BPY2 and Azoospermia: BPY2 is a protein-coding gene mapping in Yq11.223; it belongs to the VCX/VCY gene family as well, although it is not related to BPY1 [198], and it is also known as VCY2. BPY2 contains eight exons, with the initiating ATG codon in exon 4; its encoded protein (Testis-specific basic protein Y 2) interacts with ubiquitin protein ligase E3A and may be involved in male germ cell development and male infertility—in fact, its deletions are frequently found in infertile men with severe oligozoospermia or azoospermia [199].