An Academy Award winning biopic on Stephen Hawking made us ask again how the physicist has lived so long with ALS. Most people with ALS or Lou Gehrig's disease die three to five years from the onset of symptoms.

Scientists have spent years trying to understand its cause. Neurons that control voluntary movement die in ALS patients until even breathing is impossible.

Ninety to ninety five percent of all cases are not inherited. Three causes being studied are chemical imbalance, disorganized immune response and gene mutation. A recent study indeed identified a new mutated gene in about two percent of random ALS patients. The finding results from the largest gene sequencing of ALS to date and involved nearly three thousand patients and 6,400 control subjects.

It took a study of this size to detect such a rare gene variant. The gene, TANK-Binding Kinase 1 or TBK1, is involved in a cell system that degrades and recycles waste. Scientists are trying to link mutations in the gene with accumulation of protein aggregates that's killing neurons.

TBK1 is also important in the immune response. Scientists have long thought inflammation in the brain plays a role in ALS. Since TBK1 tamps down inflammation, a mutation in the gene could interfere with that function.

Researchers are also studying a gene, OPTN, that interacts with TBK1. Together they regulate cell waste disposal and inflammation. Scientists are experimenting on mice engineered with mutations in both genes to determine how they contribute to ALS.

Since ALS can be caused by dozens of gene mutations, the more we discover, the better chance we have of understanding their pathway to disease.