Identification and characterization of the cynomolgus monkey chromodomain gene cynCDY, an orthologue of the human CDY gene family.

Microdeletions within the AZF (azoospermia factor) a, b and c regions of the Y chromosome can be detected worldwide in 1-10% of infertile men. AZFc, containing genes such as DAZ, CDY, RBMY and others, is most frequently deleted and associated with oligo- or azoospermia. The function of the different genes within AZFc is not yet understood. Here we report the identification and first characterization of the cynomolgus monkey (Macaca fascicularis) homologue of the human CDY gene. cynCDY encodes a 541 aa protein, which like human CDY possesses two putative functional domains: an N-terminal chromodomain, possibly involved in heterochromatin interactions, and a C-terminal domain showing similarity to enoyl-CoA-isomerase, which is involved in fatty acid oxidation. Northern analysis and in-situ hybridization experiments revealed testis- and stage-specific expression of cynCDY mRNA, mainly confined to round and elongating spermatids. Fluorescence in-situ hybridization (FISH) performed on monkey metaphase chromosomes displayed exclusively Y-specific signals in Yq12.1. Using fibre FISH, short signal stretches that indicate the presence of three CDY copies could be visualized, although their integrity or function remains unknown. cynCDY is similar to human CDY with features of a retrotransposon, but different in the 3'UTR. It seems to represent a more ancestral form of CDY and its characterization yields insights into the evolution of candidate genes for AZF.