Molecular cloning and expression analysis of three cadherin-8 isoforms in the embryonic chicken brain

Three types of full-length cDNAs encoding chicken cadherin-8 (Cdh8) were identified and their expression in the embryonic chicken brain was investigated. The longest type of cDNA is closely similar to that of other classic cadherins, and the predicted protein shows a high similarity to rat and human Cdh8. The second type of cDNA is considerably shorter. The deduced protein lacks the cytoplasmic tail and the transmembrane domain, and contains a truncated fifth cadherin repeat in the extracellular domain (EC5; 68 amino acids), suggesting that it is a soluble isoform. The third type resembles the second one but is even shorter (only 30 amino acids in EC5). All types contain unique short sequences at their C terminus. Genomic analysis demonstrated that all of the three Cdh8 isoforms are located on chromosome 11, and consist of 12, 10, and 9 exons, respectively. Semi-quantitative RT-PCR with type-specific primers showed that the transcription of the three Cdh8 isoforms was temporally and spatially regulated in different parts of the embryonic chicken brain. The distinct regulation of gene expression suggested that the three isoforms likely play different roles during brain development. Northern blot analysis revealed that the transcription of the long isoform was much stronger than that of the two shorter ones. In situ hybridization showed that the long isoform of Cdh8 is expressed by a specific subset of brain nuclei, regions and layers in all major parts of the brain.