Michel Vanasse

Mutation of GABRA1 in an autosomal dominant form of juvenile myoclonic epilepsy.

Although many genes that predispose for epilepsy in humans have been determined, those that underlie the classical syndromes of idiopathic generalized epilepsy (IGE) have yet to be identified. We report that an Ala322Asp mutation in GABRA1, encoding the α1 subunit of the γ-aminobutyric acid receptor subtype A (GABAA), is found in affected individuals of a large French Canadian family with juvenile myoclonic epilepsy. Compared with wildtype receptors, GABAA receptors that contain the mutant subunit show a lesser amplitude of GABA-activated currents in vitro, indicating that seizures may result from loss of function of this inhibitory ligand-gated channel. Our results confirm that mutation of GABRA1 predisposes towards a common idiopathic generalized epilepsy syndrome in humans.

Excess of De Novo Deleterious Mutations in Genes Associated with Glutamatergic Systems in Nonsyndromic Intellectual Disability

Little is known about the genetics of nonsyndromic intellectual disability (NSID). We hypothesized that de novo mutations (DNMs) in synaptic genes explain an important fraction of sporadic NSID cases. In order to investigate this possibility, we sequenced 197 genes encoding glutamate receptors and a large subset of their known interacting proteins in 95 sporadic cases of NSID. We found 11 DNMs, including ten potentially deleterious mutations (three nonsense, two splicing, one frameshift, four missense) and one neutral mutation (silent) in eight different genes. Calculation of point-substitution DNM rates per functional and neutral site showed significant excess of functional DNMs compared to neutral ones. De novo truncating and/or splicing mutations in SYNGAP1, STXBP1, and SHANK3 were found in six patients and are likely to be pathogenic. De novo missense mutations were found in KIF1A, GRIN1, CACNG2, and EPB41L1. Functional studies showed that all these missense mutations affect protein function in cell culture systems, suggesting that they may be pathogenic. Sequencing these four genes in 50 additional sporadic cases of NSID identified a second DNM in GRIN1 (c.1679_1681dup/p.Ser560dup). This mutation also affects protein function, consistent with structural predictions. None of these mutations or any other DNMs were identified in these genes in 285 healthy controls. This study highlights the importance of the glutamate receptor complexes in NSID and further supports the role of DNMs in this disorder.

Neurologic Crises in Hereditary Tyrosinemia

Hereditary tyrosinemia results from an inborn error in the final step of tyrosine metabolism. The disease is known to cause acute and chronic liver failure, renal Fanconis syndrome, and hepatocellular carcinoma. Neurologic manifestations have been reported but not emphasized as a common problem. In this paper, we describe neurologic crises that occurred among children identified as having tyrosinemia on neonatal screening since 1970. Of the 48 children with tyrosinemia, 20 (42 percent) had neurologic crises that began at a mean age of one year and led to 104 hospital admissions. These abrupt episodes of peripheral neuropathy were characterized by severe pain with extensor hypertonia (in 75 percent), vomiting or paralytic ileus (69 percent), muscle weakness (29 percent), and self-mutilation (8 percent). Eight children required mechanical ventilation because of paralysis, and 14 of the 20 children have died. Between crises, most survivors regained normal function. We found no reliable biochemical marker for the crises (those we evaluated included blood levels of tyrosine, succinylacetone, and hepatic aminotransferases). Urinary excretion of delta-aminolevulinic acid, a neurotoxic intermediate of porphyrin biosynthesis, was elevated during crises but also during the asymptomatic periods. Electrophysiologic studies in seven patients and neuromuscular biopsies in three patients showed axonal degeneration and secondary demyelination. We conclude that episodes of acute, severe peripheral neuropathy are common in hereditary tyrosinemia and resemble the crises of the neuropathic porphyrias.

Increased levels of plasma malondialdehyde in Friedreich ataxia.

Friedreich ataxia is an autosomal recessive disease characterized by spinocerebellar degeneration and cardiomyopathy. It is caused by deficiency of frataxin, a highly conserved nuclear-encoded protein localized in mitochondria.1 Most patients (95%) are homozygous for the hyperexpansion of a GAA repeat sequence in the first intron of the frataxin gene, which inhibits transcription; a few are heterozygous for a GAA expansion and a frataxin point mutation.1 Data from yeast suggest that frataxin deficiency results in mitochondrial dysfunction and free radical damage. Yeast cells with a disrupted frataxin homolog gene ( YFH1 ) show a 10-fold accumulation of iron in mitochondria, lose mitochondrial DNA, and become unable to carry out oxidative phosphorylation.2 Iron in mitochondria can amplify the toxicity of reactive oxygen species (ROS) leaking from the respiratory chain by producing the free hydroxyl radical (OH•) through Fenton chemistry [Fe(II) + H2O2 → Fe(III) + OH• + OH−]. Occurrence of the Fenton reaction in ΔYFH1 yeast cells is suggested by their enhanced sensitivity to H2O2.2 Several lines of evidence support the hypothesis that similar mechanisms are involved in the human disease. First, patients with Friedreich ataxia have iron deposits in the heart …

Hyperbaric oxygen for children with cerebral palsy: a randomised multicentre trial

BACKGROUND The use of hyperbaric oxygen for children with cerebral palsy has spread worldwide, despite little scientific evidence of efficacy. We did a randomised trial to assess the efficacy and side-effects of this form of therapy in children with cerebral palsy. METHODS 111 children with cerebral palsy aged 3-12 years were randomly assigned hyperbaric oxygen (n=57) or slightly pressurised room air (n=54). All children received 40 treatments over 2 months. Hyperbaric oxygen treatment was 1 h in 100% oxygen at 1.75 atmospheres absolute (ATA); children on slightly pressurised air received air at 1.3 ATA (the lowest pressure at which pressure can be felt, thereby ensuring the maintenance of masking). The main outcome measure was gross motor function. Secondary outcomes included performance in activities of daily living, attention, working memory, and speech. FINDINGS For all outcomes, both groups improved over the course of the study, but without any difference between the two treatments. The score on the global gross motor function measure increased by 3.0% in the children on slightly pressurised air and 2.9% in those on hyperbaric oxygen. The mean difference between treatments was -0.40 (95% CI -1.69 to 0.90, p=0.544). Other changes were seen in speech, attention, memory, and functional skills. Ear problems occurred in 27 children treated by hyperbaric oxygen and in 15 treated with hyperbaric air (p=0.004). INTERPRETATION In this study, hyperbaric oxygen did not improve the condition of children with cerebral palsy compared with slightly pressurised air. The improvement seen in both groups for all dimensions tested deserves further consideration.

Mutations in the Mitochondrial Methionyl-tRNA Synthetase Cause a Neurodegenerative Phenotype in Flies and a Recessive Ataxia (ARSAL) in Humans

The study of Drosophila neurodegenerative mutants combined with genetic and biochemical analyses lead to the identification of multiple complex mutations in 60 patients with a novel form of ataxia/leukoencephalopathy.

All-cause mortality and cardiovascular outcomes with prophylactic steroid therapy in Duchenne muscular dystrophy.

OBJECTIVES This study sought to determine the impact of steroid therapy on cardiomyopathy and mortality in patients with Duchenne muscular dystrophy (DMD). BACKGROUND DMD is a debilitating X-linked disease that afflicts as many as 1 in 3,500 boys. Although steroids slow musculoskeletal impairment, the effects on cardiac function and mortality remain unknown. METHODS We conducted a cohort study on patients with DMD treated with renin-angiotensin-aldosterone system antagonists with or without steroid therapy. RESULTS Eighty-six patients, 9.1 ± 3.5 years of age, were followed for 11.3 ± 4.1 years. Seven of 63 patients (11%) receiving steroid therapy died compared with 10 of 23 (43%) not receiving steroid therapy (p = 0.0010). Overall survival rates at 5, 10, and 15 years of follow-up were 100%, 98.0%, and 78.6%, respectively, for patients receiving steroid therapy versus 100%, 72.1%, and 27.9%, respectively, for patients not receiving steroid therapy (log-rank p = 0.0005). In multivariate propensity-adjusted analyses, steroid use was associated with a 76% lower mortality rate (hazard ratio: 0.24; 95% confidence interval: 0.07 to 0.91; p = 0.0351). The mortality reduction was driven by fewer heart failure-related deaths (0% vs. 22%, p = 0.0010). In multivariate analyses, steroids were associated with a 62% lower rate of new-onset cardiomyopathy (hazard ratio: 0.38; 95% confidence interval: 0.16 to 0.90; p = 0.0270). Annual rates of decline in left ventricular ejection fraction (-0.43% vs. -1.09%, p = 0.0101) and shortening fraction (-0.32% vs. -0.65%, p = 0.0025) were less steep in steroid-treated patients. Consistently, the increase in left ventricular end-diastolic dimension was of lesser magnitude (+0.47 vs. +0.92 mm per year, p = 0.0105). CONCLUSIONS In patients with DMD, steroid therapy is associated with a substantial reduction in all-cause mortality and new-onset and progressive cardiomyopathy.

Hereditary Motor and Sensory Neuropathy with Agenesis of the Corpus Callosum

Hereditary motor and sensory neuropathy associated with agenesis of the corpus callosum (OMIM 218000) is an autosomal recessive disease of early onset characterized by a delay in developmental milestones, a severe sensory‐motor polyneuropathy with areflexia, a variable degree of agenesis of the corpus callosum, amyotrophy, hypotonia, and cognitive impairment. Although this disorder has rarely been reported worldwide, it has a high prevalence in the Saguenay‐Lac‐St‐Jean region of the province of Quebec (Canada) predominantly because of a founder effect. The gene defect responsible for this disorder recently has been identified, and it is a protein‐truncating mutation in the SLC12A6 gene, which codes for a cotransporter protein known as KCC3. Herein, we provide the first extensive review of this disorder, covering epidemiological, clinical, and molecular genetic studies. Ann Neurol 2002;54:9–18

Lipid profile, fatty acid composition and pro- and anti-oxidant status in pediatric patients with attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) is the most prevalent behavioral disorder in children and the pathophysiology remains obscure. In addition to the pharmacotherapy, which is the primary treatment of ADHD, nutritional intervention may have a significant impact on ADHD symptoms. We studied lipid and lipoprotein profiles, fatty acid (FA) composition, and oxidant-antioxidant status in 37 pediatric ADHD patients and 35 healthy control subjects. Our results show that plasma triacylglycerols and phospholipids were lower, whereas free cholesterol, HDL, and apolipoprotein A-I were higher in ADHD patients compared with controls. The proportion of plasma EPA and DHA was higher, but that of oleic and alpha-linolenic (ALA) acids was lower. As expected from these findings, the proportions of both total saturates and polyunsaturates fatty acids (PUFA) were higher and lower, respectively, in ADHD patients than in controls, which led to a significant decrease in the PUFAs/saturates ratio. On the other hand, the ratios of eicosatrienoic acid to arachidonic acid and of palmitoleic acid to linoleic acid, established indexes of essential fatty acid (EFA) status remained unchanged revealing that EFA did not affect ADHD patients. Similarly, the activity of delta-6 desaturase, estimated by the ratio of 18:2(n-6)/20:4(n-6), was found unaffected, whereas ALA/EPA was diminished. Lessened lipid peroxidation was noted in ADHD subjects as documented by the diminished values of plasma malondialdehyde accompanied by increased concentrations of gamma-tocopherol. In conclusions, significant changes occur in the lipid and lipoprotein profiles, as well as in the oxidant-antioxidant status of ADHD patients, however, the FA distribution does not reflect n-3 FA deficiency.

Intellectual disability without epilepsy associated with STXBP1 disruption.

STXBP1 (Munc18-1) is a component of the machinery involved in the fusion of secretory vesicles to the presynaptic membrane for the release of neurotransmitters. De novo missense mutations in STXBP1 were recently reported in patients with Ohtahara syndrome, a form of encephalopathy with severe early-onset epilepsy. In addition, sequencing of the coding region of STXBP1 in 95 patients with non-syndromic intellectual disability (NSID) revealed de novo truncating mutations in two patients who also showed severe non-specific epilepsy, suggesting that STXBP1 disruption has the potential of causing a wide spectrum of epileptic disorders in association with intellectual disability. Here, we report on the mutational screening of STXBP1 in a different series of 50 patients with NSID and the identification of a novel de novo truncating mutation (c.1206delT/ p.Y402X) in a male with NSID, but surprisingly with no history of epilepsy. This is the first report of a patient with a truncating mutation in STXBP1 that does not show epilepsy, thus, expanding the clinical spectrum associated with STXBP1 disruption.