Immunoreactivity of valosin-containing protein in sporadic amyotrophic lateral sclerosis and in a case of its novel mutant.

Takashi Ayaki,Hiroko Fukushima,Masafumi Ihara,Satoshi Fukui,Hirofumi Kusaka,Akemi Shodai,Hiroyuki Morino,Jun Kawamata,Takeshi Inoue,Hirofumi Yamashita,Takeshi Asano,Riki Matsumoto,Takayuki Kondo,Makoto Urushitani,Hidefumi Ito,Satoshi Nakano,Akito Ikemoto,Hideshi Kawakami,Takuji Fujita,Ryōsuke Takahashi

doi:10.1186/s40478-014-0172-0

Abstract

BackgroundMutations in the valosin-containing protein (VCP) gene were first found to cause inclusion- body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD). Mutations in the VCP gene were later reported to occur in familial amyotrophic lateral sclerosis (ALS). But the role of VCP in the neurodegenerative processes that occur in ALS remains unknown. The purpose of the present study was to elucidate the role of VCP in the neurodegeneration seen in sporadic and VCP mutant ALS.ResultsImmunohistochemistry demonstrated that the frequency of distinct VCP-positive nuclei of spinal motor neurons of patients with sporadic ALS (SALS) and the ALS with VCP novel mutation (ALS-VCP, M158V) was increased, compared with that of the control cases. No VCP-positive inclusion bodies were observed in SALS patients, a ALS-VCP patient or in control subjects. Neuropathologic examination of the ALS-VCP case showed loss of motor neurons, the presence of Bunina bodies, and degeneration of the corticospinal tracts. Bunina bodies detected in this case were confirmed to show immunohistochemical and ultrastructural features similar to those previously described. Furthermore, neuronal intracytoplasmic inclusions immunopositive for TAR DNA-binding protein 43 kDa (TDP-43), phosphorylated TDP-43, ubiquitin (Ub), p62, and optineurin were identified in the spinal and medullary motoneurons, but not in the neocortex. Gene analysis of this ALS-VCP patient confirmed the de novo mutation of M158V, which was not found in control cases; and bioinformatics using several in silico analyses showed possible damage to the structure of VCP. Immunocytochemical study of cultured cells showed increased cytoplasmic translocation of TDP-43 in cells transfected with several mutant VCP including our patient’s compared with wild-type VCP.ConclusionThese findings support the idea that VCP is associated with the pathomechanism of SALS and familial ALS with a VCP mutation, presumably acting through a dominant-negative mechanism.Electronic supplementary materialThe online version of this article (doi:10.1186/s40478-014-0172-0) contains supplementary material, which is available to authorized users.

Highlights

Valosin-containing protein (VCP) is a ubiquitous member of the AAA-ATPase supergene family
The name of multisystem proteinopathy (MSP) has been proposed, using the nomenclature of MSP1 for IBMPFD caused by a VCP mutation, MSP2 for IBMPFD related to an HNRNPA2B1 mutation, MSP3 for IBMPFD related to an Heterogeneous Nuclear Ribonucleoprotein A1 (HNRNPA1) mutation, and MSP4 for IBMPFD due to some unidentified gene [22]
Only rare VCP-positive neuronal intranuclear inclusions are detected, and those that are detected lack the characteristic lentiform morphology [23]. This finding suggests that TAR DNA-binding protein 43 kDa (TDP-43) and ubiquitin positive-inclusions do not contain VCP and supports the idea that VCP gene mutations in IBMPFD produce a dominant-negative loss of VCP function [23,25]

Summary

Introduction

Valosin-containing protein (VCP) is a ubiquitous member of the AAA-ATPase supergene family. Mutations in the VCP gene were first found to cause inclusion-body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD) [7,8]. FTD cases with a VCP mutation (MSP1) present with TAR DNA-binding protein 43 kDa (TDP-43) and ubiquitin-positive short dystrophic neurites and frequently lentiform neuronal intranuclear inclusions in their neocortex [23,24,25]. Only rare VCP-positive neuronal intranuclear inclusions are detected, and those that are detected lack the characteristic lentiform morphology [23] This finding suggests that TDP-43 and ubiquitin positive-inclusions do not contain VCP and supports the idea that VCP gene mutations in IBMPFD produce a dominant-negative loss of VCP function [23,25]. Mutations in the valosin-containing protein (VCP) gene were first found to cause inclusion- body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD).

Objectives

Methods

Results

Discussion

Conclusion