Investigating Pre-Implantation Chromosomal Instability in Assisted Reproduction

    Research project

    Description

    Program Director/Principal Investigator (Last, First, Middle): Chavez, Shawn L.Project Summary/AbstractSince its introduction over 35 years ago, human in vitro fertilization (IVF) has assumed great promise forinfertile couples, but success rates have remained only ~30% worldwide for several decades. One of theprimary reasons for this is that whole chromosomal abnormalities, or aneuploidy, are incredibly common incleavage-stage human embryos. Previously, we demonstrated that assessing the time intervals of the firstthree mitotic divisions in conjunction with a phenomenon called cellular fragmentation, which is frequentlyobserved in human embryos as well as following natural conception, largely distinguishes chromosomallynormal and abnormal cleavage-stage human embryos. We also determined that cellular fragments mightcontain genetic material that likely began as mis-segregated chromosomes were encapsulated into micronucleiduring meiosis and/or mitosis. Although cellular fragmentation is closely linked with aneuploidy generation andmicronuclei formation, the source of these fragments and their precise chromosomal content is not welldefined. In addition, whether embryos from other mammalian species more closely related to humans such asnon-human primates have a similar aneuploidy frequency remains unknown and addressing this question isessential for potential translation to early human embryogenesis. Our preliminary data reveals that rhesuscleavage-stage embryos also exhibit a high degree of aneuploidy, fragmentation, and micronucleation as wellas similar mitotic timing when compared to human. Given that humans and the rhesus monkey are also highlysimilar in terms of female reproductive physiology and fundamental aspects of early embryogenesis, wepropose to investigate aneuploidy and the fate of mis-segregated chromosomes in rhesus embryos to modelhuman pre-implantation development. By applying whole-genome next-generation sequencing (NGS) forcomprehensive chromosomal assessment, we will first determine the frequency of aneuploidy and sub-chromosomal errors during meiosis in individual mature rhesus oocytes and zygotes and potential correctionupon chromosome-induced polar body extrusion. Using a combination of NGS and non-invasive time-lapseimaging to monitor early cleavage divisions and cellular fragmentation dynamics, we will then evaluate theincidence of mitotic chromosomal mis-segregation up to the ~8-cell stage and reconstruct all whole and sub-chromosomal errors in each rhesus embryo by analyzing the genetic content of both single cells andfragments. Lastly, we will assess the potential contribution of meiotic chromosomal mis-segregation to mitoticerrors and subsequent development by performing polar body biopsy on zygotes, allowing the embryo toproceed until the ~8-cell stage, and distinguishing meiotic versus mitotic errors based on chromosomalmosaicism, fragmentation timing, and microsatellite analysis. This work will greatly contribute to our knowledgeof normal primate embryogenesis with additional implications for translational application to human infertilityand IVF treatment.OMB No. 0925-0001/0002 (Rev. 08/12 Approved Through 8/31/2015) Page Continuation Format Page
    StatusActive
    Effective start/end date7/24/165/31/21

    Funding

    • National Institutes of Health: $363,125.00

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    Chromosomal Instability
    Reproduction
    Embryonic Structures
    Aneuploidy
    Embryonic Development
    Chromosomes
    Polar Bodies
    Zygote
    Meiosis
    Fertilization in Vitro
    Primates
    Mammalian Embryo
    Macaca mulatta
    Mitosis
    Chromosome Aberrations
    Microsatellite Repeats
    Oocytes
    Research Personnel
    Genome
    Biopsy