Savitt Joseph M, Jang Susie S, Mu Weitong, Dawson Valina L, Dawson Ted M
Institute for Cell Engineering, Division of Gastroenterology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Neurosci. 2005 Jul 20;25(29):6721-8. doi: 10.1523/JNEUROSCI.0760-05.2005.
Recent findings have uncovered a role for the Bcl-x gene in the survival of dopaminergic neurons. The exact nature of this role has been difficult to examine because of the embryonic lethality of Bcl-x gene disruption in mouse models. Here we report the generation catecholaminergic cell-specific conditional Bcl-x gene knock-out mice using Cre-lox recombination technology. First we produced transgenic mice that express Cre recombinase from an exogenous rat tyrosine hydroxylase promoter (TH-Cre mice). These mice were crossed to Z/AP and Z/EG reporter mouse strains to verify catecholaminergic (TH-positive) cell-specific Cre expression. The TH-Cre mice then were mated to mice possessing the Bcl-x gene flanked by loxP sites, thereby producing offspring with Bcl-x deletion limited to catecholaminergic cells. The resulting mice are viable but have one-third fewer catecholaminergic neurons than do control animals. They demonstrate a deficiency in striatal dopamine and also tend to be smaller and have decreased brain mass when compared with controls. Surprisingly, surviving neurons were found that lacked Bcl-x immunoreactivity, thereby demonstrating that this gene is dispensable for the ongoing survival of a subpopulation of catecholaminergic cells.
最近的研究发现揭示了Bcl-x基因在多巴胺能神经元存活中的作用。由于小鼠模型中Bcl-x基因破坏会导致胚胎致死,因此难以研究该作用的确切性质。在此,我们报告利用Cre-lox重组技术生成了儿茶酚胺能细胞特异性条件性Bcl-x基因敲除小鼠。首先,我们构建了从外源性大鼠酪氨酸羟化酶启动子表达Cre重组酶的转基因小鼠(TH-Cre小鼠)。将这些小鼠与Z/AP和Z/EG报告基因小鼠品系杂交,以验证儿茶酚胺能(TH阳性)细胞特异性Cre表达。然后将TH-Cre小鼠与loxP位点侧翼的Bcl-x基因小鼠交配,从而产生Bcl-x缺失仅限于儿茶酚胺能细胞的后代。所得到的小鼠是存活的,但与对照动物相比,其儿茶酚胺能神经元数量减少了三分之一。它们表现出纹状体多巴胺缺乏,与对照相比,体型也往往较小,脑质量降低。令人惊讶的是,发现存活的神经元缺乏Bcl-x免疫反应性,从而表明该基因对于儿茶酚胺能细胞亚群的持续存活并非必需。