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Title: Defining novel signalling mechanisms in cardiovascular development
Author: Bolton, Rebecca Lauren
ISNI:       0000 0004 8508 0256
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2019
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The endothelial cell (EC) surface receptor NRP1 mediates vascular endothelial growth factor and class 3 semaphorin signalling in blood vessels and neurons. During my PhD, I sought to determine whether NRP1 has novel intracellular effector pathways and cell adhesion functions in ECs required for cardiovascular development. Bioinformatic analyses identified the nucleic acid binding protein RBMS1 as a potential NRP1 effector. Although in vitro analyses suggested that RBMS1 promotes EC motility and proliferation, endothelial-specific Rbms1-null mice, created with Cre-LoxP technology, did not have obvious blood vessel defects in the brain or retina, in which blood vessel growth relies on NRP1. Moreover, RBMS1 was dispensable for pathological angiogenesis in a choroidal neovascularisation assay that depends on NRP1. These findings suggest that RBMS1 is not required for central nervous system vascularisation. As Rbms1-null mice are not viable, further work is required to understand why RBMS1 is essential. During my RBMS1 studies, I unexpectedly found that a commonly used transgene encoding a Cre recombinase-oestrogen receptor fusion protein (CreERT) impaired retinal vascularisation in a tamoxifen-dependent manner in the absence of floxed target gene deletion. This finding impacts the interpretation of studies seeking to identify essential genes for retinal vascularisation. To investigate NRP1's cell adhesion function, I studied mice with a homozygous 4 amino acid mutation in the b2 domain (Nrp1ΔYSNN), which mediates a heterophilic interaction with unknown, ubiquitous protein(s). The homozygous Nrp1ΔYSNN mutation reduced brain vascularisation and caused a ventricular septal defect. To circumvent early postnatal lethality, I combined one Nrp1ΔYSNN allele with a conditional Nrp1-null allele for ablation in ECs via tamoxifen-induction. The ensuing mutants had impaired retinal vascularisation, independently of CreERT toxicity. These data suggest that the NRP1 adhesion domain is essential for cardiovascular development. In summary, my PhD research has uncovered a novel role for NRP1, but not the putative NRP1 effector RBMS1, in cardiovascular development.
Supervisor: Ruhrberg, C. ; Martinez-Barbera, J. P. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available