Analysis of chromosome segregation in reciprocal translocation carriers depending on prophase quadrivalent features

Background. Meiotic quadrivalent asymmetry degree or the presence of terminal breakpoints may affect the risk of unbalanced gametes’ formation due to pathological chromosome segregation in autosomal reciprocal translocations (ART) carriers during meiosis. A comprehensive analysis of these factors in preimplantation embryos allows evaluating the entire spectrum of segregation patterns in ART carriers for subsequent risk assessment. Aim: the purpose of the study was to assess the influence quadrivalent asymmetry degree and the presence of terminal breakpoints on the segregation type in ART carriers. Methods. Karyotyping for ART confirmation, preimplantation genetic testing (PGT-SP) using fluorescent in situ hybridization (FISH) on 271 embryos obtained in assisted reproductive technology (ART) cycles in 26 couples of ART carriers. The chromosome segregation patterns, the quadrivalents’ asymmetry degree, and the presence of terminal breakpoints were determined. Results. An alternative segregation type, leading to the formation of balanced gametes, was observed with the same frequency in ART carriers with and without terminal breakpoints, as well as in carriers with different quadrivalent asymmetry degrees. The 4:0 and 3:1 patterns were more common in ART carriers with severe quadrivalent asymmetry and terminal breakpoints and could result in large-scale chromosomal imbalance. The data obtained can be used in genetic counseling of ART carriers.

autosomal reciprocal translocations, preimplantation genetic testing, fluorescent in situ hybridization

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