Christine Lo

A genetic study of Wilson’s disease in the United Kingdom

Previous studies have failed to identify mutations in the Wilsons disease gene ATP7B in a significant number of clinically diagnosed cases. This has led to concerns about genetic heterogeneity for this condition but also suggested the presence of unusual mutational mechanisms. We now present our findings in 181 patients from the United Kingdom with clinically and biochemically confirmed Wilsons disease. A total of 116 different ATP7B mutations were detected, 32 of which are novel. The overall mutation detection frequency was 98%. The likelihood of mutations in genes other than ATP7B causing a Wilsons disease phenotype is therefore very low. We report the first cases with Wilsons disease due to segmental uniparental isodisomy as well as three patients with three ATP7B mutations and three families with Wilsons disease in two consecutive generations. We determined the genetic prevalence of Wilsons disease in the United Kingdom by sequencing the entire coding region and adjacent splice sites of ATP7B in 1000 control subjects. The frequency of all single nucleotide variants with in silico evidence of pathogenicity (Class 1 variant) was 0.056 or 0.040 if only those single nucleotide variants that had previously been reported as mutations in patients with Wilsons disease were included in the analysis (Class 2 variant). The frequency of heterozygote, putative or definite disease-associated ATP7B mutations was therefore considerably higher than the previously reported occurrence of 1:90 (or 0.011) for heterozygote ATP7B mutation carriers in the general population (P < 2.2 × 10(-16) for Class 1 variants or P < 5 × 10(-11) for Class 2 variants only). Subsequent exclusion of four Class 2 variants without additional in silico evidence of pathogenicity led to a further reduction of the mutation frequency to 0.024. Using this most conservative approach, the calculated frequency of individuals predicted to carry two mutant pathogenic ATP7B alleles is 1:7026 and thus still considerably higher than the typically reported prevalence of Wilsons disease of 1:30 000 (P = 0.00093). Our study provides strong evidence for monogenic inheritance of Wilsons disease. It also has major implications for ATP7B analysis in clinical practice, namely the need to consider unusual genetic mechanisms such as uniparental disomy or the possible presence of three ATP7B mutations. The marked discrepancy between the genetic prevalence and the number of clinically diagnosed cases of Wilsons disease may be due to both reduced penetrance of ATP7B mutations and failure to diagnose patients with this eminently treatable disorder.

Zebrafish as a new animal model for movement disorders

The zebrafish, long recognized as a model organism for the analysis of basic developmental processes, is now also emerging as an alternative animal model for human diseases. This review will first provide an overview of the particular characteristics of zebrafish in general and their dopaminergic nervous system in particular. We will then summarize all work undertaken so far to establish zebrafish as a new animal model for movement disorders and will finally emphasize its particular strength – amenability to high throughput in vivo drug screening.

Marijuana and chronic obstructive lung disease: a population-based study

Background: Our aim was to determine the combined and independent effects of tobacco and marijuana smoking on respiratory symptoms and chronic obstructive pulmonary disease (COPD) in the general population. Method: We surveyed a random sample of 878 people aged 40 years or older living in Vancouver, Canada, about their respiratory history and their history of tobacco and marijuana smoking. We performed spirometric testing before and after administration of 200 μg of salbutamol. We examined the association between tobacco and marijuana smoking and COPD. Results: The prevalence of a history of smoking in this sample was 45.5% (95% confidence interval [CI] 42.2%–48.8%) for marijuana use and 53.1% (95% CI 49.8%–56.4%) for tobacco use. The prevalence of current smoking (in the past 12 months) was 14% for marijuana use and 14% for tobacco use. Compared with nonsmokers, participants who reported smoking only tobacco, but not those who reported smoking only marijuana, experienced more frequent respiratory symptoms (odds ratio [OR] 1.50, 95% CI 1.05–2.14) and were more likely to have COPD (OR 2.74, 95% CI 1.66–4.52). Concurrent use of marijuana and tobacco was associated with increased risk (adjusted for age, asthma and comorbidities) of respiratory symptoms (OR 2.39, 95% CI 1.58–3.62) and COPD (OR 2.90, 95% CI 1.53–5.51) if the lifetime dose of marijuana exceeded 50 marijuana cigarettes. The risks of respiratory symptoms and of COPD were related to a synergistic interaction between marijuana and tobacco. Interpretation: Smoking both tobacco and marijuana synergistically increased the risk of respiratory symptoms and COPD. Smoking only marijuana was not associated with an increased risk of respiratory symptoms or COPD.

Prodromal Parkinsonism and Neurodegenerative Risk Stratification in REM Sleep Behavior Disorder

Objectives Rapid eye movement (REM) sleep behavior disorder (RBD) is the most specific marker of prodromal alpha‐synucleinopathies. We sought to delineate the baseline clinical characteristics of RBD and evaluate risk stratification models. Methods Clinical assessments were performed in 171 RBD, 296 control, and 119 untreated Parkinsons (PD) participants. Putative risk measures were assessed as predictors of prodromal neurodegeneration, and Movement Disorders Society (MDS) criteria for prodromal PD were applied. Participants were screened for common leucine‐rich repeat kinase 2 (LRRK2)/glucocerebrosidase gene (GBA) gene mutations. Results Compared to controls, participants with RBD had higher rates of solvent exposure, head injury, smoking, obesity, and antidepressant use. GBA mutations were more common in RBD, but no LRRK2 mutations were found. RBD participants performed significantly worse than controls on Unified Parkinsons Disease Rating Scale (UPDRS)‐III, timed “get‐up‐and‐go”, Flamingo test, Sniffin Sticks, and cognitive tests and had worse measures of constipation, quality of life (QOL), and orthostatic hypotension. For all these measures except UPDRS‐III, RBD and PD participants were equally impaired. Depression, anxiety, and apathy were worse in RBD compared to PD participants. Stratification of people with RBD according to antidepressant use, obesity, and age altered the odds ratio (OR) of hyposmia compared to controls from 3.4 to 45.5. 74% (95% confidence interval [CI] 66%, 80%) of RBD participants met the MDS criteria for probable prodromal Parkinsons compared to 0.3% (95% CI 0.009%, 2%) of controls. Conclusions RBD are impaired across a range of clinical measures consistent with prodromal PD and suggestive of a more severe nonmotor subtype. Clinical risk stratification has the potential to select higher risk patients for neuroprotective interventions.

Heterozygous mutations in the FGF8, SHH and nodal/transforming growth factor beta pathways do not confer increased dopaminergic neuron vulnerability--a zebrafish study.

Fibroblast growth factor 8 (FGF8), sonic hedgehog (SHH) and nodal signalling pathways play key roles in both development and survival of dopaminergic neurons. Both heterozygous mutations in autosomal recessively inherited Parkinsons disease (PD) genes such as parkin or PINK1 and exposure to exogenous toxins are thought to contribute to the pathogenesis of PD. The aim of our study was to investigate whether heterozygote mutations in fgf8, shh or oep lead to a reduced number of ascending dopaminergic neurons in zebrafish (Danio rerio) or confer increased susceptibility to the PD neurotoxin 1-methyl-4-phenyl-pyridinium (MPP⁺). At 3 days post fertilization, heterozygous mutations in fgf8, shh or oep did not affect the number of ascending dopaminergic neurons, nor did heterozygous mutations in fgf8, shh or oep result in increased susceptibility to MPP⁺. Further work is needed to determine whether haploinsufficiency in other neurodevelopmental genes might confer increased susceptibility to PD-related pathomechanisms.

Concurrent amyotrophic lateral sclerosis and cystic fibrosis supports common pathways of pathogenesis

Abstract We present a case of concurrent cystic fibrosis (CF) and amyotrophic lateral sclerosis (ALS). To our knowledge this is the first reported coincidence of these two diseases. Although TDP-43 dysfunction has been linked to both pathologies, it does not appear to be pivotal in this individual who does not display TDP-43 mediated aberrant splicing of the CFTR gene or carry a mutation in the TARDBP gene. Alternative reasons for the coincidence are discussed including medication, infection, hypoxia and loss of function of the CFTR channel. Our findings await validation by others, but as the prognosis of CF improves then clinicians in both fields should be aware of the possibilities highlighted by this case.