Meiotic segregation analysis of reciprocal translocations both in sperms and blastomeres

Abstract

Balanced chromosomal rearrangements could lead to unbalanced segregation gametes during meiosis. In this study, sperm flourescence in situ hybridization (FISH) analysis of meiotic segregation products of four reciprocal translocations; 46,XY,t(7;10)(q21;q22), 46,XY,t(15;17)(q11;p12), 46,XY,t(6;13)(p21.1;q32), and 46,XY,t(1;13)(q24;q10) are presented. In three out of these four cases with t(15;17), t(6;13), and t(1;13) additional blastomere FISH analyses are also provided. Multi-color FISH analysis was applied using diverse probe combinations specific for translocated chromosome segments. The average frequency of sperm nuclei bearing unbalanced products for t(7;10), t(15;17), t(6;13), and t(1;13) were 48.7%, 59.5%, 60.5%, and 62.9%, respectively. Frequencies of blastomeres comprising unbalanced products in cases with t(15;17), t(6;13), and t(1;13) were 80% (12 of 15), 60% (3 of 5), and 50% (2 of 4), respectively. Chi-square test analysis showed significant differences in the meiotic segregation patterns due to the distribution and numbers of the chiasmatas that could depend on the size of the translocated segments (P < 0.001). In conclusion, FISH analysis of sperm and blastomere for reciprocal translocation carriers effectively estimates the approximate risk of unbalanced products and this result might ensure valuable genetic counseling.

Sperm and embryo analysis of similar t(7;10) translocations transmitted in two families

“…Concerning the unbalanced gametes, the adjacent 1 segregation products were predominant in both carriers, followed by the adjacent 2, 3:1, and other products. A similar segregation profile was previously described in sperm of a t(7;10)(q21;q22) carrier: 51.3% of the alternate, 27.3% of the adjacent 1, 12.1% of the adjacent 2, and 7.5% of the 3:1 segregations (11). This supports the hypothesis that identical or similar translocations show similar segregation profiles (12,13).…”

18, X, Y aneuploidies and transmission electron microscopy studies in spermatozoa from five carriers of different reciprocal translocations

“…Because translocation carriers are candidates for ICSI, FISH analysis performed directly on sperm nuclei provides a better understanding of the meiotic process and it could improve the risk assessment of chromoso mally abnormal embryos [19].…”

Successful pregnancy after preimplantation genetic diagnosis for carrier of t(2;7)(p11.2;q22) with high rates of unbalanced sperm and embryos: a case report

“…Though the meiotic segregation pattern in spermatozoa from nearly 100 different reciprocal translocation carriers is known (Benet et al, 2005), only in less than 20 cases the comparison with PGD results was performed (Van Assche et al, 1999;Mackie Ogilvie and Scriven, 2002;Munne, 2005;Yakut et al, 2006). Compared to the percentage of unbalanced spermatozoa, the embryo data seemed to produce higher rates of unbalanced embryos than expected.…”

“…Results of PGD indicate that in the case of RCT carriers this method reduces the frequency of miscarriages, but the pregnancy rate is directly proportional to the number of normal spermatozoa (Munne et al, 1998(Munne et al, , 2000. From most of nearly 20 cases published so far where meiotic segregation patterns were compared with PGD results, it can be implied that sperm sample with more than 60% abnormal forms indicates a poor prognosis for a normal term birth (Van Assche et al, 1999;Mackie Ogilvie and Scriven, 2002;Munne, 2005;Yakut et al, 2006).…”