Pi Yuze, Huang Zhuo, Xu Xilin, Zhang Huan, Jin Miao, Zhang Shuoping, Lin Ge, Hu Liang
Institute of Reproductive and Stem Cell Engineering, School of Basic Medical Science, Central South University, Changsha, Hunan, China.
Laboratory Medicine Centre, Huazhong University of Science and Technology Union Shenzhen Hospital (Nanshan Hospital), Shenzhen, Guangdong, China.
Andrology. 2024 Mar;12(3):585-598. doi: 10.1111/andr.13521. Epub 2023 Aug 25.
Mitochondria are essential for sperm motility because they provide the energy required for the movement. Changes in sperm mtDNA, such as point mutations, large-scale deletions, or copy number variations, may interfere with ATP production and reduce sperm motility. However, it is not clear if changes in mtDNA are linked to semen quality.
To explore the association between sperm mitochondrial DNA (mtDNA) changes and semen quality.
Sixty-five oligo and/or astheno and/or terato patients (O/A/T) patients and 41 controls were recruited from couples undergoing assisted reproduction. Semen and blood samples were collected from the same individual on the day of oocyte retrieval to extract, isolate and purify mtDNA for next-generation sequencing. mtDNA copy numbers were assessed in 64 patient and 39 control sperm DNA samples using quantitative real-time PCR. The 4977 bp deletion was assessed in 20 patient and 20 control sperm DNA samples using polymerase chain reaction.
The mtDNA of patients was more likely to carry pathogenic variants or variants of unknown significance (VUSs) (P = 0.091) with higher heteroplasmy levels (P < 0.05) than that of controls. Interestingly, 33.85% of O/A/T patients (22 out of 65) lacked unique variants in their spermatozoa. but presented an exceptionally high mtDNA copy number (P < 0.0001). Moreover, we observed a decrease in the heteroplasmy level of common mtDNA variants shared by somatic and gamete cells (P < 0.0001) and the emergence of a very large number of de novo mtDNA variants with low-level heteroplasmy in spermatozoa.
The increases in the number of computationally predicted deleterious VUS and mtDNA copies in spermatozoa may be associated with semen quality. Exposure to environmental mutation pressure that causes novel mtDNA variants with low-level heteroplasmy may occur during spermatogenesis. Furthermore, when a certain harmful threshold is reached, male germ cells may degrade mtDNA with mutations and replicate the correct mtDNA sequence to maintain the mitochondrial function in spermatozoa.
线粒体对于精子运动至关重要，因为它们提供运动所需的能量。精子线粒体DNA（mtDNA）的变化，如点突变、大规模缺失或拷贝数变异，可能会干扰ATP的产生并降低精子活力。然而，尚不清楚mtDNA的变化是否与精液质量有关。
探讨精子线粒体DNA（mtDNA）变化与精液质量之间的关联。
从接受辅助生殖的夫妇中招募了65例少弱畸精子症（O/A/T）患者和41例对照者。在取卵当天从同一个体采集精液和血液样本，以提取、分离和纯化mtDNA用于下一代测序。使用定量实时PCR评估64例患者和39例对照者精子DNA样本中的mtDNA拷贝数。使用聚合酶链反应评估20例患者和20例对照者精子DNA样本中的4977 bp缺失。
与对照组相比，患者的mtDNA更有可能携带致病变异或意义未明的变异（VUS）（P = 0.091），且异质性水平更高（P < 0.05）。有趣的是，33.85%的O/A/T患者（65例中的22例）精子中缺乏独特变异，但呈现出异常高的mtDNA拷贝数（P < 0.0001）。此外，我们观察到体细胞和生殖细胞共有的常见mtDNA变异的异质性水平降低（P < 0.0001），并且精子中出现了大量低水平异质性的新生mtDNA变异。
精子中通过计算预测的有害VUS数量和mtDNA拷贝数的增加可能与精液质量有关。在精子发生过程中可能会受到环境突变压力的影响，从而导致具有低水平异质性的新型mtDNA变异。此外，当达到一定的有害阈值时，雄性生殖细胞可能会降解带有突变的mtDNA并复制正确的mtDNA序列，以维持精子中的线粒体功能。
