{"gene":"PNPLA1","run_date":"2026-04-28T19:45:44","timeline":{"discoveries":[{"year":2012,"finding":"PNPLA1 is expressed in epidermis and is essential for formation of the epidermal lipid barrier; loss-of-function mutations (premature stop codon in dogs; missense and nonsense mutations in humans) in the catalytic domain of PNPLA1 cause autosomal recessive congenital ichthyosis, establishing its role in skin barrier lipid biosynthesis.","method":"Genome-wide association study, mutation identification, and localization experiments in golden retriever dogs and human ARCI patients","journal":"Nature genetics","confidence":"High","confidence_rationale":"Tier 2 — replicated across species (dog and human), multiple orthogonal methods, foundational study with 195 citations","pmids":["22246504"],"is_preprint":false},{"year":2017,"finding":"PNPLA1 acts as a transacylase that catalyzes the final step of acylceramide (ω-O-acylceramide) synthesis by esterifying ω-hydroxyceramide with linoleic acid using triglyceride as the linoleic acid donor; ichthyosis patient-derived mutant forms of PNPLA1 show reduced or absent enzyme activity in both cell-based and in vitro assays.","method":"Cell-based acylceramide production assay, in vitro enzyme assay with recombinant PNPLA1 and triglyceride substrate, active-site mutant analysis","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1 — in vitro enzyme reconstitution plus cell-based assay plus mutagenesis, replicated in companion paper","pmids":["28248318"],"is_preprint":false},{"year":2017,"finding":"Global or keratinocyte-specific Pnpla1 knockout mice die neonatally from epidermal permeability barrier defects with severe transepidermal water loss, absent acylceramides, acylglucosylceramides and (O-acyl)-ω-hydroxy fatty acids in epidermis, and reciprocal accumulation of their precursors, confirming that PNPLA1 catalyses ω-O-esterification with linoleic acid to form acylceramides; acylceramide supplementation partially rescues the differentiation defect of Pnpla1-/- keratinocytes.","method":"Conditional and global knockout mouse model, lipidomic analysis, acylceramide rescue experiment","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 1–2 — clean KO with defined phenotype, lipidomic pathway placement, rescue experiment; replicated by companion paper","pmids":["28248300"],"is_preprint":false},{"year":2017,"finding":"Pnpla1 knockout mice show loss of ω-O-acylceramides in stratum corneum with accumulation of precursors, defective lipid coverage of the cornified envelope, and disorganized extracellular lipid matrix; these defects are recapitulated in stratum corneum of PNPLA1-mutated human patients.","method":"Pnpla1 KO mouse model, ceramide species quantification by lipidomics, electron microscopy of cornified envelope","journal":"Human molecular genetics","confidence":"High","confidence_rationale":"Tier 2 — independent lab, KO model with multiple orthogonal readouts, validated in human patient samples","pmids":["28369476"],"is_preprint":false},{"year":2018,"finding":"ABHD5 (CGI-58) acts as a coactivator of PNPLA1: it physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets where its triglyceride substrate resides, thereby stimulating PNPLA1-mediated ω-O-acylceramide biosynthesis; ichthyosis-associated ABHD5 point mutations fail to stimulate PNPLA1 activity.","method":"Co-immunoprecipitation, cell-based acylceramide production assay, immunofluorescence microscopy showing PNPLA1 relocalization to lipid droplets upon ABHD5 co-expression","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 2 — reciprocal co-IP, localization with functional consequence, disease mutation validation; replicated in companion paper","pmids":["30361410"],"is_preprint":false},{"year":2018,"finding":"ABHD5 enhances PNPLA1-catalyzed acylceramide production and causes PNPLA1 to relocalize from dispersed cytosolic distribution to lipid droplet membranes or periphery; at high expression levels, lipid droplets disappear, morphing into vesicles or becoming incorporated into the ER; ABHD5 mutations found in Chanarin-Dorfman syndrome patients reduce ABHD5's ability to promote PNPLA1-dependent acylceramide production.","method":"Cell-based acylceramide production assay, indirect immunofluorescence microscopy, immunoelectron microscopy","journal":"Journal of dermatological science","confidence":"High","confidence_rationale":"Tier 2 — multiple imaging methods, functional assay, disease-relevant mutant validation","pmids":["30527376"],"is_preprint":false},{"year":2022,"finding":"Of 16 PNPLA1 missense mutations from ichthyosis patients, 15 cause complete loss of acylceramide-producing activity, while C216R only weakly affects activity (correlating with milder disease); mutants differ in their ability to localize to lipid droplets in an ABHD5-dependent manner, classifying them into four groups by activity and localization.","method":"Cell-based acylceramide production assay, indirect immunofluorescence microscopy, structure-function analysis of patient mutations","journal":"Journal of dermatological science","confidence":"High","confidence_rationale":"Tier 2 — systematic mutagenesis panel with functional and localization readouts, genotype-phenotype correlation","pmids":["35970721"],"is_preprint":false},{"year":2023,"finding":"Recombinant truncated PNPLA1 (expressed in E. coli) catalyzes acyl transfer from trilinolein and dilinolein donors to ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid acceptors to form acylceramide, glucosyl-acylceramide, and acyl acid respectively; PNPLA1 shows 3:1 selectivity for transferring linoleate over oleate, explaining the linoleic acid enrichment of these skin barrier lipids in vivo.","method":"In vitro enzyme reconstitution with recombinant PNPLA1, HPLC-UV and LC-MS product analysis, substrate selectivity comparison","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1 — direct in vitro reconstitution with purified recombinant enzyme, substrate selectivity quantified","pmids":["37087101"],"is_preprint":false},{"year":2024,"finding":"PNPLA1 is responsible for esterification of γ-linolenic acid (GLA), in addition to linoleic acid, to ω-hydroxy fatty acids of ceramide 1 (acylceramide) subspecies in terminally differentiated human keratinocytes; siRNA knockdown of PNPLA1 causes accumulation of non-esterified ω-hydroxy ceramide precursors and decreases involucrin expression.","method":"siRNA knockdown in normal human keratinocytes, LC-MS lipidomics of ceramide subspecies, differentiation marker analysis","journal":"Biochemical and biophysical research communications","confidence":"Medium","confidence_rationale":"Tier 2 — clean siRNA KD with defined lipid and differentiation phenotypes; single lab","pmids":["38340658"],"is_preprint":false},{"year":2018,"finding":"Mutations in PNPLA1 in patient fibroblasts (p.Y245del and p.D172N) impair lipophagy-mediated degradation of lipid droplets: affected cells show abnormal lipid droplet accumulation, decreased LC3 expression, reduced autophagosome number, and decreased co-localization of lipid droplets with autophagosomes and lysosomes, indicating a role for PNPLA1 in lipid droplet regulation via lipophagy.","method":"BODIPY staining of lipid droplets in patient fibroblasts, siRNA knockdown, immunocytochemistry and immunoblotting for LC3 and PNPLA1, autophagosome/lysosome co-localization","journal":"Journal of dermatological science","confidence":"Low","confidence_rationale":"Tier 3 — single lab, indirect mechanism inference from patient cells; lipophagy role not independently confirmed","pmids":["30655104"],"is_preprint":false},{"year":2025,"finding":"ABHD5 regulates PNPLA1 by two mechanisms: (i) direct interaction through a PNPLA1-binding region on ABHD5 that recruits PNPLA1 to lipid droplets, and (ii) association of ABHD5 with lipid droplets via perilipin-binding domains; restoring co-localization of ABHD5 mutants with PNPLA1 in proteoliposomes is sufficient to rescue full PNPLA1 enzyme activity, establishing a co-localization-driven model of PNPLA1 regulation.","method":"Analysis of seven disease-associated ABHD5 missense mutations, proteoliposome reconstitution assay, enzyme activity measurement, imaging of PNPLA1 localization","journal":"Journal of lipid research","confidence":"High","confidence_rationale":"Tier 1–2 — reconstitution in proteoliposomes with multiple disease mutants tested, functional rescue experiment","pmids":["40818613"],"is_preprint":false}],"current_model":"PNPLA1 is a CoA-independent transacylase specifically expressed in differentiated keratinocytes that catalyzes the final step of ω-O-acylceramide biosynthesis by transferring linoleic acid from triglycerides to ω-hydroxyceramide acceptors; its activity and proper localization to lipid droplets depend on the coactivator ABHD5, which recruits PNPLA1 to its substrate, and loss of PNPLA1 function abolishes skin barrier acylceramides, causing lethal permeability defects in mice and autosomal recessive congenital ichthyosis in humans and dogs."},"narrative":{"teleology":[{"year":2012,"claim":"The genetic basis of PNPLA1 in skin barrier function was established when loss-of-function mutations in its catalytic domain were identified as the cause of autosomal recessive congenital ichthyosis across species, revealing that this uncharacterized PNPLA family member is essential for epidermal lipid barrier formation.","evidence":"Genome-wide association in golden retriever dogs plus mutation screening in human ARCI families","pmids":["22246504"],"confidence":"High","gaps":["Enzymatic activity unknown","Substrate and product not identified","Mechanism by which PNPLA1 contributes to barrier lipids unresolved"]},{"year":2017,"claim":"The enzymatic function of PNPLA1 was defined: it acts as a transacylase catalyzing ω-O-esterification of ω-hydroxyceramide with linoleic acid donated by triglyceride to produce acylceramides, and knockout mice confirmed this is essential for neonatal survival by demonstrating lethal barrier defects with absent acylceramides and accumulation of precursors.","evidence":"In vitro enzyme reconstitution with recombinant PNPLA1, cell-based acylceramide assays, global and keratinocyte-specific Pnpla1 KO mice with lipidomic analysis, and electron microscopy of cornified envelope in KO mice and human patient skin","pmids":["28248318","28248300","28369476"],"confidence":"High","gaps":["Mechanism of PNPLA1 activation and localization to its substrate unknown","Structural basis of substrate selectivity not determined","Whether PNPLA1 requires cofactors in vivo not established"]},{"year":2018,"claim":"The regulatory mechanism was identified: ABHD5 (CGI-58) physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets, stimulating acylceramide biosynthesis; ichthyosis-associated ABHD5 mutations and Chanarin-Dorfman syndrome mutations disrupt this activation, unifying two ichthyosis gene products in a single pathway.","evidence":"Co-immunoprecipitation, immunofluorescence showing ABHD5-dependent relocalization of PNPLA1 to lipid droplets, immunoelectron microscopy, cell-based functional assays with disease mutants","pmids":["30361410","30527376"],"confidence":"High","gaps":["Whether ABHD5 activates PNPLA1 allosterically or solely through co-localization not resolved","Structural details of the ABHD5–PNPLA1 interaction unknown","Role of perilipins in modulating the ABHD5–PNPLA1 axis in keratinocytes not tested"]},{"year":2018,"claim":"A potential connection to lipophagy was reported: patient-derived PNPLA1 mutant fibroblasts showed impaired lipid droplet degradation via autophagy with reduced LC3 and decreased co-localization of lipid droplets with autophagosomes.","evidence":"BODIPY staining and LC3 immunostaining in patient fibroblasts with PNPLA1 mutations","pmids":["30655104"],"confidence":"Low","gaps":["Lipophagy role not independently confirmed","Whether lipid droplet accumulation is a direct PNPLA1 function or secondary to acylceramide loss not distinguished","No rescue experiment performed"]},{"year":2022,"claim":"Systematic genotype–phenotype mapping of 16 ichthyosis-associated PNPLA1 missense mutations revealed that nearly all abolish transacylase activity, while residual activity (C216R) correlates with milder disease; mutations were classified into four functional groups based on enzyme activity and ABHD5-dependent lipid droplet localization.","evidence":"Cell-based acylceramide production assay and immunofluorescence of patient mutation panel","pmids":["35970721"],"confidence":"High","gaps":["No crystal structure to rationalize mutation effects","Whether any mutations affect ABHD5 binding directly versus protein folding not determined"]},{"year":2023,"claim":"In vitro reconstitution with purified recombinant PNPLA1 established its substrate scope — accepting trilinolein, dilinolein, ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid — and quantified a 3:1 selectivity for linoleate over oleate transfer, explaining the in vivo fatty acid composition of skin barrier lipids.","evidence":"Recombinant truncated PNPLA1 from E. coli, HPLC-UV and LC-MS product analysis","pmids":["37087101"],"confidence":"High","gaps":["Full-length enzyme not purified","ABHD5-dependent activation not reconstituted in vitro with purified components","Kinetic parameters not fully reported"]},{"year":2024,"claim":"PNPLA1 was shown to esterify γ-linolenic acid in addition to linoleic acid onto acylceramide subspecies in human keratinocytes, expanding its known substrate range, and its knockdown decreased involucrin expression linking it to keratinocyte terminal differentiation.","evidence":"siRNA knockdown in differentiating normal human keratinocytes with LC-MS lipidomics","pmids":["38340658"],"confidence":"Medium","gaps":["Whether GLA esterification is physiologically significant in vivo not tested","Mechanism linking PNPLA1 loss to involucrin downregulation not addressed"]},{"year":2025,"claim":"The mechanism of ABHD5-mediated PNPLA1 regulation was resolved into two separable functions — direct PNPLA1 binding and perilipin-dependent lipid droplet association — and proteoliposome reconstitution demonstrated that co-localization of ABHD5 with PNPLA1 is sufficient to fully rescue enzyme activity, establishing a co-localization-driven rather than allosteric activation model.","evidence":"Proteoliposome reconstitution with seven disease-associated ABHD5 missense mutants, enzyme activity measurement, imaging","pmids":["40818613"],"confidence":"High","gaps":["No structural model of the ABHD5–PNPLA1 complex","Whether perilipins modulate PNPLA1 activity in intact keratinocytes not tested in this system","How PNPLA1 accesses ω-hydroxyceramide acceptors at the lipid droplet surface remains unresolved"]},{"year":null,"claim":"A high-resolution structure of PNPLA1 — alone or in complex with ABHD5 — is lacking, leaving open the structural basis for linoleate selectivity, the precise ABHD5 binding interface, and the mechanism by which the enzyme simultaneously engages triglyceride donor and ω-hydroxyceramide acceptor at the lipid droplet surface.","evidence":"","pmids":[],"confidence":"High","gaps":["No crystal or cryo-EM structure available","Kinetic mechanism (ping-pong vs. ternary complex) not determined","In vivo regulation by perilipins and other lipid droplet proteins in keratinocytes untested"]}],"mechanism_profile":{"molecular_activity":[{"term_id":"GO:0016740","term_label":"transferase activity","supporting_discovery_ids":[1,2,7]},{"term_id":"GO:0008289","term_label":"lipid binding","supporting_discovery_ids":[1,7]}],"localization":[{"term_id":"GO:0005811","term_label":"lipid droplet","supporting_discovery_ids":[4,5,6,10]},{"term_id":"GO:0005829","term_label":"cytosol","supporting_discovery_ids":[5]}],"pathway":[{"term_id":"R-HSA-1430728","term_label":"Metabolism","supporting_discovery_ids":[1,2,3,7]}],"complexes":[],"partners":["ABHD5"],"other_free_text":[]},"mechanistic_narrative":"PNPLA1 is a lipid droplet-associated transacylase essential for epidermal permeability barrier formation through its catalysis of the terminal step in ω-O-acylceramide biosynthesis. It transfers linoleic acid (and γ-linolenic acid) from triglyceride donors to ω-hydroxyceramide, ω-hydroxy glucosylceramide, and ω-hydroxy fatty acid acceptors in a CoA-independent reaction, with ~3:1 selectivity for linoleate over oleate, accounting for the linoleic acid enrichment of skin barrier lipids [PMID:28248318, PMID:37087101, PMID:38340658]. Its catalytic activity and localization to lipid droplets require the coactivator ABHD5 (CGI-58), which physically interacts with PNPLA1 and recruits it to the lipid droplet surface where its triglyceride substrate resides; co-localization alone is sufficient to restore full enzymatic activity [PMID:30361410, PMID:40818613]. Loss-of-function mutations in PNPLA1 cause autosomal recessive congenital ichthyosis in humans and dogs, and Pnpla1 knockout mice die neonatally from transepidermal water loss due to complete absence of acylceramides and disorganized extracellular lipid lamellae [PMID:22246504, PMID:28248300, PMID:28369476]."},"prefetch_data":{"uniprot":{"accession":"Q8N8W4","full_name":"Omega-hydroxyceramide transacylase","aliases":["Patatin-like phospholipase domain-containing protein 1"],"length_aa":532,"mass_kda":57.9,"function":"Omega-hydroxyceramide transacylase involved in the synthesis of omega-O-acylceramides (esterified omega-hydroxyacyl-sphingosine; EOS), which are extremely hydrophobic lipids involved in skin barrier formation (PubMed:27751867, PubMed:28248318). Catalyzes the last step of the synthesis of omega-O-acylceramides by transferring linoleic acid from triglycerides to an omega-hydroxyceramide (PubMed:27751867, PubMed:28248318). Omega-O-acylceramides, are required for the biogenesis of lipid lamellae in the stratum corneum and the formation of the cornified lipid envelope which are essential for the epidermis barrier function (PubMed:22246504, PubMed:27751867, PubMed:28248318). These lipids also play a role in keratinocyte differentiation (By similarity). May also act on omega-hydroxylated ultra-long chain fatty acids (omega-OH ULCFA) and acylglucosylceramides (GlcEOS) (By similarity)","subcellular_location":"Cytoplasm","url":"https://www.uniprot.org/uniprotkb/Q8N8W4/entry"},"depmap":{"release":"DepMap","has_data":true,"is_common_essential":false,"resolved_as":"","url":"https://depmap.org/portal/gene/PNPLA1","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":[],"url":"https://opencell.sf.czbiohub.org/search/PNPLA1","total_profiled":1310},"omim":[{"mim_id":"615024","title":"ICHTHYOSIS, CONGENITAL, AUTOSOMAL RECESSIVE 10; ARCI10","url":"https://www.omim.org/entry/615024"},{"mim_id":"612121","title":"PATATIN-LIKE PHOSPHOLIPASE DOMAIN-CONTAINING PROTEIN 1; PNPLA1","url":"https://www.omim.org/entry/612121"},{"mim_id":"242300","title":"ICHTHYOSIS, CONGENITAL, AUTOSOMAL RECESSIVE 1; ARCI1","url":"https://www.omim.org/entry/242300"}],"hpa":{"profiled":true,"resolved_as":"","reliability":"","locations":[],"tissue_specificity":"Tissue enriched","tissue_distribution":"Detected in some","driving_tissues":[{"tissue":"skin 1","ntpm":22.5}],"url":"https://www.proteinatlas.org/search/PNPLA1"},"hgnc":{"alias_symbol":["FLJ38755","dJ50J22.1"],"prev_symbol":[]},"alphafold":{"accession":"Q8N8W4","domains":[{"cath_id":"-","chopping":"13-282","consensus_level":"high","plddt":90.3484,"start":13,"end":282}],"viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N8W4","model_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N8W4-F1-model_v6.cif","pae_url":"https://alphafold.ebi.ac.uk/files/AF-Q8N8W4-F1-predicted_aligned_error_v6.png","plddt_mean":63.75},"mouse_models":{"mgi_url":"https://www.informatics.jax.org/marker/summary?nomen=PNPLA1","jax_strain_url":"https://www.jax.org/strain/search?query=PNPLA1"},"sequence":{"accession":"Q8N8W4","fasta_url":"https://rest.uniprot.org/uniprotkb/Q8N8W4.fasta","uniprot_url":"https://www.uniprot.org/uniprotkb/Q8N8W4/entry","alphafold_viewer_url":"https://alphafold.ebi.ac.uk/entry/Q8N8W4"}},"corpus_meta":[{"pmid":"22246504","id":"PMC_22246504","title":"PNPLA1 mutations cause autosomal recessive congenital ichthyosis in golden retriever dogs and humans.","date":"2012","source":"Nature genetics","url":"https://pubmed.ncbi.nlm.nih.gov/22246504","citation_count":195,"is_preprint":false},{"pmid":"28248300","id":"PMC_28248300","title":"PNPLA1 has a crucial role in skin barrier function by directing acylceramide biosynthesis.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28248300","citation_count":111,"is_preprint":false},{"pmid":"28248318","id":"PMC_28248318","title":"PNPLA1 is a transacylase essential for the generation of the skin barrier lipid ω-O-acylceramide.","date":"2017","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/28248318","citation_count":105,"is_preprint":false},{"pmid":"30290227","id":"PMC_30290227","title":"The role of PNPLA1 in ω-O-acylceramide synthesis and skin barrier function.","date":"2018","source":"Biochimica et biophysica acta. Molecular and cell biology of lipids","url":"https://pubmed.ncbi.nlm.nih.gov/30290227","citation_count":45,"is_preprint":false},{"pmid":"30361410","id":"PMC_30361410","title":"ABHD5 stimulates PNPLA1-mediated ω-O-acylceramide biosynthesis essential for a functional skin permeability barrier.","date":"2018","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/30361410","citation_count":45,"is_preprint":false},{"pmid":"30527376","id":"PMC_30527376","title":"Molecular mechanism of the ichthyosis pathology of Chanarin-Dorfman syndrome: Stimulation of PNPLA1-catalyzed ω-O-acylceramide production by ABHD5.","date":"2018","source":"Journal of dermatological science","url":"https://pubmed.ncbi.nlm.nih.gov/30527376","citation_count":45,"is_preprint":false},{"pmid":"28369476","id":"PMC_28369476","title":"PNPLA1 defects in patients with autosomal recessive congenital ichthyosis and KO mice sustain PNPLA1 irreplaceable function in epidermal omega-O-acylceramide synthesis and skin permeability barrier.","date":"2017","source":"Human molecular genetics","url":"https://pubmed.ncbi.nlm.nih.gov/28369476","citation_count":42,"is_preprint":false},{"pmid":"27884779","id":"PMC_27884779","title":"Gene-Targeted Next Generation Sequencing Identifies PNPLA1 Mutations in Patients with a Phenotypic Spectrum of Autosomal Recessive Congenital Ichthyosis: The Impact of Consanguinity.","date":"2016","source":"The Journal of investigative dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/27884779","citation_count":31,"is_preprint":false},{"pmid":"28093717","id":"PMC_28093717","title":"Sixteen novel mutations in PNPLA1 in patients with autosomal recessive congenital ichthyosis reveal the importance of an extended patatin domain in PNPLA1 that is essential for proper human skin barrier function.","date":"2017","source":"The British journal of dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/28093717","citation_count":28,"is_preprint":false},{"pmid":"30655104","id":"PMC_30655104","title":"Impairment of lipophagy by PNPLA1 mutations causes lipid droplet accumulation in primary fibroblasts of Autosomal Recessive Congenital Ichthyosis patients.","date":"2018","source":"Journal of dermatological science","url":"https://pubmed.ncbi.nlm.nih.gov/30655104","citation_count":12,"is_preprint":false},{"pmid":"37087101","id":"PMC_37087101","title":"Recombinant PNPLA1 catalyzes the synthesis of acylceramides and acyl acids with selective incorporation of linoleic acid.","date":"2023","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/37087101","citation_count":8,"is_preprint":false},{"pmid":"27237723","id":"PMC_27237723","title":"Autosomal recessive congenital ichthyosis due to PNPLA1 mutation in a golden retriever-poodle cross-bred dog and the effect of topical therapy.","date":"2016","source":"Veterinary dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/27237723","citation_count":7,"is_preprint":false},{"pmid":"31120544","id":"PMC_31120544","title":"Novel and Recurrent PNPLA1 Mutations in Spanish Patients with Autosomal Recessive Congenital Ichthyosis; Evidence of a Founder Effect.","date":"2019","source":"Acta dermato-venereologica","url":"https://pubmed.ncbi.nlm.nih.gov/31120544","citation_count":7,"is_preprint":false},{"pmid":"29738490","id":"PMC_29738490","title":"Prevalence of PNPLA1 Gene Mutation in 48 Breeding Golden Retriever Dogs.","date":"2018","source":"Veterinary sciences","url":"https://pubmed.ncbi.nlm.nih.gov/29738490","citation_count":6,"is_preprint":false},{"pmid":"34899144","id":"PMC_34899144","title":"Variants in the PNPLA1 Gene in Families with Autosomal Recessive Congenital Ichthyosis Reveal Clinical Significance.","date":"2021","source":"Molecular syndromology","url":"https://pubmed.ncbi.nlm.nih.gov/34899144","citation_count":6,"is_preprint":false},{"pmid":"29624231","id":"PMC_29624231","title":"Identification of two novel PNPLA1 mutations in Turkish families with autosomal recessive congenital ichthyosis.","date":"2017","source":"The Turkish journal of pediatrics","url":"https://pubmed.ncbi.nlm.nih.gov/29624231","citation_count":6,"is_preprint":false},{"pmid":"35970721","id":"PMC_35970721","title":"Impaired production of skin barrier lipid acylceramides and abnormal localization of PNPLA1 due to ichthyosis-causing mutations in PNPLA1.","date":"2022","source":"Journal of dermatological science","url":"https://pubmed.ncbi.nlm.nih.gov/35970721","citation_count":5,"is_preprint":false},{"pmid":"31833240","id":"PMC_31833240","title":"Targeted regions sequencing identified four novel PNPLA1 mutations in two Chinese families with autosomal recessive congenital ichthyosis.","date":"2019","source":"Molecular genetics & genomic medicine","url":"https://pubmed.ncbi.nlm.nih.gov/31833240","citation_count":5,"is_preprint":false},{"pmid":"35893253","id":"PMC_35893253","title":"PNPLA1-Mediated Acylceramide Biosynthesis and Autosomal Recessive Congenital Ichthyosis.","date":"2022","source":"Metabolites","url":"https://pubmed.ncbi.nlm.nih.gov/35893253","citation_count":4,"is_preprint":false},{"pmid":"40818613","id":"PMC_40818613","title":"Defective targeting of PNPLA1 to lipid droplets causes ichthyosis in ABHD5-syndromic epidermal differentiation disorder.","date":"2025","source":"Journal of lipid research","url":"https://pubmed.ncbi.nlm.nih.gov/40818613","citation_count":3,"is_preprint":false},{"pmid":"36647593","id":"PMC_36647593","title":"Novel Pathogenic Mutation of PNPLA1 Identified in Autosomal Recessive Congenital Ichthyosis: A Case Report.","date":"2022","source":"Chinese medical sciences journal = Chung-kuo i hsueh k'o hsueh tsa chih","url":"https://pubmed.ncbi.nlm.nih.gov/36647593","citation_count":3,"is_preprint":false},{"pmid":"38340658","id":"PMC_38340658","title":"PNPLA1 knockdown inhibits esterification of γ-linolenic acid to ceramide 1 in differentiated keratinocytes.","date":"2024","source":"Biochemical and biophysical research communications","url":"https://pubmed.ncbi.nlm.nih.gov/38340658","citation_count":2,"is_preprint":false},{"pmid":"40545863","id":"PMC_40545863","title":"The First Reported Japanese Case of PNPLA1-Nonsyndromic Epidermal Differentiation Disorder (PNPLA1-nEDD) Associated With an Unreported 92-Base-Pair Duplication Variant.","date":"2025","source":"Experimental dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/40545863","citation_count":2,"is_preprint":false},{"pmid":"40150930","id":"PMC_40150930","title":"Intragenic PNPLA1 duplication in Labrador retrievers with nonepidermolytic ichthyosis.","date":"2025","source":"Veterinary dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/40150930","citation_count":2,"is_preprint":false},{"pmid":"32924119","id":"PMC_32924119","title":"[Analysis of PNPLA1 gene mutation in a child with ichthyosis].","date":"2020","source":"Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics","url":"https://pubmed.ncbi.nlm.nih.gov/32924119","citation_count":1,"is_preprint":false},{"pmid":"41530952","id":"PMC_41530952","title":"Progressive symmetrical erythrokeratoderma associated with biallelic PNPLA1 variants.","date":"2026","source":"The British journal of dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/41530952","citation_count":1,"is_preprint":false},{"pmid":"41655508","id":"PMC_41655508","title":"Genome-wide identification of the phospholipase gene family in Panax notoginseng and functional analysis of PnPLA1-8 response to Fusarium oxysporum infection.","date":"2026","source":"Plant physiology and biochemistry : PPB","url":"https://pubmed.ncbi.nlm.nih.gov/41655508","citation_count":0,"is_preprint":false},{"pmid":"41964248","id":"PMC_41964248","title":"Mutation Analysis in Ten Cases With PNPLA1-Nonsyndromic Epidermal Differentiation Disorder: Evidence of a Founder Effect.","date":"2026","source":"The Journal of dermatology","url":"https://pubmed.ncbi.nlm.nih.gov/41964248","citation_count":0,"is_preprint":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":15863,"output_tokens":2971,"usd":0.046077},"stage2":{"model":"claude-opus-4-6","input_tokens":6344,"output_tokens":2591,"usd":0.144742},"total_usd":0.190819,"stage1_batch_id":"msgbatch_01SUR8NDzVrNmyszWyJeCct7","stage2_batch_id":"msgbatch_01G7Yfutko3cDWzejrwH5AMx","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2012,\n      \"finding\": \"PNPLA1 is expressed in epidermis and is essential for formation of the epidermal lipid barrier; loss-of-function mutations (premature stop codon in dogs; missense and nonsense mutations in humans) in the catalytic domain of PNPLA1 cause autosomal recessive congenital ichthyosis, establishing its role in skin barrier lipid biosynthesis.\",\n      \"method\": \"Genome-wide association study, mutation identification, and localization experiments in golden retriever dogs and human ARCI patients\",\n      \"journal\": \"Nature genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — replicated across species (dog and human), multiple orthogonal methods, foundational study with 195 citations\",\n      \"pmids\": [\"22246504\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"PNPLA1 acts as a transacylase that catalyzes the final step of acylceramide (ω-O-acylceramide) synthesis by esterifying ω-hydroxyceramide with linoleic acid using triglyceride as the linoleic acid donor; ichthyosis patient-derived mutant forms of PNPLA1 show reduced or absent enzyme activity in both cell-based and in vitro assays.\",\n      \"method\": \"Cell-based acylceramide production assay, in vitro enzyme assay with recombinant PNPLA1 and triglyceride substrate, active-site mutant analysis\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — in vitro enzyme reconstitution plus cell-based assay plus mutagenesis, replicated in companion paper\",\n      \"pmids\": [\"28248318\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Global or keratinocyte-specific Pnpla1 knockout mice die neonatally from epidermal permeability barrier defects with severe transepidermal water loss, absent acylceramides, acylglucosylceramides and (O-acyl)-ω-hydroxy fatty acids in epidermis, and reciprocal accumulation of their precursors, confirming that PNPLA1 catalyses ω-O-esterification with linoleic acid to form acylceramides; acylceramide supplementation partially rescues the differentiation defect of Pnpla1-/- keratinocytes.\",\n      \"method\": \"Conditional and global knockout mouse model, lipidomic analysis, acylceramide rescue experiment\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — clean KO with defined phenotype, lipidomic pathway placement, rescue experiment; replicated by companion paper\",\n      \"pmids\": [\"28248300\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Pnpla1 knockout mice show loss of ω-O-acylceramides in stratum corneum with accumulation of precursors, defective lipid coverage of the cornified envelope, and disorganized extracellular lipid matrix; these defects are recapitulated in stratum corneum of PNPLA1-mutated human patients.\",\n      \"method\": \"Pnpla1 KO mouse model, ceramide species quantification by lipidomics, electron microscopy of cornified envelope\",\n      \"journal\": \"Human molecular genetics\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — independent lab, KO model with multiple orthogonal readouts, validated in human patient samples\",\n      \"pmids\": [\"28369476\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ABHD5 (CGI-58) acts as a coactivator of PNPLA1: it physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets where its triglyceride substrate resides, thereby stimulating PNPLA1-mediated ω-O-acylceramide biosynthesis; ichthyosis-associated ABHD5 point mutations fail to stimulate PNPLA1 activity.\",\n      \"method\": \"Co-immunoprecipitation, cell-based acylceramide production assay, immunofluorescence microscopy showing PNPLA1 relocalization to lipid droplets upon ABHD5 co-expression\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — reciprocal co-IP, localization with functional consequence, disease mutation validation; replicated in companion paper\",\n      \"pmids\": [\"30361410\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"ABHD5 enhances PNPLA1-catalyzed acylceramide production and causes PNPLA1 to relocalize from dispersed cytosolic distribution to lipid droplet membranes or periphery; at high expression levels, lipid droplets disappear, morphing into vesicles or becoming incorporated into the ER; ABHD5 mutations found in Chanarin-Dorfman syndrome patients reduce ABHD5's ability to promote PNPLA1-dependent acylceramide production.\",\n      \"method\": \"Cell-based acylceramide production assay, indirect immunofluorescence microscopy, immunoelectron microscopy\",\n      \"journal\": \"Journal of dermatological science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — multiple imaging methods, functional assay, disease-relevant mutant validation\",\n      \"pmids\": [\"30527376\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"Of 16 PNPLA1 missense mutations from ichthyosis patients, 15 cause complete loss of acylceramide-producing activity, while C216R only weakly affects activity (correlating with milder disease); mutants differ in their ability to localize to lipid droplets in an ABHD5-dependent manner, classifying them into four groups by activity and localization.\",\n      \"method\": \"Cell-based acylceramide production assay, indirect immunofluorescence microscopy, structure-function analysis of patient mutations\",\n      \"journal\": \"Journal of dermatological science\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 — systematic mutagenesis panel with functional and localization readouts, genotype-phenotype correlation\",\n      \"pmids\": [\"35970721\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"Recombinant truncated PNPLA1 (expressed in E. coli) catalyzes acyl transfer from trilinolein and dilinolein donors to ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid acceptors to form acylceramide, glucosyl-acylceramide, and acyl acid respectively; PNPLA1 shows 3:1 selectivity for transferring linoleate over oleate, explaining the linoleic acid enrichment of these skin barrier lipids in vivo.\",\n      \"method\": \"In vitro enzyme reconstitution with recombinant PNPLA1, HPLC-UV and LC-MS product analysis, substrate selectivity comparison\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 — direct in vitro reconstitution with purified recombinant enzyme, substrate selectivity quantified\",\n      \"pmids\": [\"37087101\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2024,\n      \"finding\": \"PNPLA1 is responsible for esterification of γ-linolenic acid (GLA), in addition to linoleic acid, to ω-hydroxy fatty acids of ceramide 1 (acylceramide) subspecies in terminally differentiated human keratinocytes; siRNA knockdown of PNPLA1 causes accumulation of non-esterified ω-hydroxy ceramide precursors and decreases involucrin expression.\",\n      \"method\": \"siRNA knockdown in normal human keratinocytes, LC-MS lipidomics of ceramide subspecies, differentiation marker analysis\",\n      \"journal\": \"Biochemical and biophysical research communications\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 — clean siRNA KD with defined lipid and differentiation phenotypes; single lab\",\n      \"pmids\": [\"38340658\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"Mutations in PNPLA1 in patient fibroblasts (p.Y245del and p.D172N) impair lipophagy-mediated degradation of lipid droplets: affected cells show abnormal lipid droplet accumulation, decreased LC3 expression, reduced autophagosome number, and decreased co-localization of lipid droplets with autophagosomes and lysosomes, indicating a role for PNPLA1 in lipid droplet regulation via lipophagy.\",\n      \"method\": \"BODIPY staining of lipid droplets in patient fibroblasts, siRNA knockdown, immunocytochemistry and immunoblotting for LC3 and PNPLA1, autophagosome/lysosome co-localization\",\n      \"journal\": \"Journal of dermatological science\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 — single lab, indirect mechanism inference from patient cells; lipophagy role not independently confirmed\",\n      \"pmids\": [\"30655104\"],\n      \"is_preprint\": false\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"ABHD5 regulates PNPLA1 by two mechanisms: (i) direct interaction through a PNPLA1-binding region on ABHD5 that recruits PNPLA1 to lipid droplets, and (ii) association of ABHD5 with lipid droplets via perilipin-binding domains; restoring co-localization of ABHD5 mutants with PNPLA1 in proteoliposomes is sufficient to rescue full PNPLA1 enzyme activity, establishing a co-localization-driven model of PNPLA1 regulation.\",\n      \"method\": \"Analysis of seven disease-associated ABHD5 missense mutations, proteoliposome reconstitution assay, enzyme activity measurement, imaging of PNPLA1 localization\",\n      \"journal\": \"Journal of lipid research\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1–2 — reconstitution in proteoliposomes with multiple disease mutants tested, functional rescue experiment\",\n      \"pmids\": [\"40818613\"],\n      \"is_preprint\": false\n    }\n  ],\n  \"current_model\": \"PNPLA1 is a CoA-independent transacylase specifically expressed in differentiated keratinocytes that catalyzes the final step of ω-O-acylceramide biosynthesis by transferring linoleic acid from triglycerides to ω-hydroxyceramide acceptors; its activity and proper localization to lipid droplets depend on the coactivator ABHD5, which recruits PNPLA1 to its substrate, and loss of PNPLA1 function abolishes skin barrier acylceramides, causing lethal permeability defects in mice and autosomal recessive congenital ichthyosis in humans and dogs.\"\n}\n```","stage2_raw":"```json\n{\n  \"mechanistic_narrative\": \"PNPLA1 is a lipid droplet-associated transacylase essential for epidermal permeability barrier formation through its catalysis of the terminal step in ω-O-acylceramide biosynthesis. It transfers linoleic acid (and γ-linolenic acid) from triglyceride donors to ω-hydroxyceramide, ω-hydroxy glucosylceramide, and ω-hydroxy fatty acid acceptors in a CoA-independent reaction, with ~3:1 selectivity for linoleate over oleate, accounting for the linoleic acid enrichment of skin barrier lipids [PMID:28248318, PMID:37087101, PMID:38340658]. Its catalytic activity and localization to lipid droplets require the coactivator ABHD5 (CGI-58), which physically interacts with PNPLA1 and recruits it to the lipid droplet surface where its triglyceride substrate resides; co-localization alone is sufficient to restore full enzymatic activity [PMID:30361410, PMID:40818613]. Loss-of-function mutations in PNPLA1 cause autosomal recessive congenital ichthyosis in humans and dogs, and Pnpla1 knockout mice die neonatally from transepidermal water loss due to complete absence of acylceramides and disorganized extracellular lipid lamellae [PMID:22246504, PMID:28248300, PMID:28369476].\",\n  \"teleology\": [\n    {\n      \"year\": 2012,\n      \"claim\": \"The genetic basis of PNPLA1 in skin barrier function was established when loss-of-function mutations in its catalytic domain were identified as the cause of autosomal recessive congenital ichthyosis across species, revealing that this uncharacterized PNPLA family member is essential for epidermal lipid barrier formation.\",\n      \"evidence\": \"Genome-wide association in golden retriever dogs plus mutation screening in human ARCI families\",\n      \"pmids\": [\"22246504\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Enzymatic activity unknown\", \"Substrate and product not identified\", \"Mechanism by which PNPLA1 contributes to barrier lipids unresolved\"]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"The enzymatic function of PNPLA1 was defined: it acts as a transacylase catalyzing ω-O-esterification of ω-hydroxyceramide with linoleic acid donated by triglyceride to produce acylceramides, and knockout mice confirmed this is essential for neonatal survival by demonstrating lethal barrier defects with absent acylceramides and accumulation of precursors.\",\n      \"evidence\": \"In vitro enzyme reconstitution with recombinant PNPLA1, cell-based acylceramide assays, global and keratinocyte-specific Pnpla1 KO mice with lipidomic analysis, and electron microscopy of cornified envelope in KO mice and human patient skin\",\n      \"pmids\": [\"28248318\", \"28248300\", \"28369476\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Mechanism of PNPLA1 activation and localization to its substrate unknown\", \"Structural basis of substrate selectivity not determined\", \"Whether PNPLA1 requires cofactors in vivo not established\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"The regulatory mechanism was identified: ABHD5 (CGI-58) physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets, stimulating acylceramide biosynthesis; ichthyosis-associated ABHD5 mutations and Chanarin-Dorfman syndrome mutations disrupt this activation, unifying two ichthyosis gene products in a single pathway.\",\n      \"evidence\": \"Co-immunoprecipitation, immunofluorescence showing ABHD5-dependent relocalization of PNPLA1 to lipid droplets, immunoelectron microscopy, cell-based functional assays with disease mutants\",\n      \"pmids\": [\"30361410\", \"30527376\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Whether ABHD5 activates PNPLA1 allosterically or solely through co-localization not resolved\", \"Structural details of the ABHD5–PNPLA1 interaction unknown\", \"Role of perilipins in modulating the ABHD5–PNPLA1 axis in keratinocytes not tested\"]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"A potential connection to lipophagy was reported: patient-derived PNPLA1 mutant fibroblasts showed impaired lipid droplet degradation via autophagy with reduced LC3 and decreased co-localization of lipid droplets with autophagosomes.\",\n      \"evidence\": \"BODIPY staining and LC3 immunostaining in patient fibroblasts with PNPLA1 mutations\",\n      \"pmids\": [\"30655104\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Lipophagy role not independently confirmed\", \"Whether lipid droplet accumulation is a direct PNPLA1 function or secondary to acylceramide loss not distinguished\", \"No rescue experiment performed\"]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Systematic genotype–phenotype mapping of 16 ichthyosis-associated PNPLA1 missense mutations revealed that nearly all abolish transacylase activity, while residual activity (C216R) correlates with milder disease; mutations were classified into four functional groups based on enzyme activity and ABHD5-dependent lipid droplet localization.\",\n      \"evidence\": \"Cell-based acylceramide production assay and immunofluorescence of patient mutation panel\",\n      \"pmids\": [\"35970721\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal structure to rationalize mutation effects\", \"Whether any mutations affect ABHD5 binding directly versus protein folding not determined\"]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"In vitro reconstitution with purified recombinant PNPLA1 established its substrate scope — accepting trilinolein, dilinolein, ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid — and quantified a 3:1 selectivity for linoleate over oleate transfer, explaining the in vivo fatty acid composition of skin barrier lipids.\",\n      \"evidence\": \"Recombinant truncated PNPLA1 from E. coli, HPLC-UV and LC-MS product analysis\",\n      \"pmids\": [\"37087101\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Full-length enzyme not purified\", \"ABHD5-dependent activation not reconstituted in vitro with purified components\", \"Kinetic parameters not fully reported\"]\n    },\n    {\n      \"year\": 2024,\n      \"claim\": \"PNPLA1 was shown to esterify γ-linolenic acid in addition to linoleic acid onto acylceramide subspecies in human keratinocytes, expanding its known substrate range, and its knockdown decreased involucrin expression linking it to keratinocyte terminal differentiation.\",\n      \"evidence\": \"siRNA knockdown in differentiating normal human keratinocytes with LC-MS lipidomics\",\n      \"pmids\": [\"38340658\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Whether GLA esterification is physiologically significant in vivo not tested\", \"Mechanism linking PNPLA1 loss to involucrin downregulation not addressed\"]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"The mechanism of ABHD5-mediated PNPLA1 regulation was resolved into two separable functions — direct PNPLA1 binding and perilipin-dependent lipid droplet association — and proteoliposome reconstitution demonstrated that co-localization of ABHD5 with PNPLA1 is sufficient to fully rescue enzyme activity, establishing a co-localization-driven rather than allosteric activation model.\",\n      \"evidence\": \"Proteoliposome reconstitution with seven disease-associated ABHD5 missense mutants, enzyme activity measurement, imaging\",\n      \"pmids\": [\"40818613\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No structural model of the ABHD5–PNPLA1 complex\", \"Whether perilipins modulate PNPLA1 activity in intact keratinocytes not tested in this system\", \"How PNPLA1 accesses ω-hydroxyceramide acceptors at the lipid droplet surface remains unresolved\"]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"A high-resolution structure of PNPLA1 — alone or in complex with ABHD5 — is lacking, leaving open the structural basis for linoleate selectivity, the precise ABHD5 binding interface, and the mechanism by which the enzyme simultaneously engages triglyceride donor and ω-hydroxyceramide acceptor at the lipid droplet surface.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"High\",\n      \"gaps\": [\"No crystal or cryo-EM structure available\", \"Kinetic mechanism (ping-pong vs. ternary complex) not determined\", \"In vivo regulation by perilipins and other lipid droplet proteins in keratinocytes untested\"]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0016740\", \"supporting_discovery_ids\": [1, 2, 7]},\n      {\"term_id\": \"GO:0008289\", \"supporting_discovery_ids\": [1, 7]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005811\", \"supporting_discovery_ids\": [4, 5, 6, 10]},\n      {\"term_id\": \"GO:0005829\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"R-HSA-1430728\", \"supporting_discovery_ids\": [1, 2, 3, 7]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"ABHD5\"\n    ],\n    \"other_free_text\": []\n  }\n}\n```"}