Knockout of Murine Mamld1 Impairs Testicular Growth and Daily Sperm Production but Permits Normal Postnatal Androgen Production and Fertility.

MAMLD1 has been implicated in testicular function in both human and mouse fetuses. Although three patients with mutations were reported to have hypergonadotropic hypogonadism in their teens, the functional significance of MAMLD1 in the postnatal testis remains unclear. Here, we analyzed the phenotype of knockout (KO) male mice at reproductive ages. The reproductive organs of KO male mice were morphologically unremarkable, except for relatively small testes. Seminiferous tubule size and number of proliferating spermatogonia/spermatocytes were reduced in the KO testis. Daily sperm production of KO mice was mildly attenuated, whereas total sperm counts in epididymal semen remained normal. Sperm motility and morphology, as well as androgen levels in serum and testicular tissues and the number of pups born from cross-mated wildtype (WT) female mice, were comparable between WT and KO male mice. These results indicate that MAMLD1 contributes to the maintenance of postnatal testicular growth and daily sperm production but is dispensable for androgen biosynthesis and fertility. MAMLD1 likely plays supporting roles in multiple and continuous steps of male reproduction.