ABSTRACT
Gastrulation is a pivotal process in mammalian embryogenesis that is essential for the establishment of
definitive germ layers and the formation of the body plan. Despite decades of research, the precise mechanisms
that regulate cell differentiation, migration, and patterning during mammalian gastrulation remain poorly
understood, particularly in primates. The study of primate gastrulation is especially challenging because this
process occurs after the embryo has implanted into the uterus, making it difficult to directly observe. Recently,
several three-dimensional (3D), stem cell-based models of primate embryos, termed “stembryos”, have been
developed for in vitro studies of embryonic development. However, most approaches for generating stembryos
exploit the inherent self-organizing capacity of stem cells to form 3D constructs and are unable to precisely
control the number of cells and cell types per construct. A lack of tools for engineering stembryos has resulted
in low yields and has limited the ability of stembryos to faithfully recapitulate primate gastrulation.
We have recently developed a stembryo model using induced pluripotent stem cells (iPSCs) from
chimpanzees along with an optofluidic (i.e., combination of optogenetic and microfluidic) device for performing
Chip-based, High-throughput Investigations into Morphogenesis in Primates, called the OptoCHIMP platform.
Our OptoCHIMP platform utilizes microfluidic encapsulation to place cells into hydrogel droplets. A downstream
droplet sorter unit allows us to select droplets of interest with prescribed cell numbers of cell ratios. This enables
us to fabricate stembryos in a precise and high-throughput manner. In this proposal, we will utilize the
OptoCHIMP platform to define the roles that 3D structure, local tissue mechanics, and spatiotemporal signaling
dynamics play in symmetry breaking during primate gastrulation. By utilizing optogenetic tools to stimulate
signaling pathways in chimpanzee stembryos, we can recreate the complex interplay of signaling
pathways between embryonic and extraembryonic tissues, induce symmetry breaking in our stembryo, and
develop a model for understanding how morphogen signaling dynamics impact tissue patterning. This proposal
will be the first time that microfluidic droplet encapsulation of stem cells, which offers precise control over the
initial conditions, has been combined with optogenetic, providing a promising approach to uncovering the
mechanisms that drive primate gastrulation.
