SPRR1 gene induction and barrier formation occur as coordinated moving fronts in terminally differentiating epithelia

Stratified, terminally differentiated epithelia, such as epidermis and oral epithelia, provide protective barriers against the environment. We recentl y developed wholemount assays that demonstrate epidermal barrier function d uring late gestation and showed that epidermal barrier forms at specific si tes (epidermal initiation sites), and then spreads around the body as appar ent moving fronts. We now ask if this is a fundamental and widespread mode of epithelial developmental change. If so, then the pattern should be appar ent when assaying for developmental change other than barrier institution ( e.g., gene induction) and similar types of patterned change should be appar ent in other types of epithelia. In this study we demonstrate patterned bar rier function in a range of additional stratified epithelia from the oral c avity and show that the gene induction pattern of a stratum corneum precurs or small proline-rich region protein 1 (SPRR1) precedes barrier function an d occurs in the barrier pattern, i.e., gene induction occurs first at initi ation sites and propagates across epithelia as apparent moving fronts. Thes e results demonstrate that late gestational developmental change in multipl e terminally differentiating epithelia occurs via initiation sites and movi ng fronts. The pattern precedes barrier formation and results in a developm ental gradient that influences gene induction.