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Phenotypic variance in monozygotic twins with SCA3.

Hua Zhao1, Lu Yang1, Yi Dong1

  • 1Department of Neurology and Research Center of Neurology in Second Affiliated Hospital, and Key Laboratory of Medical Neurobiology of Zhejiang Province, Zhejiang University School of Medicine, Hangzhou, China.

Molecular Genetics & Genomic Medicine
|July 31, 2020
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Summary

This study reports the first case of monozygotic twins with Spinocerebellar ataxia type 3 (SCA3), revealing epigenetic factors like DNA methylation may influence disease presentation and severity.

Keywords:
DNA methylationmonozygotic twinphenotypic variancespinocerebellar ataxia type 3

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Area of Science:

  • Neurogenetics
  • Epigenetics
  • Neurology

Background:

  • Spinocerebellar ataxia type 3 (SCA3) is a hereditary neurodegenerative disorder known for significant clinical variability.
  • Twin studies are crucial for dissecting genetic and environmental influences on disease phenotypes.
  • Cases of SCA3 twins are exceptionally rare, limiting research into these factors.

Observation:

  • A pair of monozygotic twins diagnosed with SCA3 were evaluated using standardized clinical assessments.
  • Genetic analysis confirmed identical CAG repeat lengths in both twins.
  • Differences in age at onset, symptom severity (constipation, blepharospasm, fasciculation), and DNA methylation patterns at specific CpG sites were observed.

Findings:

  • Despite identical genetic makeup (CAG repeat length), the SCA3 twins exhibited distinct clinical manifestations and symptom progression.
  • Significant variations in DNA methylation levels were detected between the twins, suggesting a role in phenotypic divergence.
  • The younger twin presented with an earlier onset of symptoms by two years.

Implications:

  • This is the first reported case of monozygotic twins with SCA3 globally.
  • Epigenetic modifications, specifically DNA methylation, may play a critical role in explaining the phenotypic heterogeneity observed in SCA3.
  • Understanding these epigenetic influences could offer novel therapeutic strategies for managing SCA3 symptom variability.