1. Busquets-Garcia A, Maldonado R, Ozaita A. {{New insights into the molecular pathophysiology of fragile X syndrome and therapeutic perspectives from the animal model}}. {Int J Biochem Cell Biol};2014 (May 12)
Fragile X syndrome is the most common monogenetic form of intellectual disability and is a leading cause of autism. This syndrome is produced by the reduced transcription of the fragile X mental retardation (FMR1) gene, and it is characterized by a range of symptoms heterogeneously expressed in patients such as cognitive impairment, seizure susceptibility, altered pain sensitivity and anxiety. The recent advances in the understanding of the pathophysiological mechanisms involved have opened novel potential therapeutic approaches identified in preclinical rodent models as a necessary preliminary step for the subsequent evaluation in patients. Among those possible therapeutic approaches, the modulation of the metabotropic glutamate receptor signaling or the GABA receptor signaling have focused most of the attention. New findings in the animal models open other possible therapeutic approaches such as the mammalian target of rapamycin signaling pathway or the endocannabinoid system. This review summarizes the emerging data recently obtained in preclinical models of fragile X syndrome supporting these new therapeutic perspectives.
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2. Fitzpatrick EM, Lambert L, Whittingham J, Leblanc E. {{Examination of characteristics and management of children with hearing loss and autism spectrum disorders}}. {Int J Audiol};2014 (May 16):1-10.
Objective: Up to 40% of children with hearing loss present with other developmental disabilities. The purpose of this study was to document the prevalence of autism spectrum disorders (ASD) in children with permanent hearing loss, to describe the audiologic characteristics, and to examine clinical management. Design: Prospective data related to clinical characteristics of children identified with hearing loss and ASD were examined. A retrospective chart review was also conducted to explore clinical management and uptake of amplification. Study sample: The study included all children in one Canadian region identified with permanent hearing loss and followed from 2002-2010. Results: Of a total of 785 children with permanent hearing loss, 2.2% (n = 17) also received a diagnosis of ASD. The 13 boys and 4 girls presented with a range of audiologic profiles from unilateral to profound bilateral hearing loss. Four of five children with unilateral hearing loss experienced progression to bilateral loss. Amplification was recommended for all but one child and 9 of 16 children continued to use their hearing devices. Conclusions: The higher prevalence rate of ASD in this clinical population is consistent with previous reports. Our findings suggest that some children with autism can derive benefits from the use of amplification.
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3. Iwata K, Matsuzaki H, Tachibana T, Ohno K, Yoshimura S, Takamura H, Yamada K, Matsuzaki S, Nakamura K, Tsuchiya KJ, Matsumoto K, Tsujii M, Sugiyama T, Katayama T, Mori N. {{N-ethylmaleimide-sensitive factor interacts with the serotonin transporter and modulates its trafficking: implications for pathophysiology in autism}}. {Mol Autism};2014;5:33.
BACKGROUND: Changes in serotonin transporter (SERT) function have been implicated in autism. SERT function is influenced by the number of transporter molecules present at the cell surface, which is regulated by various cellular mechanisms including interactions with other proteins. Thus, we searched for novel SERT-binding proteins and investigated whether the expression of one such protein was affected in subjects with autism. METHODS: Novel SERT-binding proteins were examined by a pull-down system. Alterations of SERT function and membrane expression upon knockdown of the novel SERT-binding protein were studied in HEK293-hSERT cells. Endogenous interaction of SERT with the protein was evaluated in mouse brains. Alterations in the mRNA expression of SERT (SLC6A4) and the SERT-binding protein in the post-mortem brains and the lymphocytes of autism patients were compared to nonclinical controls. RESULTS: N-ethylmaleimide-sensitive factor (NSF) was identified as a novel SERT-binding protein. NSF was co-localized with SERT at the plasma membrane, and NSF knockdown resulted in decreased SERT expression at the cell membranes and decreased SERT uptake function. NSF was endogenously co-localized with SERT and interacted with SERT. While SLC6A4 expression was not significantly changed, NSF expression tended to be reduced in post-mortem brains, and was significantly reduced in lymphocytes of autistic subjects, which correlated with the severity of the clinical symptoms. CONCLUSIONS: These data clearly show that NSF interacts with SERT under physiological conditions and is required for SERT membrane trafficking and uptake function. A possible role for NSF in the pathophysiology of autism through modulation of SERT trafficking, is suggested.
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4. Speirs SJ, Rinehart NJ, Robinson SR, Tonge BJ, Yelland GW. {{Efficacy of Cognitive Processes in Young People with High-Functioning Autism Spectrum Disorder Using a Novel Visual Information-Processing Task}}. {J Autism Dev Disord};2014 (May 17)
Autism spectrum disorders (ASD) are characterised by a unique pattern of preserved abilities and deficits within and across cognitive domains. The Complex Information Processing Theory proposes this pattern reflects an altered capacity to respond to cognitive demands. This study compared how complexity induced by time constraints on processing affect cognitive function in individuals with ASD and typically-developing individuals. On a visual information-processing task, the Subtle Cognitive Impairment Test, both groups exhibited sensitivity to time-constraints. Further, 65 % of individuals with ASD demonstrated deficits in processing efficiency, possibly attributable to the effects of age and clinical comorbidities, like attention deficit hyperactivity disorder. These findings suggest that for some ASD individuals there are significant impairments in processing efficiency, which may have implications for education and interventions.
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5. Tonnsen BL, Cornish KM, Wheeler AC, Roberts JE. {{Maternal predictors of anxiety risk in young males with fragile X}}. {Am J Med Genet B Neuropsychiatr Genet};2014 (May 16)
Children with fragile X syndrome (FXS) demonstrate high rates of anxiety disorders, with 65-83% meeting diagnostic criteria. The severity of anxiety symptoms in FXS has been shown to be partially predicted by elevated negative affect across early childhood [Tonnsen et al. (2013a); J Abnorm Child Psychol 41:267-280]. This association suggests that biologically driven vulnerability emerges early in development, as is reported in non-clinical populations. However, anxiety emergence is likely moderated by multifaceted genetic, biological and environmental risk and protective factors. Mothers with the FMR1 premutation have been shown to exhibit elevated parenting stress and internalizing symptoms, which have each been associated with child behavior problems [Bailey et al. (2008a); Am J Med Genet Part A 146A:2060-2069 and Bailey et al. (2008b) Am J Med Genet Part A 146A:720-729]. Despite these findings, it is unclear whether maternal factors directly relate to anxiety vulnerability in high-risk children with FXS, a question essential to informing targeted, family-sensitive treatment. The present study examines how maternal protective and risk factors relate to child inhibition reflected in (1) child anxiety symptoms, (2) child trajectories of negative affect, and (3) the association between child anxiety and negative affect. Primary predictors include maternal parenting stress, indicators of mental health risk (anxiety and depressive symptoms), and maternal optimism. We also examine genetic correlates in mothers (CGG repeats, activation ratio, mRNA). Our findings suggest that behavioral inhibition in young children with FXS is associated with higher parenting stress and lower optimism, and higher parenting stress is associated with lower maternal X-activation ratio. These findings underscore the need for family-sensitive treatment strategies for anxiety disorders in children with FXS. (c) 2014 Wiley Periodicals, Inc.
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6. Yangngam S, Plong-On O, Sripo T, Roongpraiwan R, Hansakunachai T, Wirojanan J, Sombuntham T, Ruangdaraganon N, Limprasert P. {{Mutation Screening of the Neurexin 1 Gene in Thai Patients with Intellectual Disability and Autism Spectrum Disorder}}. {Genet Test Mol Biomarkers};2014 (May 15)
Aim: Neurexin 1 has two major protein isoforms using alternative promoters, coding for the alpha-neurexin 1 (alpha-NRXN1) and beta-neurexin 1 (beta-NRXN1) genes. This study is to explore the possibility that variants of the NRXN1 gene predispose to intellectual disability (ID) and autism spectrum disorder (ASD). Methods: The coding regions in 24 exons and exon-intron boundaries of the NRXN1 gene were investigated in 115 Thai patients with ID and ASD by direct DNA sequencing. Results: Nine novel variants of the NRXN1 gene were identified. Four novel variants were found in the beta-NRXN1 gene, one variant of six GGC repeats in exon 1, and three variants at the 5’UTR. Five novel variants were identified in the alpha-NRXN1 gene, four intronic variants and one missense variant in exon 14 (c.2713T>A or p.F905I). Conclusion: Mutation screening of the NRXN1gene in patients with ID and ASD may be useful to identify potential variants predisposing to ID and ASD. However, further studies utilizing protein functional analysis of the novel variants are required for a more definite conclusion.
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7. Zhang W, Cheng Y, Li Y, Chen Z, Jin P, Chen D. {{A feed-forward mechanism involving Drosophila fragile X mental retardation protein triggers a replication stress-induced DNA damage response}}. {Hum Mol Genet};2014 (May 15)
Fragile X syndrome, a common form of inherited mental retardation, is caused by loss of the fragile X mental retardation protein (FMRP). As a selective RNA-binding protein, FMRP is localized predominately in cytoplasm, where it regulates translational control. However, there is a small portion of FMRP present in the nucleus, and its function there has been elusive. Here we show that Drosophila dFMR1 in nucleus is required for replication stress-induced H2Av phosphorylation in the DNA damage response (DDR). Replication stress could induce the expression of dFmr1 and promote the nuclear accumulation of dFMR1. We show that, upon the stimulation of replication stress, dFMR1 is associated with chromatin in a domain-specific manner, which is essential for its ability to induce the phosphorylation of H2Av. These results together reveal an unexpected nuclear role of FMRP in DDR and uncover a feed-forward mechanism by which dFmr1 and early DDR induced by replication stress reciprocally regulate each other, thereby synergistically triggering activity of the DDR signaling cascade.
