POLG1外显子1、3、4、7突变与弱精子症的相关性及其对mtDNA和4977 bp缺失的影响

Mutations in Exons 1, 3, 4, and 7 of Polymerase Gamma-1: Its Correlation with Asthenospermia and Its Effects on mtDNA Mutation and 4 977 bp Deletion

为了探索POLG1外显子1、3、4、7突变与弱精子症的相关性及对mtDNA序列突变和4 977 bp缺失的影响,按WHO标准收集了120例弱精子症和101例精子活力正常的精液标本,经PCR测序分析POLG1外显子1、3、4、7突变,继而测序检测9例外显子4 c.948 G>A突变的弱精子症标本、9例无c.948 G>A突变的弱精子症标本和9例正常对照标本的mtDNA全序列,利用巢式PCR技术分析9例c.948 G>A突变标本、9例无c.948 G>A突变的弱精子症标本和9例对照标本的4 977 bp缺失。结果显示:在120例弱精子症中发现POLG1外显子4 c.948 G>A突变9例(7.5%),显著高于对照组(0%,P<0.05)。c.948 G>A突变组mtDNA全序中突变率与对照组比无统计学差异(P>0.05)。作者关注的两组中,突变数有差异的位点累积突变频次突变组显著高于对照组(P<0.05),但与无c.948 G>A突变的弱精子症标本的累积突变频次比较无统计学意义;突变组mtDNA 4 977 bp缺失率(7/9,77.8%)显著高于对照组(2/9,22.2%,P<0.05)和无c.948 G>A突变的弱精子症组(2/9,22.2%,P<0.05)。以上结果提示,弱精子症的发生可能与POLG1 c.948 G>A突变有相关性,弱精子症线粒体DNA某些位点的累积突变率增高,但可能不是POLG1 c.948 G>A突变引起;c.948 G>A突变可能会增加mtDNA 4 977 bp缺失,从而影响精子线粒体功能,导致精子活动力下降。

The aim of this study is to investigate the correlation between mutations in exons 1, 3, 4, and 7 of polymerase gamma-1 and asthenospermia and to study the effect of POLG1 mutations on mtDNA mutation and 4 977 bp deletion. We collected 120 semen samples from patients with asthenospermia and 101 normal semen sam- ples from the healthy donors based on WHO criteria. The mutations ofPOLG1 exon 1, 3, 4, and 7 in these samples have been analyzed by sequencing. MtDNA sequences and 4 977 bp deletions have been analyzed in nine astheno- spermia samples with c.948 G〉A mutation, nine asthen0spermia samples without c.948 G〉A mutation, and in nine healthy semen, samples. The POLG1 exon 4 c.948 G〉A mutation was found in 9 （7.5%） of 120 asthenospermia samples, which was significantly higher than that of the control group. The accumulated mutation frequency at the mutation sites with different mutation number was significantly higher in the asthenospermia group with c.948 G〉A mutations than that of the control group, but not significantly different from the asthenospermia group without c.948 G〉A mutations. The mtDNA 4 977 bp deletion rate was significantly higher in the asthenospermia group with c.948 G〉A mutations （7/9, 77.8%） than that of the control group （2/9, 22.2%）, or of the asthenospermia group without c.948 G〉A mutations （2/9, 22.2%）. The accumulated mutation rate of mtDNA at some sites was increased in the asthenospermia samples, which was not caused by POLG1 c.948 G〉A mutation. The c.948 G〉A mutation increases mtDNA 4 977 bp deletion, thus affecting sperm mitochondrial function and leading to decreased sperm motility.