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PNPLA1
patatin like domain 1, omega-hydroxyceramide transacylase
PNPLA1 is located on the short (p) arm of chromosome 6, at band 6p21.31. Arm ratio per GRCh38 - banding schematic.
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Overview
The PNPLA1 gene provides instructions for making an omega-hydroxyceramide transacylase, an enzyme that performs a specialised chemical modification of ceramides in the skin. Ceramides are waxy lipid molecules that form a critical component of the stratum corneum, the outermost protective layer of the epidermis. PNPLA1 specifically converts omega-hydroxyceramides into acylceramides, which are essential for assembling the lipid lamellae that prevent water loss and block entry of pathogens and irritants.
Pathogenic variants in PNPLA1 follow an autosomal recessive inheritance pattern, meaning two altered copies are required to cause disease. When both copies are non-functional, the resulting deficiency of acylceramides leads to autosomal recessive congenital ichthyosis, a group of severe skin-scaling disorders present from birth.
What the gene does
The PNPLA1 enzyme belongs to the patatin-like phospholipase family and functions as an omega-hydroxyceramide transacylase in keratinocytes, the predominant cell type in the epidermis. During skin barrier formation, keratinocytes produce omega-hydroxylated ceramides as intermediate lipid species. PNPLA1 catalyses the transfer of a linoleic acid moiety from triglycerides to these omega-hydroxyceramides, generating protein-bound omega-hydroxy acylceramides.
These acylceramides are subsequently covalently attached to structural proteins in the cornified envelope, forming a lipid envelope that is indispensable for barrier function. Without functional PNPLA1 activity, omega-hydroxyceramides accumulate whilst acylceramides are depleted, disrupting the orderly arrangement of lipid lamellae between corneocytes. This architectural breakdown compromises the skin's ability to retain moisture and exclude harmful substances, manifesting as thickened, scaly skin with increased susceptibility to infection and inflammation.
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Chromosome location
PNPLA1 is located on the short arm of chromosome 6 at position 21.31 (6p21.31), within the major histocompatibility complex region. The gene spans multiple exons encoding a 532-amino-acid protein. This chromosomal region is gene-dense and contains numerous immunologically important genes, though PNPLA1 itself has a specialised role in lipid metabolism rather than immune function.
Protein structure
The PNPLA1 protein contains a PNPLA domain extending from amino acids 16 to 185, which houses the catalytic machinery characteristic of the patatin-like phospholipase family. Within this domain lies the GXSXG motif (amino acids 51-55), a conserved sequence that forms part of the active site responsible for lipid substrate binding and catalysis. A second conserved motif, DGA/G (amino acids 172-174), contributes to the enzyme's transacylase activity.
Outside the structured catalytic domain, PNPLA1 includes two large disordered regions spanning amino acids 290-457 and 489-532. These intrinsically disordered regions likely provide flexibility for membrane association and may play regulatory roles, though their precise functions remain under investigation. The modular architecture enables PNPLA1 to interact with lipid substrates embedded in cellular membranes whilst performing its specialised ceramide-modification reaction.
Key variants
Pathogenic variants in PNPLA1 typically result in loss of enzyme function through missense changes that disrupt the active site, nonsense mutations that introduce premature stop codons, or frameshift variants caused by small insertions or deletions. Because the enzyme's transacylase activity is essential for acylceramide synthesis, even modest reductions in activity can impair skin barrier formation when both gene copies are affected.
No pathogenic or likely-pathogenic ClinVar variants recorded yet for this gene.
Associated conditions
Biallelic pathogenic variants in PNPLA1 cause autosomal recessive congenital ichthyosis, a clinically heterogeneous group of keratinisation disorders characterised by generalised scaling of the skin from birth or early infancy. Affected individuals often present with collodion membrane at birth, a shiny, taut covering that subsequently peels to reveal underlying erythema and scaling. The severity ranges from mild generalised dryness to severe, plate-like scale with associated ectropion, eclabium, and increased risk of skin infections. The phenotype reflects the degree of lipid barrier disruption caused by deficient acylceramide production.
No disease links recorded for this gene in our reference set.
Inheritance pattern
Conditions caused by pathogenic PNPLA1 variants typically follow autosomal recessive inheritance.
When both parents are carriers, each child has a 25% chance of being affected, 50% of being a carrier, and 25% of being unaffected.
UK clinical status
PNPLA1 appears on multiple NHS Genomic Medicine Service gene panels with green (diagnostic-grade evidence) classification. It is included in the Autosomal recessive congenital ichthyosis panel, the DDG2P developmental disorders panel, and the Fetal anomalies panel (R21). Additionally, PNPLA1 features in the Ichthyosis and erythrokeratoderma (R165) and Palmoplantar keratodermas (R166) panels. This NHS recognition reflects the gene's established role in diagnosing inherited skin-barrier disorders within UK clinical genomics pathways.
Sources: NHS GMS PanelApp · Genomics England PanelApp · NHS National Genomic Test Directory
Frequently asked questions
How is PNPLA1-related ichthyosis inherited?
PNPLA1-related ichthyosis follows autosomal recessive inheritance, meaning an individual must inherit a pathogenic variant from both parents to develop the condition. Parents who each carry one altered copy typically have normal skin but have a 25% chance with each pregnancy of having an affected child.
Can PNPLA1 variants cause skin problems in carriers?
Individuals with only one pathogenic PNPLA1 variant (carriers) generally have no skin manifestations, as one functional gene copy produces sufficient enzyme activity to maintain normal barrier function. Clinical features appear only when both copies are non-functional.
Is genetic testing for PNPLA1 available on the NHS?
Yes, PNPLA1 sequencing is available through NHS clinical genomics services for individuals with features of autosomal recessive congenital ichthyosis or related keratinisation disorders. Testing is typically arranged by dermatologists or clinical geneticists following specialist assessment.