The association of this large deletion with normal fertility shows that USP9Y, hitherto considered a candidate gene for infertility and azoospermia, does not have a key role in male reproduction.
Study of azoospermia factor-a deletion caused by homologous recombination between the human endogenous retroviral elements and population-specific alleles in Japanese infertile males.
In addition, some infrequent mutations have been identified in the ubiquitin-specific protease 9, Y-linked (USP9Y) and the synaptonemal complex protein 3 (SYCP3) gene that cause azoospermia.
On the contrary, the phenotype of patients with deletion of both USP9Y and DBY seem to be invariably azoospermia with a testicular histology of Sertoli cell-only.