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beta-Amyloid precursor protein mRNA is increased in inclusion-body myositis muscle

E Sarkozi1, V Askanas, S A Johnson

  • 1Department of Neurology, University of Southern California, School of Medicine, Los Angeles 90017.

Neuroreport
|June 1, 1993
PubMed

Insights

Inclusion body myositis (IBM) muscle fibers show increased beta-amyloid precursor protein (beta APP) mRNA and protein. This suggests higher beta APP production contributes to IBM pathology, a finding previously seen only in brain diseases.

Area of Science:

  • Neurology
  • Molecular Biology
  • Muscle Diseases

Background:

  • Inclusion body myositis (IBM) is a progressive muscle-weakening disease.
  • The beta-amyloid precursor protein (beta APP) is implicated in neurodegenerative diseases like Alzheimer's.
  • The role of beta APP in IBM has not been fully elucidated.

Purpose of the Study:

  • To investigate the expression of beta-amyloid precursor protein (beta APP) mRNA and protein in muscle biopsies from IBM patients.
  • To determine if increased beta APP generation contributes to the pathology of IBM.

Main Methods:

  • Analysis of muscle biopsies from 8 IBM patients (including 2 hereditary cases) and normal controls.
  • Quantitative assessment of beta APP mRNA levels using in situ hybridization.
  • Immunohistochemical detection of beta APP and beta-amyloid protein epitopes.

Main Results:

  • All 8 IBM patients exhibited increased beta APP mRNA in vacuolated muscle fibers.
  • Increased beta APP mRNA correlated with abnormal beta APP accumulation and beta-amyloid epitopes in affected fibers.
  • In normal muscle, beta APP mRNA was localized to neuromuscular junctions.

Conclusions:

  • Abnormal accumulation of beta APP in IBM vacuolated fibers is partly due to increased beta APP generation.
  • This study demonstrates up-regulated beta APP mRNA in pathological human muscle tissue, extending findings beyond brain diseases like Alzheimer's.

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