Beyond finding a gene: Same repeated stretch of DNA in three neurodegenerative diseases

Four different rare diseases are all caused by the same short segment of DNA repeated too many times, a mutation researchers call noncoding expanded tandem repeats. Researchers suspect variations of this type of mutation may cause other diseases that have thus far evaded diagnosis by genetic testing. Researchers are excited because instead of finding unique mutations in specific genes, they identified the same mutation in different areas of the genome causing different diseases.