Microdeletions and duplications of the chromosome 15q11.2 region have been identified as a high penetrant risk copy number variance (CNV) to autism and schizophrenia. CYFIP1 (Cytoplasmic FMR1-interacting protein 1) is generally believed to be the causal risk gene in this CNV. However, the neurocellular deficits that contribute to the associated neuropsychiatric disorders remains largely unknown.
Due to their ability to give rise to all somatic cell types in vitro, human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) carrying disease risk variance serve as a powerful tool for investigating disease aetiology and developing novel therapeutic interventions. To model 15q11.2 CNV associated neurological disorders, we generated iPSC lines carrying 15q11.2 deletion (15q11.2del) and genome edited hESC lines with CYFIP1 knockout (CYFIP1KO) and overexpression (CYFIP1oe), respectively. Our ongoing work revealed pronounced deficits in cortical neural progenitor proliferation and neuronal differentiation in these cell models. Neural progenitors of 15q11.2del and CYFIP1KO exhibited precautious neuronal differentiation while CYFIP1oe neural progenitors are biased to maintain in cell cycle.
Interestingly, our genome-wide RNAseq analysis and a pilot metabolomics analysis of neurons derived from the 15q1.2del iPSCs and CYFIP1oe cells revealed striking alterations in cholesterol metabolism both quantitatively and qualitatively. For example, we observed a decrease of desmosterol and increase of 27-hydroxycholesterol in CYFIP1 overexpression neuronal samples. Moreover, we detected structure alterations in some intermediate metabolites produced by CYFIP1 overexpressing cells.
Oxysterols are oxidised forms of cholesterol or of its precursors. These molecules are allosteric activators of the hedgehog pathway via binding to smoothened. Hedgehog signalling plays a pivotal role in central nervous system development and cortical progenitor cell cycle regulation. Moreover, oxysterols has also been found to be novel ligand of the liver X receptor (LXR) and promote neuronal differentiation. Therefore, the changes in oxysterol metabolism points to a potential novel mechanism underlining the neural progenitor deficits in 15q11.2 and CYFIP1 mutant cells.
This PhD project aims to elucidate the roles of dysregulated oxysterols in altered neurogenesis in 15q11.2del and CYFP1oe cortical neurons. The project contains two specific objectives:
Objective 1 - to examine the functional role of altered sterol metabolites on neural patterning and neuronal maintenance. We have pilot data that some of the altered oxysterols regulate neurogenesis by either promote neural progenitor maintenance or neuronal differentiation, further experiments will be performed to consolidate these findings using cortical cultures derived from control iPSCs and 15q11.2 or CYFIP1 engineered hESCs. We will extend the study into other neuronal cell types (eg. striatal medium spiny neurons and cortical interneurons).
Objective 2 - to test the hypothesis that oxysterols regulate neurogenesis via interacting with SHH and/or LXR pathways. We will examine transcriptomic changes of genes in the SHH and LXR signaling pathway following oxysterol treatment. Crucially, we will interrogate SHH and LXR signalling using agonist and/or antagonists where available and investigate the effect (either mimic or rescue) on cortical neurogenesis with or without added oxysterols. Should our hypothesis to be validated, our study would have provided experimental support for tarting LXR pathway and cholesterol metabolism as a potential therapeutic intervention.
*Please note that this project can be completed as a PhD or MPhil*
A 1st or Upper 2nd class UK honours degree or equivalent. Please visit School of Biosciences Postgraduate Research for more details.
For those whose first language is not English, IELTS with an overall score of 6.5 with 5.5 in all subskills, or equivalent. Please see our English Language Requirements guidance for more details.
How to Apply
To submit a formal application via Cardiff University’s online application service, click the 'Institution Website' button on this advert; in the ‘Apply’ box at the top-right of the page, select Qualification (Doctor of Philosophy/Master of Philosophy), Mode of Study (Full Time) and Start Date (this can be flexible as it is a self-funded project). This will take you to the application portal.
Candidates must submit the following:
• Supporting statement
• Qualification certificates
• Proof of English language (if applicable)
In the research proposal section of the application, specify the project title and supervisors of the project. In the funding section, specify that you will be self-funding. If you are applying for more than one Cardiff University project with the same entry intake, please note this in the research proposal section as the form only allows you to enter one title.