Kuhtz Juliane, Schneider Eberhard, El Hajj Nady, Zimmermann Lena, Fust Olga, Linek Bartosz, Seufert Rudolf, Hahn Thomas, Schorsch Martin, Haaf Thomas
a Institute of Human Genetics ; Julius Maximilians University ; Würzburg , Germany.
Epigenetics. 2014 Dec;9(12):1648-58. doi: 10.4161/15592294.2014.988063.
The molecular basis of male infertility is poorly understood, the majority of cases remaining unsolved. The association of aberrant sperm DNA methylation patterns and compromised semen parameters suggests that disturbances in male germline epigenetic reprogramming contribute to this problem. So far there are only few data on the epigenetic heterogeneity of sperm within a given sample and how to select the best sperm for successful infertility treatment. Limiting dilution bisulfite sequencing of small pools of sperm from fertile donors did not reveal significant differences in the occurrence of abnormal methylation imprints between sperm with and without morphological abnormalities. Intracytoplasmic morphologically selected sperm injection was not associated with an improved epigenetic quality, compared to standard intracytoplasmatic sperm injection. Deep bisulfite sequencing (DBS) of 2 imprinted and 2 pluripotency genes in sperm from men attending a fertility center showed that in both samples with normozoospermia and oligoasthenoteratozoospermia (OAT) the vast majority of sperm alleles was normally (de)methylated and the percentage of epimutations (allele methylation errors) was generally low (<1%). However, DBS allowed one to identify and quantify these rare epimutations with high accuracy. Sperm samples not leading to a pregnancy, in particular in the OAT group, had significantly more epimutations in the paternally methylated GTL2 gene than samples leading to a live birth. All 13 normozoospermic and 13 OAT samples leading to a child had <1% GTL2 epimutations, whereas one (7%) of 14 normozoospermic and 7 (50%) of 14 OAT samples without pregnancy displayed 1-14% GTL2 epimutations.
男性不育的分子基础尚不清楚，大多数病例仍未得到解决。精子DNA甲基化模式异常与精液参数受损之间的关联表明，雄性生殖系表观遗传重编程紊乱是导致这一问题的原因。到目前为止，关于给定样本中精子的表观遗传异质性以及如何选择最佳精子以成功治疗不育症的数据很少。对来自可育供体的少量精子池进行有限稀释亚硫酸氢盐测序，未发现形态正常和异常的精子之间异常甲基化印记的发生率有显著差异。与标准胞浆内精子注射相比，形态学选择的胞浆内精子注射与表观遗传质量的改善无关。对一家生育中心男性精子中的2个印记基因和2个多能性基因进行深度亚硫酸氢盐测序（DBS）表明，在正常精子症和少弱畸精子症（OAT）样本中，绝大多数精子等位基因的甲基化状态正常，表观突变（等位基因甲基化错误）的比例普遍较低（<1%）。然而，DBS能够高精度地识别和量化这些罕见的表观突变。未导致妊娠的精子样本，特别是OAT组，在父源甲基化的GTL2基因中的表观突变明显多于导致活产的样本。所有13例正常精子症和13例OAT样本中导致生育的样本，其GTL2表观突变率均<1%，而14例正常精子症样本中有1例（7%）以及14例未妊娠的OAT样本中有7例（50%）的GTL2表观突变率为1%-14%。
