Chromosomal abnormalities in human preimplantation development

Student thesis: Doctoral Thesis

Abstract

Chromosomal abnormalities arising during pre-implantation embryo
development negatively influence embryo survival. Human
preimplantation embryos have high levels of aneuploidy and
mosaicism. It is suggested that embryos correct their ploidy status as
they move further in development but it is still unclear how and when
this correction occurs.
We used single-cell array comparative genomic hybridisation (array-
CGH) to study the levels of aneuploidy and mosaicism in top quality
Day-3 and Day-4 preimplantation embryos. We investigated whether
the correction of the genetic content of embryos initiates at Day-4 of
development and we aimed at visualizing the evolution of
chromosomal imbalances and mosaicism throughout the first four
days of human development.
We analysed 14 Day-3 IVF embryos and we found 71.4% of them
being mosaic. From the analysed blastomeres, 55.7% were diploid
and 44.3% had chromosomal abnormalities. Next, all blastomeres of
13 Day-4 good-quality embryos (4 fresh PGD embryos and 9
cryopreserved embryos) were analysed. In one PGD embryo all the
analysed cells were euploid and the other three were mosaic (16-
75% abnormal cells). All 9 frozen-thawed embryos were abnormal.
Six were mosaic (30-100% abnormal cells) and three had meiotic
abnormalities, in two of which co-existed with mitotic abnormalities.
Our findings highlight the high prevalence of aneuploidy and
mosaicism up to Day-4 of preimplantation development. Mitotic
chromosomal abnormalities seem to appear early in development but
do not prevent the embryo development at least until Day-4. We did
not observe signs of correction of the genetic embryo content until
Day-4 of development.
Date of Award29 Apr 2015
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
SupervisorKaren Sermon (Promotor), Claudia Spits (Promotor), Christiaan Van Schravendijk (Jury), Karine Breckpot (Jury), Martine De Rycke (Jury), Willem Verpoest (Jury), Dagan Wells (Jury) & Sophie Debrock (Jury)

Keywords

  • PGD
  • human preimplantation
  • Chromosomal abnormalities
  • embryo
  • survival

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