Interestingly, the repeat-associated non-AUG (RAN) translation products glycine:arginine (GRn) and proline:arginine (PRn) dipeptide repeat polymers from the C9orf72 hexanucleotide repeat expansion, which are low complexity by nature and a major known cause of ALS, are also found in nucleoli where they impede RNA biogenesis and increase ribosomal protein mRNA levels, which may be one cause of cell death38. This evidence concerns the gene C9orf72 and amyotrophic lateral sclerosis.