| First Author | Cattanach BM | Year | 1996 |
| Journal | Mouse Genome | Volume | 94 |
| Pages | 681-2 | Mgi Jnum | J:37391 |
| Mgi Id | MGI:84786 | Citation | Cattanach BM, et al. (1996) Five more radiation-induced large deletions. Mouse Genome 94:681-2 |
| abstractText | Full text of Mouse Genome contribution: 4. Five more radiation-induced large deletions. We have previously reported the detection of a number of cytogenetically visible deletions among Fl generation mice deriving from combined chemical - radiation experiments upon spermatogonial stem cells (Cattanach et al Nature Genetics 3:56-61, 1993; Cattanach et al Proc of the 10th ICRR, Vol. 2, in press). Here we report a further five examples. Del(8)72H. The original mutant male was investigated only because it was seen to be small at birth and weaning. On breeding, this single characteristic was transmitted to a proportion of his offspring although in later generations some such growth retarded mice exhibit dark coats and/or circling behaviour. There was a shortage of the mutant class at birth (67%) but despite being only about 70% of the size of their normal sibs almost all survived to birth. It is therefore not clear whether the shortage at birth represent prenatal loss or poor penetrance. On intercrossing, a 33% preimplantation loss was detected, suggesting that the homozygote dies early in development. G-banding analysis showed a small Chr 8 deletion removing band B1.3 comprising about 4% of the total chromosome length. The deletion therefore removes a chromosomal segment spanned by a previously described but much larger deletion, Del7H. Del72H is the fourth deletion detected in the A4 - B3 region of Chr 8 (see Beechey, Mouse Genome, 94: 74-95, 1996). Del(5)73H. The original mutant was again investigated only because of small size at birth which persisted to weaning. Some of its affected progeny and other descendants showed in addition short domed heads and occasional low grade white spotting affecting the feet only. There was a marked shortage of the mutant class at birth (30% of expected) and few survived to weaning or adult ages. Survivors were generally sickly looking animals and were therefore not kept, making the prospects for maintaining the stock limited. Both sexes were fertile. Cytogenetic analysis indicated a large deletion of proximal Chr 5 spanning bands A2 - B3, or about 15% of the physical length of the chromosome. This is first Chr 5 deletion outside of the W/Rw region (see Beechey, ibid). Del(8)74H. In this case the original mutant was investigated because of an observation of milky abdomen (chylous ascites) at birth and the usual characteristic of such mice as adults of puffy feet and thickened soft tail. The condition was clearly inherited but with variable expression. Thus some affected mice at birth were growth retarded and did not survive, while others were not identified until later ages, at several days for the milky abdomen characteristic or even as adults by their puffy feet. On intercrossing, limited opening data suggest that the homozygote dies after implantation, but this conclusion has to be verified. G-band analysis demonstrated that a further new Chr 8 deletion was involved. This removed bands B1.l - 1.3 (about 7% of the chromosome) thus spanning Del72H described above and suggesting that the chylous ascites phenotype was associated with the region proximal band B1.3. This could accord with the finding that the yet larger Del7H which spans both of these deletions is also associated with a chylous ascites. The small Del50H, also located on Chr 8, reduces the candidate area further (see Beechey, ibid). Del(12)75H. Again the original mutant was investigated because of small size at birth and weaning but with a definite head bobbing behaviour also evident. Affected progeny were 70% of normal size at birth and at this age only 70% of the expected numbers were detected. Only about 30% of these survived to weaning. Stock maintenance is therefore extremely difficult. Cytogenetic analysis indicated a small distal Chr 12 deletion involving about one-quarter of the dark band E, or merely 2% of the total chromosome length. The location of this deletion is of interest for two reasons. First, it is the first Chr 12 deletion to be found. Second, the deletion lies within the large distal segment of Chr 12 that has been found to be subject to imprinting (Cattanach and Rasberry, Mouse Genome). That the deletion is transmissible through both males and females suggests that the segment of Chr 12 involved is not responsible for the early developmental lethality associated with both maternal and paternal duplication of distal Chr 12. Del(3)76H. Usually in our phenotypic screen for deletions, small size at birth has been a key criterion for investigating mutants for deletions or other gross forms of chromosome imbalance. In this case, investigation was initiated based upon the growth retardation of the original animal, a male, which was noted only at weaning, On breeding from the animal the small size effect was clearly inherited but showed a degree of variability, some affected young being smaller than their sibs even at birth, while others showed only a marginal growth reduction at weaning to adult ages. A significant finding was that although the original male was fertile, of four male descendants tested, all were sterile. Their testis weights varied considerably but ranged from near normal (over 100 mg) to about half normal size. Sperm counts also varied, ranging from near normal to severe oligospermia. Cytogenetic analysis showed a Chr 3 deletion involving the whole of band A3, or about 10% of the chromosome length. This is of interest as five other deletions that map quite close to Del76H (see Beechey, ibid} are also male sterile. A further deletion that appears identical, Del64H, (see Beechey, ibid) is not male sterile and is associated with an abnormal head type. (Cattanach BM, Evans EP, Burtenshaw M, Woodward, and Vizor) |
