Hayashi Yoshitaka, Yamamoto Michiyo, Mizoguchi Hiroyuki, Watanabe Chika, Ito Ryoichi, Yamamoto Shiori, Sun Xiao-yang, Murata Yoshiharu
Department of Genetics, Research Institute of Environmental Medicine, Nagoya University, Japan.
Mol Endocrinol. 2009 Dec;23(12):1990-9. doi: 10.1210/me.2009-0296. Epub 2009 Oct 9.
Multiple bioactive peptides, including glucagon, glucagon-like peptide-1 (GLP-1), and GLP-2, are derived from the glucagon gene (Gcg). In the present study, we disrupted Gcg by introduction of GFP cDNA and established a knock-in mouse line. Gcg(gfp/gfp) mice that lack most, if not all, of Gcg-derived peptides were born in an expected Mendelian ratio without gross abnormalities. Gcg(gfp/gfp) mice showed lower blood glucose levels at 2 wk of age, but those in adult Gcg(gfp/gfp) mice were not significantly different from those in Gcg(+/+) and Gcg(gfp/+) mice, even after starvation for 16 h. Serum insulin levels in Gcg(gfp/gfp) mice were lower than in Gcg(+/+) and Gcg(gfp/+) on ad libitum feeding, but no significant differences were observed on starvation. Islet alpha-cells and intestinal L-cells were readily visualized in Gcg(gfp/gfp) and Gcg(gfp/+) mice under fluorescence. The Gcg(gfp/gfp) postnatally developed hyperplasia of islet alpha-cells, whereas the population of intestinal L-cells was not increased. In the Gcg(gfp/gfp), expression of Aristaless-related homeobox (Arx) was markedly increased in pancreas but not in intestine and suggested involvement of Arx in differential regulation of proliferation of Gcg-expressing cells. These results illustrated that Gcg-derived peptides are dispensable for survival and maintaining normoglycemia in adult mice and that Gcg-derived peptides differentially regulate proliferation/differentiation of alpha-cells and L-cells. The present model is useful for analyzing glucose/energy metabolism in the absence of Gcg-derived peptides. It is useful also for analysis of the development, differentiation, and function of Gcg-expressing cells, because such cells are readily visualized by fluorescence in this model.
包括胰高血糖素、胰高血糖素样肽-1（GLP-1）和GLP-2在内的多种生物活性肽均源自胰高血糖素基因（Gcg）。在本研究中，我们通过导入绿色荧光蛋白（GFP）互补DNA（cDNA）破坏了Gcg基因，并建立了一个基因敲入小鼠品系。缺乏大部分（如果不是全部）Gcg衍生肽的Gcg(gfp/gfp)小鼠以预期的孟德尔比例出生，且无明显异常。Gcg(gfp/gfp)小鼠在2周龄时血糖水平较低，但成年Gcg(gfp/gfp)小鼠的血糖水平与Gcg(+/+)和Gcg(gfp/+)小鼠相比无显著差异，即使在饥饿16小时后也是如此。自由采食时，Gcg(gfp/gfp)小鼠的血清胰岛素水平低于Gcg(+/+)和Gcg(gfp/+)小鼠，但饥饿时未观察到显著差异。在荧光下，Gcg(gfp/gfp)和Gcg(gfp/+)小鼠的胰岛α细胞和肠道L细胞易于观察。Gcg(gfp/gfp)小鼠出生后胰岛α细胞发生增生，而肠道L细胞数量未增加。在Gcg(gfp/gfp)小鼠中，无尾相关同源框（Arx）在胰腺中的表达明显增加，但在肠道中未增加，提示Arx参与了Gcg表达细胞增殖的差异调节。这些结果表明，Gcg衍生肽对于成年小鼠的生存和维持正常血糖并非必需，且Gcg衍生肽对α细胞和L细胞的增殖/分化具有差异调节作用。本模型有助于分析在缺乏Gcg衍生肽情况下的葡萄糖/能量代谢。它也有助于分析Gcg表达细胞的发育、分化和功能，因为在该模型中此类细胞可通过荧光轻易观察到。
