Using CRISPR to Identify New Genetic Suspects for Neurological Disorders

by Anjali Aryamvally on March 13, 2018 at 1:15 PM

CRISPR-Cas9, the gene editing tool, was used to rapidly identify genes in the human genome that might modify the severity of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) caused by mutations in a gene called C9orf72. The NIH-funded study conducted by a research team at Stanford and published in Nature Genetics uncovered a new set of genes that may hasten neuron death during the disease.

Accounting for nearly 40 percent of inherited cases of amyotrophic lateral sclerosis and 25 percent of inherited FTD cases, disease-causing mutations in C9orf72 insert extra sequences of DNA, called hexanucleotide repeats, into the gene. These repeats produce potentially toxic RNA and protein molecules that kill neurons resulting in problems with movement and eventually paralysis for ALS patients and language and decision-making problems for FTD patients.

CRISPR

CRISPR is a gene editing tool that is revolutionizing medical care with prospective cure for genetic diseases like cancer, diabetes, DMD, eye diseases, obesity.

‘CRISPR was used to rapidly search the entire human genome for genetic suspects behind hereditary versions of amyotrophic lateral sclerosis and frontotemporal dementia.’

Tweet it Now

Led by Aaron D. Gitler, Ph.D., and Michael C. Bassik, Ph.D., the researchers used CRISPR to disable each gene, one-by-one, in a line of human leukemia cells and then tested whether the cells would survive exposure to toxic proteins derived from the hexanucleotide repeats, called DPRs. Any disabled genes that caused cells to live longer or die faster than normal were considered suspects in DPR toxicity. They confirmed that genes that control the movement of molecules in and out of a cell's nucleus may be partners. They also identified several new players, including genes that modify chromosomes and that help cells assemble proteins passing through a maze-like structure called the endoplasmic reticulum (ER). A second CRISPR search conducted on mouse brain cells confirmed the initial results. Disabling the top 200 genes identified in the leukemia cells helped neurons survive DPR exposure.

Finally, further experiments highlighted the importance of the ER genes, especially one called TMX2. For instance, the researchers could cause neurons derived from the skin cells of ALS patients with C9orf72 to live longer than normal when they silenced the TMX2 gene, suggesting it could be exploited in designing novel therapies for ALS. Decreasing TMX2 in cells caused an increase in the production of "survival proteins" that the authors hypothesized protected the cells against DPR toxicity.

CRISPR System Identifies New Target to Treat Leukemia

Using CRISPR gene editing tool, scientists have identified some chemicals that can be used to target certain enzymes and be developed into drugs to treat the deadly disease, leukemia.

Previously such studies needed a few months to find candidate genes and could only be performed on yeast, worm, and fly genomes. With CRISPR, the researchers in this study needed just about two weeks to conduct a complete search of the human genome. The results suggest that this faster and more comprehensive approach may be used to rapidly identify genes that may be involved in other neurological disorders.

Source: Eurekalert