Mitochondrial complex I NUBPL mutations cause combined dystonia with bilateral striatal necrosis and cerebellar atrophy.

BACKGROUND AND PURPOSE: The recent advances in genetics have helped to unravel the cause of many dystonia syndromes. With the broadening spectrum of genetically defined dystonia syndromes, distinct clinico-radiological phenotypes are a welcome handle to guide the diagnostic work-up. METHODS: Exome sequencing was used to elucidate the genetic cause of a syndrome characterized by generalized dystonia, pyramidal and cerebellar involvement, with bilateral striatal necrosis (BSN) and cerebellar atrophy on magnetic resonance imaging. Homozygosity mapping and linkage analysis were used in a supportive role. Known genetic causes of BSN were excluded by use of exome data or Sanger sequencing. RESULTS: Compound heterozygous mutations were identified in the NUBPL gene in a small UK kindred. The gene lay in a region of positive linkage and segregated with disease in a family of six individuals. CONCLUSION: NUBPL mutations cause early onset, autosomal recessive generalized dystonia with cerebellar ataxia, pyramidal signs, preserved cognition and a distinct magnetic resonance imaging appearance with BSN and cerebellar atrophy.

Restless Legs Syndrome in NKX2-1-related chorea: An expansion of the disease spectrum.

BACKGROUND: Molecular technologies are expanding our knowledge about genetic variability underlying early-onset non-progressive choreic syndromes. Focusing on NKX2-1-related chorea, the clinical phenotype and sleep related disorders have been only partially characterized. METHODS: We propose a retrospective and longitudinal observational study in 7 patients with non-progressive chorea due to NKX2-1 mutations. In all subjects sleep and awake EEG, brain MRI with study of pituitary gland, chest X-rays, endocrinological investigations were performed. Movement disorders, pattern of sleep and related disorders were investigated using structured clinical evaluation and several validated questionnaires. RESULTS: In patients carrying NKX2-1 mutations, chorea was mainly distributed in the upper limbs and tended to improve with age. All patients presented clinical or subclinical hypothyroidism and delayed motor milestones. Three subjects had symptoms consistent with Restless Legs Syndrome (RLS) that improved with Levodopa. CONCLUSIONS: Patients with NKX2-1 gene mutations should be investigated for RLS, which, similarly to chorea, can sometimes be ameliorated by Levodopa.

Mitofusin-mediated ER stress triggers neurodegeneration in pink1/parkin models of Parkinson's disease.

Mutations in PINK1 and PARKIN cause early-onset Parkinson's disease (PD), thought to be due to mitochondrial toxicity. Here, we show that in Drosophila pink1 and parkin mutants, defective mitochondria also give rise to endoplasmic reticulum (ER) stress signalling, specifically to the activation of the protein kinase R-like endoplasmic reticulum kinase (PERK) branch of the unfolded protein response (UPR). We show that enhanced ER stress signalling in pink1 and parkin mutants is mediated by mitofusin bridges, which occur between defective mitochondria and the ER. Reducing mitofusin contacts with the ER is neuroprotective, through suppression of PERK signalling, while mitochondrial dysfunction remains unchanged. Further, both genetic inhibition of dPerk-dependent ER stress signalling and pharmacological inhibition using the PERK inhibitor GSK2606414 were neuroprotective in both pink1 and parkin mutants. We conclude that activation of ER stress by defective mitochondria is neurotoxic in pink1 and parkin flies and that the reduction of this signalling is neuroprotective, independently of defective mitochondria. A video abstract for this article is available online in the supplementary information.

All in the blink of an eye: new insight into cerebellar and brainstem function in DYT1 and DYT6 dystonia.

BACKGROUND AND PURPOSE: Traditionally dystonia has been considered a disorder of basal ganglia dysfunction. However, recent research has advocated a more complex neuroanatomical network. In particular, there is increasing interest in the pathophysiological role of the cerebellum. Patients with cervical and focal hand dystonia have impaired cerebellar associative learning using the paradigm eyeblink conditioning. This is perhaps the most direct evidence to date that the cerebellum is implicated in patients. METHODS: Eleven patients with DYT1 dystonia and five patients with DYT6 dystonia were examined and rates of eyeblink conditioning were compared with age-matched controls. A marker of brainstem excitability, the blink reflex recovery, was also studied in the same groups. RESULTS: Patients with DYT1 and DYT6 dystonia have a normal ability to acquire conditioned responses. Blink reflex recovery was enhanced in DYT1 but this effect was not seen in DYT6. CONCLUSIONS: If the cerebellum is an important driver in DYT1 and DYT6 dystonia our data suggest that there is specific cerebellar dysfunction such that the circuits essential for conditioning function normally. Our data are contrary to observations in focal dystonia and suggest that the cerebellum may have a distinct role in different subsets of dystonia. Evidence of enhanced blink reflex recovery in all patients with dystonia was not found and recent studies calling for the blink recovery reflex to be used as a diagnostic test for dystonic tremor may require further corroboration.