Updated project metadata. Epidermal deletion of the lipid modifying enzyme CerS4 causes epidermal barrier impairments associated with human skin diseases. Proteomes of Wt newborn and P47 mice were compared in order to identify molecular differences between barrier formation and maintenance. Proteomes of epidermal splits from Ctr and CerS4epi-/- at different ages (P21, P33, P47) were compared, to identify the effect of CerS4 on barrier maintenance.