{"gene":"DHH","run_date":"2026-04-28T17:46:02","timeline":{"discoveries":[{"year":2000,"finding":"DHH is a signaling molecule expressed by Sertoli cells whose receptor Patched (Ptc) is localized to Leydig cells and peritubular cells; loss of Dhh in mice results in failure to form adult-type Leydig cells, abnormal peritubular tissue, absent/focal basal lamina, and severely restricted spermatogenesis, establishing DHH as required for Leydig cell differentiation and seminiferous tubule morphogenesis.","method":"Genetic knockout (Dhh-null mice) with histological, immunolocalization, and morphological phenotypic readouts","journal":"Biology of reproduction","confidence":"High","confidence_rationale":"Tier 2 — clean KO with defined cellular phenotypes, receptor localization, replicated across multiple studies","pmids":["11090455"],"is_preprint":false},{"year":2010,"finding":"A missense mutation in the Dhh gene in mutant rats (mp/mp) results in loss of DHH signaling, dramatically reduced fetal Leydig cell number, absence of adult-type spindle-shaped Leydig cells, and significantly lower testosterone during embryonic development, confirming DHH is essential for Leydig cell development and androgen production.","method":"Fine linkage mapping, Sanger sequencing to identify missense mutation, immunohistochemistry with Leydig cell-specific marker, testosterone measurement","journal":"Reproduction (Cambridge, England)","confidence":"High","confidence_rationale":"Tier 2 — genetic model (missense KO equivalent) with multiple orthogonal readouts; replicates mouse Dhh-null phenotype in a different species","pmids":["21062903"],"is_preprint":false},{"year":2018,"finding":"In vitro cleavage assays demonstrated that DHH undergoes autocatalytic self-cleavage (auto-processing) to generate the active N-terminal signaling domain (DHh-N); a frameshift mutation p.(Asn337Lysfs*24) completely abolished auto-proteolysis, while p.(Glu212Lys) retained ~50% cleavage activity. Complete disruption of DHh-N (signaling domain) was associated with both gonadal dysgenesis and polyneuropathy, while disruption of auto-processing alone was associated only with gonadal dysgenesis.","method":"In vitro cleavage/auto-processing assay with mutant and wild-type DHH constructs, compared with Drosophila Hh","journal":"Human mutation","confidence":"High","confidence_rationale":"Tier 1 — in vitro biochemical assay with multiple mutants and mechanistic interpretation of cleavage activity","pmids":["30298535"],"is_preprint":false},{"year":2020,"finding":"Multiple pathogenic DHH variants associated with 46,XY gonadal dysgenesis were tested in cell-based assays; a subset was unable to perform self-cleavage, which correlated with altered subcellular localization of the resulting proteins, establishing that self-cleavage is required for proper DHH processing and trafficking.","method":"In vitro self-cleavage assay, subcellular localization imaging, structural modelling and molecular dynamics simulations","journal":"Human genetics","confidence":"Medium","confidence_rationale":"Tier 1-2 — in vitro assay plus localization, but single lab","pmids":["32504121"],"is_preprint":false},{"year":2017,"finding":"Molecular dynamics simulations showed that the DHH p.Trp173Cys mutation increases conformational flexibility of the protein and potentially alters its interaction with BOC (brother of CDO), a positive regulator of Hedgehog signalling, identifying BOC as an interaction partner of DHH and indicating that W173 is important for this interaction.","method":"Whole-exome sequencing to identify variant, molecular dynamics simulation of DHH-BOC interaction","journal":"Clinical endocrinology","confidence":"Low","confidence_rationale":"Tier 4 — interaction inferred from computational simulation only, no direct binding assay","pmids":["28708305"],"is_preprint":false},{"year":2015,"finding":"GPR37, expressed in Sertoli cells, is associated with Patched 1 (DHH receptor) in primary Sertoli cell cultures, and Gpr37-null mice show altered expression of Dhh and downstream components (Gli2, Ptched1) in prepubertal testes, placing GPR37 as a modulator of the DHH mitogenic signaling cascade in Sertoli cells.","method":"Co-immunoprecipitation/association of GPR37 with Ptc1 in primary Sertoli cells, Gpr37-null mouse model with gene expression analysis","journal":"FASEB journal","confidence":"Medium","confidence_rationale":"Tier 3 — single Co-IP plus KO mouse with expression phenotype; moderate mechanistic detail","pmids":["25609427"],"is_preprint":false},{"year":2018,"finding":"In mice lacking both Dhh and Ihh specifically in granulosa cells, theca cells failed to form and androgen production was abolished, establishing that DHH (together with IHH) signals from granulosa cells to regulate theca cell specification and steroidogenesis during folliculogenesis.","method":"Single and double conditional knockout mice (Dhh KO, Ihh KO, Dhh/Ihh DKO), reproductive fitness, hormonal profiles, ovarian transcriptomes","journal":"Endocrinology","confidence":"High","confidence_rationale":"Tier 2 — conditional KO with multiple orthogonal readouts (histology, hormones, transcriptomics), genetic dissection of individual ligand roles","pmids":["29788357"],"is_preprint":false},{"year":2023,"finding":"Using conditional mutagenesis and pharmacological Hh modulators, DHH was identified as the key Hedgehog ligand acting on fibro/adipogenic progenitors (FAPs) to prevent adipogenic differentiation and control fibrogenic fate in skeletal muscle; sustained DHH/Hh activation forces FAPs toward fibrogenesis, while loss of DHH promotes intramuscular fat formation.","method":"Conditional mutagenesis (tissue-specific KO), pharmacological Hh agonists/antagonists in vivo and in vitro, cell fate assays","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 — conditional KO plus pharmacological modulation with defined cellular fate readouts; multiple orthogonal approaches","pmids":["37355632"],"is_preprint":false},{"year":2020,"finding":"DHH signals through Ptch1/Smo/Gli1 in Sertoli and peritubular myoid cells to regulate seminiferous tubule reconstruction in vitro: Smoothened agonist (SAG) promoted peritubular myoid cell elongation and polarization of Sertoli cells, increased laminin secretion for basal membrane formation, and stimulated Gli1 expression, while cyclopamine (Smo inhibitor) suppressed Gli1 and disrupted tubule organization.","method":"In vitro tubule reconstruction assay with pharmacological Smo inhibitor (cyclopamine) and agonist (SAG), immunofluorescence, western blot","journal":"Reproductive biology","confidence":"Medium","confidence_rationale":"Tier 2 — defined cellular assay with pharmacological pathway manipulation and molecular readouts","pmids":["35987158"],"is_preprint":false},{"year":2020,"finding":"In antler chondrocytes, DHH signals through Ptch1/Smo/Gli transcription factors to stimulate cell proliferation (G1-to-S phase transition) and hypertrophic differentiation (Col X, Runx2 upregulation); Gli transcription factors downstream of DHH-Smo signaling induce Foxa1/2/3 expression, which are required for chondrocyte differentiation.","method":"Recombinant DHH treatment, siRNA knockdown of Gli1-3 and Foxa, Smo inhibitor (cyclopamine), cell cycle analysis, chondrocyte differentiation markers","journal":"Journal of cellular physiology","confidence":"Medium","confidence_rationale":"Tier 2 — multiple pharmacological and genetic perturbations with defined molecular pathway readouts in a single lab","pmids":["31960430"],"is_preprint":false},{"year":2025,"finding":"In fetal Leydig cell (FLC) progenitors, DHH and PDGF rapidly activate energy metabolism without altering gene expression, while GLI1/GLI2 (activated by DHH signaling) upregulate Ad4BP/SF-1 (NR5A1) gene expression to sustain metabolic activity in differentiated FLCs; DHH signaling also activates cholesterogenic gene expression through upregulation of Srebf2.","method":"Transcriptome analysis, CUT&RUN sequencing, metabolic activity assays, reporter gene assays with Gli1/Gli2","journal":"Endocrinology","confidence":"Medium","confidence_rationale":"Tier 1-2 — multiple orthogonal methods (transcriptomics, CUT&RUN, reporter assays) but single lab","pmids":["40878802"],"is_preprint":false},{"year":2020,"finding":"DHH expressed by Sertoli cells signals to perineurial cells to regulate perineural sheath formation; DHH null mutations cause minifascicular neuropathy with structural disorganization of peripheral nerve fascicles, demonstrating a direct role for DHH in peripheral nerve perineurium development.","method":"DHH null mutation identification (genetics), nerve biopsy histopathology, high-resolution ultrasound of peripheral nerves, comparison with Dhh-/- mouse nerve phenotype","journal":"Journal of the peripheral nervous system","confidence":"Medium","confidence_rationale":"Tier 2-3 — genetic loss-of-function with defined structural peripheral nerve phenotype validated across multiple patients and mouse model comparison","pmids":["33107133"],"is_preprint":false},{"year":2023,"finding":"PKNOX1 acts as a transcription factor for DHH, directly binding the DHH promoter region to upregulate DHH expression and activate Hedgehog signaling in stomach adenocarcinoma cells.","method":"Dual-luciferase reporter assay with DHH promoter and PKNOX1, knockdown experiments, western blot","journal":"International journal of immunopathology and pharmacology","confidence":"Medium","confidence_rationale":"Tier 1 — luciferase reporter assay directly testing PKNOX1 binding to DHH promoter; single lab","pmids":["37864517"],"is_preprint":false},{"year":2020,"finding":"GATA4 and GATA6 regulate DHH transcription in adrenocortical autografts; reporter assays using the upstream region of rat Dhh containing a GATA binding motif showed that co-transfection with Gata4 or Gata6 significantly upregulated Dhh promoter activity.","method":"Promoter-reporter assay with GATA binding motif from rDhh upstream region, PCR and RNAscope for expression validation","journal":"Scientific reports","confidence":"Medium","confidence_rationale":"Tier 1 — direct luciferase reporter assay identifying GATA4/6 as transcriptional activators of DHH; single lab","pmids":["31949236"],"is_preprint":false},{"year":2025,"finding":"In Nile tilapia stem Leydig cells (SLCs), DHH signals preferentially through Patched 2 (Ptch2, not Ptch1) as its functional receptor; downstream, Gli1 (not Gli2/3) is the primary transcriptional effector that transactivates Sf1 expression, which is indispensable for SLC differentiation into Leydig cells.","method":"CRISPR/Cas9 knockout of dhh, ptch1, ptch2, gli1, sf1; SLC transplantation rescue assays; luciferase assays in Gli-knockout SLCs; Dhh agonist treatment","journal":"bioRxiv","confidence":"Medium","confidence_rationale":"Tier 2 — multiple CRISPR KOs with functional rescue experiments; preprint, not yet peer-reviewed","pmids":["bio_10.1101_2025.06.13.659479"],"is_preprint":true}],"current_model":"DHH is a Hedgehog family signaling ligand secreted by Sertoli cells (and other cell types) that undergoes autocatalytic self-cleavage to generate an active N-terminal signaling domain; it signals through its receptor Patched (primarily Ptch1 in mammals, Ptch2 in some contexts) on Leydig cells, peritubular myoid cells, perineurial cells, FAPs, and theca cells, activating Smoothened and downstream Gli transcription factors (principally Gli1) to drive Leydig cell differentiation, seminiferous tubule morphogenesis, perineurium formation, adipogenic suppression in muscle, and theca cell specification, with GATA4/6 regulating its transcription and PKNOX1 identified as an additional transcriptional activator."},"narrative":{"teleology":[{"year":2000,"claim":"Establishing that DHH is the Sertoli-cell-derived signal required for Leydig cell differentiation and seminiferous tubule integrity resolved the long-standing question of which paracrine factor couples Sertoli cell identity to the organization of the surrounding testicular interstitium.","evidence":"Dhh-null mouse with histological, immunolocalization, and morphological analysis showing absent adult Leydig cells, defective peritubular tissue, and impaired spermatogenesis","pmids":["11090455"],"confidence":"High","gaps":["Downstream transcriptional effectors of DHH in Leydig cell progenitors not identified","Whether DHH signals through Ptch1 or Ptch2 in this context was unresolved","Role in female gonad not addressed"]},{"year":2010,"claim":"Cross-species replication using a rat missense mutant confirmed DHH as essential for both fetal and adult Leydig cell development and demonstrated that loss of DHH reduces embryonic testosterone, linking the ligand to steroidogenic output.","evidence":"Linkage mapping and sequencing of Dhh missense mutation in mp/mp rats, with Leydig cell immunohistochemistry and testosterone measurements","pmids":["21062903"],"confidence":"High","gaps":["Precise signaling cascade downstream of DHH in fetal Leydig cells undefined","Whether DHH acts directly on Leydig progenitors versus through intermediate cell types was unclear"]},{"year":2015,"claim":"Identification of GPR37 as a Patched1-associated protein in Sertoli cells that modulates DHH/Gli2 expression introduced an upstream regulatory layer to the DHH signaling cascade in the testis.","evidence":"Co-immunoprecipitation of GPR37 with Ptc1 in primary Sertoli cells; Gpr37-null mouse with altered Dhh/Gli2/Ptch1 expression","pmids":["25609427"],"confidence":"Medium","gaps":["Single co-IP without reciprocal validation","Functional consequence of GPR37-Ptch1 association on DHH signal transduction not directly tested","Whether GPR37 modulates DHH production or DHH reception is ambiguous"]},{"year":2018,"claim":"Biochemical dissection of DHH auto-processing revealed that autocatalytic self-cleavage generates the active N-terminal signaling domain and that distinct mutation classes produce graded clinical phenotypes—processing-null mutations cause gonadal dysgenesis alone, while signaling-domain mutations cause both gonadal dysgenesis and polyneuropathy.","evidence":"In vitro cleavage assays with wild-type and mutant DHH constructs; genotype–phenotype correlation in patients","pmids":["30298535"],"confidence":"High","gaps":["How partially active DHH-N (from ~50% cleavage) is sufficient for peripheral nerve but not gonadal function is unexplained","Cholesterol modification of DHH-N not directly assayed"]},{"year":2018,"claim":"Conditional deletion of Dhh and Ihh in granulosa cells demonstrated that DHH co-operates with IHH to signal from granulosa cells to specify theca cells and enable ovarian androgen production, extending DHH's morphogen role beyond the testis.","evidence":"Granulosa-cell-specific Dhh, Ihh, and double conditional KO mice with hormonal profiles, histology, and transcriptomics","pmids":["29788357"],"confidence":"High","gaps":["Relative individual contributions of DHH versus IHH to theca specification not fully separable","Receptor identity (Ptch1 vs Ptch2) on theca progenitors not determined"]},{"year":2020,"claim":"Multiple studies in 2020 consolidated the DHH–Ptch1–Smo–Gli1 signaling axis across distinct cell types: DHH drives peritubular myoid cell polarization and basal membrane formation in seminiferous tubule reconstruction, chondrocyte proliferation and hypertrophic differentiation via Gli-Foxa, and perineurial sheath formation in peripheral nerves.","evidence":"In vitro tubule reconstruction with SAG/cyclopamine (PMID:35987158); recombinant DHH treatment and siRNA knockdown in antler chondrocytes (PMID:31960430); nerve biopsy histopathology and DHH-null patient genetics (PMID:33107133)","pmids":["35987158","31960430","33107133"],"confidence":"Medium","gaps":["Whether Gli1, Gli2, or Gli3 is the primary effector varies by tissue and was not systematically resolved","Direct ligand-receptor binding affinity for DHH-Ptch1 not measured in these systems"]},{"year":2020,"claim":"Reporter and localization assays with pathogenic DHH variants established that self-cleavage is required not only for generating active ligand but also for proper subcellular trafficking, and identified GATA4/GATA6 as transcriptional activators of DHH via a conserved GATA motif in the Dhh promoter.","evidence":"Self-cleavage assay and subcellular localization imaging of DHH variants (PMID:32504121); luciferase reporter assay with GATA binding motif from rDhh upstream region co-transfected with GATA4/6 (PMID:31949236)","pmids":["32504121","31949236"],"confidence":"Medium","gaps":["Endogenous ChIP validation of GATA4/6 binding at Dhh promoter not performed","How mislocalized unprocessed DHH is degraded or causes dominant effects is unknown"]},{"year":2023,"claim":"Discovery that DHH is the key Hedgehog ligand suppressing adipogenic differentiation and promoting fibrogenesis in muscle fibro/adipogenic progenitors (FAPs) revealed a new tissue context for DHH signaling with implications for intramuscular fat accumulation.","evidence":"Tissue-specific conditional mutagenesis and pharmacological Hh agonists/antagonists in skeletal muscle, with cell fate assays","pmids":["37355632"],"confidence":"High","gaps":["Source cell type producing DHH in skeletal muscle not definitively identified","Whether FAP response to DHH involves Ptch1 or Ptch2 is unresolved"]},{"year":2023,"claim":"Identification of PKNOX1 as a direct transcriptional activator of DHH added a second upstream regulator (beyond GATA4/6) and connected DHH expression to PKNOX1-driven signaling in adenocarcinoma cells.","evidence":"Dual-luciferase reporter assay with DHH promoter and PKNOX1 constructs, knockdown experiments","pmids":["37864517"],"confidence":"Medium","gaps":["ChIP-seq confirmation of PKNOX1 occupancy at the DHH locus not performed","Physiological relevance of PKNOX1-DHH axis outside cancer cells not tested"]},{"year":2025,"claim":"Mechanistic dissection of DHH signaling in fetal Leydig cell progenitors showed that DHH rapidly activates energy metabolism independently of transcription, while Gli1/Gli2 subsequently upregulate NR5A1 (SF-1) and Srebf2-dependent cholesterogenic programs to sustain steroidogenic identity.","evidence":"Transcriptome analysis, CUT&RUN sequencing for Gli binding, metabolic activity assays, and reporter gene assays","pmids":["40878802"],"confidence":"Medium","gaps":["Mechanism of rapid metabolic activation without transcriptional change is undefined","Whether the Gli1-NR5A1 axis operates identically in adult Leydig cells is untested"]},{"year":null,"claim":"Key unresolved questions include the structural basis for DHH-Ptch binding specificity (Ptch1 vs Ptch2 in different tissues), the identity of the DHH source cell in skeletal muscle, and the mechanism by which DHH activates acute metabolic changes independent of gene expression in Leydig progenitors.","evidence":"","pmids":[],"confidence":"Low","gaps":["No crystal structure of DHH-N bound to Ptch1 or Ptch2","Relative contributions of cholesterol modification versus palmitoylation to DHH range and potency are unexplored","Whether DHH has non-canonical (Smo-independent) signaling activities is untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0140096","term_label":"catalytic activity, acting on a protein","supporting_discovery_ids":[2,3]},{"term_id":"GO:0048018","term_label":"receptor ligand activity","supporting_discovery_ids":[0,1,6,7,8,9]}],"localization":[{"term_id":"GO:0005576","term_label":"extracellular region","supporting_discovery_ids":[0,6,7,8]}],"pathway":[{"term_id":"R-HSA-162582","term_label":"Signal Transduction","supporting_discovery_ids":[0,1,6,7,8,9,10]},{"term_id":"R-HSA-1266738","term_label":"Developmental Biology","supporting_discovery_ids":[0,1,6,11]}],"complexes":[],"partners":["PTCH1","PTCH2","SMO","GLI1","GATA4","GATA6","GPR37"],"other_free_text":[]},"mechanistic_narrative":"DHH is a Hedgehog family signaling ligand that functions as a paracrine morphogen essential for gonadal somatic cell differentiation, peripheral nerve perineurium formation, and mesenchymal cell fate decisions in multiple tissues. Produced primarily by Sertoli cells (and ovarian granulosa cells), DHH undergoes autocatalytic self-cleavage to generate an active N-terminal signaling domain that signals through the Patched receptor on neighboring cells, activating Smoothened and downstream Gli transcription factors to drive Leydig cell differentiation, theca cell specification, seminiferous tubule morphogenesis, and suppression of adipogenesis in fibro/adipogenic progenitors [PMID:11090455, PMID:29788357, PMID:37355632, PMID:30298535]. Loss-of-function mutations in DHH cause 46,XY gonadal dysgenesis and minifascicular polyneuropathy in humans, with the severity depending on whether the mutation disrupts the signaling domain or only auto-processing [PMID:30298535, PMID:33107133]. DHH transcription is regulated by GATA4/GATA6 and PKNOX1, and its downstream effectors Gli1/Gli2 activate NR5A1 (SF-1) and cholesterogenic gene programs to sustain steroidogenic cell identity and metabolic function [PMID:31949236, PMID:37864517, PMID:40878802]."},"prefetch_data":{"uniprot":{"accession":"O43323","full_name":"Desert hedgehog protein","aliases":["HHG-3"],"length_aa":396,"mass_kda":43.6,"function":"The C-terminal part of the desert hedgehog protein precursor displays an autoproteolysis and a cholesterol transferase activity (By similarity). Both activities result in the cleavage of the full-length protein into two parts (N-product and C-product) followed by the covalent attachment of a cholesterol moiety to the C-terminal of the newly generated N-product (DHH-N) (By similarity). Both activities occur in the endoplasmic reticulum (By similarity). Once cleaved, the C-product is degraded in the endoplasmic reticulum (By similarity). Functions in cell-cell mediated juxtacrine signaling (PubMed:24342078). Promotes endothelium integrity (PubMed:33063110). Binds to PTCH1 receptor, which functions in association with smoothened (SMO), to activate the transcription of target genes in endothelial cells (PubMed:33063110). In Schwann cells, controls the development of the peripheral nerve sheath and the transition of mesenchymal cells to form the epithelium-like structure of the perineurial tube (By similarity) The dually lipidated desert hedgehog protein N-product is essential for a variety of patterning events during development (By similarity). Binds to the patched (PTCH1) receptor, which functions in association with smoothened (SMO), to activate the transcription of target genes (PubMed:11472839, PubMed:33063110). Required for normal testis development and spermatogenesis, namely for the formation of adult-type Leydig cells and normal development of peritubular cells and seminiferous tubules (By similarity). Activates primary cilia signaling on neighboring valve interstitial cells through a paracrine mechanism (By similarity). May induce motor neurons in lateral neural tube and may have a polarizing activity (PubMed:11472839). Prevents the desert hedgehog protein precursor binding to PTCH1 (PubMed:33063110)","subcellular_location":"Endoplasmic reticulum membrane; Golgi apparatus membrane; Secreted; Cell membrane","url":"https://www.uniprot.org/uniprotkb/O43323/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/DHH","classification":"Not Classified","n_dependent_lines":6,"n_total_lines":1208,"dependency_fraction":0.004966887417218543},"opencell":{"profiled":false,"resolved_as":"","ensg_id":"","cell_line_id":"","localizations":[],"interactors":[],"url":"https://opencell.sf.czbiohub.org/search/DHH","total_profiled":1310},"omim":[{"mim_id":"619811","title":"UHRF1-BINDING PROTEIN 1-LIKE; UHRF1BP1L","url":"https://www.omim.org/entry/619811"},{"mim_id":"617481","title":"NEURODEVELOPMENTAL DISORDER WITH MICROCEPHALY, HYPOTONIA, AND VARIABLE BRAIN ANOMALIES; NMIHBA","url":"https://www.omim.org/entry/617481"},{"mim_id":"617413","title":"PRUNE EXOPOLYPHOSPHATASE 1; PRUNE1","url":"https://www.omim.org/entry/617413"},{"mim_id":"617362","title":"DEAH-BOX HELICASE 37; DHX37","url":"https://www.omim.org/entry/617362"},{"mim_id":"609396","title":"PH DOMAIN AND LEUCINE-RICH REPEAT PROTEIN PHOSPHATASE 1; PHLPP1","url":"https://www.omim.org/entry/609396"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in single","driving_tissues":[{"tissue":"testis","ntpm":9.8}],"url":"https://www.proteinatlas.org/search/DHH"},"hgnc":{"alias_symbol":["HHG-3","MGC35145"],"prev_symbol":[]},"alphafold":{"accession":"O43323","domains":[{"cath_id":"3.30.1380.10","chopping":"46-192","consensus_level":"high","plddt":93.284,"start":46,"end":192},{"cath_id":"2.170.16.10","chopping":"195-365","consensus_level":"high","plddt":88.4853,"start":195,"end":365}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/O43323","model_url":"https://alphafold.ebi.ac.uk/files/AF-O43323-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-O43323-F1-predicted_aligned_error_v6.png","plddt_mean":84.38},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=DHH","jax_strain_url":"https://www.jax.org/strain/search?query=DHH"},"sequence":{"accession":"O43323","fasta_url":"https://rest.uniprot.org/uniprotkb/O43323.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/O43323/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/O43323"}},"corpus_meta":[{"pmid":"11090455","id":"PMC_11090455","title":"Desert hedgehog (Dhh) gene is required in the mouse testis for formation of adult-type Leydig cells and normal development of peritubular cells and seminiferous tubules.","date":"2000","source":"Biology of reproduction","url":"https://pubmed.ncbi.nlm.nih.gov/11090455","citation_count":280,"is_preprint":false},{"pmid":"15356051","id":"PMC_15356051","title":"Mutations in the desert hedgehog (DHH) gene in patients with 46,XY complete pure gonadal dysgenesis.","date":"2004","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/15356051","citation_count":109,"is_preprint":false},{"pmid":"22147708","id":"PMC_22147708","title":"Structural and functional insights into the DNA replication factor Cdc45 reveal an evolutionary relationship to the DHH family of phosphoesterases.","date":"2011","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/22147708","citation_count":49,"is_preprint":false},{"pmid":"25927242","id":"PMC_25927242","title":"46,XY Gonadal Dysgenesis due to a Homozygous Mutation in Desert Hedgehog (DHH) Identified by Exome Sequencing.","date":"2015","source":"The Journal of clinical endocrinology and metabolism","url":"https://pubmed.ncbi.nlm.nih.gov/25927242","citation_count":47,"is_preprint":false},{"pmid":"21062903","id":"PMC_21062903","title":"A missense mutation of the Dhh gene is associated with male pseudohermaphroditic rats showing impaired Leydig cell development.","date":"2010","source":"Reproduction (Cambridge, England)","url":"https://pubmed.ncbi.nlm.nih.gov/21062903","citation_count":43,"is_preprint":false},{"pmid":"21768284","id":"PMC_21768284","title":"Two DHH subfamily 1 proteins contribute to pneumococcal virulence and confer protection against pneumococcal disease.","date":"2011","source":"Infection and immunity","url":"https://pubmed.ncbi.nlm.nih.gov/21768284","citation_count":40,"is_preprint":false},{"pmid":"37355632","id":"PMC_37355632","title":"Hedgehog signaling via its ligand DHH acts as cell fate determinant during skeletal muscle regeneration.","date":"2023","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/37355632","citation_count":37,"is_preprint":false},{"pmid":"25549322","id":"PMC_25549322","title":"Evolutionary genomics and adaptive evolution of the Hedgehog gene family (Shh, Ihh and Dhh) in vertebrates.","date":"2014","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/25549322","citation_count":32,"is_preprint":false},{"pmid":"20599695","id":"PMC_20599695","title":"2',3'-cAMP hydrolysis by metal-dependent phosphodiesterases containing DHH, EAL, and HD domains is non-specific: Implications for PDE screening.","date":"2010","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/20599695","citation_count":27,"is_preprint":false},{"pmid":"29788357","id":"PMC_29788357","title":"Reproductive, Physiological, and Molecular Outcomes in Female Mice Deficient in Dhh and Ihh.","date":"2018","source":"Endocrinology","url":"https://pubmed.ncbi.nlm.nih.gov/29788357","citation_count":23,"is_preprint":false},{"pmid":"24878921","id":"PMC_24878921","title":"Unique subunit packing in mycobacterial nanoRNase leads to alternate substrate recognitions in DHH phosphodiesterases.","date":"2014","source":"Nucleic acids research","url":"https://pubmed.ncbi.nlm.nih.gov/24878921","citation_count":23,"is_preprint":false},{"pmid":"29107484","id":"PMC_29107484","title":"Structural and Biophysical Analysis of the Soluble DHH/DHHA1-Type Phosphodiesterase TM1595 from Thermotoga maritima.","date":"2017","source":"Structure (London, England : 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morphogenesis.\",\n      \"method\": \"Genetic knockout (Dhh-null mice) with histological, immunolocalization, and morphological phenotypic readouts\",\n      \"journal\": \"Biology of reproduction\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — clean KO with defined cellular phenotypes, receptor localization, replicated across multiple studies\",\n      \"pmids\": [\"11090455\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"A missense mutation in the Dhh gene in mutant rats (mp/mp) results in loss of DHH signaling, dramatically reduced fetal Leydig cell number, absence of adult-type spindle-shaped Leydig cells, and significantly lower testosterone during embryonic development, confirming DHH is essential for Leydig cell development and androgen production.\",\n      \"method\": \"Fine linkage mapping, Sanger sequencing to identify missense mutation, immunohistochemistry with Leydig cell-specific marker, testosterone measurement\",\n      \"journal\": \"Reproduction (Cambridge, England)\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — genetic model (missense KO equivalent) with multiple orthogonal readouts; replicates mouse Dhh-null phenotype in a different species\",\n      \"pmids\": [\"21062903\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In vitro cleavage assays demonstrated that DHH undergoes autocatalytic self-cleavage (auto-processing) to generate the active N-terminal signaling domain (DHh-N); a frameshift mutation p.(Asn337Lysfs*24) completely abolished auto-proteolysis, while p.(Glu212Lys) retained ~50% cleavage activity. Complete disruption of DHh-N (signaling domain) was associated with both gonadal dysgenesis and polyneuropathy, while disruption of auto-processing alone was associated only with gonadal dysgenesis.\",\n      \"method\": \"In vitro cleavage/auto-processing assay with mutant and wild-type DHH constructs, compared with Drosophila Hh\",\n      \"journal\": \"Human mutation\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro biochemical assay with multiple mutants and mechanistic interpretation of cleavage activity\",\n      \"pmids\": [\"30298535\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Multiple pathogenic DHH variants associated with 46,XY gonadal dysgenesis were tested in cell-based assays; a subset was unable to perform self-cleavage, which correlated with altered subcellular localization of the resulting proteins, establishing that self-cleavage is required for proper DHH processing and trafficking.\",\n      \"method\": \"In vitro self-cleavage assay, subcellular localization imaging, structural modelling and molecular dynamics simulations\",\n      \"journal\": \"Human genetics\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — in vitro assay plus localization, but single lab\",\n      \"pmids\": [\"32504121\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Molecular dynamics simulations showed that the DHH p.Trp173Cys mutation increases conformational flexibility of the protein and potentially alters its interaction with BOC (brother of CDO), a positive regulator of Hedgehog signalling, identifying BOC as an interaction partner of DHH and indicating that W173 is important for this interaction.\",\n      \"method\": \"Whole-exome sequencing to identify variant, molecular dynamics simulation of DHH-BOC interaction\",\n      \"journal\": \"Clinical endocrinology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 — interaction inferred from computational simulation only, no direct binding assay\",\n      \"pmids\": [\"28708305\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2015,\n      \"finding\": \"GPR37, expressed in Sertoli cells, is associated with Patched 1 (DHH receptor) in primary Sertoli cell cultures, and Gpr37-null mice show altered expression of Dhh and downstream components (Gli2, Ptched1) in prepubertal testes, placing GPR37 as a modulator of the DHH mitogenic signaling cascade in Sertoli cells.\",\n      \"method\": \"Co-immunoprecipitation/association of GPR37 with Ptc1 in primary Sertoli cells, Gpr37-null mouse model with gene expression analysis\",\n      \"journal\": \"FASEB journal\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 3 — single Co-IP plus KO mouse with expression phenotype; moderate mechanistic detail\",\n      \"pmids\": [\"25609427\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In mice lacking both Dhh and Ihh specifically in granulosa cells, theca cells failed to form and androgen production was abolished, establishing that DHH (together with IHH) signals from granulosa cells to regulate theca cell specification and steroidogenesis during folliculogenesis.\",\n      \"method\": \"Single and double conditional knockout mice (Dhh KO, Ihh KO, Dhh/Ihh DKO), reproductive fitness, hormonal profiles, ovarian transcriptomes\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO with multiple orthogonal readouts (histology, hormones, transcriptomics), genetic dissection of individual ligand roles\",\n      \"pmids\": [\"29788357\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Using conditional mutagenesis and pharmacological Hh modulators, DHH was identified as the key Hedgehog ligand acting on fibro/adipogenic progenitors (FAPs) to prevent adipogenic differentiation and control fibrogenic fate in skeletal muscle; sustained DHH/Hh activation forces FAPs toward fibrogenesis, while loss of DHH promotes intramuscular fat formation.\",\n      \"method\": \"Conditional mutagenesis (tissue-specific KO), pharmacological Hh agonists/antagonists in vivo and in vitro, cell fate assays\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — conditional KO plus pharmacological modulation with defined cellular fate readouts; multiple orthogonal approaches\",\n      \"pmids\": [\"37355632\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"DHH signals through Ptch1/Smo/Gli1 in Sertoli and peritubular myoid cells to regulate seminiferous tubule reconstruction in vitro: Smoothened agonist (SAG) promoted peritubular myoid cell elongation and polarization of Sertoli cells, increased laminin secretion for basal membrane formation, and stimulated Gli1 expression, while cyclopamine (Smo inhibitor) suppressed Gli1 and disrupted tubule organization.\",\n      \"method\": \"In vitro tubule reconstruction assay with pharmacological Smo inhibitor (cyclopamine) and agonist (SAG), immunofluorescence, western blot\",\n      \"journal\": \"Reproductive biology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — defined cellular assay with pharmacological pathway manipulation and molecular readouts\",\n      \"pmids\": [\"35987158\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In antler chondrocytes, DHH signals through Ptch1/Smo/Gli transcription factors to stimulate cell proliferation (G1-to-S phase transition) and hypertrophic differentiation (Col X, Runx2 upregulation); Gli transcription factors downstream of DHH-Smo signaling induce Foxa1/2/3 expression, which are required for chondrocyte differentiation.\",\n      \"method\": \"Recombinant DHH treatment, siRNA knockdown of Gli1-3 and Foxa, Smo inhibitor (cyclopamine), cell cycle analysis, chondrocyte differentiation markers\",\n      \"journal\": \"Journal of cellular physiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple pharmacological and genetic perturbations with defined molecular pathway readouts in a single lab\",\n      \"pmids\": [\"31960430\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In fetal Leydig cell (FLC) progenitors, DHH and PDGF rapidly activate energy metabolism without altering gene expression, while GLI1/GLI2 (activated by DHH signaling) upregulate Ad4BP/SF-1 (NR5A1) gene expression to sustain metabolic activity in differentiated FLCs; DHH signaling also activates cholesterogenic gene expression through upregulation of Srebf2.\",\n      \"method\": \"Transcriptome analysis, CUT&RUN sequencing, metabolic activity assays, reporter gene assays with Gli1/Gli2\",\n      \"journal\": \"Endocrinology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1-2 — multiple orthogonal methods (transcriptomics, CUT&RUN, reporter assays) but single lab\",\n      \"pmids\": [\"40878802\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"DHH expressed by Sertoli cells signals to perineurial cells to regulate perineural sheath formation; DHH null mutations cause minifascicular neuropathy with structural disorganization of peripheral nerve fascicles, demonstrating a direct role for DHH in peripheral nerve perineurium development.\",\n      \"method\": \"DHH null mutation identification (genetics), nerve biopsy histopathology, high-resolution ultrasound of peripheral nerves, comparison with Dhh-/- mouse nerve phenotype\",\n      \"journal\": \"Journal of the peripheral nervous system\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2-3 — genetic loss-of-function with defined structural peripheral nerve phenotype validated across multiple patients and mouse model comparison\",\n      \"pmids\": [\"33107133\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PKNOX1 acts as a transcription factor for DHH, directly binding the DHH promoter region to upregulate DHH expression and activate Hedgehog signaling in stomach adenocarcinoma cells.\",\n      \"method\": \"Dual-luciferase reporter assay with DHH promoter and PKNOX1, knockdown experiments, western blot\",\n      \"journal\": \"International journal of immunopathology and pharmacology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — luciferase reporter assay directly testing PKNOX1 binding to DHH promoter; single lab\",\n      \"pmids\": [\"37864517\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"GATA4 and GATA6 regulate DHH transcription in adrenocortical autografts; reporter assays using the upstream region of rat Dhh containing a GATA binding motif showed that co-transfection with Gata4 or Gata6 significantly upregulated Dhh promoter activity.\",\n      \"method\": \"Promoter-reporter assay with GATA binding motif from rDhh upstream region, PCR and RNAscope for expression validation\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 — direct luciferase reporter assay identifying GATA4/6 as transcriptional activators of DHH; single lab\",\n      \"pmids\": [\"31949236\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"In Nile tilapia stem Leydig cells (SLCs), DHH signals preferentially through Patched 2 (Ptch2, not Ptch1) as its functional receptor; downstream, Gli1 (not Gli2/3) is the primary transcriptional effector that transactivates Sf1 expression, which is indispensable for SLC differentiation into Leydig cells.\",\n      \"method\": \"CRISPR/Cas9 knockout of dhh, ptch1, ptch2, gli1, sf1; SLC transplantation rescue assays; luciferase assays in Gli-knockout SLCs; Dhh agonist treatment\",\n      \"journal\": \"bioRxiv\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — multiple CRISPR KOs with functional rescue experiments; preprint, not yet peer-reviewed\",\n      \"pmids\": [\"bio_10.1101_2025.06.13.659479\"],\n      \"is_preprint\": true\n    }\n  ],\n  \"current_model\": \"DHH is a Hedgehog family signaling ligand secreted by Sertoli cells (and other cell types) that undergoes autocatalytic self-cleavage to generate an active N-terminal signaling domain; it signals through its receptor Patched (primarily Ptch1 in mammals, Ptch2 in some contexts) on Leydig cells, peritubular myoid cells, perineurial cells, FAPs, and theca cells, activating Smoothened and downstream Gli transcription factors (principally Gli1) to drive Leydig cell differentiation, seminiferous tubule morphogenesis, perineurium formation, adipogenic suppression in muscle, and theca cell specification, with GATA4/6 regulating its transcription and PKNOX1 identified as an additional transcriptional activator.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"DHH is a Hedgehog family signaling ligand that functions as a paracrine morphogen essential for gonadal somatic cell differentiation, peripheral nerve perineurium formation, and mesenchymal cell fate decisions in multiple tissues. Produced primarily by Sertoli cells (and ovarian granulosa cells), DHH undergoes autocatalytic self-cleavage to generate an active N-terminal signaling domain that signals through the Patched receptor on neighboring cells, activating Smoothened and downstream Gli transcription factors to drive Leydig cell differentiation, theca cell specification, seminiferous tubule morphogenesis, and suppression of adipogenesis in fibro/adipogenic progenitors [PMID:11090455, PMID:29788357, PMID:37355632, PMID:30298535]. Loss-of-function mutations in DHH cause 46,XY gonadal dysgenesis and minifascicular polyneuropathy in humans, with the severity depending on whether the mutation disrupts the signaling domain or only auto-processing [PMID:30298535, PMID:33107133]. DHH transcription is regulated by GATA4/GATA6 and PKNOX1, and its downstream effectors Gli1/Gli2 activate NR5A1 (SF-1) and cholesterogenic gene programs to sustain steroidogenic cell identity and metabolic function [PMID:31949236, PMID:37864517, PMID:40878802].\",\n  \"teleology\": [\n    {\n      \"year\": 2000,\n      \"claim\": \"Establishing that DHH is the Sertoli-cell-derived signal required for Leydig cell differentiation and seminiferous tubule integrity resolved the long-standing question of which paracrine factor couples Sertoli cell identity to the organization of the surrounding testicular interstitium.\",\n      \"evidence\": \"Dhh-null mouse with histological, immunolocalization, and morphological analysis showing absent adult Leydig cells, defective peritubular tissue, and impaired spermatogenesis\",\n      \"pmids\": [\"11090455\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Downstream transcriptional effectors of DHH in Leydig cell progenitors not identified\", \"Whether DHH signals through Ptch1 or Ptch2 in this context was unresolved\", \"Role in female gonad not addressed\"]\n    },\n    {\n      \"year\": 2010,\n      \"claim\": \"Cross-species replication using a rat missense mutant confirmed DHH as essential for both fetal and adult Leydig cell development and demonstrated that loss of DHH reduces embryonic testosterone, linking the ligand to steroidogenic output.\",\n      \"evidence\": \"Linkage mapping and sequencing of Dhh missense mutation in mp/mp rats, with Leydig cell immunohistochemistry and testosterone measurements\",\n      \"pmids\": [\"21062903\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Precise signaling cascade downstream of DHH in fetal Leydig cells undefined\", \"Whether DHH acts directly on Leydig progenitors versus through intermediate cell types was unclear\"]\n    },\n    {\n      \"year\": 2015,\n      \"claim\": \"Identification of GPR37 as a Patched1-associated protein in Sertoli cells that modulates DHH/Gli2 expression introduced an upstream regulatory layer to the DHH signaling cascade in the testis.\",\n      \"evidence\": \"Co-immunoprecipitation of GPR37 with Ptc1 in primary Sertoli cells; Gpr37-null mouse with altered Dhh/Gli2/Ptch1 expression\",\n      \"pmids\": [\"25609427\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Single co-IP without reciprocal validation\", \"Functional consequence of GPR37-Ptch1 association on DHH signal transduction not directly tested\", \"Whether GPR37 modulates DHH production or DHH reception is ambiguous\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Biochemical dissection of DHH auto-processing revealed that autocatalytic self-cleavage generates the active N-terminal signaling domain and that distinct mutation classes produce graded clinical phenotypes—processing-null mutations cause gonadal dysgenesis alone, while signaling-domain mutations cause both gonadal dysgenesis and polyneuropathy.\",\n      \"evidence\": \"In vitro cleavage assays with wild-type and mutant DHH constructs; genotype–phenotype correlation in patients\",\n      \"pmids\": [\"30298535\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"How partially active DHH-N (from ~50% cleavage) is sufficient for peripheral nerve but not gonadal function is unexplained\", \"Cholesterol modification of DHH-N not directly assayed\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Conditional deletion of Dhh and Ihh in granulosa cells demonstrated that DHH co-operates with IHH to signal from granulosa cells to specify theca cells and enable ovarian androgen production, extending DHH's morphogen role beyond the testis.\",\n      \"evidence\": \"Granulosa-cell-specific Dhh, Ihh, and double conditional KO mice with hormonal profiles, histology, and transcriptomics\",\n      \"pmids\": [\"29788357\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Relative individual contributions of DHH versus IHH to theca specification not fully separable\", \"Receptor identity (Ptch1 vs Ptch2) on theca progenitors not determined\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Multiple studies in 2020 consolidated the DHH–Ptch1–Smo–Gli1 signaling axis across distinct cell types: DHH drives peritubular myoid cell polarization and basal membrane formation in seminiferous tubule reconstruction, chondrocyte proliferation and hypertrophic differentiation via Gli-Foxa, and perineurial sheath formation in peripheral nerves.\",\n      \"evidence\": \"In vitro tubule reconstruction with SAG/cyclopamine (PMID:35987158); recombinant DHH treatment and siRNA knockdown in antler chondrocytes (PMID:31960430); nerve biopsy histopathology and DHH-null patient genetics (PMID:33107133)\",\n      \"pmids\": [\"35987158\", \"31960430\", \"33107133\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether Gli1, Gli2, or Gli3 is the primary effector varies by tissue and was not systematically resolved\", \"Direct ligand-receptor binding affinity for DHH-Ptch1 not measured in these systems\"]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Reporter and localization assays with pathogenic DHH variants established that self-cleavage is required not only for generating active ligand but also for proper subcellular trafficking, and identified GATA4/GATA6 as transcriptional activators of DHH via a conserved GATA motif in the Dhh promoter.\",\n      \"evidence\": \"Self-cleavage assay and subcellular localization imaging of DHH variants (PMID:32504121); luciferase reporter assay with GATA binding motif from rDhh upstream region co-transfected with GATA4/6 (PMID:31949236)\",\n      \"pmids\": [\"32504121\", \"31949236\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Endogenous ChIP validation of GATA4/6 binding at Dhh promoter not performed\", \"How mislocalized unprocessed DHH is degraded or causes dominant effects is unknown\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Discovery that DHH is the key Hedgehog ligand suppressing adipogenic differentiation and promoting fibrogenesis in muscle fibro/adipogenic progenitors (FAPs) revealed a new tissue context for DHH signaling with implications for intramuscular fat accumulation.\",\n      \"evidence\": \"Tissue-specific conditional mutagenesis and pharmacological Hh agonists/antagonists in skeletal muscle, with cell fate assays\",\n      \"pmids\": [\"37355632\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Source cell type producing DHH in skeletal muscle not definitively identified\", \"Whether FAP response to DHH involves Ptch1 or Ptch2 is unresolved\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Identification of PKNOX1 as a direct transcriptional activator of DHH added a second upstream regulator (beyond GATA4/6) and connected DHH expression to PKNOX1-driven signaling in adenocarcinoma cells.\",\n      \"evidence\": \"Dual-luciferase reporter assay with DHH promoter and PKNOX1 constructs, knockdown experiments\",\n      \"pmids\": [\"37864517\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"ChIP-seq confirmation of PKNOX1 occupancy at the DHH locus not performed\", \"Physiological relevance of PKNOX1-DHH axis outside cancer cells not tested\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Mechanistic dissection of DHH signaling in fetal Leydig cell progenitors showed that DHH rapidly activates energy metabolism independently of transcription, while Gli1/Gli2 subsequently upregulate NR5A1 (SF-1) and Srebf2-dependent cholesterogenic programs to sustain steroidogenic identity.\",\n      \"evidence\": \"Transcriptome analysis, CUT&RUN sequencing for Gli binding, metabolic activity assays, and reporter gene assays\",\n      \"pmids\": [\"40878802\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Mechanism of rapid metabolic activation without transcriptional change is undefined\", \"Whether the Gli1-NR5A1 axis operates identically in adult Leydig cells is untested\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"Key unresolved questions include the structural basis for DHH-Ptch binding specificity (Ptch1 vs Ptch2 in different tissues), the identity of the DHH source cell in skeletal muscle, and the mechanism by which DHH activates acute metabolic changes independent of gene expression in Leydig progenitors.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No crystal structure of DHH-N bound to Ptch1 or Ptch2\", \"Relative contributions of cholesterol modification versus palmitoylation to DHH range and potency are unexplored\", \"Whether DHH has non-canonical (Smo-independent) signaling activities is untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0140096\", \"supporting_discovery_ids\": [2, 3]},\n      {\"term_id\": \"GO:0048018\", \"supporting_discovery_ids\": [0, 1, 6, 7, 8, 9]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005576\", \"supporting_discovery_ids\": [0, 6, 7, 8]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-162582\", \"supporting_discovery_ids\": [0, 1, 6, 7, 8, 9, 10]},\n      {\"term_id\": \"R-HSA-1266738\", \"supporting_discovery_ids\": [0, 1, 6, 11]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"PTCH1\",\n      \"PTCH2\",\n      \"SMO\",\n      \"GLI1\",\n      \"GATA4\",\n      \"GATA6\",\n      \"GPR37\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}