Defining isoform diversity consistent between the brain and blood, related to the severity of Prader-Willi Syndrome.
Funding Summary
Lay Abstract
A pressing need in the PWS field is the identification of early clinical and/or biological predictors of symptoms, including serious mental illness and constant hunger, that may be targeted with specific treatments. The underlying biological mechanisms in key areas of the human brain, linked to these phenotypes, have not been comprehensively studied. This project aims to define biological mechanisms in blood and brain underlying key symptoms of PWS to address these needs utilizing established state-of-the-art technologies, deep clinical expertise of the investigators and access to the world’s largest collection of post-mortem brain tissues from individuals with PWS. In our previous FPWR funded studies we identified 53 genes, responsible for functions of ribosomes or small components in each cell to be upregulated in different types of cells in brains of donors with PWS. There are many ribosomes in each cell with each involved in the process of making different proteins coded by the genes. Proteins are large, complex molecules that play many critical roles in the body. Each gene can produce many different proteins which depends on how this message is read by each cell. This protein specific message is known as an isoform. Of all the genes examined, we have found only one ribosomal gene called RPS18 (that contributes to important functions of the ribosome involved in protein production) to be upregulated in all types of cells in specific regions of the brain from donors with PWS. We then showed that this upregulation in blood was associated with severity of PWS in another group of living individuals, including intellectual functioning and behavioral problems. While these changes and related functions of the ribosome in making different isoforms have been previously implicated in autism, this is the first time they will be studied in the brain of donors and their levels related to severity of PWS. In this project we will analyze this rich dataset from different regions of the brain with different functions to help us understand how abnormal activity of ribosomes influences expression of unique isoforms of proteins from the same genes in different types of cells. Our previous study findings suggest that we should focus on brain immune cells (glial cells) which support the proper functioning of neurons in the brain. Once we collect this valuable information, we plan to use it as part of this competitive renewal of this project to determine how these changes are related to behavioral issues and other key clinical features seen in PWS. We will also use artificial intelligence to identify treatments from global drug databases, to target specific pathways, isoforms and proteins identified: (i) to be dysregulated in blood and brain tissues in different types of cells and (ii) to have relationships to severity in PWS. Together these will: (i) define pathways dysregulated in PWS blood and brain cells of clinical significance, and (ii) identify existing medications used for other conditions to repurpose or target these pathways found to be disturbed in future PWS clinical trials to address the needs of people with PWS, their families, and the clinicians.
Research Outcome
We studied gene activity and proteins in brain tissue from individuals with and without PWS, including people with the two main genetic classes: deletion (a missing section of chromosome 15 from the father) and uniparental disomy, or UPD (two copies of chromosome 15 inherited from the mother). We examined different brain regions and individual cell types to identify which biological processes were affected.
A key finding was altered activity of over 50 genes involved in making proteins, which are essential for normal cell and brain function. In particular, a gene called RPS18 showed increased activity across several types of brain cells in PWS. We then examined blood samples from a separate group of people living with PWS and found that higher RPS18 activity was associated with greater intellectual and behavioural difficulties. This suggests that changes detected in blood may provide clues about PWS symptoms, although further work is needed to establish whether RPS18 could be a useful biomarker.
We also found differences in gene activity and biological pathways between deletion and UPD, which may help explain why some features of PWS differ between these groups. Our detailed analyses identified changes in specific brain cell types, including nerve cells and their supporting cells called glia, and examined different forms of RNA produced by genes (isoforms) by different types of cells.
Using these findings, we applied computer-based and artificial intelligence approaches to identify existing drugs that might act on the affected biological pathways. We have shortlisted potential candidates for laboratory testing. These are promising research leads, not yet proven treatments for PWS.
The project has also generated extensive gene activity and protein datasets from brain and blood samples. Following publication of our key findings, we plan to share the data, analysis code and potential drug candidates so other researchers can build on this work. To date, the project has contributed to three publications and three international presentations, including a keynote talk.
Together, these findings provide new insight into the biology of PWS, suggest possible blood-based markers of symptom severity, and identify avenues for future treatment research.
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