Lower polyunsaturated fatty acid levels and FADS2 expression in adult compared to neonatal keratinocytes are associated with FADS2 promotor hypermethylation

Keratinocytes produce lipids that are critical for the skin barrier, however, little is known about the impact of age on fatty acid (FA) biosynthesis in these cells. We have examined the relationship between keratinocyte FA composition, lipid biosynthetic gene expression, gene promoter methylation and age. Expression of elongase (ELOVL6 and 7) and desaturase (FADS1 and 2) genes was lower in adult versus neonatal keratinocytes, and was associated with lower concentrations of n-7, n-9 and n-10 polyunsaturated FA in adult cells. Consistent with these findings, transient FADS2 knockdown in neonatal keratinocytes mimicked the adult keratinocyte FA profile in neonatal cells. Interrogation of methylation levels across the FADS2 locus (53 genomic sites) revealed differential methylation of 15 sites in neonatal versus adult keratinocytes, of which three hypermethylated sites in adult keratinocytes overlapped with a SMARCA4 protein binding site in the FADS2 promoter.