Huntingtin HTT1a is generated in a CAG repeat-length-dependent manner in human tissues

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Huntington disease (HD) is caused by a CAG trinucleotide expansion in the huntingtin (HTT) gene.
• This mutation leads to the production of a toxic HTT exon 1 protein fragment via the HTT1a RNA.
• Previous studies showed CAG repeat length dependency in mouse models, but human data were lacking.

Purpose of the Study:

• To quantify HTT1a RNA levels in human tissues.
• To determine the correlation between HTT1a expression and CAG repeat length in humans.
• To assess HTT1a as a potential biomarker for HD progression.

Main Methods:

• Development of sensitive digital PCR assays for absolute quantification of HTT1a transcripts.
• Measurement of CAG repeat sizes in all human samples.
• Statistical analysis using ANOVA and linear modeling to correlate HTT1a levels with CAG repeat length.

Main Results:

• HTT1a expression was confirmed in human post-mortem brain tissues and peripheral cell types.
• A statistically significant positive correlation between HTT1a expression and CAG repeat length was observed in PBMCs.
• Elevated HTT1a levels were detected in PBMCs even within the adult-onset CAG repeat range.

Conclusions:

• HTT1a is expressed across a wide range of human tissues and CAG repeat lengths.
• Peripheral samples demonstrate CAG repeat length-dependent HTT1a generation.
• HTT1a levels may serve as a sensitive marker for HD disease state and progression, valuable for clinical trials.