Possible involvement of antisense RNA in pathogenesis of type II citrullinemia.

精氨酸琥珀酸合成酶(ASS)是尿素循环中的一种酶，精氨酸琥珀酸合成酶(ASS)缺乏引起瓜氨酸血症。通过对70余例瓜氨酸血症患者肝、肾及培养的皮肤成纤维细胞中异常酶的分析。我们将瓜氨酸血症分为三种不同的类型。在类型I中，酶活性低的主要原因是动力学性质的异常。在类型II中，低活性是由于具有正常动力学性质的酶蛋白的减少。然而，II型瓜氨酸血症的低酶活性仅见于肝脏，而不是肾脏或培养的皮肤成纤维细胞。另一方面，在III型瓜氨酸血症测试的所有器官或细胞中都没有发现可检测到的酶活性。我们分析了II型和III型瓜氨酸血症患者的mRNA异常。2例III型肝组织ASS基因表达水平较低，1例肝组织ASS基因表达正常。在后一种情况下，…进一步分析表明，该基因在3‘端附近的编码区有约100个碱基的缺陷。结合CRM分析，患者基因组DNA的异常可能是外显子-内含子连接处的点突变，导致了mRNA的异常剪接。相反，通过SL核酸酶分析，II型瓜氨酸血症患者的肝脏ASS mRNA在肝脏内容物、大小和结构方面没有异常。结果提示，II型的发病机制是ASS的翻译抑制或降解增强。用ASS mRNA正义核探针检测II型瓜氨酸血症大鼠肝脏中反义RNA的表达，探讨反义RNA在ASS翻译抑制机制中的作用。就我们测试的情况而言。我们没有发现任何证据表明在对照组和II型瓜氨酸血症患者的肝脏中存在反义RNA。需要进一步的研究来阐明II型瓜氨酸血症的发病机制。较少

Deficiency of argininosuccinate synthetase (ASS), one of the urea cycle enzymes, causes citrullinemia. From the analysis of the abnormal enzymes in the liver, kidney and cultured skin fibroblasts of more than 70 cases of citrullinemia. we classified the citrullinemia into three distinct types. In type I, a low activity of the enzyme is mainly caused by abnormality in kinetic properties. In type II. the low activity is from a decrease in the enzyme protein which has normal kinetic properties. The low enzyme activity in type II citrullinemia, however, is seen only in the liver, but not in the kidney or cultured skin fibroblasts. on the other hand, no detectable enzyme activity is found in all the organ or cells tested in type III citrullinemia.In the present study. we analyzed abnormality in mRNA in type II and III citrullinemia. In two cases of type III. low levels of ASS mRNA were found in the liver and in one case, a normal content of hepatic ASS mRNA was detected. In the latter case, … More further analysis showed that the mRNA has an about 100 base-defect in the coding region near 3' end. Together with analysis of CRM, the abnormality in the genomic DNA of the patient is probably a point mutation at the exon-intron junction which causes abnormal splicing of mRNA.On the contrary, there were no abnormalities in hepatic ASS mRNA of type II citrullinemia concerning hepatic content, size and structure analyzed by SL nuclease. The results suggest that the pathogenesis of type II is suppressed translation or enhanced degradation of ASS. Possible involvement of antisense RNA in the mechanism of postulated suppressed translation of ASS were tested using sense Riboprobe of ASS mRNA for detection of antisense RNA in the liver of type II citrullinemia. As far as we tested. We could not find any evidence showing the presence of antisense RNA in the liver of control and type II citrullinemic patients. Further investigations will need to clarify the pathogenesis of type II citrullinemia. Less