Molecular pathways regulating stem cell divisions
Application deadline: 23 November 2018
Start date: October 2019
Research theme: Neuroscience and Mental Health
Cortical progenitors need to produce the correct amount of neurons for all 6 layers of the cerebral cortex. They do it sequentially, from the deepest to the uppermost layer. Therefore, progenitors need to balance giving rise to neurons and maintaining their own population, to avoid getting depleted before all neurons are produced. Early in development, progenitors divide symmetrically to increase their numbers. But at some point they need to change to asymmetric divisions to start producing neurons. How progenitors make this decision is currently not understood.
We have recently found that the cell adhesion protein protocadherin 19 (PCDH19) is involved in the regulation of neural progenitor behaviour. PCDH19 is present in neural progenitors around the time of the symmetric to asymmetric division switch. PCDH19+ progenitors produce neurons at different rates when they are alone than when they coexist with progenitors that lack this protein. The same is true for the PCDH19-deficient progenitors. This suggests that communication between cells is important to regulate progenitor behaviour and that we can use PCDH19 to investigate this process.
Project aims and method
This project aims to identify the molecular pathways that regulate proliferative vs. neurogenic divisions in the developing cerebral cortex by combining candidate and unbiased approaches. The candidate signalling pathways are Notch and FGF. Notch is involved in maintaining progenitor fate and in the switch from proliferative to neurogenic divisions, and it requires cell-cell contact. PCDH19 has been reported to interact with FGFR2, raising the possibility of differential signalling in the presence/absence of PCDH19.
The unbiased approach will rely on single cell RNAseq from PCDH19+ and PCDH19- progenitors obtained from E11.5 heterozygous brains to uncover molecular differences between the two populations. A complementary analysis in zebrafish will test if those pathways in turn regulate PCDH19 expression.
The project allows flexibility to devote more effort to the most interesting signaling pathways and considers a final aim in year 3 of developing a mathematical model to explain the different choices in division type.
Participation in the bioinformatics analysis of the single cell RNAseq experiment. Verification of top hits from the RNAseq analysis. Analysis of Notch activity through in utero electroporation of reporter plasmids. Analysis of FGF activity with reporter animals. Verify interactions between PCDH19 and FGFR1-3 through immunoprecipitation.
Functional analysis of altered signalling pathways identified through RNAseq. Analysis of Notch activity with reporter animals. Analysis of the influence of Notch and FGF signalling on PCDH19 expression in zebrafish. Functional analysis of FGF and Notch signalling pathways through in utero electroporation of Cre-dependent plasmids. Development of a mathematical model to integrate the results to predict progenitor behaviour.
Prof Steffen Schlepp, University of Exeter.