Genomic sequence and organization of the family of CNR/Pcdhalpha genes in rat.

CNR/Pcdhalpha family proteins are known as synaptic cadherins and Reelin receptors. Here we report the complete genomic sequence and organization of the rat CNR. The rat CNR cluster encodes 15 variable and 3 constant exons. The genomic organizations of the rat, mouse, and human CNR/Pcdhalpha are orthologous. The percentage identity of the coding regions between the rat and the mouse is 93.6% on average at the nucleic acid level, and between rat and human it is 82.8%. The rat CNRs (v1-v13) also contain an RGD motif in the extracellular cadherin 1 domains and cysteine repeats that are characteristic of the transmembrane and cytoplasmic domains of CNR proteins. The number of variable exons in the rat CNR cluster is identical to that of the human. The rat CNR cluster has one more variable exon than is found in laboratory mouse strains, because in the mouse a variable exon located between v7 and v8 is divided by the insertion of a retrotransposon. This exon is not disrupted in the rat, in which it is transcribed. By in silico analysis, CNR/Pcdhalpha was also mapped to rat chromosome 18, but the orientation was opposite for the mouse CNR/Pcdhalpha gene cluster. The relative expression profiles of the rat CNRs (v1-v13) show that all the CNRs are transcribed, but there are variations in the expression ratios among the CNRs.