HARVARD GAZETTE   Harvard researchers have succeeded in reprogramming adult mouse skin cells directly into the type of motor neurons damaged in amyotrophic lateral sclerosis (ALS), best known as Lou Gehrig's disease, and spinal muscular atropy (SMA). These new cells, which researchers are calling induced motor neurons (iMNs), can be used to study the development of the paralyzing diseases and to develop treatments for them.   “One of the utilities [of this new method for producing motor neurons] is it makes a much more rapid way to grow motor neurons. This could allow us to test very rapidly whether a new therapeutic is