ALS mutations in TLS/FUS disrupt target gene expression

Area of Science:

• Neuroscience
• Molecular Biology
• Genetics

Background:

• Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease linked to mutations in various genes.
• The FUS gene, encoding an RNA/DNA-binding protein, is one such gene implicated in ALS pathogenesis.
• MECP2 is a known target gene of FUS, suggesting a potential role in ALS mechanisms.

Purpose of the Study:

• To investigate the impact of ALS-associated mutations in FUS on the expression of its target gene, MECP2.
• To elucidate the molecular mechanisms by which FUS mutations affect MECP2 mRNA and protein levels.

Main Methods:

• Transfection of human U87 cells with wild-type and mutant FUS derivatives (e.g., FUS(C) with R521C mutation).
• Analysis of MECP2 alternative splicing and mRNA abundance using quantitative methods.
• Assessment of mRNA stability and protein levels.
• Biochemical fractionation and in vivo localization studies to determine subcellular localization of FUS and MECP2 mRNA.

Main Results:

• ALS-associated FUS mutants altered MECP2 alternative splicing.
• Mutant FUS significantly increased MECP2 mRNA abundance, primarily through enhanced mRNA stability.
• Despite increased mRNA levels, MeCP2 protein levels were paradoxically reduced in cells expressing FUS mutants.
• MECP2 mRNA was found to colocalize with cytoplasmic FUS aggregates in insoluble fractions.

Conclusions:

• Mutations in FUS associated with ALS can profoundly affect target gene expression.
• FUS-containing aggregates play a dominant role in mediating these effects, leading to altered mRNA processing and protein levels.
• The findings provide a mechanistic link between FUS aggregation and disrupted gene expression in ALS pathogenesis.