Segregation of human hypoxanthine phosphoribosyltransferase activity from somatic cell hybrids isolated from fusion of mouse gene transfer cells with Chinese hamster cells.

Abstract

Four independent mouse gene transfer clones, i.e. mouse cells which had taken up a human chromosomal fragment carrying the human gene for hypoxanthine phosphoribosyltransferase (HPRT), were characterized with the following results: 1. None of the clones expressed human α-galactosidase activity whose structural gene has been previously located on the human X-chromosome in the neighbourhood of the gene coding for HPRT. Thus the human chromosomal fragment in these mouse cells is presumably so small that it does not carry the gene for human α-galactosidase A. 2. All the gene transfer clones when maintained in logarithmic growth for at least 100 generations in selective medium became phenotypically stable, i.e. they no longer segregated the transferred human HPRT activity after being shifted to non-selective growth conditions. 3. Somatic cell hybrids were isolated after fusion of phenotypically stable mouse gene transfer cells, expressing human HPRT, with chinese hamster cells, mouse cells which were derived from the same parental line as the gene transfer cells but which expressed reverted mouse HPRT were also fused with these chinese hamster cells. All isolated hybrid cell clones were counter-selected for the absence of functional HPRT.