| First Author | Cattanach BM | Year | 1988 |
| Journal | Mouse News Lett | Volume | 80 |
| Pages | 157-58 | Mgi Jnum | J:18280 |
| Mgi Id | MGI:66283 | Citation | Cattanach BM, et al. (1988) A new steel allele with early post-implantation homozygous lethality. Mouse News Lett 80:157-58 |
| abstractText | Full text of MNL contribution: 2. A new steel allele with early post-implantation homozygous 1ethality. A new mutation giving a greyish coat, pale ears and tail, head-spotting and occasional nose- and belly spotting has been identified as a S1 allele in crosses with Sl-con. The compound in addition to showing the typical pale grey coat displayed a prominent wide white head blaze. The mutation, which derived from a mutation experiment in which males had been given 6 Gy spermatogonial X-irradiation, has been designated Sl-18H. Crosses of Sl-18H heterozygotes with + mice have yielded 205 weaning age young of which 77 were S1-18H+ and 128 were + . Since there was no difficulty in distinguishing the two classes the shortage of mutant young was attributed to a reduced (60%) viability. Consistent with this conclusion was the further finding that small pale-coloured, presumably slightly anaemic young that tended to die early were occasionally seen at birth and those that survived proved to be Sl-18H heterozygotes. Litter size was not detectably reduced. Intercrosses produced 147 weaning age young of which 80 were Sl-18H+ and 67 were +, the departure from the expected 2:1 ratio can again be attributed to a reduced viability of the heterozygote. No anaemic black-eyed-white young were produced and since the litter size was markedly low (4.6 cf. 7.5 in the outcross) pre-natal loss of the homozygotes was indicated. To investigate the time of death of the homozygotes pregnant females were opened at 17 days' gestation. The results were as follows: Cross: + females x + males; No. 11; Live embryos: 81; Late deaths: 1; Moles: 8; Corpora lutea: 100; Moles/Implants: 8.8%. Cross: + females x Sl-18H+ males; No. 6; Live embryos: 50; Late deaths: 0; Moles: 5; Corpora lutea: 58; Moles/Implants: 9.1%. Cross: Sl-18H+ females x Sl-18H+ males; No. 6; Live embryos: 36; Late deaths: 0; Moles: 16; Corpora lutea: 62; Moles/Implants: 30.8%. Whereas no anaemic live young or late deaths that could have represented homozygotes were found in the intercrosses, an excess of moles representing early post-implantation deaths was evident and it was concluded that these were attributable to homozygous Sl-18H lethality. Because heterozygotes for this Sl allele appear to show a level of anaemia S1-18H may represent an extreme allele, rather than a deletion like Sl-12H. The very early death of the homozygotes is therefore novel and suggests the locus has more extensive actions upon development than previously thought. (Cattanach and Rasberry). |
