Showing papers by "Guy A. Rouleau published in 2005"

Risk Factors for Suicide Completion in Major Depression: A Case-Control Study of Impulsive and Aggressive Behaviors in Men

Abstract: Objective: Major depression is a major risk factor for suicide. However, not all individuals with major depression commit suicide. Impulsive and aggressive behaviors have been proposed as risk factors for suicide, but it remains unclear whether their effect on the risk of suicide is at least partly explained by axis I disorders commonly associated with suicide, such as major depression. With a case-control design, a comparison of the level of impulsive and aggressive behaviors and the prevalence of associated psychopathology was carried out with control for the presence of primary psychopathology. Method: One hundred and four male suicide completers who died during an episode of major depression and 74 living depressed male comparison subjects were investigated with proxy-based interviews by using structured diagnostic instruments and personality trait assessments. Results: The authors found that current (6-month prevalence) alcohol abuse/dependence, current drug abuse/dependence, and cluster B personality disorders increased the risk of suicide in individuals with major depression. Also, higher levels of impulsivity and aggression were associated with suicide. An analysis by age showed that these risk factors were more specific to younger suicide victims (ages 18–40). A multivariate analysis indicated that current alcohol abuse/dependence and cluster B personality disorder were two independent predictors of suicide. Conclusions: Impulsive-aggressive personality disorders and alcohol abuse/dependence were two independent predictors of suicide in major depression, and impulsive and aggressive behaviors seem to underlie these risk factors. A developmental hypothesis of suicidal behavior, with impulsive and aggressive behaviors as the starting point, is discussed.

NLGN3/NLGN4 gene mutations are not responsible for autism in the Quebec population.

Abstract: Jamain [2003: Nat Genet 34:27-29] recently reported mutations in two neuroligin genes in sib-pairs affected with autism In order to confirm these causative mutations in our autistic population and to determine their frequency we screened 96 individuals affected with autism We found no mutations in these X-linked genes These results indicate that mutations in NLGN3 and NLGN4 genes are responsible for at most a small fraction of autism cases and additional screenings in other autistic populations are needed to better determine the frequency with which mutations in NLGN3 and NLGN4 occur in autism

Restless Legs Syndrome Confirmation of Linkage to Chromosome 12q, Genetic Heterogeneity, and Evidence of Complexity

Abstract: Background Genes are involved in the etiology of restless legs syndrome, a common sensorimotor disorder. Objectives To replicate and to further characterize our previously reported chromosome 12q linkage results. Design Family linkage study. Setting and Participants A total of 276 individuals from 19 families have been examined using a selection of markers spanning the identified candidate interval on chromosome 12q. Results Two-point analyses of individual pedigrees indicated that 5 kindreds were consistent with linkage to chromosome 12q. When considering these 5 pedigrees along with the family in which linkage was originally reported, we observed a maximum 2-point logarithm-of-odds score of 5.67 (at θ = 0.10; for marker D12S1636 ; autosomal recessive) and a maximum multipoint logarithm-of-odds score of 8.84 between the interval defined by markers D12S326 and D12S304 . Furthermore, our results also suggest the presence of heterogeneity in restless legs syndrome as linkage was formally excluded across the region in 6 pedigrees. Interestingly, significantly higher periodic leg movements during sleep indices were observed for all probands with restless legs syndrome from linked families. Conclusions These results support the presence of a major restless legs syndrome–susceptibility locus on chromosome 12q, which has been designated as RLS1 , and also suggest that at least one additional locus may be involved in the origin of this prevalent condition.

A Variant in XPNPEP2 Is Associated with Angioedema Induced by Angiotensin I–Converting Enzyme Inhibitors

Abstract: Angiotensin I–converting enzyme inhibitors (ACEi), which are used to treat common cardiovascular diseases, are associated with a potentially life-threatening adverse reaction known as angioedema (AE-ACEi). We have previously documented a significant association between AE-ACEi and low plasma aminopeptidase P (APP) activity. With eight large pedigrees, we hereby demonstrate that this quantitative trait is partially regulated by genetic factors. We tested APP activity using a variance-component QTL analysis of a 10-cM genomewide microsatellite scan enriched with seven markers over two candidate regions. We found significant linkage (LOD = 3.75) to a locus that includes the XPNPEP2 candidate gene encoding membrane-bound APP. Mutation screening of this QTL identified a large coding deletion segregating in one pedigree and an upstream single-nucleotide polymorphism (C–2399A SNP), which segregates in the remaining seven pedigrees. Measured genotype analysis strongly suggests that the linkage signal for APP activity at this locus is accounted for predominantly by the SNP association. In a separate case-control study (20 cases and 60 controls), we found significant association of this SNP to ACEi-induced AE (P=.0364). In conclusion, our findings provide supporting evidence that the C-2399A variant in XPNPEP2 is associated with reduced APP activity and a higher incidence of AE-ACEi.

The location of constitutional neurofibromatosis 2 ( NF2 ) splice site mutations is associated with the severity of NF2

Abstract: Neurofibromatosis 2 (NF2) patients with constitutional splice site NF2 mutations have greater variability in disease severity than NF2 patients with other types of mutations; the cause of this variability is unknown. We evaluated genotype-phenotype correlations, with particular focus on the location of splice site mutations, using mutation and clinical information on 831 patients from 528 NF2 families with identified constitutional NF2 mutations. The clinical characteristics examined were age at onset of symptoms of NF2 and number of intracranial meningiomas, which are the primary indices of the severity of NF2. Two regression models were used to analyse genotype-phenotype correlations. People with splice site mutations in exons 1–5 had more severe disease than those with splice site mutations in exons 11–15. This result is compatible with studies showing that exons 2 and 3 are required for self-association of the amino terminal of the NF2 protein in vitro, and that deletions of exons 2 and 3 in transgenic and knockout mouse models of NF2 cause a high prevalence of Schwann cell derived tumours.

Sacred disease secrets revealed: the genetics of human epilepsy

Abstract: Neurons throughout the brain suddenly discharging synchronously and recurrently cause primarily generalized seizures. Discharges localized awhile in one part of the brain cause focal-onset seizures. A genetically determined generalized hyperexcitability had been predicted in primarily generalized seizures, but surprisingly the first epilepsy gene discovered, CHRNA4, was in a focal (frontal lobe)-onset syndrome. Another surprise with CHRNA4 was its encoding of an ion channel present throughout the brain. The reason why CHRNA4 causes focal-onset seizures is unknown. Recently, the second focal (temporal lobe)-onset epilepsy gene, LGI1 (unknown function), was discovered. CHRNA4 led the way to mutation identifications in 15 ion channel genes, most causing primarily generalized epilepsies. Potassium channel mutations cause benign familial neonatal convulsions. Sodium channel mutations cause generalized epilepsy with febrile seizures plus or, if more severe, severe myoclonic epilepsy of infancy. Chloride and calcium channel mutations are found in rare families with the common syndromes childhood absence epilepsy and juvenile myoclonic epilepsy (JME). Mutations in the EFHC1 gene (unknown function) occur in other rare JME families, and yet in other families, associations are present between JME (or other generalized epilepsies) and single nucleotide polymorphisms in the BRD2 gene (unknown function) and the malic enzyme 2 (ME2) gene. Hippocrates predicted the genetic nature of the 'sacred' disease. Genes underlying the 'malevolent' forces seizing 1% of humans have now been revealed. These, however, still account for a mere fraction of the genetic contribution to epilepsy. Exciting years are ahead, in which the genetics of this extremely common, and debilitating, neurological disorder will be solved.

Interrater agreement in the assessment of motor manifestations of Huntington's disease

Abstract: With prospects improving for experimental therapeutics aimed at postponing the onset of illness in preclinical carriers of the Huntington's disease (HD) gene, we assessed agreement among experienced clinicians with respect to the motor manifestations of HD, a relevant outcome measure for preventive trials in this population. Seventy-five clinicians experienced in the evaluation of patients with early HD and six non-clinicians were shown a videotape compiled from the film archives of the United States–Venezuela Collaborative HD Research Project. Observers were asked to rate a 2–3-minute segment of the motor examination for each of 17 at-risk subjects. The rating scale ranged from 0 (normal) to 4 (unequivocal extrapyramidal movement disorder characteristic of HD). As measured by a weighted κ statistic, there was substantial agreement among the 75 clinicians in the judgment of unequivocal motor abnormalities comparing scale ratings of 4 with ratings that were not 4 (weighted κ = 0.67; standard error (SE) = 0.09). Agreement among the non-clinicians was only fair (weighted κ = 0.28; SE = 0.10). Even under the artificial conditions of a videotape study, experienced clinicians show substantial agreement about the signs that constitute the motor manifestations of illness in subjects at risk for HD. We expect these findings to translate to a similar level of interobserver agreement in the clinical trial setting involving experienced investigators examining live patients. © 2005 Movement Disorder Society

Molecular analysis of the A322D mutation in the GABA receptor alpha-subunit causing juvenile myoclonic epilepsy.

Abstract: Juvenile myoclonic epilepsy (JME) belongs to the most common forms of hereditary epilepsy, the idiopathic generalized epilepsies. Although the mode of inheritance is usually complex, mutations in single genes have been shown to cause the disease in some families with autosomal dominant inheritance. The first mutation in a multigeneration JME family has been recently found in the alpha1-subunit of the GABAA receptor (GABRA1), predicting the single amino acid substitution A322D. We further characterized the functional consequences of this mutation by coexpressing alpha1-, beta2- and gamma2-subunits in human embryonic kidney (HEK293) cells. By using an ultrafast application system, mutant receptors have shown reduced macroscopic current amplitudes at saturating GABA concentrations and a highly reduced affinity to GABA compared to the wild-type (WT). Dose-response curves for current amplitudes, activation kinetics, and GABA-dependent desensitization parameters showed a parallel shift towards 30- to 40-fold higher GABA concentrations. Both deactivation and resensitization kinetics were considerably accelerated in mutant channels. In addition, mutant receptors labelled with enhanced green fluorescent protein (EGFP) were not integrated in the cell membrane, in contrast to WT receptors. Therefore, the A322D mutation leads to a severe loss-of-function of the human GABAA receptor by several mechanisms, including reduced surface expression, reduced GABA-sensitivity, and accelerated deactivation. These molecular defects could decrease and shorten the resulting inhibitory postsynaptic currents (IPSCs) in vivo, which can induce a hyperexcitability of the postsynaptic membrane and explain the occurrence of epileptic seizures.

Ribosomal frameshifting on MJD-1 transcripts with long CAG tracts

Abstract: The expanded CAG tract diseases are a heterogeneous group of late-onset neurodegenerative disorders characterized by the accumulation of insoluble protein material and premature neuronal cell death. Recent work has provided support for several mechanisms that may account for neurodegeneration, but no unifying mechanism has emerged. We have previously demonstrated that in SCA3, the expanded CAG tract in the MJD-1 transcript is prone to frameshifting, which may lead to the production of polyalanine-containing proteins. To further examine the occurrence of frameshifting and understand its mechanism and possible role in pathogenesis, a cellular model was established. We show that this phenomenon results from ribosomal slippage to the -1 frame exclusively, that ribosomal frameshifting depends on the presence of long CAG tracts and that polyalanine-frameshifted proteins may enhance polyglutamine-associated toxicity, possibly contributing to pathogenesis. Finally, we present evidence that anisomycin, a ribosome-interacting drug that reduces -1 frameshifting, also reduces toxicity, suggesting a new therapeutic opportunity for these disorders.

Investigating responders to lithium prophylaxis as a strategy for mapping susceptibility genes for bipolar disorder.

Abstract: Attempts to map susceptibility genes for bipolar disorder have been complicated by genetic complexity of the illness and, above all by heterogeneity This paper reviews the genetic research of bipolar disorder aiming to reduce the heterogeneity by focusing on definite responders to long-term lithium treatment The available evidence strongly suggests that lithium-responsive bipolar disorder is the core bipolar phenotype, characterized by a more prominent role of genetic factors Responders to lithium have typically a family history of bipolar disorder (often responsive to lithium) They differ from responders to other mood stabilizing drugs in their family histories as well as in other clinical characteristics The molecular genetic investigations of bipolar disorder responsive to lithium indicate possibly several loci linked to and/or associated with the illness A combination of research strategies employing multiple methods such as linkage, association, and gene-expression studies will be needed to clarify which of these represent true susceptibility loci

Two mutations in the HSN2 gene explain the high prevalence of HSAN2 in French Canadians.

Abstract: Background: Hereditary sensory and autonomic neuropathy type 2 (HSAN2; MIM 201300) is a rare recessive neuropathy typically diagnosed in the first decade. The 1973 study of a French Canadian family led to the definition of HSAN2. Objectives: To demonstrate that the apparent higher prevalence of HSAN2 in Quebec is due to the presence of two HSN2 mutations and that carriers of different mutations appear to have a similar phenotype. Methods: Through attending physicians, the authors recruited French Canadian patients with HSAN2. Exclusion of linkage to the known HSAN loci and linkage to the HSAN2 was performed using standard methods. Sequencing of the HSN2 gene was used to uncover the causal mutations. Results: A large cluster of HSAN2 patients comprising 16 affected individuals belonging to 13 families was identified. The mode of inheritance is clearly autosomal recessive. All patients originated from southern Quebec, and 75% are from the Lanaudiere region. Whereas linkage to the HSAN1, 3, and 4 loci was excluded, linkage to the 12p13.33 HSAN2 locus was confirmed. Sequencing of the HSN2 gene uncovered two French Canadian mutations and a novel nonsense mutation in a patient of Lebanese origin, all predicted to lead to truncations of the HSN2 protein. The comparison of clinical variables between patients with different genotypes does not suggest any difference in phenotype. Conclusions: Two founder mutations are responsible for the apparently higher prevalence of HSAN2 in French Canadians. Genotype-phenotype correlation does not suggest any significant clinical variability.

Rare variants of the gene encoding the potassium chloride co-transporter 3 are associated with bipolar disorder.

Abstract: Recessive mutations of the potassium chloride co-transporter 3 gene (SLC12A6, KCC3) cause severe peripheral neuropathy frequently associated with agenesis of the corpus callosum and psychoses (ACCPN). SLC12A6 is localized on chromosome 15q14, a region where linkage to schizophrenia and bipolar disorder has previously been shown. Mutation analysis of SLC12A6 was carried out by direct sequencing of PCR-generated DNA fragments in two affected members of a multiplex family, and three non-affected individuals. A case-control study was performed to assess association of variants with bipolar disorder and schizophrenia in a large sample. Several variants including two rare single nucleo- tide polymorphisms (G/A, G/A) in the promoter and 5k-UTR, and a thymidine insertion in intron 4 were found. The two G variants and the insertion variant were co-inherited with chromosome 15-related schizophrenia in a large family that strongly supports the region on chromosome 15q14-15 between markers D15S144 and D15S132. Furthermore, they are in linkage disequilibrium with each other, and significantly associated with bipolar disorder in a case-control study. Our data strongly suggest that rare variants of SLC12A6 may represent risk factors for bipolar disorder. Received 2 March 2005 ; Reviewed 31 March 2005 ; Revised 17 May 2005 ; Accepted 18 May 2005

Inherited Occipital Hypoplasia/Syringomyelia in the Cavalier King Charles Spaniel: Experiences in Setting Up a Worldwide DNA Collection

Abstract: Inherited diseases commonly emerge within pedigree dog populations, often due to use of repeatedly bred carrier sire(s) within a small gene pool. Accurate family records are usually available making linkage analysis possible. However, there are many factors that are intrinsically difficult about collecting DNA and collating pedigree information from a large canine population. The keys to a successful DNA collection program include (1) the need to establish and maintain support from the pedigree breed clubs and pet owners; (2) committed individual(s) who can devote the considerable amount of time and energy to coordinating sample collection and communicating with breeders and clubs; and (3) providing means by which genotypic and phenotypic information can be easily collected and stored. In this article we described the clinical characteristics of inherited occipital hypoplasia/syringomyelia (Chiari type I malformation) in the cavalier King Charles spaniel and our experiences in establishing a pedigree and DNA database to study the disease.

Identification of genetic aberrations on chromosome 22 outside the NF2 locus in schwannomatosis and neurofibromatosis type 2

Abstract: Schwannomatosis is characterized by multiple peripheral and cranial nerve schwannomas that occur in the absence of bilateral 8th cranial nerve schwannomas. The latter is the main diagnostic criterion of neurofibromatosis type 2 (NF2), which is a related but distinct disorder. The genetic factors underlying the differences between schwannomatosis and NF2 are poorly understood, although available evidence implicates chromosome 22 as the primary location of the gene(s) of interest. To investigate this, we comprehensively profiled the DNA copy number in samples from sporadic and familial schwannomatosis, NF2, and a large cohort of normal controls. Using a tiling-path chromosome 22 genomic array, we identified two candidate regions of copy number variation, which were further characterized by a PCR-based array with higher resolution. The latter approach allows the detection of minute alterations in total genomic DNA, with as little as 1.5 kb per measurement point of nonredundant sequence on the array. In DNA derived from peripheral blood from a schwannomatosis patient and a sporadic schwannoma sample, we detected rearrangements of the immunoglobulin lambda (IGL) locus, which is unlikely to be due to a B-cell specific somatic recombination of IGL. Analysis of normal controls indicated that these IGL rearrangements were restricted to schwannomatosis/schwannoma samples. In the second candidate region spanning GSTT1 and CABIN1 genes, we observed a frequent copy number polymorphism at the GSTT1 locus. We further describe missense mutations in the CABIN1 gene that are specific to samples from schwannomatosis and NF2 and make this gene a plausible candidate for contributing to the pathogenesis of these disorders.

Acute adverse reactions associated with angiotensin-converting enzyme inhibitors: genetic factors and therapeutic implications.

Abstract: Angiotensin-converting enzyme inhibitors (ACEIs) have been used in the treatment of various cardiovascular diseases. Despite the therapeutic benefits of ACEIs, there are several reported side effects, including chronic cough, angioedema and anaphylactoid reactions. These adverse events cannot be explained by the vasodilatory effects of this group of medications. Preliminary studies have shown that patients with a history of developing these side effects have a lower activity of an enzyme called aminopeptidase-P. This enzyme has an important role in degrading bradykinin. This defect in enzymatic activity can be partially explained by genetic variation. Using genome-wide screening strategies, the locus (loci), gene(s) and untimely polymorphisms that explain the low enzymatic activity and side effects can be identified.

Patients with familial biparental hydatidiform moles have normal methylation at imprinted genes

Abstract: In molar tissues from patients with recurrent biparental hydatidiform moles, we could previously demonstrate that differentially methylated regions (DMRs) of four imprinted genes are abnormally methylated on the maternal alleles. It remained unclear if this abnormal methylation originated de novo in the molar tissues or if it is even recognizable in the patient somatic tissues. To address this question, we investigated the DNA methylation of four imprinted genes in total blood from the two sister-patients. Here, we show that both patients retain normal methylation levels at the DMRs of the four genes in blood tissues. For two maternally expressed genes, we could use informative SNPs to follow the inheritance of the abnormally methylated maternal alleles in the molar tissues. We find that the transmitted abnormally methylated maternal alleles to the moles originated from the maternal grandmother and that the same alleles are not methylated in the patients. Our data suggest that the abnormal methylation in familial biparental molar tissues was acquired de novo in the patients'germline as a result of a false reprogramming or during the postzygotic development of the conceptuses that led to moles.

Cytoplasmic targeting of mutant poly(A)-binding protein nuclear 1 suppresses protein aggregation and toxicity in oculopharyngeal muscular dystrophy.

Abstract: Oculopharyngeal muscular dystrophy (OPMD) is an adult-onset disorder characterized by progressive eyelid drooping, swallowing difficulties and proximal limb weakness. The autosomal dominant form of this disease is caused by a polyalanine expansion from 10 to 12-17 residues, located at the N-terminus of the poly(A)-binding protein nuclear 1 (PABPN1). A distinct pathological hallmark of OPMD is the presence of filamentous intranuclear aggregates in patients' skeletal muscle cells. Wildtype PABPN1 protein is expressed ubiquitously and was shown to be mostly concentrated in discrete nuclear domains called 'speckles'. Using an established cell- culture model, we show that most mutant PABPN1- positive (alanine expanded form) intranuclear aggregates are structures distinct from intranuclear speckles. In contrast, the promyelocytic leukaemia protein, a major component of nuclear bodies, strongly colocalized to intranuclear aggregates of mutant PABPN1. Wildtype PABPN1 can freely shuttle between the nucleus and cytoplasm. We determined whether the nuclear environment is necessary for mutant PABPN1 inclusion formation and cellular toxicity. This was achieved by inactivating the mutant PABPN1 nuclear localization signal and by generating full-length mutant PABPN1 fused to a strong nuclear export sequence. A green fluorescence protein tag inserted at the N-terminus of both wildtype PABPN1 (ala10) and mutant PABPN1 (ala17) proteins allowed us to visualize their subcellular localization. Targeting mutant PABPN1 to the cytoplasm resulted in a significant suppression of both intranuclear aggregates formation and cellular toxicity, two histological consequences of OPMD. Our results indicate that the nuclear localization of mutant PABPN1 is crucial to OPMD pathogenesis.

Role of the neurofibromatosis type 2 gene in the development of tumors of the nervous system.

Abstract: Germ line and somatic mutations in the neurofibromatosis Type 2 (NF2) tumor suppressor gene predispose individuals to tumors of the nervous system, including schwannomas and meningiomas Since identification of the NF2 gene more than a decade ago, a large body of information has been collected on the nature and consequences of these alterations in patients with NF2 and in individuals in whom sporadic tumors associated with NF2 develop The catalog of mutations identified thus far has facilitated extensive genetic analysis, including studies of patients with mosaicism and phenotype‐genotype correlations, and has also led to experiments that have begun to unravel the molecular biology of the NF2 gene and its role in tumorigenesis The authors describe some of the most significant findings in NF2 genetics and biology over the last decade

Chromosome 11-q24 region in Tourette syndrome: Association and linkage disequilibrium study in the French Canadian population

Abstract: Previous studies have found association and linkage between Tourette syndrome (TS) and markers at the 11q24 region, mainly with markers D11S1377 and D11S933. In order to determine if these positive findings could be replicated in our sample, we undertook a family-based association study in 199 French Canadian TS nuclear families. We genotyped 572 individuals from 174 complete and 25 incomplete TS trios. TDT analysis failed to detect an association between TS and six markers from 11q24. Furthermore, no haplotype combining alleles from D11S1377, D11S933, or any of the other four markers was associated with the disorder. Linkage disequilibrium analysis showed evidence of historical recombination between every contiguous pair of markers, indicating that these genetic variants are probably in equilibrium in the French Canadian population. Further analysis in additional families, with different methodologies (linkage and association) will be required in order to determine if the 11q24 region harbors a susceptibility locus for TS. If it does, this defect may not be frequent in the French Canadian population due to locus heterogeneity.

Vision-Based Tracking and Trajectory Generation for Robotic Capture of Objects in Space

Abstract: In this paper, we describe the development of vision-based algorithms for determining the motion of a moving object and generating trajectory for a robotic manipulator to intercept the object. The ultimate goal of this work is to develop autonomous algorithms for robotic grasping of objects in space. This problem arises in several applications, including on-orbit servicing of satellites and removal of space debris. The proposed methods have been implemented and tested in simulation and are currently being implemented on an experimental facility. The facility is based on a novel concept for experimental evaluation of robotic capture of free-floating objects, in particular, to use a small helium airship to emulate a free-floating object. The paper presents a brief overview of the main components of the facility, describes the vision-based motion estimation, trajectory generation and redundancy resolution algorithms implemented thus far and presents simulation results demonstrating the performance of these algorithms.

Clinical stringency greatly improves mutation detection in rett syndrome

Abstract: Le syndrome de Rett (RTT) est une maladie neurodeveloppementale severe observee chez les filles et causee par des mutations du gene MECP2 situe sur le chromosome X. L'identification a l'echelle mondiale du phenotype clinique du RTT au debut des annees 1980 a permis de diagnostiquer de nombreux cas et a demontre que le RTT est un des syndromes de retard mental les plus frequents chez les filles. Depuis, la description du phenotype a ete raffinee et des criteres diagnostiques revises (CDR) ont recemment ete formules. Nous avons etudie l'impact sur la detection de mutations du gene MECP2 de l'utilisation ou de la non-utilisation de ces criteres diagnostiques pour poser le diagnostic de RTT chez des patientes diagnostiquees ou soupconnees d'etre porteuses du RTT. Methodes: Au moyen de la chromatographie liquide a haute pression en condition denaturante suivie du sequencage de tous les exons du gene MECP2, nous avons compare la detection de mutations dans une cohorte historique de 35 patientes porteuses d'un diagnostic de RTT, fait sans l'aide de criteres diagnostiques specifiques, a un groupe de 101 patientes dont le diagnostic avait ete pose sur la base des CDR. Resultats: Le taux de detection de mutations du gene MECP2 etait beaucoup plus eleve chez les sujets dont le diagnostic etait base sur une utilisation rigoureuse des CDR (20% vs 72%). Conclusions: Ces resultats suggerent que la demarche utilisee pour poser le diagnostic clinique influence le taux de detection de mutations dans le RTT et, de facon plus generale, souligne l'importance des outils diagnostiques dans l'evaluation des syndromes neurocomportementaux.