title: Cytogenetic analysis of human blastocysts with the use of FISH, CGH and aCGH: scientific data and technical evaluation.
abstract: BACKGROUND
  Recent studies have suggested that biopsy of several trophectoderm (TE) cells from blastocysts followed by comparative genomic hybridization (CGH) analysis might represent an optimal strategy for aneuploidy detection, but few data on accuracy are available. The main question concerns the rate of mosaicism at the blastocyst stage, and to what extent this might cause misdiagnoses. We assessed blastocyst aneuploidy and mosaicism rates and evaluated the accuracy and efficiency of CGH and microarray-CGH (aCGH) for TE analysis.
  
  
  METHODS
  A total of 52 blastocysts, from 20 couples, were biopsied and their chromosomes examined by CGH. The remaining cells were spread and tested by fluorescent in situ hybridization (FISH). Of the 52 blastocysts, 20 underwent a second TE biopsy and were tested using aCGH.
  
  
  RESULTS
  CGH and aCGH produced results for 98% of TE samples. 42.3% of blastocysts were uniformly euploid, 30% were uniformly aneuploid and 32.4% were mosaic. Of the mosaic embryos, 15.4% were found to be composed of a mixture of different aneuploid cell lines, while 17% contained both normal and aneuploid cells. Mosaic diploid-aneuploid blastocysts with >30% normal cells accounted for <6% of analysed embryos.
  
  
  CONCLUSIONS
  Comprehensive chromosome screening and follow-up assessment of large numbers of cells provided a unique insight into the cytogenetics of human blastocysts. Meiotic and post-zygotic errors leading to mosaicism were common. However, most mosaic blastocysts contained no normal cells. Hence, CGH or aCGH TE analysis is an accurate aneuploidy detection tool and may assist in identifying viable euploid embryos with higher implantation potential.
authors.affiliation: Nuffield Department of Obstetrics and Gynaecology, University of Oxford, Oxford OX3 9DU, UK. elpida.fragouli@obs-gyn.ox.ac.uk
authors.forename: Elpida
authors.initials: E
authors.lastname: Fragouli
authors.forename: Samer
authors.initials: S
authors.lastname: Alfarawati
authors.forename: Danny D
authors.initials: DD
authors.lastname: Daphnis
authors.forename: N-Neka
authors.initials: NN
authors.lastname: Goodall
authors.forename: Anastasia
authors.initials: A
authors.lastname: Mania
authors.forename: Tracey
authors.initials: T
authors.lastname: Griffiths
authors.forename: Anthony
authors.initials: A
authors.lastname: Gordon
authors.forename: Dagan
authors.initials: D
authors.lastname: Wells
mesh_terms: D000328:Adult; D000782:Aneuploidy; D001755:Blastocyst / Q000166:cytology*; D002869:Chromosome Aberrations; D055028:Comparative Genomic Hybridization; D020732:Cytogenetic Analysis / Q000379:methods*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D046228:Microarray Analysis; D009030:Mosaicism; D020411:Oligonucleotide Array Sequence Analysis; D011247:Pregnancy