Evidence for a chromosomal breakage hotspot in a 3 Mb region of Xp11.21
- Case Western Reserve Univ., Cleveland, OH (United States)
- Case Western Reserve Univ.
In order to evaluate the molecular basis for X chromosomal rearrangements, we have analyzed a series of i(Xq)s, small mar (X)s, and X;autosome translocations using fluorescence in situ hybridization (FISH). The breakpoints of 5 of 8 cytogenetically monocentric i(Xq)s and 5 of 9 Xp breakpoints resulting in mar(X)s were initially localized to Xp11.21 using cosmids for the genes ZXDA and DXS423E. In order to more precisely define the breakpoints of these abnormal Xs, as well as a series of translocated Xs, we have used yeast artificial chromosomes (YACs) derived from a contig spanning 5 Mb of DNA in Xp11.21-Xp11.22 which contains 112 YACs mapped with 51 markers, including 10 genes. Based on the FISH results, the chromosomal breakpoints could be assigned to 5 different intervals in Xp11.21. One i(Xq) has a breakpoint in the most proximal interval which is located 1 Mb from the centromere. A 300 kb region just distal to the duplicated gene ZXDB contains breakpoints for a mar(X) and a t(X;19). A third interval, which lies {approximately}300 kb further distal, contains breakpoints for 2 Incontinentia Pigmenti type 1 (IPI) translocations, 2 i(Xq)s, and 1 mar(X). One mar(X) breakpoint is localized to <200 kb of DNA proximal to DXS991, and the most distal interval, containing 2 i(Xq) breakpoints, is defined by <500 kb of DNA at the ALAS2 locus. Thus all of the breakpoints examined map to the region between ZXDA and ALAS2, which contains only 3 Mb of DNA, indicating that there is a hotspot for chromosomal breakage in proximal Xp11.21. We hypothesize that this high frequency of aberrations (representing a mutation frequency of >10{sup 5} based on the frequency of i(Xq) and mar(X)s in surveys of liveborn) may result from misalignment and/or exchanges due to the presence of inverted repeat sequences, directly duplicated gene sequences, or one or more inversion polymorphisms in the pericentromeric region.
- OSTI ID:
- 133414
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0142
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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