BIRC6 and male infertility: While the levels of the other Nrdp1 substrates in sperm, including ErbB3 [15] and BIRC6/BRUCE [17], were not elevated by Nrdp1 deletion (Table S7 [43,44]), this study shows that deletion of Nrdp1 increased the levels of Parkin, but reduced the levels of Drp1 in sperm, suggesting that the suppressed ubiquitination of Parkin at least partially contributes to the abnormal arrangement of mitochondria in sperm, the impaired sperm motility, and male infertility.