A point mutation in the dynein heavy chain gene leads to striatal atrophy and compromises neurite outgrowth of striatal neurons.

The molecular motor dynein and its associated regulatory subunit dynactin have been implicated in several neurodegenerative conditions of the basal ganglia, such as Huntington's disease (HD) and Perry syndrome, an atypical Parkinson-like disease. This pathogenic role has been largely postulated from the existence of mutations in the dynactin subunit p150(Glued). However, dynactin is also able to act independently of dynein, and there is currently no direct evidence linking dynein to basal ganglia degeneration. To provide such evidence, we used here a mouse strain carrying a point mutation in the dynein heavy chain gene that impairs retrograde axonal transport. These mice exhibited motor and behavioural abnormalities including hindlimb clasping, early muscle weakness, incoordination and hyperactivity. In vivo brain imaging using magnetic resonance imaging showed striatal atrophy and lateral ventricle enlargement. In the striatum, altered dopamine signalling, decreased dopamine D1 and D2 receptor binding in positron emission tomography SCAN and prominent astrocytosis were observed, although there was no neuronal loss either in the striatum or substantia nigra. In vitro, dynein mutant striatal neurons displayed strongly impaired neuritic morphology. Altogether, these findings provide a direct genetic evidence for the requirement of dynein for the morphology and function of striatal neurons. Our study supports a role for dynein dysfunction in the pathogenesis of neurodegenerative disorders of the basal ganglia, such as Perry syndrome and HD.

Antibody-bound beta-amyloid precursor protein stimulates the production of tumor necrosis factor-alpha and monocyte chemoattractant protein-1 by cortical neurons.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterized by the accumulation of extracellular depositions of fibrillar beta-amyloid (A beta), which is derived from the alternative processing of beta-amyloid precursor protein (APP). Although APP is thought to function as a cell surface receptor, its mode of action still remains elusive. In this study, we found that the culture medium derived from cortical neurons treated with an anti-APP antibody triggers the death of naive neurons. Biochemical and immunocytochemical analyses revealed the presence, both in the conditioned medium and in neurons, of increased levels of tumor necrosis factor-alpha and monocyte chemoattractant protein-1. Furthermore, the expression of these proinflammatory mediators occurred through a c-Jun N-terminal protein kinase/c-Jun-dependent mechanism. Taken together, our findings provide evidence for a novel mechanism whereby neuronal APP in its full-length configuration induces neuronal death. Such a mechanism might be relevant to neuroinflammatory processes as those observed in AD.

HDAC-3 participates in the repression of e2f-dependent gene transcription in primary differentiated neurons.

Activation of e2f-1 gene expression is an event that has been now established in many models of neuronal apoptosis. Accumulated E2F-1 protein has also been observed in post mortem brains obtained from patients suffering from different neurodegenerative diseases. We have previously shown in primary neuronal cultures that e2f-1 gene transcription was actively repressed in neuroprotective conditions through HDAC-dependent regulation on the E2F-responsive elements (E2F-REs) located in the e2f-1 gene promoter. Here, we further investigated the protein complex bound to these sites by gel shift analysis. We found that the specific protein binding to E2F-REs is altered in apoptotic conditions compared to neuroprotective conditions, suggesting that the proteic constituents of the complex are likely to be modified upon apoptosis onset. Indeed, Western blot analysis showed a time-dependent degradation of the Rb/E2F binding protein HDAC-3 during apoptosis, a degradation that is caspase-dependent. Altogether, these data point to HDAC-3 as a good candidate involved in the active e2f-1 repression necessary for neuroprotection.