Haplotype-based stratification of Huntington's disease

Area of Science:

• Genetics
• Neurodegenerative Diseases
• Pharmacogenomics

Background:

• Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder.
• It is caused by a CAG trinucleotide repeat expansion in the HTT gene, leading to an extended polyglutamine tract in huntingtin.
• The HD-causing expansion arises from multiple ancestral origins and distinct haplotype backbones.

Purpose of the Study:

• To compare and integrate HTT haplotype definition systems for improved resolution of HD haplotypes.
• To identify frequent disease-associated and control chromosome backbones.
• To facilitate the development of allele-specific gene silencing therapies for Huntington's disease.

Main Methods:

• Integrated two major HTT haplotype definition systems using 74 sequence variants.
• Analyzed 4078 heterozygous HD subjects from a genome-wide association study for HD age at onset.
• Determined haplotypes in publicly available HD subject-derived cell lines (fibroblasts, iPSCs, ESCs).

Main Results:

• Common genetic variation at HTT distinguishes normal and CAG-expanded chromosomes in over 95% of European HD individuals.
• Identified frequent disease-associated and control chromosome backbones with potential for further resolution.
• Cataloged HD haplotypes in various cell lines to support therapeutic development.

Conclusions:

• Genetic characterization of HTT haplotypes provides a foundation for developing precise, allele-specific gene silencing therapies for Huntington's disease.
• This research supports the implementation of precision medicine approaches for HD treatment.
• The findings offer valuable genetic guidance for therapeutic gene-based targeting in HD.