Mitotic and meiotic instability of a telomere association involving the Y chromosome.

Constitutional telomere associations and jumping translocations (JTs) are rare events and usually occur post-zygotically. We report a telomere association involving the Y chromosome which "jumped" during meiosis. A 21-year-old woman was referred for amniocentesis due to non-immune hydrops seen in a previous pregnancy. Cytogenetic analysis of the amniocytes showed a 45,X,tas(Y;15)[4]/45,X[16] karyotype with the long arm of the Y chromosome attached to the end of the short arm of chromosome 15. Parental chromosome analyzes revealed a tas(Y;19)[63]/45,X[7] karyotype in the father with Yq attached to the end of the short arm of chromosome 19. A phenotypically normal male was born and blood chromosome analysis confirmed a 45,X,tas(Y;15)[39]/45,X[10]/46,XY[1] karyotype. Two other male children have 46,XY karyotypes, which further demonstrates the instability of the tas(Y;19) in meiosis. Fluorescence in situ hybridization (FISH) analysis with probes for theY-centromere, the Yqh region, the shared Xq/Yq telomere and SRY showed hybridization on the tas(Y;19) and tas(Y;15). A chromosome 19p specific subtelomeric probe showed hybridization to the tas(Y;19) in the father. In addition, a probe for the simple telomeric sequences TTAGGG showed positive hybridization to the junction of the associations. The presence of TTAGGG telomere repeats and unique telomere sequences indicate that the Y;15 and Y;19 associations occur with no detectable loss of any sequences. The interstitial telomere sequences at the junction of the telomere association may explain the mitotic and meiotic instability of the association. Copyright 2004 Wiley-Liss, Inc.