Complex mosaic blastocysts after preimplantation genetic testing: prevalence and outcomes after re-biopsy and re-vitrification

RESEARCH QUESTION

What is the incidence of complex mosaic in preimplantation genetic testing (PGT) blastocysts and can it be managed in clinical practice?

DESIGN

A retrospective study of PGT cycles conducted between January 2018 and October 2019 at a single centre. Biopsies of blastocysts were collected and analysed by next-generation sequencing (NGS). Complex mosaic blastocysts were defined as those with three or more mosaic chromosomes. The cryopreserved complex mosaic blastocysts underwent a second round of biopsy, NGS analysis and vitrification. The euploid blastocysts identified by the re-biopsy were warmed again for embryo transfer. The main outcomes included the prevalence of the complex mosaic and the ongoing pregnancy rate.

RESULTS

The prevalence of the complex mosaic was 2.4% (437/17,979). The prevalence of the complex mosaic was not associated with maternal age and morphological quality. A total of 89 complex mosaic blastocysts underwent re-biopsy and 96.6% (86/89) survived the first warming. For the re-biopsy samples, 61.6% (53/86) were euploid. The poor-quality blastocysts had higher rates of aneuploidy compared with good-quality blastocysts. The survival rate for blastocysts undergoing the second warming was 100% (18/18) and resulted in an ongoing pregnancy rate of 38.9% (7/18) as well as the birth of six healthy infants.

CONCLUSION

Re-biopsy may rescue blastocysts with development potential for transfer and improve the cumulative pregnancy rate per stimulation cycle in patients containing complex mosaic blastocysts.

The outcomes after transfers of embryos with chromosomal mosaicism: a single reproductive medicine center experience at iVF Riga clinic

Aim: The aim of this study is to summarize the outcomes of transfers of mosaic embryos, which were classified according to guidelines and in strong collaboration of reproductologists, clinical geneticists and patients approved as suitable for transfer. Material and Methods: Retrospective data were collected from 70 patients from a private IVF center to whom embryos with mosaic changes in chromosomal material were transferred from 2015 to 2019. Results and Conclusion: Implantation outcomes and continuing pregnancies showed slight differences, when compared to fully normal embryos. Artifacts have to be differentiated from undeniable aberrations, and correct interpretation of results must be done with following patient counselling and prenatal testing if necessary.

Outdoor air pollution and mosaic loss of chromosome Y in older men from the Cardiovascular Health Study

BACKGROUND

Mosaic loss of chromosome Y (mLOY) can occur in a fraction of cells as men age, which is potentially linked to increased mortality risk. Smoking is related to mLOY; however, the contribution of air pollution is unclear.

OBJECTIVE

We investigated whether exposure to outdoor air pollution, age, and smoking were associated with mLOY.

METHODS

We analyzed baseline (1989-1993) blood samples from 933 men ≥65 years of age from the prospective Cardiovascular Health Study. Particulate matter ≤10 μm (PM₁₀), carbon monoxide, nitrogen dioxide, sulfur dioxide, and ozone data were obtained from the U.S. EPA Aerometric Information Retrieval System for the year prior to baseline. Inverse-distance weighted air monitor data were used to estimate each participants' monthly residential exposure. mLOY was detected with standard methods using signal intensity (median log-R ratio (mLRR)) of the male-specific chromosome Y regions from Illumina array data. Linear regression models were used to evaluate relations between mean exposure in the prior year, age, smoking and continuous mLRR.

RESULTS

Increased PM₁₀ was associated with mLOY, namely decreased mLRR (p-trend = 0.03). Compared with the lowest tertile (≤28.5 μg/m³), the middle (28.5-31.0 μg/m³; β = -0.0044, p = 0.09) and highest (≥31 μg/m³; β = -0.0054, p = 0.04) tertiles had decreased mLRR, adjusted for age, clinic, race/cohort, smoking status and pack-years. Additionally, increasing age (β = -0.00035, p = 0.06) and smoking pack-years (β = -0.00011, p = 1.4E-3) were associated with decreased mLRR, adjusted for each other and race/cohort. No significant associations were found for other pollutants.

CONCLUSIONS

PM₁₀ may increase leukocyte mLOY, a marker of genomic instability. The sample size was modest and replication is warranted.

High-resolution array-comparative genomic hybridization profiling reveals 20q13.33 alterations associated with ovarian endometriosis

OBJECTIVE

The purpose of this study is to investigate the potential genetic alterations at DNA level in patients with ovarian endometriosis by high-resolution array-based comparative genomic hybridization (array-CGH) analysis.

METHODS

Following the laparoscopic surgical and the post-operative pathological examination, genomic DNA was extracted from endometriomas of 11 women with endometriosis and endometrial tissue of the controls and analyzed by array-CGH. Real-time PCR was used for confirmation the result of array-CGH analysis and detected the DNA copy number variations of the eutopic endometrium from the five patients with the duplication in 20q13.33 region.

RESULTS

All 11 patients with ovarian endometriosis were diagnosed through the laparoscopic surgical and the post-operative pathological examination. We found occurrence of genomic duplication at 20q13.33 chromosomal region with gain of GATA5 and SLCO4A1 genes in 5 of 11 endometriomas from patients.

CONCLUSION

The results of the present study suggest that there was 20q13.33 duplication in women with ovarian endometriosis. This effect might be due to the alterations of GATA5 and SLCO4A1 genes in the gain region, through involving the metabolism of the steroid hormone.

A preliminary study on chromosome aneuploidy & mosaicism in early pre-implantation human embryo by fluorescence in situ hybridization

BACKGROUND & OBJECTIVE

Chromosome aneuploidy plays an important role in infertility, early pregnancy wastage and perinatal mortality. Cytogenetic & fluorescent in situ hybridization (FISH) studies on developmentally arrested and morphologically poor embryo have shown high frequency of chromosomal abnormality and mosaicism. In this study, we attempted to evaluate chromosome aneuploidy and mosaicism on human embryos through the use of FISH.

METHODS

Sixty one grade IV un-transferable embryos were obtained from 25 patients undergoing in vitro fertilization (IVF). Forty six embryos were studied by FISH; 15 were lost during transport and handling. FISH probes (non-commercial) for centromeres of chromosome X, Y, 1 and 18 were used for the study. Zona of embryos were dissolved in 0.01N HCl containing 0.1 per cent Tween 20 for 2-3 min.

RESULTS

Interpretable FISH results were obtained in 24 embryos. Nineteen embryos (79.2%) were disomic (normal) for chromosome X/Y or 1/18 and five (20.8%) were abnormal. Among five abnormal embryos two were triploidy (from same patient), one was double mosaic aneuploidy, one was mosaic aneuploidy and one was trisomy for sex chromosome (XXY). There was eleven embryos with presence of Y chromosome i.e., male and three embryos were female.

INTERPRETATION & CONCLUSION

Skewing of sex ratio (11M vs. 3F) and low chromosome aneuploidy were observed in this preliminary study, however, it will be premature to conclude as the numbers of embryos studied were limited and so were the numbers of FISH probes used.

Y chromosome mosaicism and occurrence of gonadoblastoma in cases of Turner syndrome and amenorrhoea

In the present study, 73 cases with a clinical diagnosis of Turner syndrome, or with primary or secondary amenorrhoea without frank Turner phenotype, were evaluated for presence of low level Y chromosome mosaicism using molecular methods. Fluorescence in-situ hybridization for centromere and q arm of the Y chromosome and nested polymerase chain reaction for the sex determining region on Y (SRY) gene were performed in peripheral blood, buccal cells and gonadal biopsies. The overall frequency of Y chromosome mosaicism was found to be 18% (13/73 cases). Four cases (16%) of Turner syndrome had Y chromosome mosaicism, seven cases (28%) with primary amenorrhoea and two cases (9%) with secondary amenorrhoea had Y chromosome mosaicism. Histologically detectable gonadoblastoma was observed in one of seven cases (14%) that had Y chromosome mosaicism. This frequency is lower than that reported previously, underscoring the need for large prospective investigations to determine the frequency of Y chromosome mosaicism and occurrence of gonadoblastoma in cases of Turner syndrome and other forms of amenorrhoea.

SCN1A mutation mosaicism in a family with severe myoclonic epilepsy in infancy

PURPOSE

To investigate the genetic background of familial severe myoclonic epilepsy in infancy (SMEI) cases.

METHODS

We performed mutation analyses of the sodium-channel gene SCN1A in two Japanese brothers with clinical features of SMEI and their parents, who had no history of febrile and epileptic seizures.

RESULTS

Each patient showed nucleotide changes (c.[730G>T; 735G>T; 736A>T]) in the coding exon 6 of SCN1A that led to a truncation of the channel protein. Their father showed no mutations, but their mother showed the same mutation in a subpopulation of lymphocytes.

CONCLUSIONS

The maternal mosaicism explains the identical SCN1A mutations in the two brothers. This highlights the importance of investigating parental mosaicism even in sporadic SMEI cases.

Association of Clinical Cytogeneticists chorion villus sampling database 1987-2000

OBJECTIVES

To produce a fully searchable Microsoft Access database of mosaic and non-mosaic cytogenetic abnormalities, detected during diagnostic chorionic villi sampling (CVS) to aid laboratories in predicting pregnancy outcome, in particular differentiating between cases of likely genuine fetal cytogenetic abnormalities and those likely to represent confined placental mosaicism (CPM).

METHODS

Retrospective collection of referral data, initial karyotype data, follow-up karyotype data and pregnancy outcome data from almost all cytogenetically abnormal diagnostic CVS, processed in UK National Health Service laboratories, between 1987 and 2000. Collection of similar data from a published series of CVS and individual case reports.

RESULTS

A fully searchable database of abnormal CVS cases, containing over 5000 entries, has been produced. This is available to download at http://www.ncl.ac.uk/cvs/.

CONCLUSIONS

Following detection of a cytogenetic abnormality during prenatal diagnosis using CVS, use of this database allows rapid access to comparable cases from the United Kingdom and the literature. This database will improve the speed of availability and quality of information available to clinicians and patients for pregnancy management and counselling purposes. The database has been designed with future data collection in mind, and can be developed for wider research use, through more detailed registries of individual chromosome abnormalities.

Cytogenetic profile of Down syndrome in Alexandria, Egypt

During 1992-2001, 673 Down syndrome patients were referred to the Department of Human Genetics in Alexandria. Regular (free) trisomy 21 constituted 95.4% of cases; Robertsonian translocation 2.7%; and mosaicism 0.7%. In 8 cases, regular trisomy 21 was associated with structural or numerical chromosome anomalies. Translocation was parentally inherited for 33.3% of cases and maternal transmission was twice as common as paternal. Two translocated Down syndrome fetuses were diagnosed prenatally in a t(14;21) carrier mother. Mean maternal age was high in regular trisomy 21 (38.2 years) but not in translocation (25.3 years). There was an excess of males in all groups except the mosaic group where the male:female ratio was 0.67. Cytogenetic investigations assist in patient management and family counselling.