Analysis of infertility in systemic carnitine deficient mouse (JVS mouse)

我们1991年报道的幼年内脏脂肪变性(JVS)小鼠是一种原发性肉碱缺乏的动物模型。由于这只小鼠患有严重的雄性不育，我们对其原因和机制进行了分析。主要研究结果如下：1.候选基因分析作为编码钠依赖肉碱共转座子的人OCTN_2基因，我们分离了小鼠的OCTN_2基因，并在JVS小鼠中进行了突变筛选。DNA测序分析发现，在位于OCTN2第六跨膜结构域的第352位密码子上发生了从CTG(Leu)到CGG(Arg)的错义突变。这种氨基酸替换可能导致蛋白质的构象变化，从而导致基因产物的功能障碍。附睾症分析8~9周龄时，附睾体畸形，重量明显增加。组织学上，由于异常高水平的精子积聚，近端附睾管扩张。精子从附睾管渗出进入间质。相反，远端附睾管狭窄，不含精子。因此，附睾症引起梗阻性无精子症，导致不育。新的心脏保护剂3-(2，2，2-三甲基氢氧化锌)丙酸酯(THP)在小鼠和大鼠体内的作用部位。结果表明，THP的主要作用部位是肾脏的肉碱转运载体，而不是心脏的载体。

Juvenile Visceral Steatosis (JVS) mouse, which we reported in 1991, serves as an animal model of primary carnitine deficiency. Because this mouse is suffered from severe male infertility, we analyzed the cause and mechanism. The summary of the results is as follows ;1. Analysis of candidate geneAs a human OCTN2 gene encoding a sodium-dependent carnitine cotranspoter was isolated, we isolated the mouse octn2 gene and screened for its mutation in the JVS mouse. DNA sequencing analysis disclosed a missense mutation from CTG (Leu) to CGG (Arg) at codon 352 located within the sixth transmembrane domain of octn2. This amino acid replacement possibly causes the conformational change of the protein that leads to dysfunction of the gene product.2. Analysis of epididymisAt 8-9 weeks of age, the epididymis was deformed, and its weight was significantly increased. Histologically, the duct of proximal epididymis was dilated due to the accumulation of unusually high level of spermatozoa. Spermatozoa ware extravasated from the epididymal duct into the stroma. In contrast, the duct of the distal epididymis was constricted and contained no spermatozoa. Thus, the epididymal disorder causes obstructive azoospermia, leading to infertility.3. Discovery of camitine transport inhibitorThe site of action of 3-(2,2,2-trimethylhydrozinium) propionate (THP), a new cardioprotective agent, was investigated in mice and rats. As a result, it was indicated that the principal site of action of THP is the carnitine-transport carrier in kidney but not the carrier in heart.