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Updated: Jan 1, 2026
Pooled CRISPR-Based Genetic Screens in Mammalian Cells
Published on: September 4, 2019
Genome-wide synthetic lethal CRISPR screen identifies FIS1 as a genetic interactor of ALS-linked C9ORF72
Noori Chai1, Michael S Haney2, Julien Couthouis2
1Department of Genetics, Stanford University School of Medicine, Stanford, CA, USA; Stanford Neurosciences Graduate Program, Stanford University School of Medicine, Stanford, CA, USA.
Abstract:
Mutations in the C9ORF72 gene are the most common cause of amyotrophic lateral sclerosis (ALS). Both toxic gain of function and loss of function pathogenic mechanisms have been proposed. Accruing evidence from mouse knockout studies point to a role for C9ORF72 as a regulator of immune function. To provide further insight into its cellular function, we performed a genome-wide synthetic lethal CRISPR screen in human myeloid cells lacking C9ORF72. We discovered a strong synthetic lethal genetic interaction between C9ORF72 and FIS1, which encodes a mitochondrial membrane protein involved in mitochondrial fission and mitophagy. Mass spectrometry experiments revealed that in C9ORF72 knockout cells, FIS1 strongly bound to a class of immune regulators that activate the receptor for advanced glycation end (RAGE) products and trigger inflammatory cascades. These findings present a novel genetic interactor for C9ORF72 and suggest a compensatory role for FIS1 in suppressing inflammatory signaling in the absence of C9ORF72.
Insights
Mutations in the C9ORF72 gene cause ALS. A new study reveals FIS1 interacts with C9ORF72, suggesting FIS1 may suppress inflammation when C9ORF72 is absent.
Area of Science:
- Genetics
- Neuroscience
- Immunology
Background:
- C9ORF72 gene mutations are the leading cause of amyotrophic lateral sclerosis (ALS).
- Proposed mechanisms for C9ORF72 dysfunction include toxic gain of function and loss of function.
- C9ORF72 is increasingly recognized for its role in regulating immune function.
Purpose of the Study:
- To investigate the cellular function of C9ORF72.
- To identify genetic interactors of C9ORF72 using a genome-wide screen.
Main Methods:
- Genome-wide synthetic lethal CRISPR screen in human myeloid cells lacking C9ORF72.
- Mass spectrometry to identify protein interactions in C9ORF72 knockout cells.
Main Results:
- A significant synthetic lethal genetic interaction was identified between C9ORF72 and FIS1.
- FIS1, a mitochondrial protein, was found to bind immune regulators activating RAGE and inflammatory pathways in C9ORF72 knockout cells.
Conclusions:
- FIS1 is a novel genetic interactor of C9ORF72.
- FIS1 may play a compensatory role in mitigating inflammatory signaling in the absence of functional C9ORF72.
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