Analysis of three distinct Ly6-A-related cDNA sequences isolated from rat kidney.

Mouse Ly6A and Ly6C cDNA probes were hybridized to total RNA of rat tissues and, as in mouse, the highest level of Ly6-related transcripts was detected in kidney. Therefore, Ly6-related cDNA clones were isolated from a commercial rat kidney cDNA library in lambda gt11. Four of these (RK3, RK6, RK10, and RK11) have been fully characterized, and represent transcripts from three distinct genes. Each contains a reading frame encoding an amino acid sequence typical of the known Ly6 molecules: a 26aa leader (except in clone RK6 which has only two of its leader codons), followed by a sequence of 108 or 109aa containing 10 cysteines in excellent alignment with those of Ly6A. The three rat polypeptide sequences were more closely related to Ly6A than Ly6C, and more closely related to each other than to Ly6A. The most striking similarity between all these sequences is in the last 33aa at the C-terminal. Most of this is presumed to be cleaved off during post-translational addition of a phosphatidylinositol-glycan (PI-G) membrane anchor. Southern blot analysis of rat DNA probed with rat-Ly6 cDNA showed multiple band patterns indicative of a multigene family. No restriction fragment length polymorphism (RFLP) was evident amongst the six inbred rat strains tested. Anomalies in two of the rat cDNA clones, resulting from improper splicing of the original transcripts, correlated with Ly6Ca exon boundaries, thus suggesting conserved intron-exon organization.