Molecular characterization of the bovine chromodomain Y-like genes

The human chromodomain protein, Y-like (CDYL) gene family consists of three members, one on the Y chromosome (CDY) and two on autosomes (CDYL and CDYL2). Studies in the human and mouse showed that genes in the CDYL family are abundantly expressed in testis and play an important role in spermatogenesis. In this study, we have characterized the bovine CDYL (bCDYL) and CDYL2 (bCDYL2) genes. We found that bCDYL and bCDYL2 are very similar to the human orthologues at both mRNA (79% and 85%) and protein (89% and 93%) levels. However, the similarity between the bCDYL and bCDYL2 proteins is low (41%). The bCDYL gene is composed of nine exons, and the bCDYL2 has seven exons. The bCDYL and bCDYL2 genes were mapped by radiation hybrid mapping to bovine chromosomes (BTA) 24 and 18 respectively. The bCDYL gene has four transcript variants that produce four protein isoforms. RT-PCR expression analysis in 12 bovine tissues showed that bCDYL variant 2 was expressed in the testis only, bCDYL variants 1, 3 and 4 were expressed predominantly in the testis and at very low or undetectable levels in the remaining tissues and bCDYL2 was expressed ubiquitously. Examination of bovine testis with in situ hybridization revealed that the bCDYL and bCDYL2 transcripts were found mainly in spermatids, though the amounts of transcripts varied among genes/variants. In addition, antisense transcripts were detected in bCDYL variants 2/3 and 4, as well as in the bCDYL2 gene.