Genetically determined protein polymorphism in the rabbit nervous system.

One of the polypeptides (H1) of the rabbit nervous system occurs in an altered form (H2) in some rabbits. The electrophoretic mobility of H2 on sodium dodecyl sulfate-polyacrylamide gels is about 6% greater than that of H1, suggesting that the two polypeptides differ in molecular weight by about 10,000. The alteration is genetically determined since (i) rabbit phenotypes corresponding to all possible genotypes (H1H1, H1H2, H2H2) were present in an outbred population of rabbits, (ii) the frequency of the phenotype corresponding to the heterozygous genotype (H1H2) was smaller in partially inbred rabbit populations than in outbred populations, and (iii) all of the individuals examined from two partially inbred strains (WH/J and X/J) were of the phenotype that would be expected if they were homozygous (H2H2) for the rare allele of the gene. Preliminary evidence indicates that this polymorphic polypeptide is most abundant in the white matter of the nervous systems of several mammalian species, and is distributed with buffers of low ionic strength and centrifuged at 100,000 Xg.