Small swaying lethal; a new spontaneous neurological mutation on Chromosome 6.

Patricia Ward-Bailey, Louise Dionne, Richard Samples, Roderick Bronson, and Kenneth R. Johnson

Source of Support: This research was supported by NIH/NCRR grant RR01183 to the Mouse Mutant Resource (M.T. Davission, PI) and Cancer Center Core Grant CA34196.

Mutation (allele) symbol: ssl

Mutation (allele) name: small swaying lethal

Gene symbol:

Strain of origin: BALB/cJ

Current strain name: BALB/cJ-ssl/J

Stock #: 006019 (view JAX Mice© Data Sheet for additional information including Price and Supply Information)

Phenotype categories: neurological

Abstract

A new spontaneous recessive mutation has been identified and mapped to Chromosome 6. Mice homozygous for the ssl mutation are smaller than their littermates and lean and fall over on their sides.

Origin and Description

Mice carrying the small swaying lethal (ssl) mutation were discovered by Amy Fickett in a production colony of BALB/cJ at the Jackson Laboratory in May of 2001. The mutants are recognized at 12-15 days of age. As the affected mice age, their neurological phenotype becomes more pronounced, and they do not survive past four to five weeks of age. Ovarian transplants of homozygous females have not been successful. The BALB/cJ-ssl/J colony is maintained by progeny testing.

Genetic Analysis

Using our standard mapping protocols a linkage cross was set up by mating a female heterozygous for the ssl mutation to a CAST/EiJ male mouse. The mutation carrying offspring of this mating were then intercrossed and produced 50 affected F2 mice that were used for linkage analysis. Using standard PCR protocols a genome scan confirmed linkage of the ssl mutation on Chromosome 6. The mutation maps between D6Mit38 (NCBI 36 position 100.0 Mb). and D6Mit55 (NCBI 36 position 112.4 Mb) and is non-recombinant with D6Mit107 (NCBI 36 position 113.5 Mb) and D6Mit11(NCBI 36 position 114.2 Mb).

Based on phenotype and map position similarities, a direct test for allelism was set up with deaf waddler by mating a C3H/HeJ-Atp2b2dfw/J with a mouse carrying the new ssl mutation. This mating produced no affected progeny out of 27 born, so it is unlikely that the new ssl mutation is an allele of deaf waddler.

Pathology

A pathological screen of 3 homozygous mutants at three weeks of age revealed atrophy of the thymus in one mutant and no gross lesions in the other two animals.

Hearing as assessed by auditory brainstem response testing (ABR) of one homozygous mutant at three weeks of age revealed no hearing loss, providing further evidence that  ssl is not allelic with deaf waddler.

The eyes of a 19 day old female mouse appeared normal when examined with an opthalamascope, but ERG testing of the same animal showed normal rods and poor cones.

Acknowledgements

The authors thank Heping Yu for hearing assessment, Norm Hawes for eye examination, and Coleen Marden for excellent pathological techniques.