C9orf72; abnormal RNA expression is the key.

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• The C9orf72 gene hexanucleotide repeat expansion is the most common genetic cause of frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS).
• The precise function of the C9orf72 protein remains largely unknown, hindering a full understanding of the disease mechanisms.
• Despite early-stage research, insights into the disease mechanisms driven by this repeat expansion are rapidly advancing.

Purpose of the Study:

• To review the current genetic, population, and functional data related to the C9orf72 repeat expansion.
• To discuss emerging insights into the biology of C9orf72 and the associated repeat expansion diseases.
• To consolidate understanding of the leading hypotheses explaining the disease pathogenesis.

Main Methods:

• Review of existing genetic and population studies.
• Analysis of functional data investigating C9orf72 biology.
• Synthesis of current hypotheses on disease mechanisms.

Main Results:

• The GGGGCC hexanucleotide repeat expansion in C9orf72 is a primary cause of FTD and ALS.
• Three main hypotheses explain the disease: 1) haploinsufficiency, 2) toxic RNA accumulation, and 3) toxic protein species from abnormal translation.
• Ongoing research is rapidly increasing our understanding of C9orf72 and its role in neurodegeneration.

Conclusions:

• The C9orf72 repeat expansion is a significant driver of FTD and ALS pathogenesis.
• Understanding the complex interplay of haploinsufficiency, RNA toxicity, and protein toxicity is crucial.
• Continued research into C9orf72 biology is vital for developing effective therapeutic strategies.