Elizabeth A. Nichols

A review of enzyme polymorphism, linkage and electrophoretic conditions for mouse and somatic cell hybrids in starch gels.

The selective loss of human chromosomes from both mouse + human and Chinese hamster x human somatic cell hybrids makes these two systems useful for studying problems in gene regulation and gene mapping. The loss of a particular human chromosome may be correlated with the loss of a human enzyme from the hybrid as demonstrated by gel electrophoresis permitting the mapping of the corresponding gene. The use of human translocation cell lines as one of the parental lines in the hybrids makes it possible to map genes to specific sections of the human chromosomes as Ricciuti and Ruddle (34) have recently done for phosphoglycerate kinase (PGK), hypoxanthine guanine phosphoribosyl transferase (HGPRT), and glucose 6-phosphate dehydrogenase (G6PD). We review here the polymorphism and electrophoretic phenotypes and staining conditions for 30 enzymes which may be examined in somatic cell hybrids of’ mouse, human or Chinese hamster cell lines. In most instances the genes for these enzymes have been mapped.

Polymorphism and linkage for mannosephosphate isomerase in Mus musculus

Electrophoretic variants of the enzyme mannosephosphate isomerase (E.C. 5.3.1.8) (MPI) have been discovered in the mouse. The MPI-IA phenotype was found in Mus castaneus and in the inbred strain MA/J of Mus musculus. Other inbred strains of Mus musculus examined possessed the MPI-1B phenotype. Genetic studies show that the MPI variants segregate as codominant alleles of a single autosomal locus, designated Mpi-1 in linkage group II. The gene order Mod-1-d-Mpi-1 has been established. Human and murine forms of MPI differ and can be detected in in vitro fibroblasts and somatic cell hybrid populations.

Gene linkage analysis in the mouse by somatic cell hybridization: assignment of adenine phosphoribosyltransferase to chromosome 8 and alpha-galactosidase to the X chromosome.

Somatic cell hybridization techniques were applied to gene linkage analysis in the laboratory mouse. Cells of an established line of Chinese hamster lung fibroblasts were fused with mouse embryo fibroblasts and with mouse peritoneal macrophages obtained from different inbred strains: From 3 hybridization experiments, 123 primary and secondary clones were isolated in HAT selective medium and 24 were back-selected in 8-azaguanine. Hybrid clones were characterized for the expression of 16 murine isozymes by starch, acrylamide, and Cellogel electrophoresis, and on the basis of segregation data, 3 syntenic associations could be made. Malate oxidoreductase decarboxylating (MOD) and mannose phosphate isomerase (MPI) segregated concordantly, confirming an established linkage relationship;adenine phosphoribosyltransferase (APRT) segregated concordantly with glutathione reductase (GR) which is known to be on chromosome 8;α-galactosidase was observed to be syntenic with hypoxanthine phosphoribosyltransferase (HPRT), and X-linked enzyme. All other isozymes examined segregated independently of one another.

Polymorphism and linkage of glutathione reductase in Mus musculus

Using an electrophoretic variant for glutathione reductase, we have been able to map the structural gene for this enzyme to chromosome 8 in Mus musculus.

A new electrophoretic technique for mouse, human, and chinese hamster galactokinase.

In this paper we describe an electrophoretic, autoradiographic technique for galactokinase which will separate the mouse, Chinese hamster, and human enzyme.

Esterase-8 (Es-8): characterization, polymorphism, and linkage of an erythrocyte esterase locus on chromosome 7 of Mus musculus.

An electrophoretic polymorphism of an erythrocyte esterase, esterase-8, specific for the substrates α- and β-naphthyl acetate has been observed in the Asian house mouse, Mus musculus castaneus. M. m. castaneus is interfertile with inbred strains of mice, and F1 hybrids (C57BL/6J × castaneus)F1 and (SWR/J × castaneus)F1 show a double-banded phenotype similar to a mixture of parental forms. This pattern suggests codominant expression of a structural gene difference. In backcrosses, ES-8 segregated as a single autosomal gene, designated Es-8, linked to Gpi-1 on chromosome 7. A gene order of Es-8, Gpi-1, c, Mod-2, and Hbb was determined from a series of crosses.

Linkage of the locus for serum albumin in the house mouse, Mus musculus

An electrophoretic variant for serum albumin in Mus musculus has been used to map the structural gene for this protein to chromosome 5.

Assignment of the gene for adenosine kinase to chromosome 14 in Mus musculus by somatic cell hybridization.

Evidence is presented for the assignment of the gene for adenosine kinase to Mus musculus chromosome 14 by synteny testing and karyotypic analysis of mouse X Chinese hamster somatic cell hybrid clones. ADOK and two enzymes previously mapped to mouse chromosome 14, NP and ES-10, were expressed concordantly in 29 hybrid clones. Chromosome analysis confirmed this assignment. Syntenic evidence is also presented using several clones of a gene transfer system in which the gene for human HPRT had integrated into modified mouse chromosome 14s.

Comparative sensitivities of electrophoretic assays for human enzymes.

The sensitivities of 26 starch gel electrophoretic enzyme assays have been compared using HeLa human cells and A9 mouse cells grown in vitro.

Assignment of the gene for glyoxylase I to mouse chromosome 17 by somatic cell genetics.

Evidence is presented for the assignment of the gene for glyoxylase I to mouse chromosome 17 using mouse × Chinese hamster somatic cell hybrids. GLO I was not expressed concordantly with any known marker enzymes which represented 11 linkage groups. The presence of chromosome 17 and expression of GLO I were concordant in 31/31 clones. GLO I is thus linked to the H-2 histocompatibility locus in the mouse.