Institute of Reproduction and Stem Cell Engineering, School of Basic Medical Science, Central South University, Changsha, Hunan, PR China.
Reproductive and Genetic Hospital of CITIC-Xiangya, Changsha, Hunan, PR China.
Mol Genet Genomic Med. 2020 Apr;8(4):e1165. doi: 10.1002/mgg3.1165. Epub 2020 Feb 11.
Premature ovarian insufficiency (POI) is one major cause of female infertility, minichromosome maintenance complex component 8 (MCM8) has been reported to be responsible for POI.
Whole-exome sequencing was performed to identify the genetic variants of women with POI. Sanger sequencing was used to validate the variants in all the family members. Various bioinformatic software was used for the pathogenicity assessment. Reverse transcription polymerase chain reaction (RT-PCR), real-time quantitative PCR, and a chromosomal instability study induced by mitomycin C were performed to analyze the functional effects of the variant.
A novel homozygous frameshift mutation (NM_032485.4:c.351_354delAAAG) of MCM8 gene was identified in the patients, segregated with POI in this family. This mutation is predicted to produce truncated MCM8 protein and to be pathogenic. Reverse transcription polymerase chain reaction revealed that the frameshift mutation led to a remarkably reduced level of MCM8 transcript products, and chromosomal instability study showed that the ability of mutant MCM8 to repair DNA breaks was impaired.
We identified a novel homozygous frameshift mutation in the MCM8 gene in two affected sisters with POI, and functional analysis revealed that this mutation is pathogenic. Our findings enrich the MCM8 mutation spectrum and might help clinicians to make a precise diagnosis, thereby allowing better family planning and genetic counseling.
卵巢早衰（POI）是女性不孕的主要原因之一，微染色体维持复合物组件 8（MCM8）已被报道与 POI 有关。
对 POI 女性进行全外显子组测序以鉴定遗传变异。对所有家族成员进行 Sanger 测序验证变异。使用各种生物信息学软件进行致病性评估。进行逆转录聚合酶链反应（RT-PCR）、实时定量 PCR 和丝裂霉素 C 诱导的染色体不稳定性研究，以分析变异的功能影响。
在患者中鉴定出 MCM8 基因的一个新的纯合移码突变（NM_032485.4：c.351_354delAAAG），该突变在这个家族中与 POI 共分离。该突变预计会产生截短的 MCM8 蛋白，具有致病性。逆转录聚合酶链反应显示移码突变导致 MCM8 转录产物水平显著降低，染色体不稳定性研究表明突变型 MCM8 修复 DNA 断裂的能力受损。
我们在两名患有 POI 的受影响姐妹中鉴定出 MCM8 基因的一个新的纯合移码突变，功能分析表明该突变具有致病性。我们的发现丰富了 MCM8 突变谱，可能有助于临床医生做出精确诊断，从而实现更好的计划生育和遗传咨询。
