Gene transfer and expression of human ornithine aminotransferase

A generalized deficiency in the mitochondrial enzyme, ornithine aminotransferase (OAT), is present in the hereditary blinding disease, gyrate atrophy (GA). Because the OAT gene is a multi-gene family, and the native OAT enzyme is an oligomer, it would be important to identify the gene locus actually responsible for the OAT activity and affected in GA. A mammalian expression clone containing a previously characterized human OAT cDNA (pHOAT), corresponding to the OAT gene on chromosome 10, was prepared (pcDHOAT), transfected, and tested for expression in NIH3T3 cells and OAT(-) Chinese hamster ovary (CHO) cells. Incorporation of pcDHOAT and synthesis of human OAT mRNAs and active enzyme were demonstrated in both cell types, confirming the completeness of the coding sequence of pHOAT. The results indicated that the chromosome 10 gene corresponding to the cDNA is the functional gene fully capable of expressing the active oligomeric enzyme by itself and is, therefore, consistent with being the site of the molecular defect in GA.