Abstract:
Differentiation from pluripotent cells entails specification of cell intermediates
with progressively limited potency. Understanding the molecular mechanisms that
specify these intermediates can aid their expansion for therapeutic application and drug
testing. In this thesis, we show that human Ovarian Carcinoma Immuno-reactive
Antigen Domain containing 1 (OCIAD1), is expressed in human embryonic stem cells
(hESCs) and cardiovascular lineages. OCIAD1 depletion by CRISPR/Cas9-mediated
knockout promotes hESC differentiation to early mesodermal progenitors (EMPs).
Conversely, OCIAD1 overexpression in transgenic hESC lines reduced differentiation
to EMPs. OCIAD1 localizes to endosomes and mitochondria. In hESCs, it
predominantly resides in the mitochondria. Cellular processes such as endocytosis and
mitochondrial oxidative phosphorylation regulate stem cell differentiation but their
contribution to specification of mesodermal lineages is not well understood. We show
that OCIAD1 interacts with electron transport chain complex members and reduces
oxidative phosphorylation activity, thus keeping cells undifferentiated. In the absence of
OCIAD1, Complex I activity increases, resulting in increased oxidative phosphorylation
and reduced dependence on glycolysis, thus promoting hESC differentiation.
Lysophosphatidic acid, a small molecule inducer of OCIAD1, can regulate EMP
differentiation in wild type hESCs, phenocopies the genetic overexpression and rescues
the depletion phenotype. Thus, OCIAD1 expression levels affect cell fate choices by
impacting mitochondrial activity. Genetic overexpression of OCIAD1 leads to carcinoma development in human. We provide a non-genetic reversible tool to modulate
OCIAD1 and hence mesodermal precursor generation. Generation of functional cells for stem cell-based cell therapies targeted at curing
several severe diseases is a major endeavor of regenerative medicine. The current focus is on
harnessing the developmental function of key pluripotency regulators for the development of
lineage-restricted progenitor cell lines. However, genetic manipulations and the time required
for generating desired cell types pose serious limitations. Non-genetic, reversible
technologies that could speed up the development of functional cell therapies and reduce
costs are an urgent requirement. Our interest is in understanding cell fate specification during
development of the blood, vascular and cardiac lineages from mesoderm. Improved
understanding of mechanisms that specify mesoderm lineage precursors from stem cells will
contribute significantly to our ability to manipulate and regulate the process for cell-based
therapies.
