1. Goto J, Talos DM, Klein P, Qin W, Chekaluk YI, Anderl S, Malinowska IA, Di Nardo A, Bronson RT, Chan JA, Vinters HV, Kernie SG, Jensen FE, Sahin M, Kwiatkowski DJ. {{Regulable neural progenitor-specific Tsc1 loss yields giant cells with organellar dysfunction in a model of tuberous sclerosis complex}}. {Proc Natl Acad Sci U S A};2011 (Oct 24)
Tuberous sclerosis complex (TSC) is a multiorgan genetic disease in which brain involvement causes epilepsy, intellectual disability, and autism. The hallmark pathological finding in TSC is the cerebral cortical tuber and its unique constituent, giant cells. However, an animal model that replicates giant cells has not yet been described. Here, we report that mosaic induction of Tsc1 loss in neural progenitor cells in Tsc1(cc) Nestin-rtTA(+) TetOp-cre(+) embryos by doxycycline leads to multiple neurological symptoms, including severe epilepsy and premature death. Strikingly, Tsc1-null neural progenitor cells develop into highly enlarged giant cells with enlarged vacuoles. We found that the vacuolated giant cells had multiple signs of organelle dysfunction, including markedly increased mitochondria, aberrant lysosomes, and elevated cellular stress. We found similar vacuolated giant cells in human tuber specimens. Postnatal rapamycin treatment completely reversed these phenotypes and rescued the mutants from epilepsy and premature death, despite prenatal onset of Tsc1 loss and mTOR complex 1 activation in the developing brain. This TSC brain model provides insights into the pathogenesis and organelle dysfunction of giant cells, as well as epilepsy control in patients with TSC.
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2. Indhumathi N, Singh D, Chong SS, Thelma BK, Arabandi R, Srisailpathy CR. {{Fragile X CGG Repeat Variation in Tamil Nadu, South India: A Comparison of Radioactive and Methylation-Specific Polymerase Chain Reaction in CGG Repeat Sizing}}. {Genet Test Mol Biomarkers};2011 (Oct 24)
Fragile X syndrome is the most frequent hereditary cause of mental retardation after Down syndrome. Expansion of CGG repeats in the 5′ UTR of the fragile X mental retardation gene 1 (FMR1) causes gene inactivation in most of the cases. The FMR1 gene is classified into normal 5-44; gray zone 45-54; premutation 55 to <200; and full mutation >/=200 repeats. Precise sizing of FMR1 alleles is important to understand their variation, predisposition, and for genetic counseling. Meta-analysis reveals prevalence of premutation carriers as 1 in 259. No such reports are available in India. About 705 women from Tamil Nadu, South India, were screened for the FMR1 allelic variation by using radioactive polymerase chain reaction-polyacrylamide gel electrophoresis (PAGE) analysis. The women who were homozygous by radioactive polymerase chain reaction (rPCR) were reanalyzed by methylation-specific polymerase chain reaction (Ms-PCR) and GeneScan analysis. The techniques were validated and compared to arrive at a correction factor. Among 122 genotypes, 35 repeat variants ranging in size from 16 to 57 were observed. The most common repeat is 30 followed by 29. One in 353 women carried the premutation. No full mutations were observed. Screening populations with low frequency of premutations may not be applicable. Ms-PCR is more suitable for routine screening and clinical testing compared with rPCR-PAGE analysis.
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3. Page DT. {{A candidate circuit approach to investigating autism}}. {Anat Rec (Hoboken)};2011 (Oct);294(10):1671-1684.
A major problem in understanding mechanisms of pathogenesis in autism spectrum disorder (ASD) is deciphering how risk factors act via the brain to influence the behavioral symptoms of this disorder. We may start to bridge this gap in our understanding by systematically examining the structure and function of cell types that make up circuits underlying behavioral endophenotypes in animal models for ASD. A confluence of advances in basic behavioral neurobiology, in ASD mechanisms and animal models, and in genetic tools for imaging and manipulating brain circuits will make this possible. Through a process of elimination of candidates and comparison across models, we may hope to understand how ASD risk factors influence the development and function of neural circuitry at the level of genetically defined cell types. As an example of how this candidate circuit approach may be applied to investigating ASD, here I focus on social behavior as an endophenotype, and I discuss recent findings regarding the development and function of the oxytocin system, which is implicated in both normal social behavior and ASD pathogenesis. I stress the importance of a collaborative, multidisciplinary approach to probing candidate cell types and circuits across mouse models of ASD.
4. Simpson KL, Weaver KJ, de Villers-Sidani E, Lu JY, Cai Z, Pang Y, Rodriguez-Porcel F, Paul IA, Merzenich M, Lin RC. {{Perinatal antidepressant exposure alters cortical network function in rodents}}. {Proc Natl Acad Sci U S A};2011 (Oct 24)
Serotonin (5-HT) plays a key role in early brain development, and manipulation of 5-HT levels during this period can have lasting neurobiological and behavioral consequences. It is unclear how perinatal exposure to drugs, such as selective serotonin reuptake inhibitors (SSRIs), impacts cortical neural network function and what mechanism(s) may elicit the disruption of normal neuronal connections/interactions. In this article, we report on cortical wiring organization after pre- and postnatal exposure to the SSRI citalopram. We show that manipulation of 5-HT during early development in both in vitro and in vivo models disturbs characteristic chemoarchitectural and electrophysiological brain features, including changes in raphe and callosal connections, sensory processing, and myelin sheath formation. Also, drug-exposed rat pups exhibit neophobia and disrupted juvenile play behavior. These findings indicate that 5-HT homeostasis is required for proper brain maturation and that fetal/infant exposure to SSRIs should be examined in humans, particularly those with developmental dysfunction, such as autism.
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5. Wang L, Angley MT, Gerber JP, Sorich MJ. {{A review of candidate urinary biomarkers for autism spectrum disorder}}. {Biomarkers};2011 (Nov);16(7):537-552.
Context: Autism is a complex, heterogeneous neurodevelopmental condition with a strong genetic component potentially impacted by various environmental factors influencing susceptibility. There are no reliable laboratory tests available to confirm an autism diagnosis. Objective: To examine the published literature and identify putative urinary biomarkers of autism. Methods: A comprehensive literature search was conducted using electronic bibliographic databases. Results: Putative autism biomarkers were identified that could be categorized according to the key theories that exist regarding the etiology of autism: gastrointestinal factors, immune dysregulation, heavy metal toxicity, neurotransmitter abnormalities, and oxidative stress. Conclusion: There is scope for specific urinary biomarkers to be useful for identification of autistic metabolic phenotypes.
