title: Incidence of chromosomal mosaicism in human embryos at different developmental stages analyzed by fluorescence in situ hybridization.
abstract: Chromosomal mosaicism has been reported in in vitro-cultured embryos at early cleavage stages, as well as in morulae and blastocysts. We have assessed the incidence and pattern of mosaicism during in vitro development of human embryos from early-cleavage stages to morula and blastocyst. Fifty spare embryos were fixed for fluorescence in situ hybridization (FISH) analysis for chromosomes X, Y, 13, 18, and 21 on days 2 or 3 (4- to 10-cell stage) (n = 16), on day 4 (morula stage) (n = 14), on day 5 (pre-expanded blastocyst) (n = 5), and the expanded blastocyst stages (n = 15). Blocked embryos (no cleavage observed within the last 24 hr) were not included. A total of 2367 cells were analyzed. Four early-cleavage stage embryos were found uniformly diploid; all of the others were mosaic for the chromosomes analyzed (mean diploid nuclei 48.3% +/- 28.7). All of the embryos at more advanced developmental stages, except one fully normal morula, had mosaic chromosome constitutions, with an increase in the percentage of diploid cells in morulae, pre-expanded, and expanded blastocysts, respectively (mean diploid nuclei 78.6% +/- 11.7, 66.0% +/- 20.8, 79.6% +/- 12.8), in comparison with earlier stages. Hypotheses about the origin of mosaicism and embryo regulation mechanisms will be discussed.
authors.affiliation: Fertility Clinic, Department of Obstetrics and Gynaecology, and Laboratory of Research on Human Reproduction, Erasmus Hospital-ULB, Free University of Brussels, Belgium. ergonzal@ulb.ac.be
authors.forename: Eric
authors.initials: E
authors.lastname: Gonzalez-Merino
authors.forename: Serena
authors.initials: S
authors.lastname: Emiliani
authors.forename: Gilbert
authors.initials: G
authors.lastname: Vassart
authors.forename: Marc
authors.initials: M
authors.lastname: Van den Bergh
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Vannin
authors.forename: Marc
authors.initials: M
authors.lastname: Abramowicz
authors.forename: Danièle
authors.initials: D
authors.lastname: Delneste
authors.forename: Yvon
authors.initials: Y
authors.lastname: Englert
mesh_terms: D000782:Aneuploidy; D001755:Blastocyst / Q000648:ultrastructure; D002877:Chromosomes, Human / Q000235:genetics; D002970:Cleavage Stage, Ovum / Q000648:ultrastructure; D004171:Diploidy; D005314:Embryonic and Fetal Development / Q000235:genetics*; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D066298:In Vitro Techniques; D008297:Male; D008957:Models, Genetic; D009028:Morula / Q000648:ultrastructure; D009030:Mosaicism