Incidence of chromosomal mosaicism in morphologically normal nonhuman primate preimplantation embryos

ObjectiveTo establish the exact rates of chromosomal mosaicism in morphologically normal rhesus macaque embryos by determining the chromosomal complement of all blastomeres.DesignRetrospective rhesus monkey IVF study.SettingAcademic laboratory and primate research center.Patient(s)Young fertile rhesus macaque females.Intervention(s)Morphologically normal in vitro–produced rhesus macaque embryos were dissociated and cytogenetically assessed using a five-color fluorescent in situ hybridization assay developed for rhesus macaque chromosomes homologous to human chromosomes 13, 16, 18, X, and Y.Main Outcome Measure(s)The incidence and extent of chromosomal mosaicism in rhesus macaque preimplantation embryos.Result(s)Seventy-seven preimplantation embryos, displaying normal morphology and development, from 17 young rhesus macaque females were analyzed. Overall, 39 embryos (50.6%) were normal, 14 embryos (18.2%) were completely abnormal, and 24 embryos (31.2%) were mosaic. Of the 226 blastomeres analyzed in the mosaic group, 110 blastomeres (48.7%) were normal.Conclusion(s)The observed rate of mosaicism in good-quality rhesus embryos resembles previously documented frequencies in poor-quality human preimplantation embryos. A high incidence of mosaicism may limit the diagnostic accuracy of preimplantation genetic diagnosis.