INBORN ERRORS OF A PURINE SALVAGE PATHWAY

腺嘌呤磷酸核糖基转移酶(APRT)催化 含有5-磷酸核糖基-1-焦磷酸的腺嘌呤，可产生腺苷 单磷酸盐和焦磷酸盐。在APRT完全缺乏的情况下 在人体内，腺嘌呤被黄嘌呤氧化酶氧化形成高度的 不溶性和肾毒性的衍生物，2，8-二羟基腺嘌呤(DHA)。这个 在某些情况下，这种化合物的积累可能会导致生命- 威胁到尿石症。APRT缺陷，这是在 常染色体隐性遗传方式，是一种较为罕见的嘌呤先天错误 新陈代谢。然而，大约1%的人口是杂合子 阿普特。因此，观察到的aprt缺陷纯合子要少得多。 比杂合子的频率预测的要高。 我们建议： 1.从额外的APRT缺陷中鉴定突变的APRT等位基因 患者的DNA序列和单倍型。因此，我们将 研究生殖系细胞的分子机制(突变) 这种病。 2.鉴定体内发生的T细胞APRT体细胞突变。 因此，我们将确定T细胞是否发生突变，这是很远的 比种系突变更容易研究，可以作为模型系统使用 用于研究生殖系诱变的机制。体细胞 突变对于了解癌症也很重要。 3.根据降低的红细胞aprt水平鉴定aprt杂合子 并对它们的突变等位基因进行测序。因此，我们将确定 无论杂合子中突变等位基因的谱是否 不同于在酶缺陷纯合子中观察到的。这 分析可能会揭示这些纯合子的明显匮乏。 4.建立人APRT缺乏症转基因小鼠模型。这 这种疾病的动物模型将用于研究潜在的 一般嘌呤的生化机制及生化变化 新陈代谢。例如，核苷酸池，代谢的处置 腺嘌呤，以及对从头产生嘌呤的影响将被研究。 这些动物还将提供常染色体体细胞的模型系统 将补充人类T细胞模型的突变。

Adenine phosphoribosyltransferase (APRT) catalyzes the reaction of adenine with 5-phosphoribosyl-1-pyrophosphate that produces adenosine monophosphate and pyrophosphate. In cases of complete APRT deficiency in man, adenine is oxidized by xanthine oxidase to form the highly insoluble and nephrotoxic derivative, 2,8-dihydroxyadenine (DHA). The accumulation of this compound may, in some instances, lead to life- threatening urolithiasis. APRT deficiency, which is inherited in an autosomal recessive manner, is a relatively rare inborn error of purine metabolism. However, about 1% of the population is heterozygous at APRT. Thus, far fewer APRT-deficient homozygotes have been observed than the frequency of heterozygotes would predict. We propose to: 1. Characterize mutant APRT alleles from additional APRT-deficient patients with regard to their DNA sequence and haplotype. Thus, we will investigate germline cell molecular mechanisms (mutations) that produce this disease. 2. Characterize APRT somatic mutations arising in vivo in T cells. Thus, we will determine whether or not T cell mutation, which is far easier to study than germline mutation, can be used as a model system for investigating mechanisms of germline mutagenesis. Somatic cell mutation is also important for understanding cancer. 3. Identify APRT heterozygotes by their reduced levels of red cell APRT activity and sequence their mutant alleles. Thus, we will determine whether or not the spectrum of mutant alleles in heterozygotes is different from that observed in enzyme-deficient homozygotes. This analysis may shed light on the apparent paucity of these homozygotes. 4. Produce a transgenic mouse model for human APRT deficiency. This animal model for the disease will be used for studies of underlying biochemical mechanisms and biochemical changes in general purine metabolism. For example, nucleotide pools, the disposition of metabolic adenine, and effects on de novo purine production will be studied. These animals will also provide a model system for autosomal somatic mutation that will complement the human T cell model.