Mirza Momina, Petersen Cecilia, Nordqvist Katarina, Sollerbrant Kerstin
Ludwig Institute for Cancer Research, Stockholm Branch, Karolinska Institutet, Box 240, SE-17177, Stockholm, Sweden.
Endocrinology. 2007 Nov;148(11):5459-69. doi: 10.1210/en.2007-0359. Epub 2007 Aug 9.
The coxsackievirus and adenovirus receptor (CAR) is a cell adhesion molecule expressed in epithelial tight junctions and other cell-cell contacts. Using indirect immunofluorescence, quantitative RT-PCR, and Western blots, the expression and distribution of CAR in developing and adult testis are examined. CAR is highly expressed in both Sertoli and germ cells during perinatal and postnatal development, followed by a rapid down-regulation of both mRNA and protein levels. Interestingly, we find that CAR is a previously unknown downstream target for FSH because CAR mRNA levels were induced in primary cultures of FSH-stimulated Sertoli cells. In contrast to other epithelia, CAR is not a general component of tight junctions in the seminiferous epithelium, and Sertoli cells in the adult testis do not express CAR. Instead, CAR expression is stage dependent and specifically found in migratory germ cells. RT-PCR also demonstrated the presence of junctional adhesion molecule-like (JAML) in the testis. JAML was previously reported by others to form a functional complex with CAR regulating transepithelial migration of leukocytes. The expression of JAML in the testis suggests that a similar functional complex might be present during germ cell migration across the blood-testis barrier. Finally, an intermediate compartment occupied by CAR-positive, migrating germ cells and flanked by two occludin-containing junctions is identified. Together, these results implicate a function for CAR in testis morphogenesis and in migration of germ cells across the blood-testis barrier during spermatogenesis.
柯萨奇病毒和腺病毒受体（CAR）是一种在上皮紧密连接和其他细胞间接触部位表达的细胞粘附分子。利用间接免疫荧光、定量逆转录聚合酶链反应（RT-PCR）和蛋白质免疫印迹法，研究了CAR在发育中和成年睾丸中的表达及分布情况。在围产期和出生后发育阶段，CAR在支持细胞和生殖细胞中均高表达，随后mRNA和蛋白质水平迅速下调。有趣的是，我们发现CAR是促卵泡激素（FSH）一个此前未知的下游靶点，因为在FSH刺激的支持细胞原代培养物中，CAR mRNA水平被诱导升高。与其他上皮组织不同，CAR并非生精上皮紧密连接的常见组成成分，成年睾丸中的支持细胞不表达CAR。相反，CAR的表达具有阶段依赖性，且特异性地存在于迁移中的生殖细胞中。RT-PCR还证实睾丸中存在连接粘附分子样蛋白（JAML）。此前有其他人报道JAML可与CAR形成功能复合物，调节白细胞的跨上皮迁移。JAML在睾丸中的表达提示，在生殖细胞跨越血睾屏障迁移过程中可能存在类似的功能复合物。最后，鉴定出一个由CAR阳性的迁移生殖细胞占据的中间区室，其两侧为两个含闭合蛋白的连接结构。总之，这些结果表明CAR在睾丸形态发生以及精子发生过程中生殖细胞跨越血睾屏障的迁移中发挥作用。
