The genetic control of two types of esterases in inbred strains of the mouse.

N a previous paper, we described three different esterases determined by starch I gel electrophoresis in inbred strains of mice (Mus musculus). Two of these esterases were unequivocably controlled by unlinked autosomal loci ( RUDDLE and RODERICK 1965). One locus, Es-3, controlled the formation of an esterase which was named esterase A, and which has been subsequently renamed esterase IV-40 according to a new system of nomenclature based on electrophoretic mobility (RUDDLE 1966). Esterase IV-40 was distinctive in that it was inhibited by eserine sulphate ( lo-"). In the previous study, we made crosses between strain RF/J which expresses esterase IV-40 and strain C5 7BL/6J which expresses no corresponding eserine sensitive esterase hereafter called eserine sensitive minus (ESM). The patterns of inheritance resulting from these and further crosses indicated the presence of two alleles at locus Es-3. These were designated Es-3" and E S ~ ~ ; allele Es-3" was associated with the absence of detectable esterase (ESM) , whereas the allele E s ~ ~ was associated with the expression of the eserine sensitive esterase IV-40. A second locus, Es-4, controlled the formation of an esterase which was named esterase B, and which has subsequently been renamed esterase IV-20. Esterase IV-20, a slower migrating band, was distinctive in that it was resistant to high concentrations of eserine sulphate. In the previous study, genetic crosses were carried out kctween strain RF/J which expresses esterase IV-20 and strain C5 7BL/6J which expresses no corresponding esterase of comparable electrophoretic mobility. The patterns of inheritance resulting from a variety of crosses indicated the presence of two alleles at locus Es-4. These are designated Es-4'l and E S ~ ~ ; allele Es-4" was associated with the absence of detectable esterase, whereas the allele E S ~ ~ was associated with the expression of the eserine resistant esterase IV-20. Two new findings reported by RUDDLE (1966) modified and extended the earlier genetic data of RUDDLE and RODERICK (1965) reviewed above. The first finding was that in a number of inbred strains of mice including strain SJL/J, there is expressed an eserine sensitive esterase called IV-10 which migrates more slowly than the eserine sensitive esterase IV-40. Thus, there are three phenotypic expressions which might be related genetically. These are (1) a fast eserine sensitive esterase IV-40, native to RF/J, whose electrophoretic mobility is determined by allele E s ~ ~ , (2) a condition where no detectable esterase is observed, as