Related Experiment Video

Updated: May 11, 2026

Efficient and Scalable Production of Full-length Human Huntingtin Variants in Mammalian Cells using a Transient Expression System
10:52

Efficient and Scalable Production of Full-length Human Huntingtin Variants in Mammalian Cells using a Transient Expression System

Published on: December 10, 2021

Characterization of the Huntington intermediate CAG repeat expansion phenotype in PHAROS

Annie Killoran1, Kevin M Biglan, Joseph Jankovic

  • 1University of Rochester, Rochester, NY, USA. Killoran:ankilloran@hsc.wvu.edu

Neurology
|April 30, 2013
PubMed

Insights

Individuals with an intermediate-length huntingtin allele (IA) show behavioral issues like apathy and suicidal ideation, but normal motor and cognitive function. This may signal an early stage of Huntington disease (HD).

Area of Science:

  • Neurogenetics
  • Neurology
  • Clinical Phenotyping

Background:

  • Huntington disease (HD) is a neurodegenerative disorder caused by CAG repeat expansion in the Huntingtin gene.
  • Intermediate-length alleles (IA) in the Huntingtin gene are typically considered non-pathogenic but may influence clinical presentation.

Purpose of the Study:

  • To characterize the clinical phenotype associated with intermediate-length Huntingtin gene CAG repeat expansions.
  • To investigate behavioral, motor, and cognitive differences in individuals with IA compared to controls and expanded alleles.

Main Methods:

  • Utilized data from the Prospective Huntington At Risk Observational Study (PHAROS).
  • Assessed 983 participants using the Unified Huntington's Disease Rating Scale (UHDRS) by blinded investigators.
  • Compared UHDRS scores across three groups: nonexpanded (<26 CAG repeats), intermediate (27-35 CAG repeats), and expanded (>36 CAG repeats).

Main Results:

  • Fifty participants (5.1%) possessed an intermediate allele (IA).
  • The IA group exhibited similar motor, cognitive, and functional scores to controls but significantly worse behavioral scores, including apathy and suicidal ideation.
  • IA participants showed worse behavioral scores than controls and expanded groups, with expanded groups also scoring worse than controls on specific behavioral measures.
  • Four-year retention rates were lower for the IA group (48%) compared to expanded (58%) and control (60%) groups.

Conclusions:

  • Intermediate-length Huntingtin alleles are associated with significant behavioral abnormalities, including apathy and suicidal ideation, despite normal motor and cognitive function.
  • This behavioral phenotype may represent a prodromal stage of Huntington disease or a distinct phenotype.
  • Further research is needed to understand the long-term implications and underlying pathology of intermediate-length alleles.
Abstract

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