Original Paper

Acta Neuropathologica

, Volume 121, Issue 4, pp 519-527

Optineurin inclusions occur in a minority of TDP-43 positive ALS and FTLD-TDP cases and are rarely observed in other neurodegenerative disorders

  • Tibor HortobágyiAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry Email author 
  • , Claire TroakesAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry
  • , Agnes L. NishimuraAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry
  • , Caroline VanceAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry
  • , John C. van SwietenAffiliated withDepartment of Neurology, Erasmus University Medical Center Rotterdam
  • , Harro SeelaarAffiliated withDepartment of Neurology, Erasmus University Medical Center Rotterdam
  • , Andrew KingAffiliated withDepartment of Clinical Neuropathology, King’s College Hospital
  • , Safa Al-SarrajAffiliated withDepartment of Clinical Neuropathology, King’s College Hospital
  • , Boris RogeljAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry
    • , Christopher E. ShawAffiliated withDepartment of Clinical Neuroscience, King’s College London, MRC Centre for Neurodegeneration Research, Institute of Psychiatry

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Abstract

Optineurin (OPTN) is a multifunctional protein involved in vesicular trafficking, signal transduction and gene expression. OPTN mutations were described in eight Japanese patients with familial and sporadic amyotrophic lateral sclerosis (FALS, SALS). OPTN-positive inclusions co-localising with TDP-43 were described in SALS and in FALS with SOD-1 mutations, potentially linking two pathologically distinct pathways of motor neuron degeneration. We have explored the abundance of OPTN inclusions using a range of antibodies in postmortem tissues from 138 cases and controls including sporadic and familial ALS, frontotemporal lobar degeneration (FTLD) and a wide range of neurodegenerative proteinopathies. OPTN-positive inclusions were uncommon and detected in only 11/32 (34%) of TDP-43-positive SALS spinal cord and 5/15 (33%) of FTLD-TDP. Western blot of lysates from FTLD-TDP frontal cortex and TDP-43-positive SALS spinal cord revealed decreased levels of OPTN protein compared to controls (p < 0.05), however, this correlated with decreased neuronal numbers in the brain. Large OPTN inclusions were not detected in FALS with SOD-1 and FUS mutation, respectively, or in FTLD-FUS cases. OPTN-positive inclusions were identified in a few Alzheimer’s disease (AD) cases but did not co-localise with tau and TDP-43. Occasional striatal neurons contained granular cytoplasmic OPTN immunopositivity in Huntington’s disease (HD) but were absent in spinocerebellar ataxia type 3. No OPTN inclusions were detected in FTLD-tau and α-synucleinopathy. We conclude that OPTN inclusions are relatively rare and largely restricted to a minority of TDP-43 positive ALS and FTLD-TDP cases. Our results do not support the proposition that OPTN inclusions play a central role in the pathogenesis of ALS, FTLD or any other neurodegenerative disorder.

Keywords

Amyotrophic lateral sclerosis (ALS) Frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) Immunohistochemistry Motor neurone disease (MND) Optineurin (OPTN) Western blotting