AJP - Cell Physiology, Vol 252, Issue 5 C515-C522, Copyright © 1987 by American Physiological Society
Selectable mutations altering two mechanisms of mammalian K+ transport are dominant
J. J. Gargus
Somatic cell mutants with altered K+ transport have previously been
isolated from mutagenzied LMTK- cells for their ability to grow at
subthreshold low-potassium concentrations (0.2 mM). These mutants fall into
two classes: one class, LTK-5, possesses a functionally altered
furosemide-sensitive Na+-K+-Cl- cotransport system and the other, LTK-1, an
altered K+-conducting channel. Somatic cell hybrids have been formed
between each of these cell lines and a wild-type L-cell line, making use of
complementing selectable marker mutations carried by these parents, to
establish the dominance of the K+ transport mutations. Hybrids were
isolated and studied in two ways: clonal hybrid cell lines were selected in
a manner unbiased toward their K+ transport phenotype, which was later
assayed; and the number of independent hybrids arising in this
single-selective condition was compared with the number arising in a
condition which is double selective for the mutant phenotype as well. By
both assays, hybrids formed with LTK-1 or LTK-5 as a parent uniformly
exhibited the mutant phenotype by growth and cloning, whereas control
hybrids with LMTK- as parent never did. This demonstrates both transport
mutations to be dominant and thus potentially isolatable.
