The Hypoxanthine Phosphoribosyltransferase Gene: A Model for the Study of Mutation in Mammalian Cells

Publisher Summary In mammalian cells, the principal genetic locris that has proved to be amenable to mutation studies is the one coding for hypoxanthine phosphoribosyltransferase (HPRT). This chapter provides a review of results obtained from the various approaches that have been applied to the study of mutation at the hypoxanthine phosphoribosyltransferase (HPRT) locus and summarizes recent advances made in the molecular cloning of HPRT genes. The availability of cloned probes leads to detailed molecular study of both experimentally induced and naturally occurring mutations at the HPRT locus. Although the gene is very large, a number of changes that involve substantial deletions or rearrangements have already been identified; even smaller changes have been examined either by protein-sequencing techniques or selective restriction-enzyme cleavage studies. Further development of methods for using specific primers to examine mRNA sequences directly or the application of recombination “rescue” approaches to isolate defined regions for detailed analysis may increase the feasibility of a routine examination of minor changes in nucleotide sequences. The fact that small expressing-vectors constructed from HPRT cDNA sequences can be used in gene-transfer experiments allows the potential for site-directed mutagenesis in vitro, followed by an examination of the in vivo effects and may well provide a good system for future studies on gene correction.