Analysis of LHX gene on human development

背景：许多男性不育症被诊断为特发性，反映了对异常背后的分子缺陷了解不足。随着越来越多引起小鼠雄性不育的基因突变的发现，人类雄性不育的遗传病因学知识可以扩大，前景越来越好。Sycp3编码突触复合体的一个组成部分，小鼠中Sycp3的零突变导致无精子症伴减数分裂停止。我们验证了人类睾丸特异性SYCP3突变与人类非阻塞性无精子症相关的假设。方法：根据小鼠SYCP3 cDNA与人类基因组序列在氨基酸水平上的同源性，分离出人SYCP3。采用人cDNA PCR分析SYCP3的组织特异性表达。通过对SYCP3基因的序列分析，对19例无精子症成熟停止患者和75例正常生育对照男性的DNA样本进行了SYCP3基因突变的筛选。通过对野生型和截断的SYCP3蛋白的蛋白质相互作用研究，分析了发现的突变的功能意义。研究结果：我们在两名患者中发现了1 bp的缺失（643delA），导致SYCP3蛋白的c端卷曲-卷曲形成区域过早停止密码子和截短。在体外实验中，突变蛋白与野生型蛋白的相互作用大大降低，并干扰培养细胞中SYCP3纤维的形成。解释：我们认为SYCP3在人类精子发生中具有重要的减数分裂功能，该功能通过显性负干扰被突变蛋白破坏。

BACKGROUND : Many cases of male infertility are diagnosed as idiopathic, reflecting poor understanding of the molecular defects underlying the abnormality. As more gene mutations causing male infertility in mice become known, there are improving prospects that knowledge about the genetic aetiology of human male infertility can be expanded. Sycp3 encodes a component of the synaptonemal complex A null mutation of Sycp3 in mice causes azoospermia with meiotic arrest. We tested the hypothesis that mutation of the human testis-specific SYCP3 is associated with human non-obstructive azoospermia.METHODS : Human SYCP3 was isolated on the basis of homology between mouse Sycp3 cDNA and human genome sequences at the aminoacid level. Tissue-specific expression of SYCP3 was analysed by PCR of human cDNA. Samples of DNA from 19 azoospermic patients with maturation arrest and 75 normal fertile control men were screened for mutations in the SYCP3 gene by sequence analysis of the gene. The functional significance of the mutations found was analysed by a protein interaction study of the wild-type and truncated SYCP3 proteins.FINDINGS : We identified in two patients a 1 bp deletion (643delA) that results in a premature stop codon and truncation of the C-terminal, coiled-coil-forming region of the SYCP3 protein. The mutant protein showed greatly reduced interaction with the wild-type protein in vitro and interfered with SYCP3 fibre formation in cultured cells.INTERPRETATION : We suggest that SYCP3 has an essential meiotic function in human spermatogenesis that is compromised by the mutant protein via dominant negative interference.