Alpha-1-antitrypsin is a plasma protease inhibitor that accounts for 90% of the total anti-protease activity in blood. Although synthesized mainly in the liver, its physiological function is to diffuse into the lung and protect this important organ from destruction by excessive polymorphonuclear leukocyte elastase. Genetic deficiency of alpha 1-antitrypsin predisposes affected individuals to develop chronic obstructive pulmonary emphysema. The deficiency is inherited as an autosomal recessive trait, and has a prevalence of about 1 in 3,000-4,000 among Caucasians of Northern European Ancestry. There is no cure for the genetic disorder at the present time. The protein in deficient individuals has a lysine instead of a glutamate at residue 342 in the carboxyl region. Having cloned and analyzed the human alpha 1-antitrypsin cDNA and its corresponding gene, we demonstrated that the amino acid substitution is caused by a G to A transition at the corresponding position in the gene. Specific oligonucleotides were then designed and used to determine the genotypes of random individuals and in several instances the gene mapping methodology has been applied for prenatal diagnosis of the genetic disorder. More recently, we have introduced the human chromosomal alpha 1-antitrysin gene into the germ line of mice and created transgenic animals. High levels of the human protein was present in the plasma of these mice and it was demonstrated that the human gene was expressed primarily in the mouse liver as it is in man. The cis-acting element in the gene responsible for its tissue-specificity as well as high level expression in the liver has subsequently been refined to a 700 bp DNA segment immediately flanking the 5' end of the gene. Within this region, there is apparently an enhancer plus a tissue-specific promoter element. This DNA segment is not only able to drive the transcription of a reporter gene in cultured hepatoma cells, but also in the livers of transgenic mice. The current proposal primarily deals with the engineering of the human alpha 1-antitrypsin cDNA and its cis- acting control elements into recombinant retroviruses for efficient transfer into cultured hepatoma cells, primary hepatocytes and whole laboratory animals as model for exploiting the potential of somatic gene therapy for the deficiency syndrome.
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