Pubmed du 26/01/15

Pubmed du jour

2015-01-26 12:03:50

1. Davis T, Clifton D, Papadopoulos C. {{Identifying autism early: The Toddlers at Risk of Autism Clinic model}}. {J Paediatr Child Health}. 2015.

AIM: This paper describes the Toddlers at Risk of Autism Clinic (TRAC), which utilises the Social Attention and Communication Study (SACS) and/or Autism Detection in Early Childhood (ADEC) play-based assessments to facilitate the early diagnosis of autism. METHODS: A retrospective audit was conducted of all 42 children assessed over a 3-year period in the TRAC. A semi-structured interview and play-based assessment (SACS and ADEC) were used to aid experienced clinicians in diagnosing autism. Intervention was recommended, and families were routinely followed up. Analysis was conducted on the tools used, the outcomes of assessment, diagnosis and stability of diagnosis on follow-up. RESULTS: During this period, 35 boys and 7 girls were assessed, with a mean age of 25 months. The average waiting time for clinic was 11.6 weeks. Twenty-five patients were diagnosed with autism; 90.5% of toddlers given an initial diagnosis retained that diagnosis at follow-up. Out of the 17 children who were not diagnosed with autism in the TRAC, one child was later diagnosed with autism. CONCLUSION: Experienced clinicians can use the SACS and/or ADEC to assist with a Diagnostic and Statistical Manual diagnosis of autism in toddlers.

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2. Hagerman PJ, Hagerman RJ. {{Fragile X-associated tremor/ataxia syndrome}}. {Ann N Y Acad Sci}. 2015.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder that affects some but not all carriers of small, noncoding CGG-repeat expansions (55-200 repeats; premutation) within the fragile X gene (FMR1). Principal features of FXTAS include intention tremor, cerebellar ataxia, Parkinsonism, memory and executive function deficits, autonomic dysfunction, brain atrophy with white matter disease, and cognitive decline. Although FXTAS was originally considered to be confined to the premutation range, rare individuals with a gray zone (45-54 repeats) or an unmethylated full mutation (>200 repeats) allele have now been described, the constant feature of the disorder remaining the requirement for FMR1 expression, in contradistinction to the gene silencing mechanism of fragile X syndrome. Although transcriptional activity is required for FXTAS pathogenesis, the specific trigger(s) for FXTAS pathogenesis remains elusive, highlighting the need for more research in this area. This need is underscored by recent neuroimaging findings of changes in the central nervous system that consistently appear well before the onset of clinical symptoms, thus creating an opportunity to delay or prevent the appearance of FXTAS.

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3. Murdoch JD, Gupta AR, Sanders SJ, Walker MF, Keaney J, Fernandez TV, Murtha MT, Anyanwu S, Ober GT, Raubeson MJ, DiLullo NM, Villa N, Waqar Z, Sullivan C, Gonzalez L, Willsey AJ, Choe SY, Neale BM, Daly MJ, State MW. {{No Evidence for Association of Autism with Rare Heterozygous Point Mutations in Contactin-Associated Protein-Like 2 (CNTNAP2), or in Other Contactin-Associated Proteins or Contactins}}. {PLoS Genet}. 2015; 11(1): e1004852.

Contactins and Contactin-Associated Proteins, and Contactin-Associated Protein-Like 2 (CNTNAP2) in particular, have been widely cited as autism risk genes based on findings from homozygosity mapping, molecular cytogenetics, copy number variation analyses, and both common and rare single nucleotide association studies. However, data specifically with regard to the contribution of heterozygous single nucleotide variants (SNVs) have been inconsistent. In an effort to clarify the role of rare point mutations in CNTNAP2 and related gene families, we have conducted targeted next-generation sequencing and evaluated existing sequence data in cohorts totaling 2704 cases and 2747 controls. We find no evidence for statistically significant association of rare heterozygous mutations in any of the CNTN or CNTNAP genes, including CNTNAP2, placing marked limits on the scale of their plausible contribution to risk.

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4. Yuen RK, Thiruvahindrapuram B, Merico D, Walker S, Tammimies K, Hoang N, Chrysler C, Nalpathamkalam T, Pellecchia G, Liu Y, Gazzellone MJ, D’Abate L, Deneault E, Howe JL, Liu RS, Thompson A, Zarrei M, Uddin M, Marshall CR, Ring RH, Zwaigenbaum L, Ray PN, Weksberg R, Carter MT, Fernandez BA, Roberts W, Szatmari P, Scherer SW. {{Whole-genome sequencing of quartet families with autism spectrum disorder}}. {Nat Med}. 2015.

Autism spectrum disorder (ASD) is genetically heterogeneous, with evidence for hundreds of susceptibility loci. Previous microarray and exome-sequencing studies have examined portions of the genome in simplex families (parents and one ASD-affected child) having presumed sporadic forms of the disorder. We used whole-genome sequencing (WGS) of 85 quartet families (parents and two ASD-affected siblings), consisting of 170 individuals with ASD, to generate a comprehensive data resource encompassing all classes of genetic variation (including noncoding variants) and accompanying phenotypes, in apparently familial forms of ASD. By examining de novo and rare inherited single-nucleotide and structural variations in genes previously reported to be associated with ASD or other neurodevelopmental disorders, we found that some (69.4%) of the affected siblings carried different ASD-relevant mutations. These siblings with discordant mutations tended to demonstrate more clinical variability than those who shared a risk variant. Our study emphasizes that substantial genetic heterogeneity exists in ASD, necessitating the use of WGS to delineate all genic and non-genic susceptibility variants in research and in clinical diagnostics.

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