Fertility Labs of Colorado, 10290 Ridgegate Circle, Lone Tree CO, 80124, USA.
Colorado Center for Reproductive Medicine, 10290 Ridgegate Circle, Lone Tree CO, 80124, USA.
Hum Reprod. 2017 Dec 1;32(12):2443-2455. doi: 10.1093/humrep/dex317.
Is there a distinct sperm histone-retained epigenetic signature in unexplained male factor infertility patients resulting in compromised blastocyst development?
Using only donor oocyte IVF cycles, sperm DNA methylation patterns and miRNA profiles were significantly altered in normozoospermic patients resulting in poor blastocyst development, reflecting a subset of unexplained male factor infertility.
Aberrant sperm DNA methylation has been associated with known male factor infertility, particularly noted in oligozoospermic patients. Unexplained male factor infertility remains a significant proportion of in vitro fertilization failures having unknown underlying physiology.
STUDY DESIGN, SIZE, DURATION: Sperm samples (n = 40) and blastocysts (n = 48) were obtained during fertile donor oocyte IVF cycles with normozoospermic parameters, thereby excluding known female and male infertility factors. Samples were divided into two groups based on blastocyst development (Good Group = ≥20% embryos with D5 grade 'AA' blastocysts, and ≥60% embryos of transferable quality on D5 and D6; Poor Group = ≤10% embryos with D5 grade 'AA' blastocysts, and ≤40% embryos of transferable quality on D5 and D6).
PARTICIPANTS/MATERIALS, SETTING, METHODS: Samples were obtained from patients undergoing IVF treatments with informed consent and institutional review board approval. The Infinium HumanMethylation450 BeadChip microarray was used to identify histone-retained CpG island genes and genomic regions showing differences in sperm DNA methylation between the Good Group and the Poor Group. Pathway and gene network analysis for the significantly altered genes was performed, and targeted DNA methylation validation was completed for 23 genes and two imprinting control regions. Sperm miRNA profiles were assessed using the TaqMan® Human MicroRNA Array Card, with corresponding blastocyst mRNA gene expression examined by qRT-PCR.
Our study is the first to investigate unexplained male factor infertility while significantly eliminating confounding female factors from our sample population by using only young fertile donor oocytes. We identified 1634 CpG sites located at retained histone CpG island regions that had significant sperm DNA methylation differentials between the two embryogenesis groups (P < 0.05). A largely hypermethylated profile was evident in the Good Group, with a small but distinct and statistically significant shift (P < 0.05) observed in the Poor Group. Genes involved in embryonic development were highly represented among histone-retained CpG sites with decreased methylation in the Poor Group (P < 0.05). Ten significantly altered sperm miRNAs (P < 0.05), correlated with altered target gene mRNA expression in the blastocysts from the Poor Group (P < 0.05). Taken together, significantly impacted sperm miRNA and target transcript levels in blastocysts from the Poor Group may contribute alongside aberrant sperm DNA methylation to the compromised blastocyst development observed.
LIMITATIONS, REASONS FOR CAUTION: Our examination of CpG island regions restricted to retained histones represents only a small part of the sperm epigenome. The results observed are descriptive and further studies are needed to elucidate the functional effects of differential sperm DNA methylation on unexplained male factor infertility and blastocyst development.
Slight epigenetic changes in sperm may have a cumulative effect on fertility and embryonic developmental competence. Knowledge of sperm epigenetics and inheritance has important implications for future generations, while providing evidence for potential causes of unexplained male factor infertility.
STUDY FUNDING/COMPETING INTEREST(S): No external funding was used for this study. None of the authors have any competing interest.
在导致囊胚发育受损的不明原因男性因素不育患者中，是否存在独特的精子组蛋白保留表观遗传特征？
仅使用供体卵母细胞 IVF 周期，在导致正常精子数量患者中，精子 DNA 甲基化模式和 miRNA 谱发生显著改变，导致囊胚发育不良，反映了一部分不明原因的男性因素不育。
异常的精子 DNA 甲基化与已知的男性因素不育有关，尤其是在少精子症患者中。不明原因的男性因素不育仍然是体外受精失败的一个重要比例，其潜在的生理学原因未知。
研究设计、大小、持续时间：在具有正常精子参数的有生育能力的供体卵母细胞 IVF 周期中获得精子样本（n = 40）和囊胚（n = 48），从而排除已知的女性和男性不育因素。根据囊胚发育情况将样本分为两组（良好组=≥20%胚胎具有 D5 级“AA”囊胚，且≥60%胚胎在 D5 和 D6 时具有可转移质量；不良组=≤10%胚胎具有 D5 级“AA”囊胚，且≤40%胚胎在 D5 和 D6 时具有可转移质量）。
参与者/材料、设置、方法：从接受知情同意和机构审查委员会批准的 IVF 治疗的患者中获得样本。使用 Infinium HumanMethylation450 BeadChip 微阵列来鉴定精子 DNA 甲基化在良好组和不良组之间存在差异的组蛋白保留 CpG 岛基因和基因组区域。对显著改变的基因进行途径和基因网络分析，并对 23 个基因和两个印迹控制区完成了靶向 DNA 甲基化验证。使用 TaqMan® Human MicroRNA Array Card 评估精子 miRNA 谱，通过 qRT-PCR 检查相应的囊胚 mRNA 基因表达。
我们的研究首次调查了不明原因的男性因素不育，同时通过仅使用年轻有生育能力的供体卵母细胞，从我们的样本人群中显著消除了混杂的女性因素。我们在两组胚胎发生中鉴定了 1634 个位于保留组蛋白 CpG 岛区域的 CpG 位点，这些位点在精子 DNA 甲基化方面存在显著差异（P < 0.05）。在良好组中，存在明显的高甲基化谱，而在不良组中，存在小但明显且具有统计学意义的变化（P < 0.05）。胚胎发育相关基因在保留组蛋白 CpG 位点中高度表达，在不良组中（P < 0.05）观察到其甲基化减少。10 个显著改变的精子 miRNA（P < 0.05）与不良组囊胚中改变的靶基因 mRNA 表达相关（P < 0.05）。总之，在不良组囊胚中，显著受影响的精子 miRNA 和靶转录物水平可能与异常的精子 DNA 甲基化一起，导致观察到的囊胚发育受损。
局限性、谨慎的原因：我们对保留组蛋白的 CpG 岛区域的检查仅代表精子表观基因组的一小部分。观察到的结果是描述性的，需要进一步研究来阐明精子 DNA 甲基化差异对不明原因的男性因素不育和囊胚发育的功能影响。
精子的微小表观遗传变化可能对生育能力和胚胎发育能力产生累积影响。精子表观遗传学和遗传知识对未来几代人具有重要意义，同时为不明原因的男性因素不育提供了潜在原因的证据。
研究资金/竞争利益：本研究没有使用外部资金。作者均无任何竞争利益。
