Systems Oncology (ONCOSYS) Research Program, Research Programs Unit, Faculty of Medicine, University of Helsinki, Haartmaninkatu 8 (PO Box 63), FI-00014 Helsinki, Finland.
Doctoral Program in Integrative Life Sciences, University of Helsinki, Viikinkaari 1 (PO Box 65), FI-00014 Helsinki, Finland.
Mutagenesis. 2021 Jul 7;36(3):237-244. doi: 10.1093/mutage/geab010.
DNA mismatch repair (MMR) proteins play an important role in maintaining genome stability, both in somatic and in germline cells. Loss of MLH1, a central MMR protein, leads to infertility and to microsatellite instability (MSI) in spermatocytes, however, the effect of Mlh1 heterozygosity on germline genome stability remains unexplored. To test the effect of Mlh1 heterozygosity on MSI in mature sperm, we combined mouse genetics with single-molecule PCR that detects allelic changes at unstable microsatellites. We discovered 4.5% and 5.9% MSI in sperm of 4- and 12-month-old Mlh1+/- mice, respectively, and that Mlh1 promoter methylation in Mlh1+/- sperm correlated with higher MSI. No such elevated MSI was seen in non-proliferating somatic cells. Additionally, we show contrasting dynamics of deletions versus insertions at unstable microsatellites (mononucleotide repeats) in sperm.
DNA 错配修复 (MMR) 蛋白在维持基因组稳定性方面发挥着重要作用，无论是在体细胞还是生殖细胞中。中央 MMR 蛋白 MLH1 的缺失会导致不育和精母细胞中的微卫星不稳定 (MSI)，然而，Mlh1 杂合性对生殖系基因组稳定性的影响仍未被探索。为了测试 Mlh1 杂合性对成熟精子中 MSI 的影响，我们将小鼠遗传学与单分子 PCR 相结合，该技术可检测不稳定微卫星中的等位基因变化。我们发现 4 个月和 12 个月大的 Mlh1+/- 小鼠精子中的 MSI 分别为 4.5%和 5.9%，并且 Mlh1+/- 精子中的 Mlh1 启动子甲基化与更高的 MSI 相关。在非增殖性体细胞中未观察到这种升高的 MSI。此外，我们还展示了在不稳定微卫星（单核苷酸重复）中，精子中缺失与插入的相反动态。
