A conditional pan-neuronal Drosophila model of spinocerebellar ataxia 7 with a reversible adult phenotype suitable for identifying modifier genes.

Spinocerebellar ataxia 7 (SCA7) is a neurodegenerative disease caused by a polyglutamine (polyQ) expansion in the ataxin 7 (ATXN7) protein, a member of a multiprotein complex involved in histone acetylation. We have created a conditional Drosophila model of SCA7 in which expression of truncated ATXN7 (ATXN7T) with a pathogenic polyQ expansion is induced in neurons in adult flies. In this model, mutant ATXN7T accumulated in neuronal intranuclear inclusions containing ubiquitin, the 19S proteasome subunit, and HSP70 (heat shock protein 70), as in patients.

Ultrastructural localization of parkin in the rat brainstem, thalamus and basal ganglia.

The parkin gene encodes a 52 kd putative E3 ubiquitin-protein ligase involved in an autosomal recessive form of early onset parkinsonism. Parkin ultrastructural localization was studied by immunohistochemistry in the adult rat brain and in a parkin inducible PC12 cell line (HS22). In the rat brain, parkin immunoreactivity was detected in neuronal and glial cell bodies and in nerve processes.

Increased expression and redistribution of the antiapoptotic molecule Bcl-xL in Parkinson's disease.

In the present study, we tried to clarify the potentially protective role of Bcl-x(L), an anti-apoptotic member of the Bcl-2 family of proteins, in Parkinson's disease (PD). Using in situ hybridization on human postmortem mesencephalon sections, we show that in PD patients Bcl-x(L) mRNA expression per dopaminergic neuron was almost double that of controls. We also show that, ultrastructurally, this effect may be mediated by a redistribution of Bcl-x(L) from the cytosol to the outer mitochondrial membrane.

FADD: A link between TNF family receptors and caspases in Parkinson's disease.

Fas-associating protein with a death domain (FADD) is a proximal adaptor protein of the tumor necrosis factor (TNF) receptor family death pathway. This human postmortem study showed a significant decrease in the percentage of FADD-immunoreactive dopaminergic (DA) neurons in the substantia nigra pars compacta of patients with PD compared with controls (-24.8%).

Caspase-8 is an effector in apoptotic death of dopaminergic neurons in Parkinson's disease, but pathway inhibition results in neuronal necrosis.

Caspase-8 is a proximal effector protein of the tumor necrosis factor receptor family death pathway. In the present human postmortem study, we observed a significantly higher percentage of dopaminergic (DA) substantia nigra pars compacta neurons that displayed caspase-8 activation in Parkinson's disease (PD) patients compared with controls. In an in vivo experimental PD model, namely subchronically 1,2,3,6-tetrahydropyridine-treated mice, we also show that caspase-8 is indeed activated after exposure to this toxin early in the course of cell demise, suggesting that caspase-8 activation precedes and is not the consequence of cell death.