Pubmed du 6/01/09

mercredi 7 janvier 2009

1. Baris I, Battaloglu E. A Multiplexed ARMS-PCR Approach for the Detection of Common MECP2 Mutations. Genet Test ;2009 (Jan 2)

Rett syndrome (RTT), an X-linked dominant neurodevelopmental disorder, is caused mainly by de novo mutations in the methyl-CpG-binding protein 2 gene (MECP2). Although more than 200 different MECP2 mutations have been identified throughout the gene, 7 of those (p.R133C, p.T158M, p.R168X, p.R255X, p.R270X, p.R294X, and p.R306C) account for up to two-thirds of pathogenic mutations in RTT patients. A rapid and efficient screening strategy for these mutations can be used as a preliminary step for genetic diagnosis of RTT. The current protocols used for this purpose are of high cost and require special equipment. We have designed a simpler multiplex amplification refractory mutation system (ARMS)-PCR strategy that allows identification of these common MECP2 mutant alleles in four PCR reactions. The assay was tested in 14 RTT patients who were previously genotyped using PCR-restriction fragment length polymorphism and DNA sequencing. A complete concordance was observed between the results of the two methods. The multiplex ARMS-PCR does not require any special equipment, and it provides rapid, reproducible, and cost-effective detection of common MECP2 mutations. The assay can be carried out efficiently in a standard molecular genetics laboratory and suitable as a preliminary screen for all patients with RTT diagnosis.

2. Cunningham AB, Schreibman L. Stereotypy in Autism : The Importance of Function. Res Autism Spectr Discord ;2008 ;2(3):469-479.

We argue for the utility of a functional definition of stereotypy based on evidence of both sensory automatic and socially mediated reinforcement contingencies in the occurrence of stereotypy in children with autism. A predetermined sensory function of stereotypy is often invoked in the behavioral literature and the term "self-stimulatory behavior" is commonly misused as interchangeable with "stereotypy." We discuss evidence for a variety of potential functional properties of stereotypy. Diagnostic definitions are reviewed and support for both sensory and social functions is outlined. We argue that stereotypies should be described and categorized according to their function, rather than form. Furthermore, treatment decisions should be based on a functional interpretation of stereotypy, which acknowledges its operant and heterogeneous quality in autism.

3. Gadow KD, Roohi J, Devincent CJ, Hatchwell E. Association of ADHD, tics, and anxiety with dopamine transporter (DAT1) genotype in autism spectrum disorder. J Child Psychol Psychiatry ;2008 (Dec) ;49(12):1331-1338.

Background : Autism spectrum disorder (ASD) is associated with high rates of psychiatric disturbance to include attention-deficit/hyperactivity disorder (ADHD), tic disorder, and anxiety disorders. The aim of the present study was to examine the association between a variable number tandem repeat (VNTR) functional polymorphism located in the 3’-untranslated region of the dopamine transporter gene (DAT1) and the severity of these symptoms as well as the association between the DAT1 DdeI polymorphism and severity of tics. Methods : Parents (n = 62) and teachers (n = 57) completed a DSM-IV-referenced rating scale for 67 children with ASD. Results : According to parent ratings, children with the 10-10 repeat allele (versus a combined group of all other genotypes) exhibited less severe symptoms of hyperactivity and impulsivity as well as less severe language deficits. Teacher ratings indicated that social anxiety and tic symptoms were more severe for children with the 10-10 genotype versus all others. Exploratory analyses provided preliminary support for the notion that heterozygosity (9-10 repeat genotype) may be a risk/protective factor. There were no associations of tic severity with the DAT1 DdeI polymorphism. Conclusion : Collectively, these results suggest that the extraordinary variability in ASD clinical phenotypes may be explained in part by the same genes that are implicated in a host of other psychiatric disorders in non-ASD populations. Nevertheless, replication with independent samples is necessary to confirm this preliminary finding.

4. Keehn B, Joseph RM. Impaired prioritization of novel onset stimuli in autism spectrum disorder. J Child Psychol Psychiatry ;2008 (Dec) ;49(12):1296-1303.

Background : Deficiency in the adaptive allocation of attention to relevant environmental stimuli is an associated feature of autism spectrum disorder (ASD). Recent evidence suggests that individuals with ASD may be specifically impaired in attentional prioritization of novel onsets. Method : We investigated modulation of attention by novel onset stimuli in 22 children with ASD and 22 age- and IQ-matched typically developing (TD) children using a preview visual search task (Donk & Theeuwes, 2003). In preview search, a subset of search stimuli (old) is presented briefly before the remaining stimuli (new) with the effect that search times for targets appearing among the new elements are typically shorter than for those appearing among the old elements. Results : Whereas the TD group exhibited faster reaction time (RT) to targets occurring as novel search elements, the ASD group performed similarly in target new and old conditions, indicating impaired attentional prioritization of novel onsets. Group differences in eye-movement behavior, including fixation frequency and saccadic error for novel onset stimuli, were consistent with the RT findings. Attentional modulation by novel onsets varied inversely with social-communicative symptom severity in the ASD group. Conclusions : The results provide further evidence of reduced sensitivity to novel onsets in ASD, and suggest that impaired processing of dynamic stimuli, possibly associated with abnormalities in the dorsal visual processing stream, may be implicated in the core symptoms of ASD.


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