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

尿素循环酶之一精氨酸琥珀酸合成酶（ASS）缺乏可引起瓜氨酸血症。通过对70多例瓜氨酸血症患者肝、肾及培养皮肤成纤维细胞酶异常的分析。我们将瓜氨酸血症分为三种不同的类型。在I型中，酶活性低主要是由于动力学性质异常引起的。II型。低活性是由于具有正常动力学性质的酶蛋白减少所致。然而，II型瓜氨酸血症的低酶活性仅见于肝脏，而不见于肾脏或培养的皮肤成纤维细胞。另一方面，在III型瓜氨酸血症的所有器官或细胞中均未发现可检测到的酶活性。在目前的研究中。我们分析了II型和III型瓜氨酸血症中mRNA的异常。在两个III型病例中。肝脏中发现低水平的ASS mRNA， 1例肝脏中检测到正常的ASS mRNA含量。进一步分析表明，该mRNA在3′端编码区存在约100个碱基缺陷。结合CRM分析，患者基因组DNA异常可能是外显子-内含子连接处的点突变，导致mRNA剪接异常。与此相反，ⅱ型瓜氨酸血症在肝脏含量、大小和结构等方面均未见异常。结果表明，II型瓜氨酸血症的发病机制是抑制了ASS的翻译或增强了ASS的降解。我们利用ASS mRNA的sense Riboprobe检测II型瓜氨酸血症肝脏中的反义RNA，来验证反义RNA可能参与了假设的ASS抑制翻译的机制。根据我们的测试。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。进一步的研究将需要澄清II型瓜氨酸血症的发病机制。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