The twitcher mouse: determination of genetic status by galactosylceramidase assays on clipped tail

Galactosylceramidase activity in whole homogenates of clipped tails could be used successfully to determine the genetic status of the twitcher mouse, a newly discovered neurological mutant caused by a galactosylceramidase deficiency. Normal, heterozygous, and affected animals were clearly segregated at 7 days. The results were consistently confirmed by galactosylceramidase assays on brain or liver tissues, development of clinical disease, or by mating experiments. For technical reasons, identification of carriers in adult mice was less clear-cut and should be avoided, whenever possible. Tail clippings of mice of different ages cannot be mixed because of normal developmental changes in the enzymatic activity. Early identification of affected mice makes it possible to study the disease process before the clinical onset. Early identification of carriers permits efficient maintenance of the breeding colony. The technique should be applicable to other mutants when the primary genetic defects are known.