Comparison of Trembler and Trembler-J Mouse Phenotypes

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Abstract
Trembler (Tr) is an autosomal dominant mutation which produces hypomyelination and demyelination in the mouse peripheral nervous system. This paper compares the genetic, behavioral, and pathological aspects of trembler-J, (TrJ) to those of the original Tr mutation. We found that TrJ was tightly linked on chromosome 11 to vestigial tail, vt, as is Tr. Most TrJ/? animals were more mildly affected behaviorally and pathologically than Tr/? animals. Tr/? animals were rather uniformly affected. In contrast, with matings of mildly affected TrJ/? (putative TrJ/+) animals to each other, and not with matings of putative TrJ/+ × +/+, some offspring, putative homozygotes. TrJ/TrJ, were more severely affected behaviorally and had more extreme peripheral hypomyelination than any Tr/? animals. In spite of their differences. Tr/?, putative TrJ/+, and putative TrJ/TrJ animals shared a failure or marked delay of Schwann cells to progress from the stage of axonal ensheathment in a 1:1 relationship to myelination. We conclude that Tr and TrJ are probably allelic, and that despite their phenotypic differences, their actions are fundamentally similar. While Tr is a dominant, we believe that TrJ behaves as a semidominant, which in homozygotes, TrJ/TrJ, produces the most severe heritable peripheral myelin deficiency hitherto described.