Gene Expression in Cultured Mammalian Cells

This chapter discusses the gene expression in cultured mammalian cells. Cell and tissue culture provides a simple system for investigating a variety of fundamental problems involved in gene expression. Cells can be grown under relatively controlled environmental conditions that permit analysis of the physiology, biochemistry, and genetics of cells in culture. New methods of cell fusion and hybridization allow some aspects of recombination analysis in mammalian cell culture, and the recent development of methods for enucleating mammalian cells with the recovery of cytoplasm and nuclei separately permits reconstruction of cells by fusing nuclear and cytoplasmic components derived from different cell types. The chapter emphasizes on mutant cell cultures, as well as examples of enzyme regulation and metabolic control that reflect gene expression in cultured mammalian cells. Studies on mutant mammalian cells, particularly those that show temperature sensitivity toward expressing differentiated activities, may be useful in separating and analyzing the required biochemical events. Difficulty in selecting for such mutant cells is a serious limitation, but recent studies on cell lines selected for temperature-sensitive differences in contact inhibition of cell growth confirm the resolving power of such methods. Cell lines derived from mutant subjects and from multipotential tumors are particularly informative for investigating basic mechanisms of gene expression and determination. Cell fusion and the subsequent analysis of complementation in heterokaryons and synkaryons may provide insight into the nature of mutations at the levels of the defective protein and interactions of the regulatory process.