SEPTIN12 and male infertility: Moreover, the significant region detected in BTA25 but at 3–4 Mb also contains candidate genes for bull fertility, such as SEPT12 and MGRN1. Indeed, SEPT12 is expressed specifically in the testis and encodes a GTP-binding protein that has been implicated in sperm morphogenesis, sperm motility and male infertility [52, 53].