Abstract
PurposeTo analyse the meiotic segregation modes of chromosomal structural rearrangements (PGT-SR) of reciprocal translocation in biopsied blastocysts from preimplantation genetic testing and to investigate whether any features of reciprocal translocation, such as carrier gender or the presence of acrocentric chromosomes or terminal breakpoints, affect meiotic segregation modes.MethodsComprehensive chromosomal screening was performed by next generation sequencing (NGS) on 378 biopsied blastocysts from 102 PGD cycles of 89 reciprocal translocation carriers. The segregation modes of a quadrivalent in 378 blastocysts were analysed according to the carrier’s gender, chromosome type and the location of chromosome breakpoints.ResultsThe results showed that 122 out of 378 blastocysts (32.3%) were normal or balanced, 209 (55.3%) were translocated chromosomal abnormalities, and 47 (12.4%) were abnormalities of non-translocated chromosomes. The proportion of translocated chromosomal abnormalities in translocations without acrocentric chromosomes was significantly higher than that in blastocysts from carriers with acrocentric chromosomes (14.8% versus 5.9%, P = 0.032). Translocation with acrocentric chromosomes exhibited a significantly higher proportion of 3:1 segregation (24.8% versus 5.1%, P < 0.0001) and a lower rate of 2:2 segregation (70.3% versus 87.0%, P = 0.00028) compared with the proportions in blastocysts from carriers without acrocentric chromosomes. The frequency of adjacent-2 segregation was significantly different in translocations with terminal breakpoints compared to the frequency in blastocysts from carriers without terminal breakpoints (6.7% versus 15.5%, P = 0.013).ConclusionsThis study indicates that the segregation modes in blastocysts were affected by the presence of acrocentric chromosomes and terminal breakpoints, but not by the carrier’s sex. Our data may be useful for predicting the segregation pattern of a reciprocal translocation and could support genetic counselling for balanced translocation carriers for PGT cycles using blastocyst biopsy.
Highlights
Reciprocal translocations are the most common structural chromosomal abnormalities, which result from the exchange of terminal segments from different chromosomes
We evaluated the meiotic segregation modes in blastocysts from reciprocal translocation carriers via comprehensive analysis with the use of Next generation sequencing (NGS)
Clinical outcomes of reciprocal translocation carriers In this study, we analysed the clinical outcome of 102 preimplantation genetic testing (PGT) cycles in 89 reciprocal translocation carriers from January 2016 through December 2017
Summary
Reciprocal translocations are the most common structural chromosomal abnormalities, which result from the exchange of terminal segments from different chromosomes. Such translocations occur in 0.14% of the neonatal population and are found in 0.6% of infertile couples [1, 2]. Balanced reciprocal translocation carriers possess no numerical genetic material abnormalities and most are phenotypically normal. They have a high risk of recurrent spontaneous abortions or birth of affected children, which is due to chromosomally abnormal embryos as a result of the production of unbalanced gametes by the carriers. Two normal/balanced gametes are produced from the alternate segregation mode, and the others are chromosomally unbalanced
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