SLC22A4 and male infertility: The third member of OCTN subfamily, even if OCTN3 has not yet been genetically identified in human genome, has been associated with male infertility in rat and in mice at different degrees of severity ranging from oligospermia to aspermia [75, 76, 96, 97], being mainly expressed in testis, besides intestine like OCTN1 and 2.