Certain genetic mutations have the ability to alter a protein’s whole amino acid sequence and warp proteins into toxic, misfolded shapes which disrupt cellular functions. These mutations can eventually lead to diseases such muscular dystrophy, Huntington’s disease, and Alzheimer’s.
In most areas, genome editing technology has become a critical tool in targeting toxic proteins and fighting against diseases such as cancer, HIV, and sickle cell anemia. CRISPR technology (clustered regularly interspaced short palindromic repeats) is frequently utilized, employing a Cas9 protein and guide RNA to target specific and edit specific DNA sequences.
Neurodegenerative diseases including Alzheimer’s and Parkinson’s are strongly associated with accumulation of misfolded proteins in the brain. This specific protein misfolding is influenced by a variety of factors and is seen as very complex. While CRISPR/Cas9 has potential for correcting the protein misfolding associated with neurodegenerative disorders, another new gene editing tool SPLICER, is coming in hot to address this problem.
To test the capability of SPLICER’s promise in gene editing for neurodegenerative disorders, a research team from the University of Illinois conducted a study to test if SPLICER can reduce plaque accumulation in the brains of live mice, potentially lowering the risk of Alzheimer’s disease.
SPLICER is a gene-editing tool that utilizes exon skipping, a technique that modifies gene expression by skipping and splicing certain exons during the protein synthesis process. Built upon the CRISPR gene editing platform, SPLICER offers greater flexibility. Traditional CRISPR-Cas 9 gene editing systems require a specific DNA sequence to latch on, bind, and edit genes, limiting which genes can be edited. However, SPLICER employs newer Cas-9 enzymes that function without these restrictions. Additionally, there are two important sequence areas, one at the beginning and end of a gene, that make cellular machinery aware of which parts of a gene to use for protein synthesis. While CRISPR and traditional exon skipping tools use only one of these sequences, SPLICER edits both, allowing the exon-skipping process to be more efficient.
The Illinois team targeted a specific exon in an Alzheimer’s related gene that codes for an amino acid sequence within a precursor protein. Usually, this protein would undergo a modification where it gets cleaved to form amyloid-beta, a peptide which accumulates to form plaques on neurons in the brain. While analyzing the DNA and RNA output in SPLICER treated mice, it was discovered that there was a significant decrease in amyloid-beta production. The researchers found that the targeted exon was reduced by 25% in the SPLICER-treated mice, demonstrating the effectiveness of this technique.
As a part of our recent Molecular Genetics Unit, we have learned the process of gene expression, where a portion of DNA is transcribed into an mRNA strand, which is then translated into a peptide chain and forms a protein. However, after the transcription of the mRNA, RNA splicing occurs where a spliceosome cuts out the introns (non-coding sequences) and joins the ends of exons (the coding/expressed sequences) together. The purpose of SPLICER is to remove specific exons or coding sequences from the mRNA, potentially producing a modified but still functional protein after the translation phase and reducing the formation of misfolded and toxic proteins.
The study concluded that SPLICER, which combines newer base editors with the dual sequence editing, enabled exon skipping at a much higher rate than older available technologies. By efficiently skipping target exons in the mice, the tool reduces amyloid-beta production, leading to less plaque buildup and a lower likelihood of developing Alzheimer’s or other neurodegenerative diseases.
However, this approach does have limitations. Exon skipping only works if the product protein is still functional, meaning not all diseases can be treated this way. However, for diseases like Alzheimer’s, Parkinson’s, Huntington’s or Duchenne’s muscular dystrophy, this approach holds a lot of potential. Further research is needed to confirm that removing targeted exons is safe and does not lead to the production of toxic and nonfunctional proteins. While SPLICER represents a significant advancement in gene editing, continued research and refinement are necessary before it can be considered for human application.
As part of my Independent Service Project, I will be volunteering with adults who are suffering from dementia and other neurodegenerative diseases. Even before beginning this work, witnessing and understanding the challenges they face each day has strengthened my hope for advancements in treatment. While continued research and refinement are necessary before SPLICER technology is considered for human application, I am grateful that we are making progress to combat these devastating diseases.
https://www.sciencedaily.com/releases/2024/12/241223153410.htm– original article
https://www.xiahepublishing.com/m/1555-3884/GE-2024-00002– additional research on CRISPR technology
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