Multiple aneuploidies in the oocytes of balanced translocation carriers: a preimplantation genetic diagnosis study using first polar body (original) (raw)
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Aneuploidy 12 in a Robertsonian (13;14) carrier: Case report
Human Reproduction, 2005
In translocation carriers, the presence of aneuploidy for the chromosomes unrelated to the rearrangement may lead to an additional risk of abnormal pregnancy or implantation failure. Consequently, it may be important to analyse not only the chromosomes involved in the rearrangement but also the rest of chromosomes. We combined spectral karyotyping (SKY) and comparative genomic hybridization (CGH) to karyotype one unfertilized oocyte and its first polar body (1PB) from a Robertsonian translocation carrier t(13;14) aged 29 years who was undergoing IVF and preimplantation genetic diagnosis (PGD) for translocations and aneuploidy screening. Two out of four embryos were aneuploid, as a result of an adjacent segregation. The unfertilized oocyte had a normal/ balanced constitution of the chromosomes involved in the reorganization. However, this 1PB-metaphase II doublet was aneuploid for chromosome 12, the oocyte being hyperhaploid (24, X, 112) and its 1PB hypohaploid (22, X, 212). The application of CGH for the study of Robertsonian translocations of maternal origin will be useful to study imbalances of the chromosomes involved in the rearrangement, as well as alterations in the copy number of any other chromosome. The combination of PGD for translocations with aneuploidy screening could help to reduce the replacement of chromosomally abnormal embryos.
The importance of aneuploidy screening in reciprocal translocation carriers
Reproduction, 2006
The purpose of this study is to investigate the aneuploidy rate and the mosaicism of chromosomes not involved in reciprocal translocations. Aneuploidy screening (AS) (13, 16, 18, 21 and 22) was performed as a re-analysis on fixed blastomeres from 126 embryos already analysed in preimplantation genetic diagnosis (PGD) cycles of eight female and five male reciprocal translocation carriers who had not achieved a pregnancy. A successful diagnosis for AS was achieved in 91.3% of embryos; 30.9% were euploid and 60.3% were aneuploid for the five chromosomes analysed. Of the embryos, 8.7% were euploid for AS and normal-balanced for the translocation and 22.2% were euploid for AS but unbalanced for the translocation; 8% of the embryos were aneuploid for AS but normal-balanced for the translocation and 52.4% were aneuploid for AS and also unbalanced for the translocation. At least 58.7% of the embryos were mosaic regarding mosaicism for the chromosomes involved and not involved in the translocations. Six of the 16 embryos transferred in the PGD cycles were aneuploid for the AS study; four of them were also mosaics. AS should be performed in reciprocal translocation carriers after segregation analysis in PGD.
Possible interchromosomal effect in embryos generated by gametes from translocation carriers
Human Reproduction, 2002
BACKGROUND: The incidence of abnormal pregnancies in carriers of balanced translocations depends strictly on the chromosomes involved in the translocations. The aim of this study was to verify whether conventional aneuploidy screening could be advantageously combined with preimplantation genetic diagnosis (PGD) for translocations. METHODS: Twenty-eight carriers of Robertsonian and reciprocal translocations underwent 43 PGD cycles; specific probes were used to screen the translocation in 172 embryos generated by 35 cycles; most of these embryos were also screened for chromosomes 13, 16, 18, 21, 22 (n ⍧ 166), XY (n ⍧ 107), 1 (n ⍧ 17) and 15 (n ⍧ 88). For the remaining eight cycles (carriers of reciprocal translocations) only the chromosomes involved in common aneuploidy screening were investigated on the 40 embryos generated in vitro. RESULTS: In Robertsonian translocations, the proportion of embryos with abnormalities due to the translocation was 21%, common aneuploidies contributed 31% of total abnormalities, whereas the remaining 36% of embryos had abnormalities due to both types of chromosome. For reciprocal translocations, the chromosomes involved in the translocation were responsible for 65% of total abnormalities; only 6% of the embryos were abnormal for common aneuploidies and 16% carried abnormalities due to both the chromosomes involved in the translocation and those not related to the translocation. CONCLUSIONS: An interchromosomal effect seems to play a role in the case of Robertsonian translocations, where the relevant contribution of aneuploidy exposes the couple to an additional risk of abnormal pregnancy.
European Journal of Human Genetics, 2003
We used fluorescent in situ hybridisation (FISH) to detect nine chromosomes and X) in 89 first Polar Bodies (1PBs), from in vitro matured oocytes discarded from IVF cycles. In 54 1PBs, we also analysed the corresponding oocyte in metaphase II (MII) to confirm the results; the other 35 1PBs were analysed alone as when preimplantation genetic diagnosis using 1PB (PGD-1PB) is performed. The frequency of aneuploid oocytes found was 47.5%; if the risk of aneuploidy for 23 chromosomes is estimated, the percentage rises to 57.2%. Missing chromosomes or chromatids found in 1PBs of 1PB/MII doublets were confirmed by MII results in 74.2%, indicating that only 25.8% of them were artefactual. Abnormalities observed in 1PBs were 55.8% whole-chromosome alterations and 44.2% chromatid anomalies. We observed a balanced predivision of chromatids for all chromosomes analysed. Differences between balanced predivision in 1PB and MII were statistically significant (Po0.0001, v 2 test); the 1PB was most affected. The mean abnormal segregation frequency for each chromosome was 0.89% (range 0.52-1.70%); so, each of the 23 chromosomes of an oocyte has a risk of 0.89% to be involved in aneuploidy. No significant differences were observed regarding age, type of abnormality (chromosome or chromatid alterations) or frequency of aneuploidy. Nine of the 35 patients (25.7%) whose 1PB and MII were studied presented abnormalities (extra chromosomes) that probably originated in early oogenesis. Analysis of 1PBs to select euploid oocytes could help patients of advanced age undergoing in vitro fertilization (IVF) treatment.
Preimplantation genetic diagnosis of aneuploidy: Were we looking at the wrong chromosomes?
1999
stage embryos. These frequencies were compared to spontaneous abortion data to determine differences in survival rate of their aneuploidies. Methods: One hundred ninety-four embryos were analyzed with multicolor fluorescence in situ hybridization. Embryos were divided into three maternal age groups: 20 to 34.9 years, (2) 35 to 39.9 years, and (3) 40 years and older. Embryos were also divided into two developmental and morphological groups: arrested and nonarrested embryos. Results: The rate of aneuploidy was 14.51%, 14.10%, and 31.48% for age groups 1, 2, and 3, respectively (P < 0.005). The chromosomes most frequently involved in aneuploidy events were 22, 15, 1, and 17. Conclusions: The chromosomes most involved in spontaneous abortions are not necessarily the ones causing a decrease in implantation rates with maternal age. Other aneuploidies, such as for chromosomes 1 and 17, may seldom implant or die shortly after implantation.
Aneuploid and unbalanced sperm in two translocation carriers: Evaluation of the genetic risk
Molecular Human Reproduction
Translocation carriers have an increased risk of reproductive failure or affected offspring, because of the production of unbalanced gametes by meiotic segregation or the possible presence of interchromosomal effects (ICE). We therefore performed an analysis of meiotic segregation using the human-hamster IVF technique, and an aneuploidy assay for chromosomes 6, 18, 21, X and Y, using dual and triple-colour fluorescence in-situ hybridization, in two translocation carriers, t(1;13)(q41;q22) and t(3;19)(p21;p13.3). Sperm chromosome complements were analysed by whole chromosome painting. The frequencies observed for alternate, adjacent I, adjacent II and 3:1 segregations were, for t(1;13), 41.6, 41.6, 14.5 and 2.3% respectively, and for t(3; 19), the frequencies were 39.1, 35.9, 21.8 and 3.2% respectively. More than 20 000 sperm per subject were analysed in the aneuploidy assay. Disomy 21 was found to be higher than other autosome disomies. Evidence for a possible ICE was found only in t . This study has shown that unbalanced sperm are more frequent than aneuploid sperm in the total sperm population. However, data in the literature suggest that the importance of each aberrant population seems to be more significant for embryo viability than would be expected from the increases in the percentages of abnormal sperm.
Journal of Andrology, 2006
Reciprocal chromosomal translocations (RCT) have long been recognized as important etiological factors in reproductive failure. In the present study, the meiotic segregation patterns of the spermatozoa of two related t(4;5)(p15.1;p12) carriers (proband and his father) were compared to the empirical data from a three-generation pedigree for risk assessment. Cytogenetic analysis of the metaphase chromosomes was performed, and triple color fluorescence in situ hybridization (FISH) was applied to the sperm heads. Similar patterns of meiotic segregation were observed for both carriers, despite the finding of teratozoospermia in the proband but not in his father. In addition, an increase of aneuploidy in chromosome 15 in the proband and aneuploidy of chromosomes X and Y in the father were observed. The high rate of miscarriages (6/10 pregnancies and 4/7 pregnancies after ascertainment correction) in this family could be explained by the genetically unbalanced karyotype and fertilization mediated by the unbalanced spermatozoa observed for both men at a frequency of more than 60%. The risk assessment for unfavorable pregnancy outcomes was predicted as 1.6% for unbalanced progeny at birth and about 30% for miscarriage. These figures may be used as guidelines for the genetic counseling of families with similar RCT.
Chromosomal segregation in spermatozoa of five Robertsonian translocation carriers t(13;14)
Journal of Assisted Reproduction and Genetics, 2011
Purpose To analyse the segregation of a Robertsonian translocation t(13;14) in five male carriers, and to verify a possible inter-chromosomal effect (ICE) of the Robertsonian translocation on chromosomes 18, X, and Y. Methods The spermatozoa of these patients (n=5) and of 15 donors with normal semen parameters and 46,XY karyotype were analysed using triple colour FISH with locus specific probes for chromosomes 13, 14, and 21 and by triple colour FISH for chromosomes X, Y, and 18. Results The frequency of balanced spermatozoa resulting from alternate segregation varied between 62.16% and 81.70% with a mean of 71.5%. The rates of unbalanced spermatozoa resulting from adjacent segregation varied between 13.4% and 25.1% with a mean of 18.26%. Triple colour FISH X-Y-18 showed a significant increase in disomy frequencies of these chromosomes in comparison with controls, indicating an ICE. Conclusion In spite of the high number of normal/balanced frequencies, there remain many unbalanced spermatozoa resulting from adjacent mode of segregation. This raises the question of the unbalanced chromosomal risk for the offspring of 45,XY, t(13;14) males and the importance of the genetic counselling prior to ICSI or IVF treatment for couples where the male is a Robertsonian translocation carrier.
Human Reproduction Update, 2001
Preimplantation genetic diagnosis (PGD) using the ®rst polar body (1PB) is a modality of PGD that can be used when the woman is the carrier of a genetic disease or of a balanced chromosomal reorganization. PGD using 1PB biopsy in carriers of balanced chromosome reorganizations has not become generalized. Here, we describe our experience based on the analysis of unfertilized or fresh, non-inseminated control oocytes, by ®xing separately the 1PB and the corresponding oocyte, and on the study of six clinical cases of PGD using 1PB biopsy (four Robertsonian translocations and two reciprocal translocations). In fresh oocytes, the chromosome morphology of the 1PB was well preserved, and the results were always concordant for each oocyte±1PB pair. This indicates that the 1PB can be reliably used for the diagnosis of chromosome reorganizations. In these studies the technical problems encountered when performing PGD using 1PB biopsies for chromosome studies are also addressed. Three different strategies of 1PB biopsy (laser beam, partial zona dissection and acid Tyrode's) and two different protocols (intracytoplasmic sperm injection before or after 1PB biopsy) and their effect on the percentage of oocytes diagnosed and the fertilization rate, are discussed. In reciprocal translocation cases, published in the literature or studied by us, in which at least nine oocytes had been diagnosed, a correlation has been found between the frequency of nondisjunction observed and the theoretical recombination rate. To date, PGD by 1PB analysis alone or combined with blastomere biopsies in female carriers of chromosomal rearrangements has been used in 18 cases, with a further six cases reported here. A total of 325 cumulus±oocyte complexes have been obtained, of which 294 were biopsied and 224 were diagnosed. A total of 52 embryos was transferred, 19 of which implanted and 17 produced full-term pregnancies.