The Genetics Behind Amyotrophic Lateral Sclerosis

Amyotrophic Lateral Sclerosis (also known as ALS) is a rare type of neurological disease. It affects a person’s nerve cells, making it difficult and even impossible to control their muscles.

The disease specifically affects our voluntary movements. This means that walking, talking, and chewing becomes a tiring and difficult task. As the disease takes hold, patience finds it difficult to breathe and eventually passes away due to a lack of oxygen.

But how does someone develop ALS? The answer is in their genetics. 

The Genetics Of Amyotrophic Lateral Sclerosis

Multiple clinical trials and basic research have found that there are multiple causes of Amyotrophic Lateral Sclerosis, but the most important and common component was found in the genes. 

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Looking at the genetic history of the patients in the trial, we can see that at least 10% of those coping with Amyotrophic Lateral Sclerosis have had at least one other biological family member with the same condition. In all of the 10%, it was clear that the medical condition was inherited. 

However, a large portion of people (90%) didn’t have a family member with the same condition. 

Using advanced technology, scientists could look at the molecular structure of the patient’s genes. Specifically using genome sequencing techniques, these scientists created “next-generation” and “first-generation” examples of each patient type.

This allowed scientists to compare those who have had ALS in their family to those without a history of ALS. They could then pinpoint the change or difference to locate the gene which causes this effect.

Through this study, the scientists found that around 50% of patients did have familial Amyotrophic Lateral Sclerosis, which meant that others in their family would have had this disease first. This went against the historical evidence brought in by family members.

At this point, it should be noted that poor medical history, lack of familial knowledge, and poor medical technology could be the reason for this disparity. 

The pathogenic variants which have been shown a connection or causation to ALS are most commonly TARDBP, SOD1, FUS, and C9ORF72. However, over 50 different genomes have been identified as having a disease-modifying element to create or deteriorate into cell-eating ALS.

These genes and pathogens are most commonly found in Asian and European genetic backgrounds.

You may have noticed that the majority of patients still don’t fit into the genetic understanding of ALS. This could be because our understanding is still limited, or it could be due to other factors in play.

In one study, twins were studied for the connection between ALS and heritability. In the study, just 60% of the participants both had the neurological disease. This, again, suggests that there are other factors at play.

What We Still Don’t Know About Missing Heritability In Amyotrophic Lateral Sclerosis

The biggest reason for our lack of understanding comes from technology or lack thereof. ALS is a complex disease, and due to its complex nature, we need technology to develop faster than the disease itself.

So far, most studies have relied almost completely on high throughput sequencing technology which uses the short reading function. This technique is extremely helpful when trying to find single-nucleotide polymorphisms. However because the vast majority of our genes are not understood or even characterized in single threads or short-read platforms, it means the primary data is already limited.

To try and solve this problem some research has been put into mapping the short-read files and creating an algorithm to find patterns – thereby making the data still useful. 

This is slowly becoming a more common practice, and this data is sometimes used to diagnose patients as well as test possible delaying medications. 

The next problem comes from the fact that most ALS patients didn’t develop their disease hereditary (or so we currently believe). This means that genetic study is unlikely to give a wider understanding of the disease. 

Recently a study showed how looking for structural variations instead of single-nucleotide polymorphisms detected 7 times more sequences. Through this study, the researchers were more likely to find the expression of a gene.

They concluded that the structural variance may be the cause or increased likelihood of developing the disease. This could in turn explain why some people seem to develop the illness without a family history. Perhaps, the family history was always there but laid dormant due to its gene structure.


There is still a lot we do not know about Amyotrophic Lateral Sclerosis, but more research shows that the illness is genetic even if it isn’t 100% hereditary. 


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