| First Author | Cattanach BM | Year | 1993 |
| Journal | Mouse Genome | Volume | 91 |
| Issue | 4 | Pages | 853-4 |
| Mgi Jnum | J:16264 | Mgi Id | MGI:64348 |
| Citation | Cattanach BM, et al. (1993) Radiation-induced deletions. Mouse Genome 91(4):853-4 |
| abstractText | Full text of Mouse Genome contribution: Radiation-induced deletions. We have recently reported that the combination of growth retardation with phenotypic abnormalities provides an effective criteria for detecting animals carrying large cytogenetically-visible deletions and other gross forms of chromosome imbalance (Cattanach et al. Nature Genetics 356-61, 1993; Cattanach and Evans, CEC Commission Publication, in press 1993). Several further examples have now been identified by this means and characterised cytogenetically. Unless otherwise stated, each appeared among the F1 progeny of spermatogenically X-irradiated males in specific locus mutation tests. Chr 1 deletions, Del(1)Swf27H and DeI(1)Sdm33H. A very large deletion removing about 25% of the central part of chr 1 (bands C5-E4) has already been described. Characterised by a domed head (Dmh), small size; and low post-natal viability, it was named Del(1)Dmh6H. Crosses with leaden (In) mice showed that this locus was missing. Two new chr 1 deletions have since been found, both of which lie within the span of the Dmh deletion. The first, named Del(1)Swf27H is characterised by small size, frequently with white feet and dark coat, and occasionally tremor and/or waltzer-like behaviour. Head shape is mildly affected but the doming of the head is subtly different from that of Dmh. Viability is near-normal. The breakpoint is at the C/D boundary, slightly below that of Dmh: the distal breakpoint is at E4 but above that of Dmh. The In locus does not lie within this deletion and on the basis of its close linkage with the T44H, T45Dn and T1Wa translocations should lie between the proximal breakpoints of the two deletions. Linkage studies with fz and In are in progress and seem likely to confirm that In lies in this position. The second new deletion is characterised by small size, dark coat and a definite but more mildly domed head than Dmh. It has been named Del(1)Sdm33H. The viability is higher than that of Dmh, although still clearly reduced (60%) and, as with the Swf deletion, the In locus is not involved. The proximal breakpoint is at the D/E boundary, below that of the Swf deletion, and the distal breakpoint lies at the junction of bands E2.3/3. Linkage studies indicated the deletion lies distal to In thus, backcrosses of + + Sdm/fz In + males and females to fz In have produced progeny of the following phenotypic classes: 26 fz In, 6 Sdm, 5 fz In Sdm, 2 +, 2 fz + Sdm, 15 + In + only, total 56. The absence of the double crossover fz and + In Sdm classes confirms the order is as shown. The calculated fz - In RF is 30.36 +/- 6.14% in reasonable agreement with map distance (Lyon and Kirby, Mouse Genome, 91:40-80, 1993) and that for In - Sdm, 12.50 +/- 4.42%. Del(16)Sml34H. This deletion has been reported before (Cattanach and Evans ibid) but not named. Deletion carriers are characterised by small size principally but the head shape is also variably affected, the skull appearing shorter than normal. Post-natal viability is markedly low (21%). The breakpoints lie in bands A2 and proximal B2. Approximately 13% of the chromosome is missing. Del(2)Swt35H. This deletion has been reported before (Cattanach and Evans, ibid) but not named. Fairly constant characteristics are small size, white hind toes. The viability is lower (13%) than might have been expected from the relatively small size of the deletion (4% loss). The breakpoints lie in band E5. Chr 14 deletions, Del(14)s(186H)38H, Del(14)s(187H)39H and Del(14)s(188H)40H. Twelve mutations at the piebald spotting (s) locus variably associated with small size and other phenotypic effects including head shaking and waltzer-like behaviour have been found to be deletions (as referenced above). In two of the cases the neighbouring slaty (slt) locus was also deleted. A correlation between size of the deletions and occurrence and severity of other effects was indicated. High expression of spotting was a fairly constant character. Three further s mutations representing deletions have since been found. All have shown small size and high s expression but no other effects and, in two studied (s(187H) and s(188H)) the slt locus was not deleted. Consistent with the limited level of effect, all three deletions proved on cytogenetic analysis to be small (2.5%), involving only band E4. Therefore, all radiation induced s mutations so far studied have proven to be deletions. Del(8)Bru44H. The ethylnitrosourea-induced bruised (Bru) mutation causes a bruising about the head and hindquarters at birth and a reduced pre-weaning viability (Lyon et al. Mouse News Letter, 71:26). These characteristics suggested that Bru may represent a deletion. Cytogenetic studies have confirmed this (Cattanach and Evans, CEC Commission Report, in press 1993). The deletion involves only band A1.3 and represents about 4% of the chromosome. Despite the relatively small size of the deletion, analysis of the breeding records has shown the viability to be markedly low (30%). The deletion has now been named as shown. (Cattanach, Evans, Burtenshaw, Glenister, Vizor and Woodward). (This work was supported in part by Euratom Contract F13P-CT920055). |
