Objectives: To analyse genotype information from cleavage-stage human embryos and assess the chromosomal status and feasibility of performing aneuploidy screening by microsatellite analysis.
Methods: DNA from 49 blastomeres from eight cleavage-stage human embryos was amplified using multiple displacement amplification, then tested for panels of 64 polymorphic microsatellite markers on seven different chromosomes, and for two non-polymorphic sequences on the X and Y chromosomes.
Results: There was an overall allele drop out (ADO) rate of 28%. Novel alleles in single cells were seen in 0.3% of amplifications, interpreted as either somatic microsatellite mutation events or 'slippage' of the MDA phi 29 polymerase. Three-allele results for a single marker in a single cell were found in 0.07% of amplifications, interpreted as 'slippage' of the MDA phi 29 polymerase. One apparent segmental duplication was found. Only one embryo with no normal cells was found, probably arising from the chaotic cleavage division following a triploid conception. Six embryos were mosaic, of which four had only one abnormal cell.
Conclusions: Abnormalities in human embryos may be present in only a single cell, leading to potentially false abnormal results at pre-implantation genetic diagnosis. ADO associated with MDA reduces the efficacy of this approach for detection of aneuploidy. Statistical analysis showed that, for ADO of 28%, seven informative markers would be required to give 95% confidence of detecting trisomic embryos.
Copyright (c) 2007 John Wiley & Sons, Ltd.