The canonical members of the Ras gene family (H-ras, N-ras, and K-ras) encode four protein isoforms (H-Ras, N-Ras, K-Ras4A and 4B) regulating cell proliferation, differentiation or death/survival. Whereas genomic disruption of K-ras4B causes embryonic lethality, H-ras, N-ras and K-ras4A knockout mice are viable. H-ras and N-ras double KO (DKO) mice are also viable but show increased perinatal mortality suggesting critical physiological roles of those proteins around birth. Our characterization of DKO (Hras-/-;Nras-/-) mice uncovered a significant mortality rate due to respiratory failure during the first two postnatal days. Although DKO mice develop normal lung branching, they show delayed pulmonary maturation, a defect affecting both bronchiolar (Ciliated and Clara Cells) and alveolar lineages (type I and type II Pneumocytes), plus a reduced alveolar space and thicker septa. Clara Cells showed abnormal morphology and lack of proteoglycans production, whereas Ciliated Cells showed incorrect cilia structure. Additionally, these cells were not evenly juxtaposed in the bronchiolar space but formed a continuous layer in which markers for both cell types merged. Alveolar cells showed also abnormal phenotypes. Whereas type II Pneumocytes were wrongly localized inside a cell mass instead of surrounding the alveolar spaces, the type I cells did not exhibit typical flat shape, pointing to a defect in differentiation. The delay in lung maturation was further supported by the observation of increased number of precursors cells of alveolar lineage (more RCA/SftpC+ cells) as well as by higher proliferation rates. Our data uncover important, specific functional roles of H-Ras and N-Ras for lung maturation and neonatal survival that cannot be substituted by K-Ras action.

Resumen del póster presentado al XXXIX Congreso de la Sociedad Española de Bioquímica y Biología Molecular, celebrado en Salamanca del 5 al 8 de septiembre de 2016.

Peer reviewed