BACKGROUND: In order to assess the frequency of aneuploidy and mosaicism in embryos obtained from IVF patients aged <38 years, preimplantation genetic screening (PGS) was performed after biopsy of ...two blastomeres. Furthermore, the reliability of this diagnosis was assessed by performing reanalysis of the embryo on day 5. METHOD: The copy numbers of 10 chromosomes (1, 7, 13, 15, 16, 18, 21, 22, X and Y) were investigated by fluorescence in situ hybridization (FISH) analysis. Embryos that were found to be abnormal or of insufficient morphological quality were cultured until day 5 and reanalysed. Results obtained were compared to the day 3 blastomere analysis. RESULTS: After analysis of 196 embryos (one cell in 38% and two cells in 62%), only 36% of the embryos were found to be normal on day 3. After analysis of two blastomeres, 50% showed chromosomal mosaicism. Comparison of the FISH results from day 3 blastomeres and day 5 embryos yielded an overall cytogenetic confirmation rate of 54%. CONCLUSIONS: The rates of mosaicism and aneuploidy in these embryos from young IVF patients are similar to those published for older women. We found the best confirmation rate after a diagnosis based on two cells, where both blastomeres showed the same chromosomal abnormality. In contrast, after a mosaic diagnosis the confirmation rate was low. The present study provides the first detailed reanalysis data of embryos analysed by PGS and clearly demonstrates the impact of mosaicism on the reliability of the PGS diagnosis.
The introduction of non-invasive prenatal testing (NIPT) for foetal aneuploidies is currently changing the field of prenatal screening in many countries. As it is non-invasive, safe and accurate, ...this technique allows for a broad implementation of first-trimester prenatal screening, which raises ethical issues, related, for instance, to informed choice and adverse societal consequences. This article offers an account of a leading international ethical framework for prenatal screening, examines how this framework is used by professionals working in the field of NIPT, and presents ethical guidance for the expansion of the scope of prenatal screening in practice.
A comparative analysis of authoritative documents is combined with 15 semi-structured interviews with professionals in the field of prenatal screening in the Netherlands. Data were recorded, transcribed verbatim and analysed using thematic analysis.
The current ethical framework consists of four pillars: the aim of screening, the proportionality of the test, justice, and societal aspects. Respondents recognised and supported this framework in practice, but expressed some concerns. Professionals felt that pregnant women do not always make informed choices, while this is seen as central to reproductive autonomy (the aim of screening), and that pre-test counselling practices stand in need of improvement. Respondents believed that the benefits of NIPT, and of an expansion of its scope, outweigh the harms (proportionality), which are thought to be acceptable. They felt that the out-of-pocket financial contribution currently required by pregnant women constitutes a barrier to access to NIPT, which disproportionally affects those of a lower socioeconomic status (justice). Finally, professionals recognised but did not share concerns about a rising pressure to test or discrimination of disabled persons (societal aspects).
Four types of limits to the scope of NIPT are proposed: NIPT should generate only test outcomes that are relevant to reproductive decision-making, informed choice should be (made) possible through adequate pre-test counselling, the rights of future children should be respected, and equal access should be guaranteed. Although the focus of the interview study is on the Dutch healthcare setting, insights and conclusions can be applied internationally and to other healthcare systems.
BACKGROUND
Chromosome segregation errors during human oocyte meiosis are associated with low fertility in humans and the incidence of these errors increases with advancing maternal age. Studies of ...mitosis and meiosis suggest that defective remodeling of chromatin plays a causative role in aneuploidy. We analyzed the histone deacetylation pattern during the final stages of human oocyte maturation to investigate whether defective epigenetic regulation of chromatin remodeling in human oocytes is related to maternal age and leads to segregation errors.
METHODS
Human surplus oocytes of different meiotic maturation stages germinal vesicle (GV), metaphase (M)I and MII were collected from standard IVF/ICSI treatments. Oocytes were analyzed for acetylation of different lysines of histone 4 (H4K5, H4K8, H4K12 and H4K16) and for α-tubulin.
RESULTS
Human GV oocytes had an intense staining of the chromatin for all four histone 4 lysine acetylations. MI and MII stage oocytes showed either normal deacetylation or various amounts of defective histone deacetylation. Residual H4K12 acetylation was more frequently found in oocytes obtained from older women, with a significant correlation between defective deacetylation and maternal age (r = 0.185, P = 0.007). Eighty-eight percent of the oocytes with residual acetylation had misaligned chromosomes, whereas only 33% of the oocytes that showed correct deacetylated chromatin had misaligned chromosomes (P < 0.001).
CONCLUSIONS
We conclude that defective deacetylation during human female meiosis increases with maternal age and is correlated with misaligned chromosomes. As chromosome misalignment predisposes to segregation errors, our data imply that defective regulation of histone deacetylation could be an important factor in age-related aneuploidy.
Objective
Isolated agenesis of the corpus callosum on fetal ultrasound has a varied prognosis. Microarray and exome sequencing (ES) might aid in prenatal counseling.
Method
This study includes 25 ...fetuses with apparently isolated complete corpus callosum (cACC) on ultrasound. All cases were offered single nucleotide polymorphism array. Complementary ES was offered postnatally in selected cases. Clinical physical and neurodevelopmental follow‐up was collected.
Results
Eighteen cases opted for single nucleotide polymorphism array testing, which detected a causal anomaly in 2/18 (11.1%; 95% CI 2.0%‐31%). Among ongoing pregnancies without a causal anomaly on microarray, 30% (95% CI 8.5%‐60%) showed intellectual disability. Postnatal magnetic resonance imaging and physical examination often (64%; 95% CI 38%‐85%, and 64%; 95% CI 38%‐85%, respectively) revealed additional physical anomalies in cases without a causal anomaly on microarray. Two cases appeared truly isolated after birth. Postnatal sequencing in 4 of 16 cases without a causal anomaly on microarray but with intellectual disability and/or additional postnatal physical anomalies revealed 2 single‐gene disorders. Therefore, the estimated diagnostic yield of ES in chromosomally normal cACC fetuses is between 2/4 (50%; 95% CI 11%‐89%) and 2/16 (13.3%; 95% CI 2.4%‐36%).
Conclusion
In accordance with current guidelines, we conclude that microarray should be offered in case of isolated cACC on ultrasound. ES is likely to be informative for prenatal counseling and should be offered if microarray is normal.
What's already known about this topic?
Agenesis of the corpus callosum is associated with a varied fetal prognosis. The presence of a genetic syndrome is an important determinant in the fetal prognosis.
What does this study add?
Single nucleotide polymorphism array and exome sequencing can be informative for prenatal counseling in fetuses with isolated complete ACC on prenatal ultrasound.
Genomic microarray may detect susceptibility loci (SL) for neurodevelopmental disorders such as autism and epilepsy, with a yet unquantifiable risk for the fetus. The prenatal disclosure of ...susceptibility loci is a topic of much debate. Many health care professionals fear that reporting susceptibility loci may put a psychological burden on pregnant couples. It is our policy to disclose prenatal susceptibility loci as we recognize them as actionable for prospective parents. The aim of this report was to evaluate the psychological impact of disclosing a prenatal diagnosis of susceptibility loci. The psychological impact of disclosing susceptibility loci was evaluated in the first patients who received such results. Eight out of 15 women who had a susceptibility locus disclosed and four of their partners consented to share their experiences through a telephonic evaluation (
n
= 12). Follow-up time ranged from 3 to 15 months after their prenatal test result. The reporting of susceptibility loci was initially ‘shocking’ for five parents while the other seven felt ‘worried’. Ten out of 12 participants indicated they would like to be informed about the susceptibility locus again, two were unsure. Most had no enduring worries. Participants unanimously indicated that pregnant couples should have an individualized pre-test choice about susceptibility loci (non)disclosure. We observed no negative psychological impact with the prenatal diagnosis and disclosure of SL on participants. A key factor in mitigating parental anxiety with SL disclosure appears to be post-test genetic counseling. Our report confirms that pregnant women and their partners prefer an individualized choice regarding the scope of prenatal testing.
Genomic array detects more pathogenic chromosome aberrations than conventional karyotyping (CK), including genetic variants associated with a susceptibility for neurodevelopmental disorders; ...susceptibility loci (SL). Consensus regarding the scope of invasive prenatal diagnosis (PND) pregnant couples should be offered is lacking. This study examined pregnant couples' preferences, doubts and satisfaction regarding the scope of invasive PND. Eighty‐two couples choosing prenatal screening (PNS) and 59 couples choosing invasive PND were offered a choice between 5 (comparable to CK) and 0.5 Mb resolution array analysis outcomes, the latter with or without reporting SL. A pre‐test self‐report questionnaire and post‐test telephone interview assessed their choices in‐depth. Actual (PND) and hypothetical (PNS) choices differed significantly (p < 0.001). Ninety‐five percent of the couples in the PND group chose 0.5 Mb array, vs 69% in the PNS group. Seven percent of the PND group wished not to be informed of SL. Ninety percent was satisfied with their choice and wished to decide about the scope themselves. Pregnant couples wish to make their own choices regarding the scope of invasive PND. It therefore seems justified to offer them a choice in both the resolution of array and disclosure of SL.
Section Editor:
Aad Tibben, email: a.tibben@lumc.nl
Angelman syndrome (AS) is associated with maternal deletions of human chromosome 15q11-q13 and with paternal uniparental disomy for this region indicating that deficiency of an imprinted, maternally ...expressed gene within the critical interval is the likely cause of the syndrome. Although the gene for E6-AP ubiquitin-protein ligase (UBE3A) was mapped to the critical region for AS, evidence of expression from both parental alleles initially suggested that it was an unlikely candidate gene for this disorder. Because attempts to identify any novel maternally expressed transcripts were unsuccessful and because the UBE3A gene remained within a narrowed AS critical region, we searched for mutations in UBE3A in 11 AS patients without known molecular defects (large deletion, uniparental disomy, or imprinting mutation). This analysis tested the possibility that deficiency of an undefined, maternally expressed transcript or isoform of the UBE3A gene could cause AS. Four mutations were identified including a de novo frameshift mutation and a de novo nonsense mutation in exon 3 and two missense mutations of less certain significance. The de novo truncating mutations indicate that UBE3A is the AS gene and suggest the possibility of a maternally expressed gene product in addition to the biallelically expressed transcript. Intragenic mutation of UBE3A in AS is the first example of a genetic disorder of the ubiquitin-dependent proteolytic pathway in mammals. It may represent an example of a human genetic disorder associated with a locus producing functionally distinct imprinted and biallelically expressed gene products.
Congenital diaphragmatic hernia (CDH) has an incidence of 1 in 3,000 births and a high mortality rate (33%–58%). Multifactorial inheritance, teratogenic agents, and genetic abnormalities have all ...been suggested as possible etiologic factors. To define candidate regions for CDH, we analyzed cytogenetic data collected on 200 CDH cases, of which 7% and 5% showed numerical and structural abnormalities, respectively. This study focused on the most frequent structural anomaly found: a deletion on chromosome 15q. We analyzed material from three of our patients and from four previously published patients with CDH and a 15q deletion. By using array-based comparative genomic hybridization and fluorescent in situ hybridization to determine the boundaries of the deletions and by including data from two individuals with terminal 15q deletions but without CDH, we were able to exclude a substantial portion of the telomeric region from the genetic etiology of this disorder. Moreover, one patient with CDH harbored a small interstitial deletion. Together, these findings allowed us to define a minimal deletion region of ∼5 Mb at chromosome 15q26.1-26.2. The region contains four known genes, of which two—
NR2F2 and
CHD2—are particularly intriguing gene candidates for CDH.
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