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Genetic cause of neurodegenerative disorders unravelled

Analysis of a study published in a science journal   |   By Dr Anna Pokorska-Bocci   |   Published 30 September 2011
Study: A Hexanucleotide Repeat Expansion in C9ORF72 Is the Cause of Chromosome 9p21-Linked ALS-FTD
By: Renton A.E. et al. (77 authors total)
In: Neuron
Link: http://dx.doi.org/10.1016/j.neuron.2011.09.010
What this study set out to do:

To methodically study the loci associated with the amyotrophic lateral sclerosis, also known as motor neuron disease (MND) to identify genetic elements responsible for this neurodegenerative disorder. 

How they went about it:

The researchers have previously discovered a strong association signal with one chromosomal region, 9p21, in MND patients. In this study, they used next generation sequencing technology to complete a full assessment of that region.

Outcome:

The study showed the mutations to be located within a very small, 30 base pair region and indicated the presence of a six-nucleotide long repeat located in the vicinity of the C9ORF72 protein-coding region.

Conclusion:

The six-nucleotide long repeat was present in nearly half of familial MND cases, and data also indicated that that repeat is twice as common as mutations in the SOD1 gene, previously known to be associated with familial MND. Identification of the likely cause of chromosome 9p21-linked neurodegeneration may help to improve the screening and diagnosis of patients with different forms of neurodegenerative disorders. 

Our view:

This is yet another example of the implications of applying next generation sequencing technology for thorough and systematic analysis of genetic causes of disease. The identified repeat appears to be the most common genetic cause of this neurodegenerative disorder discovered to date, and will undoubtedly facilitate the design of novel, better-targeted therapeutics. 

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