Ice Water and ALS

I've seen a lot of people dumping ice water over their heads, but not a lot of people talking about the underlying die off of motor neurons - the hallmark of ALS. Why just motor neurons and not sensory neurons? What is special about outgoing neurons compared to incoming neurons?

According to OMIM - online mendelian inheritance in man. There are ALS tagged genes on chromosomes 1 2 3 6 7 9 10 12 14 15 16 18 20 21 22. That is over 65% of the chromosomes in the human genome.

OMIM

This is bad. It could mean this is a complex, multi-factor disease, like cancer which requires suppressor genes (the brakes) to be turned off and accelerator genes (growth or oncogenes) to be turned on in several places for cancer to emerge. Suppose there is a simpler explanation, say that ALS is a motor-neuron specific auto immune disease, say lupus for motor neurons.  What happens if we make a similar query for lupus?

Lupus is on everything!

Then the genes we're seeing just code for motor neuron proteins that are attacked in this auto immune circumstance. The question that we must always ask is, what advantage did ALS confer on its bearers in the evolutionary sense? For example sickle cell anemia confers on its 1 hit bearers (heterozygotes) resistance to the worldwide killer of malaria at the cost of seriously harming its 2 hit bearers (homozygotes). Survival at any cost... It's very important not to confuse a single factor single-point mutation disease like sickle cell with a complex disease like ALS.

What if we ask the question, what chromosomes have BOTH ALS and lupus marked players? Anding the two charts just give us the first one since lupus is everywhere.

Lou Gehrig was a champion baseball player. This means he had very quick reflexes and effective motor execution relative to the population of competitors. Why would a better motor nervous system confer on one a greater likelihood of auto immunity, or a Huntington's chorea-like duplication error? Huntington's looks different, it is a CG repeat disease on the tip of chromosome 4. These repeats cause errors in vital brain proteins sentencing the sufferers to progressive dementia and eventually death.


Maybe there is a clue in the Zeitgeist having to do with cold water. Will cold water protect the motor neurons? Is there a temperature-sensitive component to the mechanism of this disease?