Molecular Psychiatry (1998) 3, 462–465 1998 Stockton Press All rights reserved 1359–4184/98 $12.00 GUEST EDITORIAL Lewy body diseases and multiple system atrophy as ␣-synucleinopathies Parkinson’s disease and dementia with Lewy bodies synuclein are the first known genetic causes of Parkin- are among the most common neurodegenerative dis- son’s disease. They are located in the amino-terminal eases. They share the Lewy body and the Lewy neurite half of ␣-synuclein, which consists of seven imperfect as their defining neuropathological characteristics. repeats of 11 amino acids each, with the consensus Originally described in 1912 as a light-microscopic sequence KTKEGV (Figure 1). It has been suggested entity, the Lewy body was shown to be made of abnor- that ␣-synuclein may bind through these repeats to mal filaments in the 1960s. Over the past year, the bio- membranes rich in acidic phospholipids.3 chemical nature of the Lewy body filament has been This work raised the question whether ␣-synuclein revealed. is a component of Lewy bodies and Lewy neurites of A large number of different proteins has been idiopathic Parkinson’s disease and of dementia with reported to be present in Lewy bodies and Lewy neur- Lewy bodies. Using well-characterised anti-␣-synuc- ites by immunohistochemical methods. However, these lein antibodies, Spillantini et al showed strong staining findings do not permit us to distinguish between of both Lewy bodies and Lewy neurites in idiopathic intrinsic Lewy body components and normal cellular Parkinson’s disease and dementia with Lewy bodies.4 constituents that get merely trapped in the filaments They also reported the lack of staining of these patho- that make up the Lewy body. A similar problem plagued logical structures with an antibody directed against the the field of the neurofibrillary lesions of Alzheimer’s related ␤-synuclein. Several subsequent papers,5–8 one disease over part of the 1980s. It was solved with the of which is published by Mezey et al in this issue of purification and analysis of paired helical and straight Molecular Psychiatry9 have reported similar results. filaments, the filamentous constituents of the neurofi- All studies to date have shown strong staining of Lewy brillary lesions. Unfortunately, a similar approach bodies and Lewy neurites in every case of Parkinson’s with Lewy bodies has only met with partial success, disease and dementia with Lewy bodies investigated. mainly because Lewy bodies and Lewy neurites are Paradoxically, there have been no reports so far on the much less abundant than neurofibrillary lesions. staining for ␣-synuclein of Lewy bodies and Lewy neu- This was the situation until the middle of last year, rites in brain tissue from individuals with the A53T or when genetics came to the rescue, taking us straight to A30P mutations. the very core of the Lewy body filament. In June 1997, Several studies have shown that the staining of Lewy Polymeropoulos et al reported a missense mutation in bodies and Lewy neurites for ␣-synuclein is more ␣-synuclein in a large pedigree with early-onset Parkin- extensive than the staining for ubiquitin,7,8,10 until now son’s disease and in three smaller, apparently unre- the most sensitive immunohistochemical marker. This lated kindreds.1 The mutation is an alanine to thre- implies that ubiquitination is a later event than onine change at residue 53 of ␣-synuclein, an abundant accumulation of ␣-synuclein and means that staining 140-amino acid presynaptic protein of unknown func- for ␣-synuclein will replace staining for ubiquitin as tion. Somewhat surprisingly, rodent and zebrafinch ␣- the preferred means for identifying Lewy bodies and synucleins carry a threonine residue at position 53, like Lewy neurites in tissue sections. In dementia with the mutated human protein. This, together with the fact Lewy bodies, the Lewy body pathology frequently co- that all families with the A53T mutation are of either exists with a neurofibrillary pathology like that found Southern Italian or Greek origin, and that this part of in Alzheimer’s disease. Ubiquitin antibodies stain both Italy was colonized by Greece a long time ago, led some the Lewy body and the neurofibrillary pathologies. By to propose that the A53T change may be nothing more contrast, ␣-synuclein antibodies only stain the Lewy than a rare benign polymorphism. However, the dis- body pathology, whereas anti-tau antibodies only stain covery earlier this year of an alanine to proline the neurofibrillary pathology. mutation at residue 30 of ␣-synuclein in a family of Taken together, the genetic and the neuropatholog- German descent with Parkinson’s disease,2 has settled ical evidence suggests, but does not prove, that ␣-syn- this controversy in favour of the relevance of ␣-synucl- uclein is a major component of the abnormal filaments ein for the aetiology and pathogenesis of some familial that make up Lewy bodies and Lewy neurites. Two cases of Parkinson’s disease. The two mutations in ␣- recent studies have investigated this question directly by immunoelectron microscopy of filaments from pur- ified Lewy bodies,7 or of sarcosyl-insoluble filaments Correspondence: M Goedert, MRC Laboratory of Molecular extracted from cingulate cortex of patients with 10 Biology, Hills Rd, Cambridge CB2 2QH, UK. E-mail: mgȰmrc- dementia with Lewy bodies. Both studies have dem- lmb.cam.ac.uk onstrated strong labelling of filaments with ␣-synuclein Guest editorial 463 Figure 1 Mutations in the ␣-synuclein gene in familial Parkinson’s disease. (a) Schematic diagram of human ␣-synuclein. The seven repeats with the consensus sequence KTKEGV are shown as green bars. The hydrophobic region is shown in blue and the negatively charged carboxy-terminus in red. The two known missense mutations are indicated. (b) Repeats in human ␣- synuclein. Residues 7–87 of the 140-amino acid protein are shown. Amino acid identities between at least five of the seven repeats are indicated by black bars. The alanine to proline mutation at residue 30 between repeats two and three and the alanine to threonine mutation at residue 53 between repeats four and five are shown. antibodies. They provide the first demonstrations of component of Lewy body filaments. It follows that Par- the morphologies of ␣-synuclein filaments. Baba et al kinson’s disease and dementia with Lewy bodies are also provided the first immunoblot analysis of ␣-syn- ␣-synucleinopathies. uclein from purified Lewy bodies.7 Interestingly, in Several groups have looked at the possible presence addition to full-length ␣-synuclein, truncated proteins of ␣-synuclein in the filamentous inclusions of other were also found. The nature and significance of the neurodegenerative diseases, resulting in the discovery truncations in ␣-synuclein remain to be determined. that multiple system atrophy (MSA) is a third ␣-synu- Sarcosyl-insoluble ␣-synuclein filaments have a cleinopathy.12–14 Neuropathologically, glial cytoplas- diameter of 5–10 nm.10 They were labelled along their mic inclusions, which consist of filamentous aggre- entirety by an antibody which recognises the carboxy- gates, are the defining feature of MSA. They are found terminal region of ␣-synuclein, indicating that they mostly in the cytoplasm and, to a lesser extent, the contain ␣-synuclein as a major component (Figure 2). nuclei of oligodendrocytes. Inclusions are also The filament morphologies are consistent with a model observed in the cytoplasm and nuclei of some nerve in which the ␣-synuclein molecules assemble to form cells, as well as in neuropil threads. They consist of a 5-nm protofilament, two of which could associate to straight and twisted filaments, with reported diameters produce a variably twisted filament. It suggests that ␣- of 10–30 nm. Until very recently, the biochemical com- synuclein molecules, which are believed to be position of MSA filaments was unknown. extended and relatively unstructured,11 may run paral- This has changed with the discovery that glial cyto- lel to the filament axis. This differs from the packing plasmic inclusions are strongly immunoreactive for ␣- of tau protein in filaments from Alzheimer’s disease synuclein12–14 and that filaments from brains of and other tauopathies, where individual tau molecules patients with MSA are strongly labelled by ␣-synuclein are believed to run mainly perpendicular to the fila- antibodies.14 Filament morphologies and antibody ment axis. An antibody which recognises amino acids labelling characteristics are very similar to those of the 11–34 of ␣-synuclein only ever labelled one filament ␣-synuclein filaments from dementia with Lewy bod- end.10 This suggests that the epitope of this antibody ies.10,14 This work indicates that ␣-synuclein is the is buried in the body of the filament and exposed only major component of MSA filaments and reveals an at one end and that ␣-synuclein filaments are polar unexpected molecular link between MSA and Lewy structures. The recent immunoelectron microscopy body diseases. work leaves little doubt that ␣-synuclein is the major It appears likely that nerve cells and glial cells Guest editorial 464 Figure 2 Filaments from cingulate cortex of patients with dementia with Lewy bodies immunolabelled for ␣-synuclein. (a and b) Small clumps of labelled ␣-synuclein filaments. (c) A labelled ␣-synuclein filament and an unlabelled paired helical filament (arrow). The labelled filaments have various morphologies, including: 5-nm filament (d); 10-nm filament with dark stain pen- etrating centre line (e); twisted filament showing alternating width (f); 10-nm filament with slender 5-nm extensions at ends (g, also c). Scale bar, 100 nm (in c) (from Reference 10). degenerate in Parkinson’s disease, dementia with Lewy References bodies and multiple system atrophy, because of the 1 Polymeropoulos MH, Lavedan C, Leroy E, Ide SE, Dehejia A, Dutra presence of abnormal ␣-synuclein filaments. It follows A et al. Mutation in the ␣-synuclein gene identified in families that the events that lead to assembly of the normally with Parkinson’s disease.