PROJECT SUMMARY/ABSTRACT [30 LINES MAX]
Biomedical advances over the past twenty years have reduced the infant mortality rate in the US throughout
the 21st century. However, congenital malformations that arise from dysregulated morphogenesis remain the
leading cause of US infant mortality. An especially critical period of morphogenesis is gastrulation, a period of
dynamic cellular rearrangements that establish the three tissue germ layers of ectoderm, mesoderm, and
endoderm in the embryo. One notable cellular rearrangement in gastrulation is the collective migration of the
mesendoderm along the blastocoel roof. Our laboratory identified α5ß1 integrin adhesion to fibronectin as a
critical regulator of mesendoderm motility in gastrulation. During collective mesendoderm migration, the front
row of migrating cells (leader cells) establishes substantial traction stress on the fibronectin extracellular matrix
through α5ß1 integrin that allows for cells in rows behind the leader cells (follower cells) to be pulled forward.
While the morphogenetic movements of gastrulation have been characterized, the metabolic processes that
support these energetically expensive movements remain poorly understood. The experiments proposed
herein will aim to unveil the mechanisms that integrate mechanical and metabolic signals in collective
mesendoderm motility. Preliminary live imaging of mitochondrial activity and localization in collectively
migrating mesendoderm explants supports the hypothesis that α5ß1 integrin mechanotransduction is a potent
inducer of mitochondrial activity and recruitment to adhesions. In Specific Aim 1, we will test the role of α5ß1
integrin in organizing mitochondrial activity and localization, the spatial distribution of metabolites, and rates of
glycolysis and mitochondrial respiration. We will induce differential activation of α5ß1 integrin in mesendoderm
explants and dissociated primary cells via various fibronectin fusion proteins and varied mechanical
environments. We will also modulate α5ß1 integrin activation in the mesendoderm of intact embryos via
integrin-targeted monoclonal antibodies. In Specific Aim 2, we will explore the effects of mitochondrial and
metabolic dynamic regulators on collective mesendoderm migration using live, high spatiotemporal resolution
imaging of mitochondrial activity, mitochondrial localization, the spatial distribution of metabolites, and the
function of metabolic regulatory proteins within the context of α5ß1 integrin-driven collective mesendoderm
migration. In summary, the experiments proposed will reveal how α5ß1 integrin adhesion and signaling impact
the metabolic processes that fuel energetically expensive gastrulation movements. By expanding our
knowledge of the mechanisms that engage and fuel tissue rearrangements in gastrulation, we will form a better
understanding of processes that contribute to congenital malformations in humans. This proposed fellowship
will be performed in a collaborative and supportive environment to develop the trainee’s scientific
independence and prepare him for a career as an independent physician-scientist in pediatric pathology. The
applicant will be mentored by a supportive dissertation mentor (sponsor) and expert dissertation committee.
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