Abstract
A diploid genome is necessary for normal mammalian development, thus haploid parthenogenetic embryos undergo frequent self-diploidization during preimplantation development; however, the underlying mechanism is unclear. In this study, time-lapse recording revealed that human haploid parthenotes (HPs) undergo self-diploidization via failed cytokinesis (FC) and endomitosis (EM). The frequencies of FC/EM were significantly higher in HPs than in normal fertilized embryos (26.3% vs. 1.6%, P < 0.01; 19.7% vs. 0, P < 0.01), and above 90% of FC/EM occurred at the first cell cycle in HPs. Fluorescent in situ hybridization of chromosome 16,18 and X in HPs identified diploid recovery after the appearance of FC/EM, and FC/EM HPs showed improved blastocyst formation compared with non-FC/EM HPs (18.8% and 40.0% vs. 15.4%, P > 0.05). In 66.7% of the 1-cell stage HPs, furrow ingression was not observed during the time for normal cleavage, and both immunostaining and gene expression analysis of 1-cell stage HPs revealed the absence or down-regulation of several key genes of the Rho pathway, which regulates cytomitosis. Our results suggested that the major mechanism for self-diploidization is Rho pathway inhibition leading to FC/EM in the first cell cycle, and fine-tuning of this signalling pathway may help to generate stable haploid embryos for stem cell biology studies.
Highlights
Haploid development is a normal part of the life cycle in some lower animals[1], but it is not observed in mammals
Under subsequent time-lapse monitoring, we observed four kinds of cleavage behaviours related to self-diploidization in haploid parthenotes (HPs) during the three initial divisions, which were defined as: (i) failed cytokinesis (FC, the cleavage furrow appeared but the cell recovered into one cell again rather than dividing into two daughter blastomeres) (Fig. 1B, Supplementary Video S2); Figure 1
Normal and four kinds of self-diploidization-related cleavage behaviours were recorded by timelapse photography in haploid parthenotes (HPs). (A) Normal cleavage (NC), cleavage from one cell to two even blastomeres; (B) Failed cytokinesis (FC), a cleavage furrow appeared but the cell recovered into one cell again rather than divide into two daughter blastomeres; (C) Endomitosis (EM), replication of the nucleus was complete, but there was no appearance of the cleavage furrow; (D) Endocycling (EC), the duration of the pronuclear phase was extended obviously and more than one cell cycle occurred; and (E) Blastomere fusion (BF), one cell divided into two daughter blastomeres, which fuse into one blastomere again after a mitotic cycle
Summary
Haploid development is a normal part of the life cycle in some lower animals[1], but it is not observed in mammals. Advances in culture conditions and flow cytometric cell sorting have facilitated the derivation of embryonic stem cells (ESCs) from mammalian haploid parthenogenetic and androgenetic embryos[12,13,14,15]. These haploid ESCs exhibit an intrinsic tendency for diploidization following passaging in vitro[13]. We investigated whether human HPs undergo self-diploidization through specific cleavage behaviours and at which stage of development haploid cells become diploid. We explored the underlying mechanism that regulates self-diploidization of human HPs during preimplantation development
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
