3059 – THE ABSENCE OF PROSTASIN LEADS TO IMPAIRED TERMINAL EMBRYONIC ERYTHROID DIFFERENTIATION

The serine protease prostasin, encoded by Prss8, has been studied for its role in cancer and epidermal dysfunction. It is expressed in several epithelia, where it is involved in the regulation of several substrates such as the epithelial sodium channel (ENaC), protease-activated receptors (PARs), and extracellular matrix components. However, the physiological role of this serine protease is still unknown. In human, dysregulation of prostasin expression and activity has been associated with severe pre-eclampsia, and with premature embryonic death in knockout mice. In this study we analyzed the phenotype of the mouse Prss8-/- embryos at E11.5 and 12.5 prior to their premature death at E13.5 focusing on yolk sac, the aorta-gonad-mesonephros (AGM) and fetal liver. In absence of prostasin, we found an overall reduced number of fetal erythrocytes, while reticulocytes count was increased, suggesting a defect in the terminal erythroid differentiation. Indeed, imaging flow cytometry revealed that Prss8-/- fetal liver exhibited a significantly lower number and percentage of BasoE, PolyE and more predominantly of OrthoE. We also assessed the ability of E11.5 AGM-derived cells to form erythroid colonies using a colony-forming assay. Counting revealed significantly less colonies in the Prss8-/- cultures although, the number of hematopoietic stem cells (HSCs) was comparable between the two genotypes. This suggests that in absence of prostasin, erythrocytes specification is impaired. Furthermore, in the yolk sac of E12.5 Prss8-/- embryos an aberrant vascular remodeling was observed. Despite that, comparable numbers of endothelial cells were detected by FACS, suggesting that vasculogenesis is not affected in absence of prostasin and vessel remodeling is impaired likely because of reduced circulating erythrocytes.