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5 results

  • Chapter 15 - Cell-Free DNA Analysis for PGT-A

  • Edited by Catherine Racowsky, Hôpital Foch, France, Jacques Cohen, IVF 2.0, New York, Nicholas Macklon, London Women's Clinic
  • Book:
    Manual of Embryo Selection in Human Assisted Reproduction
    Published online:
    26 April 2023
    Print publication:
    26 January 2023, pp 158-167

  • Summary

    It is well known that chromosomal abnormalities are among the major causes of implantation failure especially in patients at high risk of generating aneuploid embryos. Preimplantation genetic testing for aneuploidy (PGT-A) plays an important role in select patient populations for embryo selection by identifying euploid embryos. The current PGT-A technology involves analysis of trophectoderm (TE) cell biopsies removed from expanded blastocysts. However, when an embryo is mosaic, the chromosome copy number of the biopsied cells may not reflect that of the inner cell mass, thereby leading to false positive and false negative results. Recognizing these shortfalls of TE biopsy, studies have been undertaken to investigate the potential value of cell-free DNA (cfDNA) shed from the embryo as a more accurate reflection of the embryo chromosome copy number. Two approaches for acquiring such PGT-A samples have been investigated: collection of the blastocoelic fluid, and collection of the spent medium in which embryos were cultured. In this chapter, we focus on these two approaches, and present current findings supporting a potential role for each of these developing techniques for PGT-A. We highlight that blastocoelic fluid represents a valuable source of cfDNA, and that it provides important insight regarding blastocyst viability; and that while evidence for analysing cfDNA in spent medium holds promise, care must be taken to reduce the risk of maternal DNA contamination. We conclude that although both these approaches appear valuable in improving the sensitivity and specificity of PGT-A, clinical trials are required to evaluate their efficacy before being accepted into mainstream clinical IVF.

  • Evaluation of extracellular vesicles and gDNA from culture medium as a possible indicator of developmental competence in human embryos

  • Daniel Veraguas, Constanza Aguilera, Carlos Henriquez, Alejandra E. Velasquez, Barbara Melo-Baez, Pedro Silva-Ibañez, Fidel O. Castro, Lleretny Rodriguez-Alvarez
  • Journal:
    Zygote / Volume 29 / Issue 2 / April 2021
    Published online by Cambridge University Press:
    29 October 2020, pp. 138-149

  • Human embryos generated in vitro have a high incidence of chromosomal abnormalities that negatively affect pregnancy rate. Embryos generated in vitro secrete extracellular vesicles (EVs) into the culture medium that could be used potentially as indicators of embryo competence. This research aimed to evaluate the concentration and size of EVs and their gDNA content as an indicator of developmental competence in human embryos. Human embryos generated by intracytoplasmic sperm injection (ICSI) were classified morphologically as of either TOP, FAIR or POOR quality. Culture medium and developmentally arrested embryos (which were not able to be used for embryo transfer) were collected. Microvesicles, exosomes (MV/Exo) and apoptotic bodies (ABs) were isolated from culture medium. Nanoparticle tracking analysis (NTA) and array comparative genomic hybridization (aCGH) analysis were performed to evaluate EVs and their gDNA content. From NTA, the diameter (mean) of MVs/Exo from TOP quality embryos was higher (112.17 nm) compared with that of FAIR (108.02) and POOR quality embryos (102.78 nm) (P < 0.05). aCGH analysis indicated that MVs/Exo and ABs carried gDNA with the presence of 23 chromosome pairs. However, when arrested embryos were compared with their respective MVs/Exo and ABs, the latter had an increased rate of chromosomal abnormalities (24.9%) compared with embryos (8.7%) (P < 0.05). In conclusion, the size of EVs from culture medium might be an alternative for evaluating competence of human embryos, however more studies are needed to validate the use of gDNA from EVs as an indicator of embryo competence.

  • Array CGH as a first-tier test for neonates with congenital heart disease

  • Kristine K. Bachman, Stephanie J. DeWard, Constantinos Chrysostomou, Ricardo Munoz, Suneeta Madan-Khetarpal
  • Journal:
    Cardiology in the Young / Volume 25 / Issue 1 / January 2015
    Published online by Cambridge University Press:
    06 November 2013, pp. 115-122
  • Objective

    Efficient diagnosis of an underlying genetic aetiology in a patient with congenital heart disease is essential to optimising clinical care. Copy number variants are one aetiology of congenital heart disease; the majority are identifiable by targeted fluorescence in situ hybridisation or array comparative genomic hybridisation, not by classical cytogenetic analysis. This study assessed the utility of array comparative genomic hybridisation as a first-tier diagnostic test for neonates with congenital heart disease.

    Study design

    A prospective chart review of neonates with congenital heart disease in the Cardiac Intensive Care Unit at Children’s Hospital of Pittsburgh of UPMC was performed. Patients were tested by array comparative genomic hybridisation and classical cytogenetic analysis simultaneously. Data collected included all chromosome abnormalities detected, physical examination findings, and imaging results. McNemar’s test was used to compare detection of array comparative genomic hybridisation and classical cytogenetic analysis.

    Results

    Of 45 patients, three (6.7%) had an abnormality detected by classical cytogenetic analysis and an additional 10 (22.2%) had a copy number variant detected by array comparative genomic hybridisation, highlighting an increased detection rate (p=0.008). Several of these copy number variants had unclear clinical significance, requiring additional investigation. The prevalence of dysmorphology and/or comorbidity in this population was 72%. Identification of dysmorphic features was greater when assessed by a geneticist than by providers of different subspecialties.

    Conclusions

    Array comparative genomic hybridisation has significant clinical utility as a first-tier test in this population, but it carries the potential for incidental findings and results of uncertain clinical significance. Collaboration between cardiologists and medical geneticists is essential to providing optimal clinical care.

  • Antenatally Detected Klinefelter's Syndrome in Twins

  • D.B. Flannery, J.A. Brown, F.O. Redwine, P. Winter, W.E. Nance
  • Journal:
    Acta geneticae medicae et gemellologiae: twin research / Volume 33 / Issue 1 / January 1984
    Published online by Cambridge University Press:
    01 August 2014, pp. 51-56
    Print publication:
    January 1984
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  • An increased incidence of twinning has been reported among patients with Klinefelter's syndrome (XXY) and their relatives, but no data have been reported about the incidence of XXY among twins. Results from our institution's antenatal testing clinic provide data about twins and XXY. In 1842 pregnancies tested, 21 were noted to be twin gestations. Five fetuses with XXY were detected in all pregnancies, of which there was a pair of MZ twins concordant for XXY and a pair of DZ twins discordant for XXY. The incidence of XXY in twins was thus 7,1%. The fetal phenotype of XXY was examined in aborted MZ twins and found to be mild. Notably, the testicular histology was normal. These cases confirm the previously reported association of twinning and XXY. The association of twinning and XXY implies a commonality of causation; however, a maternal age effect cannot be excluded. Our data suggest that there is an increased risk of XXY among twins.