ALPHA-1-ANTITRYPSIN GENE AND PULMONARY EMPHYSEMA

α-1-抗胰蛋白酶是一种血浆蛋白水解酶抑制剂，占90% 血液中总的抗蛋白酶活性。降低血清中的 这种蛋白质在某些个体中构成一种遗传性疾病，称为 α-1-抗胰蛋白酶缺乏症，使受影响的个体容易患上 发展为慢性阻塞性肺气肿的高风险。这个 缺乏症的特征是存在变异型α-1抗胰蛋白酶 Z或S表型，而不是正常的M表型，并且是 由常染色体隐性遗传的。血清中的水平 ZZ纯合子和SZ杂合子的α-1-抗胰蛋白酶分别为12%和35% 分别是正常个体的。Z和S的频率 基因是这样的，美国1/3000到1/4000的高加索人是 ZZ表型和1/800为SZ表型。一直以来 据估计，80%-90%的ZZ纯合子会患上肺气肿 各种严重程度，目前还没有治愈这种遗传性疾病的方法 现在的时间。α-1-抗胰蛋白酶中的微妙氨基酸取代 Z和S缺乏表型与正常M表型之间存在差异 已经上报了。因为只有正常和有限的氨基酸序列 已经确定了变异蛋白质，是否有额外的氨基酸 这些蛋白质之间的酸取代作用目前尚不清楚。 时间到了。利用重组DNA技术，我们建议分离和 正常人和缺陷型人α-1抗胰蛋白酶基因的特征 通过分子克隆获得个体。两种结构的比较 克隆的基因之间的组织和核苷酸序列应该揭示 变异蛋白质中任何额外的氨基酸替换，都会 从而在基因水平上建立了该缺陷的分子基础。 这些信息将允许开发一种简单而可靠的 遗传性疾病的基因定位产前诊断方法。 及早发现患有遗传性疾病的个人将有助于更好地 对缺陷的管理，这将反过来降低其风险 在晚年患上肺气肿。最后，尝试将是 为了更好地了解缺陷的原因(S)，通过检查 缺陷基因经DNA导入后的表达 介导的基因转移人肝癌细胞系合成 并分泌正常的α-1-抗胰蛋白酶。

Alpha-1-antitrypsin is a plasma protease inhibitor that accounts for 90% of the total anti-protease activities in the blood. Reduced serum levels of this protein in certain individuals constitute a genetic disorder known as alpha-1-antitrypsin deficiency, which predisposes affected individuals to high risk of developing chronic obstructive pulmonary emphysema. The deficiency is characterized by the presence of variant alpha-1-antitrypsin of the Z or S phenotypes instead of the normal M phenotype, and is inherited by an autosomal recessive trait. Serum levels of alpha-1-antitrypsin in ZZ homozygotes and SZ heterozygotes are 12 and 35% of the normal individuals, respectively. The frequencies of the Z and S genes are such that 1/3000 to 1/4000 of caucasians in the United States are of the ZZ phenotype and 1/800 are of the SZ phenotype. It has been estimated that 80-90% of ZZ homozygotes will develop pulmonary emphysema of various severity, and there is no cure for this genetic disorder at the present time. Subtle amino acid substitutions in alpha-1-antitrypsin between the Z and S deficient phenotypes and the normal M phenotype have been reported. Since only limited amino acid sequence of the normal and variant proteins have been determined, whether there are additional amino acid substitutions between these proteins are not known at the present time. Using Recombinant DNA Technology, we propose to isolate and characterize the human Alpha-1-antitrypsin gene from normal and deficient individuals by molecular cloning. Comparison of the structural organization and nucleotide sequence between the cloned genes should reveal any additional amino acid substitutions in the variant proteins and would thereby establish the molecular basis of the deficiency at the gene level. This information will then permit the development of a simple and reliable method for prenatal diagnosis of the genetic disorder by gene mapping. Early detection of individuals with the genetic disorder will permit better management of the deficiency, which will in turn reduce the risk of their developing pulmonary emphysema later in life. Finally, attempts will be made to better understand the cause(s) of the deficiency by examining the expression of the deficient genes after their introduction through DNA mediated gene transfer into a human hepatoma cell line which synthesizes and secretes normal Alpha-1-antitrypsin.