Transgenic Mice Expressing hnRNP B0 bound to Single-Stranded Telomere DNA

核内不均一核糖核蛋白（hnRNP）B 0是核内RNA结合蛋白hnRNP A2/B1的睾丸特异性剪接异构体。体外分析表明，B 0与端粒DNA单链结合，与端粒的维持和功能有关。为了阐明B 0在体内的作用，我们利用发育工程的方法对B 0进行了进一步的研究：1）将人hnRNP B 0的编码序列导入到pEF-BOS（translation elongation factor promoter）表达载体中; 2）将pEF-BOS-B 0构建体显微注射到BDF 1小鼠的受精卵中，并按照前面所述的方法制备转基因小鼠。结果，获得了7只携带B 0转基因的独立建立者小鼠（B 0-TG小鼠）。3）对携带B_0基因的257号建群鼠进行系统分析，发现B_0基因在建群鼠体内的表达量明显降低，而B_0基因在建群鼠体内的表达量明显降低，其中3只建群鼠的出生率明显降低， ...更多信息 B 0-TG小鼠的死亡不是由发育异常引起的，而是由雄性小鼠生育能力差引起的。在B 0纯合子雄性小鼠中，B 0蛋白表达水平增加，精子发生在减数分裂后的单倍型圆形精子细胞阶段停止，圆形精子细胞进入凋亡。阐明了在减数分裂前期的粗线期染色体发生同源重组时，分子水平的异常已经被观察到。然而，端粒长度并没有像最初预期的那样发生明显的变化，个体寿命的变化目前也不清楚。除睾丸外，其他器官均无形态学变化。综上所述，利用发育工程学的研究阐明了B 0蛋白仅在睾丸中具有体内作用，并抑制精子发生的成熟。目前，对端粒在减数分裂中的作用的研究已进入分子水平。B 0-Tg小鼠似乎提供了作为雄性不育模型动物的重要信息。少

Heterogeneous nuclear ribonucleoprotein (hnRNP) B0 is a testis-specific splicing isoform of hnRNP A2/B1 which is a kind of nuclear RNA binding proteins. The in vitro analysis demonstrated that B0 specifically binds to single-stranded telomere DNA and has a relation to the maintenance and function of telomere. For purpose of clarifying in vivo role of B0, we further studied about B0 using a developmental engineering.1) The coding sequence of human hnRNP B0 was introduced in the pEF-BOS (translation elongation factor promoter) expression vector.2) pEF-BOS-B0 construct was microinjected in fertilized eggs obtained from BDF1 mice and transgenic mice were generated as previously described. As the result, seven independent founder mice carrying B0 transgene (B0-TG mice) were obtained. Four stably expressed B0 transgene in whole body, and three of them showed decreased birthrate.3) Systematical analysis of #257 founder which carrying a single copy of B0 revealed that the decreased birth rate … More of B0-TG mice was not caused by the developmental anomalies but was caused by the poor fertility of male mice. In B0-homozygote male mice, which expressed increased level of B0 protein, the spermatogenesis stops in the stage of the haploidic round spermatid after the meiosis, and the round spermatids fall into apoptosis. It was clarified that the abnormality of molecular level is already seen at the Pachyten stage of the meiosis prophase in which the homologous recombination of the chromosome occur. However, the telomere length did not apparently change as it anticipates at the beginning, and change in the individual lifespan are not clear at present, either. There was no morphological change in the organs except for the testis.In summary, it was clarified by the study using developmental engineering that B0 protein has in vivo role only in the testis and suppresses the maturation of spermatogenesis. At present, the further analysis of molecular level is advanced, including and it the telomere function in meiosis. The B0-Tg mice seem to give important information as a model animal of male infertility. Less