Citrin/Mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice recapitulate features of human citrin deficiency
Citrin/Mitochondrial glycerol-3-phosphate dehydrogenase double knock-out mice recapitulate features of human citrin deficiency
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DOI：
10.1074/jbc.m702031200
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发表时间：
2007-08-24
影响因子：
4.8
通讯作者：
Kobayashi, Tsuyoshi
中科院分区：
文献类型：
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作者：
Saheki, Takeyori;Iijima, Mikio;Kobayashi, Tsuyoshi
Citrin 是肝型线粒体天冬氨酸-谷氨酸载体，通过将天冬氨酸从线粒体供应到胞质溶胶来参与尿素、蛋白质和核苷酸生物合成途径。 Citrin 还作为苹果酸-天冬氨酸穿梭的一个组成部分，在将胞质 NADH 还原当量转运到线粒体中发挥作用。在人类中，编码柠檬酸的 SLC25A13 基因的功能丧失突变会导致成人发病的 II 型瓜氨酸血症和新生儿肝内胆汁淤积，统称为人类柠檬酸缺乏症。 Citrin 基因敲除小鼠无法表现出人类 Citrin 缺乏症的特征。基于增强的磷酸甘油穿梭活性可能补偿小鼠柠檬酸功能丧失的假设，我们培育了柠檬酸和线粒体甘油3-磷酸脱氢酶基因联合破坏的小鼠。由此产生的双基因敲除小鼠表现出瓜氨酸血症、高氨血症（口服蔗糖后进一步升高）、低血糖和脂肪肝，这些都是人类瓜氨酸缺乏症的特征。与对照组相比，双基因敲除小鼠的肝脏乳酸/丙酮酸比率增加，口服蔗糖也进一步升高，这表明细胞质 NADH/NAD(+) 比率的改变与观察到的高氨血症密切相关。微阵列分析鉴定出超过 100 个基因，这些基因在双敲除小鼠中与野生型对照相比有差异表达，揭示了可能参与组合突变的补偿或下游效应的基因。总之，我们的数据表明，柠檬酸/线粒体甘油-3-磷酸脱氢酶双敲除小鼠中存在的更严重的表型代表了比柠檬酸敲除小鼠更准确的人类柠檬酸缺乏模型。
Citrin is the liver-type mitochondrial aspartate-glutamate carrier that participates in urea, protein, and nucleotide biosynthetic pathways by supplying aspartate from mitochondria to the cytosol. Citrin also plays a role in transporting cytosolic NADH reducing equivalents into mitochondria as a component of the malate-aspartate shuttle. In humans, loss-of-function mutations in the SLC25A13 gene encoding citrin cause both adult-onset type II citrullinemia and neonatal intrahepatic cholestasis, collectively referred to as human citrin deficiency. Citrin knock-out mice fail to display features of human citrin deficiency. Based on the hypothesis that an enhanced glycerol phosphate shuttle activity may be compensating for the loss of citrin function in the mouse, we have generated mice with a combined disruption of the genes for citrin and mitochondrial glycerol 3-phosphate dehydrogenase. The resulting double knock- out mice demonstrated citrullinemia, hyperammonemia that was further elevated by oral sucrose administration, hypoglycemia, and a fatty liver, all features of human citrin deficiency. An increased hepatic lactate/ pyruvate ratio in the double knock- out mice compared with controls was also further elevated by the oral sucrose administration, suggesting that an altered cytosolic NADH/NAD(+) ratio is closely associated with the hyperammonemia observed. Microarray analyses identified over 100 genes that were differentially expressed in the double knock- out mice compared with wild- type controls, revealing genes potentially involved in compensatory or downstream effects of the combined mutations. Together, our data indicate that the more severe phenotype present in the citrin/ mitochondrial glycerol-3-phosphate dehydrogenase double knock- out mice represents a more accurate model of human citrin deficiency than citrin knock- out mice.