Results of preimplantation genetic testing for aneuploidies as a basis for parental karyotypes correction

Abstract

Introduction Chromosomal abnormalities are the most common genetic cause of infertility. An information about karyotypes of patients undergoing in vitro fertilization (IVF) is not always known. Therefore, IVF patients can be potential carriers of structural chromosomal rearrangements. We report three cases, in which results of preimplantation genetic testing for aneuploidies (PGT-A) allowed us to suspect the presence of parental reciprocal translocations. In each case, the parental reciprocal translocation was confirmed. Material & Methods PGT-A was performed by microarray comparative genomic hybridization (aCGH) (24sure, Illumina) or by next generation sequencing (NGS) (VeriSeq, Illumina). Indications for preimplantation testing were advanced maternal age (case 1 and 2) and paternal pericentric inversion of chromosome 10 (case 3). Parental karyotypes were not known before PGT-A in cases 1 and 2. In case 3 patients’ karyotypes was known before PGT-A and were 46,XX and 46,XY,inv(10)(p11.2;q22). The trophectoderm biopsy was performed at 5-6 day of embryo development. Analysis of parental karyotypes after obtaining PGT results was performed by standard cytogenetic study or by fluorescence in situ hybridization (FISH) on peripheral blood lymphocyte culture. The choice of method of parental karyotypes analysis was determined by size of the embryo chromosomal imbalance. Results PGT-A results showed a nonrandom pattern of segmental loses and gains in each case (table 1). These facts were the basis for parental karyotypes analysis. It was confirmed, that in each case one of the couple was the carrier of reciprocal translocation. In case 1 a paternal reciprocal translocation between chromosomes 11 and 22 was found – 46,XY,t(11;22)(q23.3;q13). In case 2 a maternal reciprocal translocation between chromosomes 10 and 12 was found – ish t(10;12)(D10S2290-, D12S158+; D10S2290+, D12S158-). In case 3 a maternal reciprocal translocation between chromosomes 2 and 12 was found - ish t(2;12)(D2S2147-,D12S399+; D2S2147+, D12S399-). Table 1 Case № Number of embryos Number of embryos with nonrandom pattern of segmental abnormalities Chromosomes involved in nonrandom segmental abnormalities Case 1 5 3 Chromosomes 11 and 22 Case 2 4 4 Chromosomes 10 and 12 Case 3 4 3 Chromosomes 2 and 12 Conclusions It is very importantto draw attention to pattern of segmental chromosomal abnormalities of embryos. 24-chromosome aneuploidy testing is not only an actual method for detection of embryo chromosomal imbalance, but in some cases also can help to correct parental karyotypes.