Repeat expansions in the gene C9ORF72 may be the most common cause of familial ALS (fALS) according to two studies published this week. Researchers identified these so-called expanded repeat sequences in the gene in nearly 25% of 229 familial cases. And in Finland, researchers identified these sequences in upwards of 50% of 402 cases. This is more than twice the number of people with ALS harboring mutations in the superoxide dismutase 1 (SOD1) gene. The C9ORF72 gene is the fourteenth to be linked to the disease. Repeat expansion underlies a growing number of neurological disorders including Huntington’s disease and Fragile X syndrome.

Don't repeat that. Researchers discovered expansions of GGGGCC repeat sequences in between two sections (blue) of the C9ORF72 gene in people with ALS. These expanded repeats, upwards of 1600 by one team’s rough estimates, may block the expression of the C9ORF72 gene resulting in the disease. 



DeJesus-Hernandez, M. et al. (2011) Expanded GGGGCC Hexanucleotide Repeat in Noncoding Region of C9ORF72 Causes Chromosome 9p-Linked FTD and ALS.  Neuron 72(2), 245-256.  Abstract | Full Text (Subscription Required)

Renton, A.E. et al. (2011) A Hexanucleotide Repeat Expansion in C9ORF72 Is the Cause of Chromosome 9p21-Linked ALS-FTD. Neuron 72(2), 257-268.  Abstract | Full Text (Subscription Required)