Molecular mechanisms underlying nucleotide repeat expansion disorders.

Area of Science:

• Genetics
• Molecular Biology
• Neuroscience

Background:

• The human genome harbors over one million short tandem repeats (STRs).
• Expansion of specific STR tracts is implicated in over fifty human genetic disorders, including neurodegenerative and intellectual disability conditions.
• These disorders include amyotrophic lateral sclerosis (ALS), frontotemporal dementia (C9orf72), Huntington disease, myotonic dystrophy, and Fragile X syndrome.

Purpose of the Study:

• To review the major mechanisms by which expanded STRs cause human disease.
• To explore the interplay and synergistic effects of these pathogenic mechanisms.
• To discuss the native functions of STRs and their potential role in disease pathogenesis.

Main Methods:

• Literature review of studies on short tandem repeat expansion disorders.
• Analysis of four primary mechanisms of STR-mediated pathogenesis.
• Examination of somatic repeat instability and its influence on disease.
• Investigation of the crosstalk between different disease mechanisms.

Main Results:

• Four key mechanisms of STR expansion-induced disease are identified: transcription repression, RNA-mediated gain of function, repeat-harboring protein gain of function, and repeat-associated non-AUG translation.
• Somatic repeat instability modulates disease onset and tissue specificity.
• Disease mechanisms often synergize to drive pathogenesis.
• Emerging evidence suggests native functions of repeat elements may also contribute to disease.

Conclusions:

• Expanded STRs represent a significant class of genetic disease-causing elements.
• Understanding the interplay of multiple pathogenic mechanisms is crucial for comprehending disease.
• Identifying common therapeutic targets across these disorders holds promise for broad clinical application.