DNMT3A and Azoospermia: Germline deficiency of DNMT3a [23], involved predominantly in de novo methylation during gametogenesis [24], [25], and DNMT3L [26], [27], an enzyme with no intrinsic methyltransferase activity [28] but that cooperates with DNMT3a in de novo methylation [29], both result in azoospermia and infertility [25], [30], [31], [32].