Distribution and regional expression of citrin in human tissues, genetic abnormality and possible role in clinical features of type II citrullinemia

II型瓜氨酸血症（CTLN 2）是一种常染色体隐性遗传疾病，其特征是由于与高氨血症和严重脑水肿相关的脑病导致的成人发作的复发性意识障碍和/或行为异常。CTLN 2患者的组织学研究显示严重的肝脏特异性乙酰氨基琥珀酸合成酶（ASS）缺乏，这与肝细胞胞浆中的氨代谢有关。未发现ASS基因突变或mRNA表达异常。SLC 25 A13基因的突变已被确定为CTLN 2的遗传原因。SLC 25 A13基因编码一种线粒体溶质载体蛋白citrin。近年来研究发现SLC 25 A13基因突变也可引起新生儿特发性肝炎（idiopathic neonatal hepatitis，NICCD）。目的：研究Citrin蛋白及其mRNA在人体多器官中的分布和区域表达。方法：对5例因各种疾病死亡的病人的心、肾、肝、胰、骨骼肌、肺、脑等器官进行了检查，并对5例病人的心脏、肾、肝、胰、骨骼肌、肺、脑等器官进行了解剖学观察。 ...更多信息 用抗柠檬酸蛋白多克隆抗体免疫组化和原位杂交方法，对各部位的分布进行了详细的观察。我们还在人对照器官中进行了蛋白质印迹。研究结果：在Western blotting上，柠檬酸蛋白抗体仅检测到一条74 kDa的条带，主要在肝脏和肾脏中，在胰腺和脑中中等，在肺中轻微，但在心脏和骨骼肌中未检测到。免疫组化显示Citrin抗体在肝组织的肝细胞、近端和远端小管上皮细胞、肾组织的足细胞中呈强阳性染色，在胰腺组织的中央腺泡细胞、脑组织的星形胶质细胞和肺组织的肺细胞中呈中度阳性染色。原位杂交组化结果显示，柠檬苦素mRNA在组织中的分布与免疫组化结果基本一致。结论：Citrin蛋白和mRNA在几个器官中的分布是有限的。Citrin在肝细胞中大量表达，表明该分子的功能障碍可能导致高氨性脑病和脂肪肝。本研究还提示星形胶质细胞和中央腺泡细胞Citrin功能障碍可能是CTLN 2脑病和慢性胰腺炎的促进因子。少

Type II citrullinemia (CTLN2) is autosomal recessive disorder, characterized by adult-onset recurrent consciousness disturbance and/or abnormal behavior due to encephalopathy associated with hyperammonemia and severe brain edema. Histopathological study of CTLN2 patients shows severe liver-specific deficiency of argininosuccinate synthetase (ASS), which relates to ammonia metabolism in cytosole of hepatocytes. No mutations or abnormal mRNA expression in ASS gene have been found in this disorder. Mutations in SLC25A13 gene have been identified as genetic cause of the CTLN2. SLC25A13 gene encodes a mitochondrial solute carrier protein named citrin. Recent study showed that mutation of SLC25A13 also cause idiopathic neonatal hepatitis (NICCD). OBJECTIVE: To examine distribution and regional expression of citrin protein and mRNA in multiple human organs. METHODS: The hearts, kidneys, livers, pancreas, skeletal muscles, lungs and brains from 5 patients died with various diseases were examin … More ed. Detailed regional distributions were determined by immunohistochemistry with using polyclonal antibody to citrin and in situ hybridization. We also conducted western blotting in human control organs. RESULTS: On western blotting, only one band of 74 kDa was detected by the antibody to citrin predominantly in liver and kidney, moderately in pancreas and brain, slightly in lung, but not in heart and skeletal muscle. Immunohistochemistry using the antibody to citrin showed positive staining strongly in hepatocytes of liver tissues, epithelial cells of proximal and distal tubules, and podocyte in kidney tissues, moderately in centroacinar cells of pancreas tissues, astrocytes in brain tissues, and pneumocytes in lung tissues. In situ hybridization histochemistry revealed that mRNA of citrin was showed almost the same distribution in comparison with immunohistochemistry. CONCLUSIONS: Distributions of citrin protein and mRNA were limited in several organs. Citrin was greatly expressed in hepatocyte, indicating that dysfunction of this molecule might cause hyperammonic encephalopathy and fatty liver seen in this disorder. Our study also indicated that citrin dysfunction in astrocytes and centroacinar cells might plays a role of the promotion factor about encephalopathy and chronic pancreatitis in CTLN2. Less