"No structural model of LDHC distinguishing it from somatic LDH isozymes in the corpus\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016491\", \"supporting_discovery_ids\": [0, 1, 2, 11, 16]},\n      {\"term_id\": \"GO:0140098\", \"supporting_discovery_ids\": [0, 2, 11]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [2, 16]},\n      {\"term_id\": \"GO:0005929\", \"supporting_discovery_ids\": [16]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2, 10, 12]},\n      {\"term_id\": \"R-HSA-1474165\", \"supporting_discovery_ids\": [0, 1, 2, 15]},\n      {\"term_id\": \"R-HSA-74160\", \"supporting_discovery_ids\": [3, 4, 5, 6, 8, 10]}\n    ],\n    \"complexes\": [\"LDH-C4 homotetramer\"],\n    \"partners\": [\"MYBL1\", \"CREB\", \"CBP\", \"SP1\"],\n    \"other_free_text\": []\n  }\n}","audit_flag":null,"evaluation":{"faith_supported":7,"faith_total":7,"faith_pct":100.0}}