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Title: The role of Olig2 regulation in ventral neural tube patterning
Author: Exelby, Katherine
ISNI:       0000 0004 9352 5833
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2020
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In the developing spinal cord, a ventral to dorsal gradient of Sonic Hedgehog (Shh) protein directs spatial organisation of neural progenitor domains that subsequently di erentiate to molecularly distinct neurons. Graded Shh signalling is interpreted by a gene regulatory network (GRN) that restricts expression of di erent transcription factors to progenitor domains delimited by sharp boundaries. This GRN, comprising of four key transcription factors, has been modelled in a deterministic mathematical model. To explore how this GRN ensures robustness in patterning, the interactions between nodes of the network required further investigation. In this study, we investigate interactions at a particular node, Olig2, expressed in the ventral neural tube in the motor neuron progenitor (pMN) domain. We fo- cused on the -33 kb enhancer of Olig2 that has binding sites for all major inputs in the GRN. CRISPR/Cas9-mediated excision of this enhancer in vitro severely disrupted Olig2 expression in mouse ES cells directly di erentiated towards spinal cord progenitors. Remaining Olig2 expression highlighted a second regulatory re- gion, +75 kb, that became accessible at later stages. Deletion of both -33 and +75 kb enhancers led to a complete loss of Olig2 expression in vitro. Excision of the -33 kb enhancer in vivo resulted in embryos having reduced Olig2 expression in a smaller pMN domain which was more severe when combined with deletion of the +75 kb enhancer. In addition to reduced Olig2 expression, a loss of precision was observed at the p3/pMN boundary in the developing neural tube. In collaboration with Edgar Herrera Delgado, we modelled this loss of precision in silico and have been able to uncover a mechanism encoded within GRN structure that drives precision in patterning even in the presence of noisy gene expression. Through analyses of Olig2 enhancers both in vitro and in vivo, we demonstrate how enhancers contribute to robustness in gene regulatory networks driving patterning.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available