Psoriasis susceptibility 1 candidate 2 (PSORS1C2) encodes a small proline-rich protein of unknown function. Here we determined the expression pattern of PSORS1C2 at the RNA and protein levels in human tissues. RT-PCR showed expression of PSORS1C2 highest in the skin and weak expression in the thymus. Comparison of the proliferating versus differentiating keratinocytes revealed that when primary keratinocytes were grown in sub-confluent cultures expression of PSORS1C2 was low, whereas induction of differentiation by post-confluent culture caused upregulation of PSORS1C2. By immunohistochemistry, PSORS1C2 protein was localized in the epidermis and in the thymus. In both tissues, PSORS1C2 was specifically present in cornifying cells of the stratum granulosum layer and the Hassall´s bodies, respectively. PSORS1C2 is conserved in the mouse and other terrestrial mammals whereas it has been lost in aquatic mammals. The results of this study indicate that the expression of PSORS1C2 is linked to epithelial cell cornification and suggest that the PSORS1C2 protein is a component of the epidermal barrier. Based on this study, the PSORS1C2 gene knock down system in the 3D human full skin reconstruction model will be carried out to test the structural role of this protein in the skin barrier function.

PSORS1C2, a potential skin barrier modifier, expressed in terminally differentiated epidermal keratinocytes