Analyzing glucose phosphate isomerase isozymes in chimeric mouse tissues by electrophoresis

INTRODUCTIONMouse strains carry different alleles at the ubiquitously expressed Gpi1 (glucose phosphate isomerase) locus (Gpi1(a), Gpi1(b), Gpi1(c)), and this is the basis for a widely used method for determining the genotypic composition of different tissues in mouse chimeras. To determine chimerism by this method, it is necessary to separate the differently charged isozymes from tissue homogenates electrophoretically and to visualize them using a color reaction. Because GPI is a dimer, tissues that normally form by cell fusion (e.g., skeletal muscle) have a heterodimeric form of GPI in a chimera.