Mammalian spermatogenesis is a complex developmental process. Mutations at multiple loci and in structurally and functionally disparate genes in the genome affect gametogenesis. The analysis of mutations has provided insight into biochemical pathways required for completion of this process. The basic protein on Y chromosome 2 gene (BPY2, also designated VCY2) is located in a frequently deleted azoospermia factor c region. Three copies (paralogs) of the BPY2 gene (BPY2A, BPY2B, BPY2C) reside in the AZFc region. BPY2 protein expression is localized to the nuclei of spermatogonia, spermatocytes and round spermatids, but is absent from elongated spermatids. Impaired expression of BPY2 in infertile men suggests its involvement in male germ cell development. BPY2 interacts with MAP-1S, which shares homology with microtubule-associated proteins (MAPs), suggesting a role for BPY2 within the cytoskeletal network.