| First Author | Keightley PD | Year | 1991 |
| Journal | Mouse Genome | Volume | 89 |
| Pages | 410 | Mgi Jnum | J:14309 |
| Mgi Id | MGI:62480 | Citation | Keightley PD, et al. (1991) Rimy: a new mutation affecting coat colour and body size. Mouse Genome 89:410 |
| abstractText | Full text of Mouse Genome contribution: Rimy: A New Mutation Affecting Coat Colour and Body Size. Peter D. Keightley and Simon Hawkins. Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Rd., Edinburgh EH93JT, Scotland. The mutation designated rmy was found in a line under selection for increased body size in a wild type inbred strain (C3H/He) (1), and behaves as an autosomal recessive with reduced viability. The allelic ratios were 13 mutant to 40 wild type from crosses between mutant females and heterozygous males, and 8 mutants to 32 wild type from crosses between heterozygotes. Males appear to be infertile. Phenotype. On the agouti (A) background, the yellow phaeomelanin pigment band is white giving a grey coat colour similar to chinchilla (c ch). Mutants are distinguishable on the non-agouti (a) background by the presence of white rather than yellow hairs on and around the ears and genitalia, but the black eumelanin pigment appears to be unaffected. This differs from chinchilla on the non-agouti background which has reduced eumelanin resulting in a dark sooty grey overall appearance (2). Homozygotes are about 10% lighter at birth than their littermates; this weight difference increases to 30% by three weeks of age. Thereafter, mutants appear to catch up, but are still 20% lighter at 8 weeks. Allelism Tests and Linkage. An allelism test with albino (c) was negative which rules out chinchilla (c ch). Grizzled (gr) seems to be the only mutation with a similar phenotype to rimy (2, 3), but is no longer available in the UK. To test linkage with gr, the following back-cross to steel-contrasted (Slcon), a semi-dominant marker 9cM from gr was performed: + Slcon/rmy + X rmy +/rmy + In the 17 progeny there were 8 parental types (steel-contrasted +/rmy Slcon/+ 5, rimy rmy/rmy +/+ 3), and 9 recombinant types (rimy steel-contrasted rmy/rmy Slcon/+ 1, wild type +/rmy +/+ 8). The probability of obtaining 9 or more recombinants from 17 offspring is 5 x 10(-6) if the map distance is 9cM, so it can be inferred that rmy is not 9cM from SlCon. To test whether the mutant is caused by a proviral insertion, Southern blot analysis using probes which hybridize to ecotropic (Emv) and various classes of non-ecotropic murine leukemia proviruses (4) was carried out, but no new proviral sequences were detected. Concluding Remarks. Rimy and grizzled have a similar coat colour phenotype which suggests that they affect some aspect of phaeomelanin synthesis. They contrast with the albino mutation which in extreme form removes tyrosinase activity and blocks synthesis of both eumelanin and phaeomelanin altogether. Pleiotropic effects on other traits differ slightly between rimy and grizzled. Grizzled has a smaller effect on body size than rimy and the weight difference is more constant with age in the former. Grizzled males are fertile, and a kinked tail phenotype was noted which has not been observed in rimy mice. The specific biochemical nature of these mutations which have striking pleiotropic effects on body size is unclear, however. Acknowledgements. We are grateful to Jo Peters for advice. This work was supported by a grant from the AFRC. References. (1) Keightley, P.D. and Hill, W.G. (1990). In Proceedings of the 4th World Congress on Genetics Applied to Livestock Production (ed. W.G. Hill, R. Thompson and J.A. Woolliams.) Edinburgh: 4WCGALP. (2) Silvers, W.K. (1979). The Coat Colours of Mice. Springer Verlag, New York. (3) Bloom, J.L., and Falconer, D.S. (1966) Genet. Res 7, 159-167. (4) Stoye, J.P. and Coffin, J.M. (1987). J. Virol. 61, 2659-2669. |
