CLONING OF MOUSE C-ROS RENAL CDNA, ITS ROLE IN DEVELOPMENT AND RELATIONSHIP TO EXTRACELLULAR-MATRIX GLYCOPROTEINS

Renal organogenesis ensues following reciprocal interactions between t he uninduced metanephric mesenchyme and the ureteric bud. Conceivably, the presence of ligands or growth factors on a given cell type, and e xpression of receptors, including receptor proto-oncogenes, on the oth er cell type of different lineage would facilitate such epithelial-mes enchymal interactions. During these interactions, other macromolecules , such as extracellular matrix (ECM) proteins, present at the epitheli al-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 acid 30 cysteine residues. The transm embrane segment had a hydrophobicity approaching similar to 3.5. Multi ple phosphorylation sites, typical of a PTK catalytic unit, were prese nt 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 expres sed on the ureteric bud branches and their tips and on the developing glomeruli. Competitive RT-PCR analyses revealed the c-ros expression w as the highest at 13th day of gestation, and it declined to very low l evels during the neonatal period. Exposure of metanephric kidneys to c -los antisense-oligonucleotide, derived from the PTK domain, caused dy smorphogenesis of the kidney and loss of c-ros expression on the urete ric bud branches. Concomitant with the reduced c-ros gene expression, a decreased expression of ECM glycoproteins, in particular the proteog lycans, was observed. These findings suggest that the c-los plays a ro le in the metanephric development, and its effects may be modulated by the ECM macromolecules present at the epithelial-mesenchymal interfac e.