Brain Advance Access originally published online on August 11, 2009
Brain 2009 132(11):2922-2931; doi:10.1093/brain/awp214
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A new subtype of frontotemporal lobar degeneration with FUS pathology
1 Institute of Neuropathology, University Hospital of Zürich, Zürich, Switzerland 2 Mayo Clinic – Neuroscience, Jacksonville, FL, USA 3 Center for Neuropathology and Prion Research, Ludwig-Maximilians-University, Muenchen, Germany 4 Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada
Correspondence to: Ian Mackenzie, Department of Pathology, University of British Columbia, Vancouver, British Columbia, Canada E-mail: ian.mackenzie{at}vch.ca
Frontotemporal dementia (FTD) is a clinical syndrome with a heterogeneous molecular basis. The neuropathology associated with most FTD is characterized by abnormal cellular aggregates of either transactive response DNA-binding protein with Mr 43 kDa (TDP-43) or tau protein. However, we recently described a subgroup of FTD patients, representing around 10%, with an unusual clinical phenotype and pathology characterized by frontotemporal lobar degeneration with neuronal inclusions composed of an unidentified ubiquitinated protein (atypical FTLD-U; aFTLD-U). All cases were sporadic and had early-onset FTD with severe progressive behavioural and personality changes in the absence of aphasia or significant motor features. Mutations in the fused in sarcoma (FUS) gene have recently been identified as a cause of familial amyotrophic lateral sclerosis, with these cases reported to have abnormal cellular accumulations of FUS protein. Because of the recognized clinical, genetic and pathological overlap between FTD and amyotrophic lateral sclerosis, we investigated whether FUS might also be the pathological protein in aFTLD-U. In all our aFTLD-U cases (n = 15), FUS immunohistochemistry labelled all the neuronal inclusions and also demonstrated previously unrecognized glial pathology. Immunoblot analysis of protein extracted from post-mortem aFTLD-U brain tissue demonstrated increased levels of insoluble FUS. No mutations in the FUS gene were identified in any of our patients. These findings suggest that FUS is the pathological protein in a significant subgroup of sporadic FTD and reinforce the concept that FTD and amyotrophic lateral sclerosis are closely related conditions.
Key Words: frontotemporal lobar degeneration; frontotemporal dementia; FUS; fused in sarcoma; TLS; translocated in liposarcoma
Abbreviations: aFTLD-U, atypical frontotemporal lobar degeneration with neuronal inclusions composed of an unidentified ubiquitinated protein; ALS, amyotrophic lateral sclerosis; FALS, familial amyptrophic lateral sclerosis; FTD, frontotemporal dementia; FTLD, frontotemporal lobar degeneration; FUS, fused in sarcoma; IHC, immunohistochemistry; p62, ubiquitin proteasome system associated sequestosome p62; SALS, sporadic amyotrophic lateral sclerosis; SDS, sodium dodecyl sulphate; TDP-43, transactive response DNA-binding protein with Mr 43 kDa.
Received May 5, 2009. Revised July 6, 2009. Accepted July 7, 2009.
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  S. Weintraub and M. Mesulam With or without FUS, it is the anatomy that dictates the dementia phenotype Brain, November 1, 2009; 132(11): 2906 - 2908. [Full Text] [PDF]
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