| First Author | Fisher G | Year | 1992 |
| Journal | Mouse Genome | Volume | 90 |
| Issue | 3 | Pages | 430-32 |
| Mgi Jnum | J:2504 | Mgi Id | MGI:51027 |
| Citation | Fisher G, et al. (1992) The position of the locus DXWas70 in relation to 3 X chromosome rearrangements. Mouse Genome 90(3):430-32 |
| abstractText | Full text of Mouse Genome contribution: The position of the locus DXWas70 in relation to 3 X chromosome rearrangements. Graham Fisher and Charles Tease; MRC Radiobiology Unit, Chilton, Didcot, Oxon., OX11 ORD, U.K. Introduction The locus DXWas70, identified by the repeat sequence probe 70-38, has been shown to lie approximately at the junctions of the A1/A2 bands of the X chromosome by isotopic in situ hybridisation (Disteche et al., 1985, 1989). Two recent correlations of the genetic and cytogenetic maps show DXWas70 as the most proximally identified locus on the mouse X, representing the "distal border of the centromere", and also proximal to the breakpoint of the reciprocal translocation T(X;11)38H (Brown et al., 1991; Lyon and Kirby, 1992). However, the breakpoint of T(X;11)38H has been reported to be in band A1 of the X chromosome (Evans et al., 1987) which would place it proximal rather than distal to DXWas70 according to Disteche et al.Õs (1985, 1989) estimation of the locus' position. We have carried out a nonisotopic in situ hybridisation study using the probe 70-38 to clarify the position of DXWas70 in relation to the breakpoint of T(X; 11)38H and also to 2 other X chromosome rearrangements. Materials and methods Two reciprocal translocations and a paracentric inversion were used. The breakpoints of T(X;4)37H (abbreviated to T37H) are XA2 and 4D3; those of T(X; 11)38H (abbreviated to T38H) are XA1 and 11E1 (Searle et al., 1983; Evans et al., 1987). The breakpoints of the inversion In(X)1H are in bands A1 and F3/4 (Evans et al., 1982). Both translocations gave rise to short marker chromosomes, X4 and X11 respectively, that carry the proximal end of the X chromosome, and to long marker chromosomes, 4X and 11X respectively, that include the remainder of the long arm of the X. Somatic chromosome preparations were made from bone marrow cells from females heterozygous for each translocation. Meiotic chromosome preparations were prepared from spermatocytes of an In(X)1H hemizygous male. The X chromosome, and its orientation, can be identified by its characteristic bivalent configuration with the Y chromosome at diakinesis/metaphase I. The probe 70-38 (Disteche et al., 1985) was biotinylated using a nick translation kit. In situ hybridisation was carried out using a standard protocol and hybridisation was detected using the streptavidin - alkaline phosphatase method (Boyd and Williamson, pers. comm.). Results and discussion If the breakpoint of a rearrangement is proximal to DXWas70 then the position of the hybridisation signal will be altered from its normal position adjacent to the centric end of the X chromosome. In the case of a reciprocal translocation, a hybridisation signal on the long marker chromosome would indicate a breakpoint proximal to DXWas70, and conversely if the signal is on the small marker then the breakpoint is distal to the locus. Characteristic examples of the X and translocation chromosomes in cells from T37H and T38H are given in Figure 1. The hybridisation signal is on the short marker chromosome in T37H indicating a breakpoint distal to DXWas70 in this translocation. However, the signal is on the long marker in T38H showing that the breakpoint is proximal to DXWas70. In a normal XY bivalent, the probe hybridises to the proximal end of the X at the opposite end of the chromosome to the XY pairing region. However, in the inversion hemizygote there was clearly an alteration of the position of the signal from its usual centric position to a novel distal location. Thus the breakpoint of the inversion is also proximal to DXWas 70. The observations made here are not informative with regard to the relative positions of the breakpoints of T38H and In(X)1H. Nevertheless, we can conclude that the sequence on the X chromosome is: centromere - T38H/In(X)1H - DXWas70 - T37H. Figure 1. (a) (Legend). T37H : hybridisation is restricted to the centric end of the normal X and the X4 small marker; no signal is present on the long marker 4X. (b) T38H : hybridisation signal is present on the normal X and the 11X long marker, but not on the small marker X11. (c) In(X)1H: 2 overlapping metaphase I cells in which the hybridisation signal is present on the X chromosome adjacent to the XY pairing region rather than at the centric end of the X. Acknowledgements We thank Professor Maj Hulten for the gift of the probe 70-38. We are indebted to Dr Yvonne Boyd and her colleagues for their help with the in situ hybridisation method. This work was supported in part by Euratom contract Bi6-143. References Brown SDM, Avner P, Chapman VM, Hamvas RMJ, Herman GE (1991) Mammalian Genome 1, S318-S331. Disteche CM, McConnell GK, Grant SG, Stephenson DA, Chapman VM, Gandy S, Adler DA (1989) Genomics 5, 177-184. Disteche CM, Tantravahi U, Gandy S, Eisenhard M, Sahar E, Travis B, Latt SA (1985) Cytogenet Cell Genet 39, 262-268. Evans EP, Burtenshaw MD, Cattanach BM (1982) Nature 300, 443-445. Evans EP, Burtenshaw MD, Lyon MF (1987) Mouse News Letter 77, 147. Lyon MF, Kirby MC (1992) Mouse Genome 90, 22-44. Searle AG, Beechey CV, Evans EP, Kirk M (1983) Cytogenet Cell Genet 35, 279-292. |
