Genetic screens to understand the C9ORF72 repeat expansion in amyotrophic lateral sclerosis
Abstract/Contents
- Abstract
- Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative movement disorder. The most common known genetic cause of ALS to date is a GGGGCC hexanucleotide repeat expansion in the C9ORF72 gene. There are currently three hypotheses as to how this mutation can cause neurodegeneration in ALS. First, the repeat expansion leads to reduced gene expression and therefore, C9ORF72 haploinsufficiency could contribute to the disease. The remaining two hypotheses focus on gain-of-function consequences arising from the bidirectional transcription and translation of the repeat. Both the sense and anti-sense repeat RNA form foci that may sequester RNA binding proteins, preventing them from performing their normal functions. Finally, the non-canonical translation of both the GGGGCC and GGCCCC transcripts produces six distinct species of dipeptide repeat proteins (DPRs): glycine-arginine, glycine-alanine, glycine-proline, proline-arginine, proline-alanine, and proline-glycine. The arginine-rich DPRs cause overt toxicity in various model systems, suggesting an obvious link to neurodegeneration, but many questions remain about all three hypotheses and their relative roles in driving ALS pathogenesis. This dissertation is an attempt at addressing some of these questions. Chapter 2 examines the glycine-arginine and proline-arginine DPRs to see whether the two species have a shared mechanism of toxicity. Yeast genetic screens identified numerous genes that block glycine-arginine toxicity when deleted. After comparing our findings to previously identified modifiers of proline-arginine toxicity, we discovered that only half the proline-arginine hits were identified in the glycine-arginine screens. This incomplete overlap suggests that glycine-arginine and proline-arginine may act on distinct pathways within the cell. Chapter 3 shifts to address the question of endogenous C9ORF72 function. In hopes of gaining additional insight into C9ORF72 function, we performed a genome-wide synthetic lethal CRISPR screen in human myeloid cells to identify genetic interactors of C9ORF72. We discovered that loss of FIS1, a gene encoding a mitochondrial membrane protein, is synthetic lethal with loss of C9ORF72. FIS1's role in mitophagy suggested an obvious parallel to C9ORF72's role in autophagy, but surprisingly, follow-up experiments moved the genetic interaction away from mitochondria and pointed instead to a role for FIS1 and C9ORF72 in immune regulation
Description
| Type of resource | text |
|---|---|
| Form | electronic resource; remote; computer; online resource |
| Extent | 1 online resource |
| Place | California |
| Place | [Stanford, California] |
| Publisher | [Stanford University] |
| Copyright date | 2020; ©2020 |
| Publication date | 2020; 2020 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Author | Chai, Noo Ri |
|---|---|
| Degree supervisor | Gitler, Aaron D |
| Thesis advisor | Gitler, Aaron D |
| Thesis advisor | Bassik, Michael |
| Thesis advisor | Reimer, Richard J |
| Thesis advisor | Wyss-Coray, Anton |
| Degree committee member | Bassik, Michael |
| Degree committee member | Reimer, Richard J |
| Degree committee member | Wyss-Coray, Anton |
| Associated with | Stanford University, Neurosciences Program |
Subjects
| Genre | Theses |
|---|---|
| Genre | Text |
Bibliographic information
| Statement of responsibility | Noo Ri Chai |
|---|---|
| Note | Submitted to the Department of Neurosciences Program |
| Thesis | Thesis Ph.D. Stanford University 2020 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2020 by Noo Ri Chai
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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