Molecular Mechanism of Late Onset Type of Ornithine Transcarbamylase Deficiency in Males

男性迟发型鸟氨酸转氨甲酰酶缺乏症的分子机制

• 批准号: 06670843
• 负责人: YOSHINO Makoto
• 金额: $ 1.09万
• 依托单位: Kurume University School of Medicine
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (C)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06670843/
• 关键词: Ornithine transcarbamylase; Hyperammonemia; Late onset; Male; Mutation; Ornithine transcarbamylase gene; 変異遺伝子; 発現; 遅発; 分子機構

Mutation analysis of ornithine transcarbamylase (OTC) gene in adolescent and adult male patients with OTC deficiency revealed a mutation that changes arginine at codon 40 to histidine (R40H) in 6 patients from 5 families and another one converting tyrosine at codon 55 to aspartate (Y55D) in one patient. Expression experiment using Cos-1 cells revealed that the R40H and Y55D mRNA levels were similar to that of wild-type OTCmRNA,so was OTC mRNA in liver tissue of one R40H patient, indicating that at least R40H OTC is normally spliced and as stable as wild-type mRNA.The activities of R40H and Y55D OTC's in the transfected Cos-1 cells were, however, reduced to 28% of that of wild-type OTC and the amounts of cross reactive material were reduced in both mutant OTC's. The activity of R40H OTC lecreased to 5.5% of the wild-type OTC when it was treated by five cycles of freezing and thawing, indicating instability of the mutant OTC protein. In contrast, Y55D OTC did not decrease after the treatment. Apparent Km values and pH-activity profile were studied in liver tissue of one R40H patient. These were comparable to those of normal enzyme. These results suggest that the mechanism (s) of enzyme deficiency in R40H mutation involve accelerated degradation due to instability of the mutant OTC,inadequate mitochondrial localization of the preOTC or both. The mechanism of deficiency of Y55D OTC remains to be elucidated. In one family, transmission of R40H gene from a father to a daughter was documented. This paternal transmission of R40HOTC gene may render it to be retained in general population more frequently than those associated with early onset disease which are exclusively transmitted throught maternal lineage.

对青少年和成年男性OTC缺乏症患者的鸟氨酸转氨基甲酰基酶（OTC）基因进行突变分析，发现来自5个家族的6例患者密码子40处精氨酸转化为组氨酸（R40H）， 1例患者密码子55处酪氨酸转化为天冬氨酸（Y55D）。cox -1细胞表达实验显示，R40H和Y55D mRNA水平与野生型OTCmRNA相似，1例R40H患者肝组织中OTCmRNA水平与野生型OTCmRNA相似，说明至少R40H OTC正常剪接，且与野生型mRNA一样稳定。然而，在转染的Cos-1细胞中，R40H和Y55D OTC的活性降低到野生型OTC的28%，两种突变型OTC的交叉反应物质数量均减少。经5次冻融循环处理后，R40H OTC的活性下降到野生型OTC的5.5%，表明突变体OTC蛋白具有不稳定性。而Y55D OTC治疗后无明显下降。研究了1例R40H患者肝组织的表观Km值和ph活性谱。这些与正常酶相当。这些结果表明，R40H突变中酶缺乏的机制包括由于突变体OTC的不稳定性、OTC前的线粒体定位不足或两者兼而有之而加速降解。Y55D OTC缺乏症的机制尚不清楚。在一个家庭中，R40H基因从父亲传给女儿被记录下来。R40HOTC基因的父系遗传可能使其在一般人群中比那些仅通过母系传播的早发性疾病更频繁地保留。

项目成果

Nishiyori,A.: "The R40H Mutation in a Late Onset Type of humna Ornithine Transcarbamylase Deficiency" American Journal of Human Genetics. submitted.

Nishiyori,A.：“晚发型人类鸟氨酸转氨甲酰酶缺乏症中的 R40H 突变”美国人类遗传学杂志。

Nishiyori, A., et al.: "The Y55D mutation in ornithine transcarbamylase associated with late-onset hyperammonemia in a male" Hum Mutation. (submitted).

Nishiyori, A. 等人：“鸟氨酸转氨甲酰酶中的 Y55D 突变与男性迟发性高氨血症相关”Hum 突变。

西依 淳: "男子遅発型オルニチントランスカルバミラーゼ欠損症患者にみられた変異遺伝子の発現" 日本小児科学会雑誌. 99. 290 (1995)

Jun Nishii：“在迟发性鸟氨酸转氨甲酰酶缺乏症的男性患者中观察到的突变基因的表达”日本儿科学会杂志 99. 290 (1995)。

Nishiyori, A.et al.: "Expression and characterization of mutant OTC genes associated with late onset OTC deficiency in male patients" J Jpn Pediatr Soc.99 (1). 290 (1995)

Nishiyori, A.等人：“与男性患者晚发 OTC 缺乏相关的突变 OTC 基因的表达和特征”J Jpn Pediatr Soc.99 (1)。

西依 淳: "遅発型男子オルニチントランスカルバミラーゼ欠損症患者にみられた変異遺伝子の発現" 日本先天代謝異常学会雑誌. 10. 60 (1994)

Jun Nishii：“在晚发型男性鸟氨酸转氨甲酰酶缺乏症患者中观察到的突变基因的表达”，日本遗传代谢紊乱学会杂志，10. 60 (1994)。