ALS researchers from around the world continue to build upon existing work and make new discoveries in the hopes of realizing a future without ALS. In the July 2024 Research Update, explore new insights into the progression of ALS at the cellular level, promising new therapeutic targets and biomarker candidates, modern genetic techniques, large-scale analyses enhancing our understanding of ALS, and more.
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Cryptic peptides: A promising new biomarker candidate to facilitate earlier diagnosis of ALS?
Researchers identify downstream effects of TDP-43 dysfunction that could lead to promising new biomarkers for the early detection of ALS.
Inside the nucleus of every cell in the body, DNA carries the master blueprint—the full set of genetic instructions needed for the body to grow, live, and reproduce. Surprisingly, of the 3.2 billion building blocks in the human genome, only about 1-2% actually code for the formation of proteins – the workhorses of the cell responsible for nearly all cellular functions required to sustain life.
The sections of DNA that code for the formation of proteins are called exons, while the “junk” sections of DNA that are usually removed before the instructions are read are called introns. Sometimes, errors occur within cells where introns are treated like exons. These are referred to as cryptic exons, and they can lead to the creation of abnormal versions of proteins, called cryptic peptides, or prevent the formation of critical proteins.
Researchers believe that in ALS, TDP-43 dysfunction, which is present in approximately 97 per cent of ALS cases, may contribute to the disease by promoting widespread inclusion of cryptic exons, and the creation of many of these unusual proteins. To better understand the link between TDP-43 dysfunction, cryptic exons, and ALS, researchers used motor neurons derived from induced pluripotent stem cells (iPSCs) to model TDP-43 dysfunction and map cryptic exons. Through their analyses, the team identified 65 cryptic peptides resulting from 12 cryptic exons. The team also studied cerebrospinal fluid (CSF) samples from people living with the disease and found 18 of these cryptic peptides present in the CSF.
In a second study, researchers took it a step further to investigate whether cryptic peptides could serve as a biomarker for TDP-43 dysfunction in ALS. The team first developed an antibody in the lab that could selectively target a specific cryptic peptide, called HDGFL2, found in the CSF of individuals with C9ORF72-linked ALS. They then tested the ability for this antibody to detect HDGFL2 in CSF samples from pre-symptomatic C9ORF72 mutation carriers. Remarkably, the team found that the cryptic peptide was present in pre-symptomatic individuals as well, suggesting that TDP-43 dysfunction occurs early in disease, even pre-symptomatically, and that in combination with other emerging biomarkers, detection of HDGFL2 could help to signal the underlying onset of ALS long before symptoms begin. Researchers note, however, that further studies are required to validate these finding in individuals with sporadic ALS.
Ultimately, the results from the first study highlight an important downstream effect of TDP-43 dysfunction that helps to broaden our understanding of the disease. Additionally, both studies point to promising new biomarkers that could support earlier diagnosis of ALS, allowing for prompt therapeutic intervention. This type of biomarker could also help researchers monitor the effectiveness of future treatments aimed at restoring TDP-43 function and even improve clinical trial and drug design.
New ALS model identifies NPTX2 as potential treatment target
Researchers have developed a new laboratory model to study ALS and have identified a protein linked to TDP-43 dysfunction that could serve as a new treatment target.
In over 97 per cent of ALS cases a protein called TDP-43, which is normally found within the nucleus of a cell, becomes trapped outside in the cytoplasm where it forms clumps or aggregates. While mutations in the TDP-43 gene are responsible for this dysfunction in a small subset of cases, the cause for most people living with ALS is still unknown, making it more difficult to study human TDP-43 dysfunction in the laboratory.
In this study, researchers set out to better understand the role of TDP-43 in ALS. Using specialized human cells, they created a network of cells called iNets that mimic the behaviour of neurons in the disease. This model is unique because it can live and function in a laboratory dish for up to 12 months, allowing researchers to observe disease-related changes over time, which could be important in age-related diseases like ALS.
Using the iNets model, researchers found that when TDP-43 behaves abnormally in neurons, it causes the toxic build-up of another protein, called NPTX2. Researchers then confirmed the link between TDP-43 dysfunction and the build-up of NPTX2 in post-mortem brain tissue samples. Reducing NPTX2 levels was also found to prevent some of the toxic side effects of TDP-43 dysfunction and improve motor neuron health in the iNets model.
The results from this study suggest that reducing NPTX2 could be a promising treatment strategy for ALS. It’s important to note, however, that this work is preliminary, and more studies are required to fully understand the potential of NPTX2 as a treatment target in a human setting. Overall, the study provides another important puzzle piece for better understanding the biology of ALS and a step towards developing more effective treatments for the disease.
Modern genetic techniques improve our understanding of C9ORF72-linked ALS
Advanced genetic techniques provide researchers with a deeper understanding of C9ORF72-linked ALS at the cellular level, helping to inform the future development of targeted therapies.
Mutations in the C9ORF72 gene are the most common genetic cause of ALS. Unlike most other ALS-linked genes, where there is often a mistake in a single piece of DNA, C9ORF72 mutations involve an expanded section of DNA that is abnormally repeated hundreds or even thousands of times. It is believed that these repeat mutations result in less of the normal C9ORF72 protein being produced while also promoting the formation of additional, potentially toxic substances, such as repeat-containing forms of RNA and dipeptide repeat proteins. Exactly how these changes contribute to causing ALS, however, is not fully known.
In this study, researchers used advanced genetic techniques to alter the C9ORF72 gene in cells derived from people living with ALS and healthy controls. By comparing the genetically altered cells to their original forms, researchers were able to investigate how the specific changes they made impacted disease characteristics.
The analyses revealed that the expanded form of C9ORF72 produced more RNA than the normal form, and when the abnormal copy of the C9ORF72 gene was removed (humans have two copies of every gene and usually only one will have the expansion), motor neurons still produced normal levels of the C9ORF72 protein. This finding goes against the theory that the loss of normal levels of the C9ORF72 protein contributes to disease. When researchers removed the mutated genetic sequence from cells entirely, it appeared to reverse several disease markers. This suggests that modern gene-editing techniques, such as CRISPR-Cas9 (“CRISPR”), may represent a promising therapeutic strategy for C9ORF72-linked ALS.
Overall, this study provides important insights into the mechanisms underlying C9ORF72-linked ALS. By further untangling the downstream effects of C9ORF72 mutations, these findings pave the way for developing more targeted therapies that aim to correct genetic errors at the cellular level.
Large-scale analyses reveal genetic factors that may be important in ALS
For most people living with ALS, the cause of the disease is unknown, with only approximately 20% of cases linked to a known genetic variant. While certain genes have been associated with a higher risk of ALS, many genetic risk factors still remain undiscovered. Researchers believe that additional genetic factors, referred to as epigenetics, could play an important role in ALS by altering gene activity without changing the underlying DNA sequence.
To explore these factors, researchers analyzed DNA packaging (an epigenetic property also referred to as chromatin) in motor neurons derived from induced pluripotent stem cells (iPSCs). They studied samples from 380 people living with ALS and 80 healthy controls, collected as part of the Answer ALS consortium, to see how differences in chromatin might influence changes in gene activity.
ALS-specific changes in chromatin were identified, particularly for the C9ORF72 gene, which is the most common genetic cause of ALS. Researchers found that variations in this gene were associated with altered chromatin and reduced gene activity. Additionally, changes in chromatin were able to predict ALS progression rates as effectively as current methods based on clinical evaluations and biomarkers, such as neurofilament light (NfL).
The large-scale analyses conducted highlight the value of utilizing iPSCs to create and study human motor neurons in the laboratory. Overall, this research improves our understand of the genetic and epigenetic factors related to ALS, potentially paving the way for more personalized treatment strategies and developing additional tools for predicting disease progression.
Novel insights into the role mitochondria play in the progression of ALS
Large-scale genetic analyses reveal important insights into the role of mitochondrial function in ALS.
Mitochondria are energy-producing structures within cells, often referred to as the power plant of the cell, as they provide the energy needed for survival. Researchers have long suspected that problems with mitochondria may play a role in ALS. However, whether mitochondrial dysfunction contributes to the risk of developing ALS, the rate of progression, or both, remains unclear.
In this study, researchers investigated how genetic variations influencing mitochondrial function may contribute to ALS. The team analyzed data from 6,374 people living with ALS and found that certain genetic markers linked to mitochondrial function were associated with longer survival after the onset of the disease. They also looked at a specific gene linked to mitochondrial function, called DNA2, and found that variants in this gene resulting in a loss of function were associated with shorter survival. These results suggest that mitochondrial targets like DNA2 could be represent promising targets for future ALS treatments.
This study provides important insights into the biology of ALS, highlighting that improving mitochondrial health may help slow the progression of ALS and improve patient outcomes. This new understanding of the role of mitochondrial function in ALS will be valuable when developing future treatments.
Bringing you the latest news on advancements in ALS research, the ALS Canada research team regularly summarizes the most significant discoveries throughout the year.
Note: We have included links to the publications because we know you may be interested in the original source papers. While abstracts are always available, many journals are subscription based, and in some cases, full papers may only be accessed at a cost.