Molecular Mechanism of Localization of the Mutant Ornithine Transcarbamylase to Mitochondrial Compartment

1)野生型和突变型鸟氨酸转氨酶(OTC)向线粒体转运的研究从野生型和突变型OTC基因中提取OTC信使RNA。用S35进行体外翻译，并将标记的OTC加入分离的大鼠肝线粒体。孵育后，将标记掺入Sephadex柱上分离的不同分子大小的蛋白质组分中。就洗脱体积和蛋白质组分中的放射性而言，标记的加入是不能重复性的，因此有必要进一步改进实验条件。2)对有OTC缺乏症风险的新生儿进行产前监测。在一名死于高氨血症危象的男性新生儿中发现了OTC基因I261T突变。在连续怀孕期间进行了产前诊断，结果显示胎儿是女性，并且没有携带突变的等位基因。家系中的基因追踪显示，该突变是新近发生在母亲身上的。3)男性迟发性OTC缺乏症患者的预后因素分析。为探讨影响患者生存预后的因素，对10例男性患者进行了回顾性分析，均未发现OTC基因R40H突变和Y55D突变。首次比较两组共32个因素，进一步进行简单回归分析，发现发病年龄、血氨峰值、血浆8种氨基酸浓度是有意义的预测因素。

1) Research on the transport of wild-type and mutant ornithine transcarbamylase (OTC) into mitochondrial compartmentOTC messenger RNA was isolated from cells transfected with either the wild-type or the R40H OTC cDNA. The mRNA was in vitro-translated with S35, and the labeled OTC was added to isolated rat liver mitochondria. After incubation, incorporation of the label into the protein fractions of various molecular sizes separated on a sephadex column were measured. The incorporation of the label was not reproducible in terms of elution volume and radioactivity in the protein fraction, and further refinements of the experimental conditions were necessary.2) Prenatal monitoring of a pregnancy at risk for OTC deficiency with neonatal onsetThe I261T mutation in the OTC gene was identified in a male neonate who died from hyperammonemic crisis. prenatal diagnosis was done in the successive pregnancy, which revealed that the fetus was female, and that it did not carry the mutant allele. Gene tracking in the family revealed that the mutation was freshly occurred in the mother.3) Analysis of prognostic factors in male patients with late-onset OTC deficiencyPrognosis of life has been generally poor in male patients with the late-onset OTC to deficiency. To elucidate factors that are concerned with prognosis of life, retrospective analysis was done in ten male patients with the disease, none of whom carried the R40H mutation and the other, the Y55D mutation in the OTC gene. A total of 32 factors were first compared in the two groups were further subjected to simple regression analysis, which revealed that age at onset, peak plasma ammonia concentration, concentrations in plasma of eight amino acids were determined to be significant predictors.