Shirneshan Katayoon, Binder Stefan, Böhm Detlef, Wolf Stephan, Sancken Ulrich, Meinhardt Andreas, Schmid Michael, Engel Wolfgang, Adham Ibrahim M
Institute of Human Genetics, University of Göttingen, Heinrich-Düker-Weg 12, D-37073 Göttingen, Germany.
Mol Cell Endocrinol. 2008 Nov 25;295(1-2):79-86. doi: 10.1016/j.mce.2008.07.007. Epub 2008 Jul 23.
The primary goal of this study was to determine the 5'region of the Insl3 gene that specifically targets the expression of human insulin to Leydig cells, and to explore whether the testicular proinsulin is efficiently processed to insulin that is able to rescue the diabetes in different mouse models of diabetes. We show here that the sequence between nucleotides -690 and +4 of mouse Insl3 promoter is sufficient to direct the Leydig cell-specific expression of the human insulin transgene (Insl3-hIns). We also found that the 3'untranslated region (3'UTR) of Insl3 was effective in enhancing transgene expression of the insulin in vivo. Expression analysis revealed that the temporal expression pattern of the hIns transgene in Leydig cells of transgenic testes is roughly the same as that of the endogenous Insl3. Despite the Leydig cells translate human proinsulin and secrete a significant level of free C-peptide into the serum, the Leydig cell-derived insulin is not able to overcome the diabetes in different mouse models of diabetes, suggesting a lack of glucose sensing mechanisms in the Leydig cells. A consequence of overexpression of the human proinsulin in Leydig cells was the decrease of fertility of transgenic males at older ages. Germ cells in transgenic males were able to initiate and complete spermatogenesis. However, there was a progressive and age-dependent degeneration of the germ cells that lead to male infertility with increasing age.
本研究的主要目标是确定胰岛素样肽3（Insl3）基因的5'区域，该区域可特异性地将人胰岛素表达靶向至睾丸间质细胞，并探究睾丸中的胰岛素原是否能有效加工成胰岛素，从而在不同的糖尿病小鼠模型中挽救糖尿病。我们在此表明，小鼠Insl3启动子核苷酸-690至+4之间的序列足以指导人胰岛素转基因（Insl3-hIns）在睾丸间质细胞中的特异性表达。我们还发现，Insl3的3'非翻译区（3'UTR）在增强体内胰岛素转基因表达方面有效。表达分析显示，转基因睾丸的睾丸间质细胞中hIns转基因的时间表达模式与内源性Insl3大致相同。尽管睾丸间质细胞能翻译人胰岛素原并向血清中分泌大量游离C肽，但睾丸间质细胞来源的胰岛素无法在不同的糖尿病小鼠模型中克服糖尿病，这表明睾丸间质细胞缺乏葡萄糖感应机制。睾丸间质细胞中人胰岛素原过表达的一个后果是转基因雄性小鼠在老年时生育能力下降。转基因雄性小鼠的生殖细胞能够启动并完成精子发生。然而，生殖细胞会随着年龄增长逐渐发生退化，导致雄性不育。
