Genomic organization, expression and evolution of porcine CRSP1, 2, and 3

Recently we identified and characterized porcine calcitonin receptor-stimulating peptide (CRSP) 1, CRSP2 and CRSP3 as members of the calcitonin/calcitonin gene-related peptide (CT/CGRP) family. In the present study, the genomic sequences and organization of CRSP1, 2, and 3 were determined, and the expression of the genes in the porcine brain was investigated using in situ hybridization. Analysis of 5'-upstream regions of the three CRSPs demonstrated that CRSP1 and CRSP2 have almost identical sequences (>98% similarity) and high sequence similarities including functional transcription binding sites with the corresponding region of human CALCA (CT/alpha CGRP), whereas CRSP3 retains less similarity with the above genes. RH mapping of CRSPs demonstrated that they resided in a region of swine chromosome 2 (SSC2). The arrangement of the genes in the region was found to be conserved in corresponding human and mouse regions. In situ hybridization demonstrated sense transcripts of the three genes in cerebrum, hippocampus, hypothalamus, pons/midbrain, and thalamus of 3-month-old pigs, and CRSP2 sense transcripts additionally in tractus opticus. The sense transcripts of alpha CGRP and CALCB (beta CGRP) were detected in cerebrum, hippocampus, and pons/midbrain of newborn mice, and to a lesser extent in pons/midbrain of 8-week-old mice. These results taken together with the chromosomal conservation and phylogenetic clustering of CT/CGRP family indicate that CRSP1, 2, and 3 may be functionally different from alpha CGRP and beta CGRP, though they are indicated to have a common progenitor gene.