Analysis of LHX gene on human development

背景：许多男性不育病例被诊断为特发性，反映出对这种异常背后的分子缺陷缺乏了解。随着更多导致小鼠男性不育的基因突变被发现，关于人类男性不育的遗传病因学的知识有望得到扩大。Sycp3编码联会复合体的一个组成部分。在小鼠中，Sycp3的零突变会导致无精症和减数分裂停滞。我们验证了人类睾丸特异的SYCP3突变与人类非梗阻性无精子症相关的假设。方法：根据小鼠Sycp3与人类基因组氨基酸水平的同源性，分离出人类SYCP3。用人cDNAPCR方法分析SYCP3的组织特异性表达。对19例无精子症成熟停滞患者和75例正常生育男性的DNA样本进行了SYCP3基因序列分析。通过对野生型和截短型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。FINDINGS：我们在两名患者中发现了1个碱基缺失(643delA)，导致SYCP3蛋白的C末端卷曲形成区过早停止密码子和截断。突变蛋白在体外与野生型蛋白的相互作用大大减少，并干扰培养细胞中SYCP3纤维的形成。干预：我们认为SYCP3在人类精子发生中具有重要的减数分裂功能，该功能被突变蛋白通过显性负干扰而破坏。

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.