Therapeutic approaches for repeat expansion diseases: a comprehensive review

Abstract

Repeat expansion diseases (REDs) are genetic disorders caused by unusual expansions of DNA sequences within certain genes. They cause several neurodegenerative diseases including Huntington’s disease (HD), myotonic dystrophy (DM), spinal and bulbar muscular atrophy (SBMA), fragile X syndrome (FXS), and others. The pathogenic repeat expansions disrupt normal cellular processes by producing aberrant RNA repeat sequences, leading to toxic protein aggregation, RNA foci, and altered gene expression. Although they belong to the rare disease group, such diseases must be investigated to understand integral mechanisms and prevention. Current methods for alleviating these diseases involve—gene silencing therapies by antisense oligonucleotides (ASOs) and RNA interference (RNAi), CRISPR/Cas9 gene editing, small molecule therapies, etc. ASOs and RNAi reduce toxic protein production genes while CRISPR/Cas9 excise or alter expanded repeats. Small molecule therapies targeting RNA repeat-binding or proteostasis regulation are being developed to alleviate toxic protein accumulation, prevent RNA toxic foci formation, and promote the degradation of misfolded proteins. Additionally, gene replacement and regulatory element modification restore normal gene function. Some researchers tried to modulate toxic protein aggregation using heat shock proteins and chemical chaperones. This is a comprehensive review on the available research on RED treatment and their ongoing challenges, such as efficient delivery of therapies to the central nervous system, minimizing off-target effects in gene editing, sustaining therapeutic efficacy, and addressing toxicity and scalability in large-scale applications.

Keywords

• repeat expansion diseases (reds)
• gene therapy
• antisense oligonucleotides (asos)
• rna interference (rnai)
• crispr/cas9 gene editing