Neural crest are a population of multipotent stem cells that originate in the dorsal part of the forming
neural tube. Around the time of neural tube closure, they lose their epithelial characteristics and delaminate, by
process known as epithelial-to-mesenchymal transition (EMT), acquiring migratory ability. Once neural crest
cells reach their destination, they differentiate into numerous derivatives including neurons and glia of sensory
ganglia. In a manner that is essentially the reverse of EMT, the formation of sensory ganglia requires the
coalescence of neural crest cells via a process of mesenchymal-to-epithelial transition (MET). Both embryonic
EMT and MET bear similarities to the molecular pathways and cellular changes undertaken by cancer cells
during metastasis and establishment of secondary tumors. In recent years, there has been demonstrated that
epigenetic-miRNA circuitries regulate EMT in various type of cancerous cells. However, the in vivo study of MET
in cancer cells is very complex and unpredictable. In contrast, neural crest development is highly regulated and
predictable, since the migratory pathways and process of condensation into sensory ganglia are well
characterized.
Based on this, we hypothesize that reversible epigenetic-microRNA regulatory networks may occur
during transitional states of neural crest cells delamination (EMT) and sensory ganglia coalescence (MET). In
this context, the goal of Aim 1 is to identify a core miRNA signature necessary for neural crest
delamination and sensory ganglion condensation. Here we propose to perform using Ago2-HITS-CLIP
assays, the first transcriptome-wide map of miRNA targeting events associated with epithelial plasticity during
neural crest delamination and sensory ganglia condensation. Then, we will perform gain and loss-of-function
experiments in chick embryos to validate the role of selected miRNAs in vivo. Next, we propose to determine
the epigenetic regulation of core miRNAs expression (Aim 2). To this end, we will determine the DNA
methylation status of selected miRNAs loci during transitional states of neural crest delamination and
coalescence. Finally, Aim 3 will evaluate the epigenetic writers and erasers that control the core miRNA
expression. Based on the proposed reversibility of the EMT and MET processes, we will examine the role of
DNA methyltransferases (DNMT) and ten-eleven translocation (TET) as key regulators of DNA
methylation/demethylation status of the core miRNAs necessary for neural crest delamination and sensory
ganglion coalescence.
Taken together, this study proposes to identify a core miRNA signature, their epigenetic regulation and
regulators necessary for the EMT and MET during sensory ganglion formation. These studies hopes to lay the
foundation for therapeutic intervention for certain types of neurocristopathies, neuropathies, and neural crest-
derived cancers like neuroblastoma.