Molecular analysis of radial glial-like cells and their roles in nervous system regeneration - PROJECT SUMMARY. In adult vertebrates, various populations of radial glia-like cells (RGLCs) have been
associated with neurogenesis, playing a similar role to that of their embryonic counterparts, the radial glia, from
which they originate. These cells have also been shown to play a pivotal role in driving nervous system
regeneration in echinoderms, a group of animals with extensive capacity for regenerating their central nervous
system (CNS). In these animals, RGLCs give rise to glia and neurons of regenerated radial nerve cords (RNCs).
RNCs are ganglionated nerves, similar to the vertebrate spinal cord, composed of neurons, glia, and fiber tracts.
The sea cucumber Holothuria glaberrima, a member of the Echinodermata phylum, has been extensively studied
to understand the regenerative role of RGLCs and the genetic molecules that facilitate the process. In a collection
of articles dating back two decades, it has been demonstrated that: (1) that adult sea cucumbers are capable of
complete regeneration after RNC transection, (2) the regeneration process has been characterized at the cellular
level, and (3) a RGLC population has been shown to mediate CNS regeneration. The aim of this project is to
identify molecular markers of the echinoderm RGLCs and their mode of action in mediating RNC regeneration.
One glial type, the RGLC, has been shown to exist in H. glaberrima. However, complete understanding of this
cell has been limited by the availability of RGLC markers. Hence, Specific aim 1 will determine the presence of
vertebrate RGLC markers in the holothurian glial population. This will determine if different types of RGLCs are
present and will test the hypothesis that echinoderm RGLC are evolutionarily related to vertebrate radial glia.
This will be achieved using an RNC transcriptome and gene presence validation via in situ hybridization. In this
way, description of the RGLC population and new tools to study the echinoderm glial population will be provided.
The initial event during H. glaberrima early-stage nervous tissue regeneration is the de-differentiation of RGLCs.
De-differentiation is a hallmark of the regeneration processes in multiple tissues of echinoderms and those
vertebrates with high regenerative potential, such as salamanders and zebrafish. Therefore, there is a need to
understand the gene activation pathways that regulate cell de-differentiation and their impact on regeneration.
Specific aim 2 will address this issue, by focusing on possible transcription factors associated with the de-
differentiation event. Initially, it will be on two TFs: Klf1/2/4 and SoxC by determining their spatial temporal
expression in the RNCs and their potential roles during RGLC de-differentiation. Preliminary data has shown
differential gene expression of both factors. Future studies will validate their presence in RGLCs, and knockdown
experiments will provide further insight regarding the association between them and RGLC de-differentiation.
This project will achieve a comprehension of the genetic elements involved in echinoderm CNS regeneration, by
underpinning knowledge that will help overcome the regenerating barrier present in mammals. The present study
anticipates holothurians RGLC as a model to understand their potential as stem cell therapeutic targets.
