Pedro Gonzalez-Alegre

Background: Adolescent idiopathic scoliosis (AIS) is characterized by a complex curvature of the spine of unknown etiology. Unknown genetic factors likely play a role in disease pathogenesis. Recent studies suggest that AIS could result from central nervous system dysfunction and be related to dystonia. On the basis of this information, we hypothesized that genes linked to dystonia contribute to the pathogenesis of AIS. Methods: To test this hypothesis, we evaluated the potential association between sequence variants in candidate dystonia genes and AIS. We sequenced the coding region of 5 selected dystonia-causing genes in 24 subjects with AIS, followed by targeted confirmation in additional 89 patients and 73 controls. Results: No mutations were identified in any of the dystonia genes studied. Conclusions: We found no genetic link between dystonia and AIS. Clinical Relevance: This investigation is a genetic evaluation of the association between dystonia and AIS. Despite the support in the literature for a pathogenic link between both the disorders, we have not identified any mutations in dystonia genes in patients with AIS.

DYT1 is caused by a partly penetrant dominant mutation in TOR1A that leads to a glutamic acid deletion (ΔE) in torsinA. Identifying environmental factors that modulate disease pathogenesis and penetrance could help design therapeutic strategies for dystonia. Several cell-based studies suggest that expression of torsinA(ΔE) increases the susceptibility of neuronal cells to challenges to their oxidative/energy metabolism. Based on those reports, we hypothesized that mice expressing torsinA(ΔE) would be more susceptible than control littermates to the effects of oxidative stress and ATP deficits caused by disruption of the mitochondrial respiratory chain in neurons. To test this hypothesis, we administered 20 or 50 mg/kg/day of the irreversible complex-II inhibitor 3-nitropropionic acid (3-NP) intraperitoneally for 15 consecutive days to young heterozygote DYT1 knock-in (KI) mice and wild type littermates. Repeated phenotypic assessments were performed at baseline, during and after the injections. Animals were then sacrificed and their brains processed for protein analysis. The administration of 20 mg/kg 3-NP led to increased levels of torsinA in the striatum, the main target of 3-NP, but did not cause motor dysfunction in DYT1 KI or control mice. The administration of 50 mg/kg/day of 3-NP caused the death of ∼40% of wild type animals. Interestingly, DYT1 KI animals showed significantly reduced mortality. Surviving animals exhibited abnormal motor behavior during and right after the injection period, but recovered by 4 weeks postinjection independent of genotype. In contrast to the findings reported in cultured cells, these studies suggest the DYT1 mutation does not sensitize central neurons against the toxic effects of oxidative stress and energy deficits.

Therapeutic RNA interference (RNAi) has emerged as a promising approach for the treatment of many incurable diseases, including cancer, infectious disease or neurodegenerative disorders. Demonstration of efficacy and safety in animal models is necessary before planning human application. Our group and others have previously shown the potential of this approach for the dominantly inherited neurological disease DYT1 dystonia by achieving potent short-hairpin RNA (shRNA)-mediated silencing of the disease protein, torsinA, in cultured cells. To establish the feasibility of this approach in vivo, we pursued viral delivery of shRNA in two different mouse models. Surprisingly, intrastriatal injections of adeno-associated virus serotype 2/1 (AAV2/1) vectors expressing different shRNAs, whether targeting torsinA expression or mismatched controls, resulted in significant toxicity with progressive weight loss, motor dysfunction and animal demise. Histological analysis showed shRNA-induced neurodegeneration. Toxicity was not observed in animals that received control AAV2/1 encoding no shRNA, and was independent of genotype, occurring in both DYT1 and wild-type animals. Interestingly, the different genetic background of both mouse models influenced toxicity, being earlier and more severe in 129/SvEv than in C57BL/6 mice. In conclusion, our studies demonstrate that expression of shRNA in the mammalian brain can lead to lethal toxicity. Furthermore, the genetic background of rodents modifies their sensitivity to this form of toxicity, a factor that should be taken into consideration in the design of preclinical therapeutic RNAi trials.

DYT1 dystonia is caused by a glutamic acid deletion (ΔE) in the endoplasmic reticulum (ER) protein torsinA. Previous studies suggest that torsinA modulates the aggregation of cytosolic misfolded proteins and ER stress responses, although the mechanisms underlying those effects remain unclear. In order to investigate the bases of these observations, we analyzed the interaction between torsinA expression, protein aggregation and ER stress in PC6.3 cells. Unexpectedly, we found that expression of torsinA(wt) or (ΔE) does not influence the inclusion formation by an expanded polyglutamine reporter protein in this cellular model. Furthermore, torsinA does not prevent the activation of ER stress induced by thapsigargin or the reducing agent DTT. Interestingly, DTT induces post-translational changes in torsinA, more prominently for torsinA(wt) than (ΔE). This work highlights the importance of model system selection for the study of torsinA function. Furthermore, it provides additional evidence suggesting that torsinA is sensitive to changes in the cellular redox potential.

Sir Charles Bell is better known among neurologists for his descriptions of the clinical consequences of facial nerve lesions. However, as an accomplished physician, anatomist, and artist, he made many other contributions to the fields of neurology and neuroscience. Among those, his descriptions of patients with what we now know as cervical dystonia have not received much attention. In this report, Bell's depictions of patients presenting with a syndrome consistent with cervical dystonia will be discussed, including the identification of many of the different clinical features we currently use for the diagnosis of this disorder and his thoughts about its pathogenesis. © 2010 Movement Disorder Society

The discovery of RNA interference (RNAi), a biological way to control gene expression, has revolutionised the field of biomedical research. Of the many applications of RNAi, perhaps its use for therapeutic purposes is the most promising. One group of diseases where the use of therapeutic RNAi is being actively explored is that of neurodegenerative disorders. To provide both the clinical neurologist and the basic researcher with an updated summary of the development of therapeutic RNAi for neurodegenerative diseases. The technical progress made in the manipulation of RNAi in neurons and the recent advances in our knowledge of the pathogenesis of neurodegenerative processes have been valuable aids in designing therapeutic RNAi for both hereditary and idiopathic diseases. Several pre-clinical trials have been successfully completed in animal models, thus clearing the way towards the design of clinical trials in humans. Nevertheless, before reaching that point more experimental studies need to be carried out in animals to prove the effectiveness of this mode of therapy and, still more important, to be able to predict the possible side effects of this procedure in the human brain. Although it is still in the pre-clinical stages, the use of RNAi for therapeutic purposes in neurodegenerative diseases is producing some very promising results. The evolution of this field over the next few years may be critical for beginning its clinical application.