Anaphase lagging mainly explains chromosomal mosaicism in human preimplantation embryos.
BACKGROUND
Cleavage stage embryos as well as postimplantation embryos have been studied extensively over the years. However, our knowledge with respect to the chromosomal constitution of human embryos at the blastocyst stage is still rudimentary.


METHODS
In the present paper, a large series of human blastocysts was examined by means of fluorescent in situ hybridization (FISH).


RESULTS
It was found that only one in four blastocysts (25%) displayed a normal chromosomal pattern. We defined a group of blastocysts (26%) displaying a simple mosaic chromosome pattern (different cell lines resulting from one chromosomal error), an about equally large group of blastocysts (31%) displaying a complex mosaic chromosome pattern, and a smaller group of blastocysts (11%) showing a chaotic chromosome distribution pattern. Six per cent of all blastocysts analysed could not be assigned one of the previously mentioned chromosomal patterns.


CONCLUSIONS
Anaphase lagging appeared to be the major mechanism through which human embryos acquire a mosaic chromosome pattern during preimplantation development to the blastocyst stage.
Coonen
Edith
E
Research Institute Growth & Development (GROW), Maastricht University and Department of Obstetrics & Gynaecology, Academic Hospital Maastricht, The Netherlands. eco@sgyn.azm.nl
Derhaag
Josien G
JG
Dumoulin
John C M
JC
van Wissen
Lucie C P
LC
Bras
Marijke
M
Janssen
Marij
M
Evers
Johannes L H
JL
Geraedts
Joep P M
JP
D000705:Anaphase / Q000235:genetics*; D001755:Blastocyst / Q000648:ultrastructure*; D002877:Chromosomes, Human / Q000235:genetics*; D002970:Cleavage Stage, Ovum / Q000648:ultrastructure; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D009030:Mosaicism / Q000235:genetics*; D011247:Pregnancy; D020554:Sperm Injections, Intracytoplasmic