If this result is verified, then future studies should investigate whether diverse subtypes of spinal cord neurons, such as motor neurons, can be produced—for example, if an earlier embryonic spinal cord source is used, or if the cells are treated with growth factors such as Shh prior to transplantation—generating large quantities of motor neurons will be beneficial for treating neurodegenerative diseases such as ALS (amyotrophic lateral sclerosis). This evidence concerns the gene SHH and neurodegenerative disease.