Mechanisms of cell cycle regulation in embryos of normal and unusual size

PROJECT SUMMARY
Mammalian development is a remarkably robust process that employs self-organization and corrective
processes to coordinate individual cell behaviors for proper development. One example is the embryo’s capacity
for cell number regulation. In mouse embryos in which cell number is experimentally doubled (2x), cell number
correction was shown to occur shortly after the embryo implants into the uterine wall and was suggested to
involve lengthening of cell cycles. This early postimplantation period is known to be a time of dramatic transitions
where a slowly proliferating clump of cells that makes up the embryonic portion of the conceptus - the epiblast
(EPI) - transforms into a rapidly dividing polarized epithelium that demonstrates interkinetic nuclear migrations
(IKNM) in conjunction with the cell cycle. Previous studies analyzing fixed 2x embryo samples have described
abnormalities in polarization and epithelial organization of these embryos, however, how these morphogenetic
differences influence cell cycle dynamics remains unknown. The proposed study will utilize ex vivo live imaging
of early postimplantation embryos and stem cell models with a novel fluorescent cell cycle reporter to investigate
the details of this cell cycle slowing as it relates to cell number regulation, determine how cell cycle regulation is
rooted in morphogenetic abnormalities and probe the molecular link between the two processes. Aim 1 will
investigate the requirements for proper morphogenesis in the initiation and maintenance of rapid cell cycles and
use an embryonic stem cell model to precisely test the mechanistic links between the two. Aim 2 will investigate
the polarization defects in 2x embryos, precisely quantify the cell cycle remodeling thought to underlie size
regulation and attempt to overcome slowed cell cycles by artificially accelerating morphogenesis. Ultimately,
these studies will be the first to describe phase-resolved dynamics of the cell cycle at this developmental period
and increase our understanding of the embryo-intrinsic regulatory mechanisms that govern mammalian
development.
My training plan is precisely designed to develop the technical and professional skills that will support me in
becoming an interdisciplinary independent researcher. Princeton University and the Posfai lab specifically
possess the advanced facilities and collaborative, intellectual environment ideal for achieving this goal. My
developmental biology training, overseen by my supportive sponsor and co-sponsor and enriched by the
expertise of collaborators such as Dr. Stanislav Shvartsman and Dr. Daniel Cohen, will increase my skillset in
live imaging, embryology, computational approaches, and quantitative data analysis. Combined with my access
to professional training including frequent presentations in colloquia, workshops covering manuscript writing and
computational skills, exposure to science communication, and my outreach work, this plan will ensure the
success of my training.

Grant Number: 5F31HD115409-02
NIH Institute/Center: NIH
Principal Investigator: Alana Bernys