Cloning of mouse c-ros renal cDNA, its role in development and relationship to extracellular matrix glycoproteins

Renal organogenesis ensues following reciprocal interactions between the uninduced metanephric mesenchyme and the ureteric bud. Conceivably, the presence of ligands or growth factors on a given cell type, and expression of receptors, including receptor proto-oncogenes, on the other cell type of different lineage would facilitate such epithelial-mesenchymal interactions. During these interactions, other macromolecules, such as extracellular matrix (ECM) proteins, present at the epithelial-mesenchymal surface, also play a role in the kidney morphogenesis. In this study the proto-oncogene, c-ros, was cloned and sequenced; its role in the metanephric development was examined, and correlated with the changes in the expression of ECM proteins. The mouse c-ros renal cDNA, belonging to phosphotyrosine kinase (PTK) receptor family, had a translation product of 2340 amino acids. The extracellular domain had 32 N-linked glycosylation sites and 30 cysteine residues. The transmembrane segment had a hydrophobicity approaching ~ 3.5. Multiple phosphorylation sites, typical of a PTK catalytic unit, were present in the cytoplasmic domain. The 3' noncoding region did not contain any A(U)(n)A mRNA instability motifs. The c-ros mRNA was highly expressed on the ureteric bud branches and their tips and on the developing glomeruli. Competitive RT-PCR analyses revealed the c-ros expression was the highest at 13th day of gestation, and it declined to very low levels during the neonatal period. Exposure of metanephric kidneys to c-ros antisense-oligonucleotide, derived from the PTK domain, caused dysmorphogenesis of the kidney and loss of c-ros expression on the ureteric bud branches. Concomitant with the reduced c-ros gene expression, a decreased expression of ECM glycoproteins, in particular the proteoglycans, was observed. These findings suggest that the c-ros plays a role in the metanephric development, and its effects may be modulated by the ECM macromolecules present at the epithelial-mesenchymal interface.