Isolation of cDNA clones for the chicken neural cell adhesion molecule (N-CAM)

Abstract

Enriched mRNA coding for the neural cell adhesion molecule (N-CAM) was prepared from 9-day embryonic chicken brains by immunoprecipitation of polysomes with antibodies to N-CAM. This mRNA programmed the translation in vitro of N-CAM polypeptide chains in a rabbit reticulocyte lysate system. Two independent N-CAM cDNA clones (designated pEC001 and pEC020) were derived from the enriched RNA. The specificity of pEC001 for N-CAM mRNA was verified by hybrid selection experiments. Both plasmids hybridized to two discrete 6- to 7-kilobase-long RNA species in poly(A)+ RNA from embryonic chicken brain and to lesser amounts of polydisperse material of smaller sizes (probably degradation products of the large RNAs). No hybridization was detected to poly(A)+ RNA from embryonic liver. Southern blotting experiments with pEC001 detected only one hybridizing fragment in chicken genomic DNA digested with several different restriction enzymes, suggesting that sequences corresponding to those within this region of N-CAM mRNA are present at most only a few times, and possibly only once, in the chicken genome.