ALOX12B and PNPLA1 Have Distinct Roles in Epidermal Lipid Lamellar Organization.

The stratum corneum (SC) has remarkable permeability barrier properties that are attributable to highly ordered lipid lamellae (LL) that fill the extracellular spaces between corneocytes (Ribaud et al., 1994). Corneocytes also have a lipid monolayer covalently bound to their surfaces, called the corneocyte lipid envelope (CLE)(Crumrine et al., 2019). LL composition influences their organization and permeability function; for example, esterified omega-hydroxy (EO)-ceramides, which are synthesized by patatin-like phospholipase domain-containing 1 (PNPLA1), have been shown in vitro to mediate formation of the “long periodicity phase” triplet repeat pattern that characterizes normal LL (Opálka et al., 2016).