TBK1 Mutation Spectrum in an Extended European Patient Cohort with Frontotemporal Dementia and Amyotrophic Lateral Sclerosis.

We investigated the mutation spectrum of the TANK-Binding Kinase 1 (TBK1) gene and its associated phenotypic spectrum by exonic resequencing of TBK1 in a cohort of 2,538 patients with frontotemporal dementia (FTD), amyotrophic lateral sclerosis (ALS), or FTD plus ALS, ascertained within the European Early-Onset Dementia Consortium. We assessed pathogenicity of predicted protein-truncating mutations by measuring loss of RNA expression. Functional effect of in-frame amino acid deletions and missense mutations was further explored in vivo on protein level and in vitro by an NFκB-induced luciferase reporter assay and measuring phosphorylated TBK1. The protein-truncating mutations led to the loss of transcript through nonsense-mediated mRNA decay. For the in-frame amino acid deletions, we demonstrated loss of TBK1 or phosphorylated TBK1 protein. An important fraction of the missense mutations compromised NFκB activation indicating that at least some functions of TBK1 are lost. Although missense mutations were also present in controls, over three times more mutations affecting TBK1 functioning were found in the mutation fraction observed in patients only, suggesting high-risk alleles (P = 0.03). Total mutation frequency for confirmed TBK1 LoF mutations in the European cohort was 0.7%, with frequencies in the clinical subgroups of 0.4% in FTD, 1.3% in ALS, and 3.6% in FTD-ALS.

Phenotypical characterization of α-galactosidase A gene mutations identified in a large Fabry disease screening program in stroke in the young.

OBJECTIVE: In the Belgian Fabry Study (BeFaS), the prevalence of Fabry disease was assessed in 1000 young patients presenting with stroke, unexplained white matter lesions or vertebrobasilar dolichoectasia. The results of the BeFaS suggested that Fabry disease may play a role in up to 1% of young patients presenting with cerebrovascular disease. However, the clinical relevance was unclear in all cases. We report on detailed phenotyping in subjects identified with α-galactosidase A (α-Gal A) enzyme deficiency or GLA mutations identified in the BeFaS (n=10), and on the results of family screening in this population. METHODS: Family screening was performed to identify additional mutation carriers. Biochemical and/or clinical evaluation of all subjects (BeFaS index patients and relatives carrying a GLA mutation) was performed. RESULTS: Genetic family screening revealed 18 additional GLA mutation carriers. Bloodspot α-Gal A enzyme activity was normal in all GLA mutation carriers, even in 2 males with the p.A143T mutation. Plasma Gb3 and lyso-Gb3 levels were normal in all subjects. Elevated Gb3 in urine was detected in 2 subjects. Some classic clinical signs of Fabry disease, like angiokeratoma or cornea verticillata, could not be detected in our population. Cardiac symptoms of Fabry disease were found in 6 out of 10 p.A143T carriers. No signs of cerebrovascular disease were found in the relatives with a GLA mutation. CONCLUSIONS: We could not identify mutations causing the classical clinical phenotype of Fabry disease in our cerebrovascular disease population. Enzyme activity analysis in bloodspots and plasma may fail to identify late-onset variants of Fabry disease. We recommend genetic testing when an atypical, late-onset variant of Fabry disease is suspected in a male cerebrovascular disease patient. However, this may lead to the identification of non-disease causing or controversial genetic variants.

Ataxin-2 polyQ expansions in FTLD-ALS spectrum disorders in Flanders-Belgian cohorts.

There exists considerable clinical and pathological overlap between frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), which implies that these 2 neurodegenerative conditions share common pathogenic mechanisms. Recently, intermediate-length (27-33) polyglutamine (polyQ) expansions in ataxin-2 (ATXN2) have been associated with increased risk for ALS, while expansions of > 34 repeats are known to cause spinocerebellar ataxia type 2 (Sca-2). We identified in 72 ALS patients one patient with a 33 polyQ expansion that was absent in 810 control individuals. This allele was also found in one patient with concomitant ALS-Sca-2. In contrast, in a Flanders-Belgian series of 270 FTLD and 22 FTLD-ALS patients, we found no association with intermediate-length polyQ expansions nor did we observe patient-specific long expansions in agreement with the recent observation in a screening of a substantial sized cohort of patients with diverse neurodegenerative brain diseases. Our results provide further support to the notion that ATXN2 associated polyglutamine amplification is specific to the ALS-end of the FTLD-ALS disease spectrum.

A time course analysis of the changes in spontaneous and evoked behaviour in a rat model of neuropathic pain.

We have previously demonstrated that scratching was significantly increased in a rat model of polyarthritis and that this could be reversed by morphine and electrical stimulation of pain-modulating brain areas. We therefore proposed that scratching might represent a parameter of chronic pain. In this study, we examined the spontaneous behaviour of rats in a model of peripheral neuropathy induced by loosely tying 4 ligatures around the right common sciatic nerve. In half of the animals (N = 7), the ligatures were made with resorbable sutures and, in the other half (N = 7), with non-resorbable sutures of the same size. Postoperatively, scratching was significantly increased at the ligated side. This increase was already observed on the first postoperative day, and maximal effects were reached on the 3rd day. We also observed a qualitative change in the scratching behaviour; postoperatively, scratching was often a vibratory-like shaking of the hind paw in the air. The time course of the increased scratching was time-locked with the development of allodynia to thermal stimulation. No differences were found either in the time course of the increased scratching behaviour or in the time course of the thermal allodynia between the rats ligated with resorbable and with non-resorbable sutures. However, a difference in the walking pattern, as measured by the sciatic functional index (SFI), was observed between the two groups: whereas the SFI normalized after 4 weeks in rats ligated with resorbable sutures, it remained disturbed until the end of the 16-week observation period in the rats ligated with non-resorbable sutures. Morphine 1, 2 and 5 mg/kg dose-dependently reduced the increased scratching behaviour. This was not due to a general depressant effect on the rats' behaviour. This finding is discussed in light of the debate on opioid sensitivity of neuropathic pain. The present results add new evidence that scratching is a possible sign of chronic pain in the animal.