Investigating the cell biology of novel protein hydroxylases implicated in human developmental disorders

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Hall, Charlotte Louise (2020). Investigating the cell biology of novel protein hydroxylases implicated in human developmental disorders. University of Birmingham. Ph.D.

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Abstract

The 2-oxyglutarate oxygenase family of enzymes catalyse post-translational hydroxylation of substrates associated with fundamental cellular processes and are often implicated in disease. The focus of this thesis was two poorly characterised 2-oxyglutarate oxygenases, JMJD7 and JMJD5.
JMJD7 was recently assigned as a novel lysyl hydroxylase that targets two substrates, Developmentally Regulated GTPases (DRG) 1 and 2. Although the molecular function of DRG hydroxylation is unclear, the JMJD7-DRG pathway may play a role in neurodevelopment due to the association of JMJD7 and DRG mutations with Autism Spectrum Disorder (ASD) and intellectual disability. Here we begin to address the potential role of this novel pathway in neuronal differentiation and ASD. We successfully characterise key stages of cortical neuron differentiation and develop JMJD7 loss of function models in neuronal-like SHSY5Y cell lines. On the basis of this work we hypothesise how dysregulation of the JMJD7 pathway might contribute to neurodevelopmental disorders and propose future areas for investigation.

The second enzyme investigated was JMJD5, a JMJD7-related oxygenase whose catalytic activity remains controversial. Here we characterise JMJD5 mutations identified in patients with a novel human developmental disorder, which we demonstrate is associated with DNA replication stress. We propose two novel candidate hydroxylation substrates of JMJD5, minichromosome maintenance (MCM) subunits 3 and 5, which form part of the essential DNA helicase required for replication. Future investigation will aim to decipher the molecular mechanism of JMJD5-associated replication stress and whether this is mediated by hydroxylation of MCM3/5.

Overall, our work highlights the importance of protein hydroxylation in fundamental cellular processes and human development and demonstrates the benefit that studies of human disorders can provide in elucidating the function of poorly characterised 2-oxyglutarate oxygenases.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):