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Variations in EEG discharges predict ADHD severity within individual Smith-Lemli-Opitz patients.

June 13, 2014 - 7:44am

Variations in EEG discharges predict ADHD severity within individual Smith-Lemli-Opitz patients.

Neurology. 2014 Jun 11;

Authors: Schreiber JM, Lanham DC, Trescher WH, Sparks SE, Wassif CA, Caffo BS, Porter FD, Tierney E, Gropman AL, Ewen JB

Abstract
OBJECTIVE: We sought to examine the prevalence of EEG abnormalities in Smith-Lemli-Opitz syndrome (SLOS) as well as the relationship between interictal epileptiform discharges (IEDs) and within-subject variations in attentional symptom severity.METHODS: In the context of a clinical trial for SLOS, we performed cross-sectional and repeated-measure observational studies of the relationship between EEG findings and cognitive/behavioral factors on 23 children (aged 4-17 years). EEGs were reviewed for clinical abnormalities, including IEDs, by readers blinded to participants' behavioral symptoms. Between-group differences in baseline characteristics of participants with and without IEDs were analyzed. Within-subject analyses examined the association between the presence of IEDs and changes in attention-deficit/hyperactivity disorder (ADHD) symptoms.RESULTS: Of 85 EEGs, 43 (51%) were abnormal, predominantly because of IEDs. Only one subject had documented clinical seizures. IEDs clustered in 13 subjects (57%), whereas 9 subjects (39%) had EEGs consistently free of IEDs. While there were no significant group differences in sex, age, intellectual disability, language level, or baseline ADHD symptoms, autistic symptoms tended to be more prevalent in the "IED" group (according to Autism Diagnostic Observation Schedule-2 criteria). Within individuals, the presence of IEDs on a particular EEG predicted, on average, a 27% increase in ADHD symptom severity.CONCLUSIONS: Epileptiform discharges are common in SLOS, despite a relatively low prevalence of epilepsy. Fluctuations in the presence of epileptiform discharges within individual children with a developmental disability syndrome may be associated with fluctuations in ADHD symptomatology, even in the absence of clinical seizures.

PMID: 24920862 [PubMed - as supplied by publisher]

Screening of 50 cypriot patients with autism spectrum disorders or autistic features using 400K custom array-CGH.

June 13, 2014 - 7:44am
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Screening of 50 cypriot patients with autism spectrum disorders or autistic features using 400K custom array-CGH.

Biomed Res Int. 2013;2013:843027

Authors: Kousoulidou L, Moutafi M, Nicolaides P, Hadjiloizou S, Christofi C, Paradesiotou A, Anastasiadou V, Sismani C, Patsalis PC

Abstract
Autism spectrum disorders (ASDs) comprise a distinct entity of neurodevelopmental disorders with a strong genetic component. Despite the identification of several candidate genes and causative genomic copy number variations (CNVs), the majority of ASD cases still remain unresolved. We have applied microarray-based comparative genomic hybridization (array-CGH) using Agilent 400K custom array in the first Cyprus population screening for identification of ASD-associated CNVs. A cohort of 50 ASD patients (G1), their parents (G2), 50 ethnically matched normal controls (G3), and 80 normal individuals having children with various developmental and neurological conditions (G4) were tested. As a result, 14 patients were found to carry 20 potentially causative aberrations, two of which were de novo. Comparison of the four population groups revealed an increased rate of rare disease-associated variants in normal parents of children with autism. The above data provided additional evidence, supporting the complexity of ASD aetiology in comparison to other developmental disorders involving cognitive impairment. Furthermore, we have demonstrated the rationale of a more targeted approach combining accurate clinical description with high-resolution population-oriented genomic screening for defining the role of CNVs in autism and identifying meaningful associations on the molecular level.

PMID: 24260744 [PubMed - indexed for MEDLINE]

Rare variants analysis of neurexin-1β in autism reveals a novel start codon mutation affecting protein levels at synapses.

June 13, 2014 - 7:44am
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Rare variants analysis of neurexin-1β in autism reveals a novel start codon mutation affecting protein levels at synapses.

Psychiatr Genet. 2013 Dec;23(6):262-6

Authors: Camacho-Garcia RJ, Hervás A, Toma C, Balmaña N, Cormand B, Martinez-Mir A, Scholl FG

Abstract
Neurexins are synaptic plasma membrane proteins encoded by three genes (NRXN1, -2, -3) with alternative promoters. Mutations in neurexin genes have been identified in different neurodevelopmental disorders, including autism. Recently, two point mutations altering the translation initiation site of NRXN1β (c.-3G>T and c.3G>T) have been described in patients with autism and mental retardation. In this study, we analyzed the NRXN1β gene in a sample of 153 patients with autism. We report the identification of a novel mutation, c.3G>A (p.Met1), affecting the translation initiation site. Expression analysis showed that the c.3G>A mutation switches the translation start site of NRXN1β to an in-frame downstream methionine and decreases synaptic levels of the mutant protein in cultured neurons. These data reinforce a role for synaptic defects of NRXN1β in neurodevelopmental disorders.

PMID: 24064682 [PubMed - indexed for MEDLINE]

Focal malformations of cortical development: new vistas for molecular pathogenesis.

June 12, 2014 - 7:23am
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Focal malformations of cortical development: new vistas for molecular pathogenesis.

Neuroscience. 2013 Nov 12;252:262-76

Authors: Lim KC, Crino PB

Abstract
Focal malformations of cortical development (FMCD) are highly associated with several neurological disorders including intractable epilepsy and neurocognitive disabilities. Over the past decade, several FMCD subtypes have been linked to hyperactivation of the mammalian target of rapamycin (mTOR) signaling cascade. In view of the roles that mTOR plays in cell proliferation, size, motility, and stem cell phenotype, many of the features of FMCD such as cytomegaly, disorganized lamination, and expression of stem cell markers can be explained by enhanced mTOR signaling. FMCD result from several distinct and fascinating molecular mechanisms including biallelic gene inactivation, somatic mutation, and potentially, viral infection. These mechanisms have been directly linked to mTOR activation. Perhaps most compelling, pharmacological inhibition of mTOR has been implemented successfully in clinical trials for select FMCD and provides a new vista for treatment.

PMID: 23892008 [PubMed - indexed for MEDLINE]

No association of Val158Met variant in the COMT gene with autism spectrum disorder in Thai children.

June 10, 2014 - 6:13am

No association of Val158Met variant in the COMT gene with autism spectrum disorder in Thai children.

Psychiatr Genet. 2014 Jun 6;

Authors: Limprasert P, Maisrikhaw W, Sripo T, Wirojanan J, Hansakunachai T, Roongpraiwan R, Sombuntham T, Ruangdaraganon N, Guo X

PMID: 24912046 [PubMed - as supplied by publisher]

Haploinsufficiency of XP01 and USP34 by a de novo 230 kb deletion in 2p15, in a patient with mild intellectual disability and cranio-facial dysmorphisms.

June 10, 2014 - 6:13am

Haploinsufficiency of XP01 and USP34 by a de novo 230 kb deletion in 2p15, in a patient with mild intellectual disability and cranio-facial dysmorphisms.

Eur J Med Genet. 2014 Jun 6;

Authors: Fannemel M, Barøy T, Holmgren A, Rødningen OK, Haugsand TM, Hansen B, Frengen E, Misceo D

Abstract
2p15p16.1-deletion syndrome was first described in 2007 based on the clinical presentation of two patients. The syndrome is characterized by intellectual disability, autism spectrum disorders, microcephaly, dysmorphic facial features and a variety of congenital organ defects. The precise genotype-phenotype correlation in 2p15- deletion syndrome is not understood. However, greater insight can be obtained by thorough clinical investigation of patients carrying deletions, especially those of small size. We report a 21-year-old male patient with features overlapping the clinical spectrum of the 2p15p16.1 deletion syndrome, such as intellectual disability, dysmorphic facial features, and congenital defects. He carried a 230 kb de novo deletion (chr2:61500346-61733075 bp, hg19), which affects the genes USP34, SNORA70B and XPO1. While there is a lack of functional data on SNORA70B, the involvement of USP34 and XPO1 in the regulation of fundamental developmental processes is well known. We suggest that haploinsuffiency of one or both of these genes is likely to be responsible for the disease in our patient.

PMID: 24911659 [PubMed - as supplied by publisher]

A Familial Heterozygous Null Mutation of MET in Autism Spectrum Disorder.

June 10, 2014 - 6:13am

A Familial Heterozygous Null Mutation of MET in Autism Spectrum Disorder.

Autism Res. 2014 Jun 6;

Authors: Lambert N, Wermenbol V, Pichon B, Acosta S, van den Ameele J, Perazzolo C, Messina D, Musumeci MF, Dessars B, De Leener A, Abramowicz M, Vilain C

Abstract
Autism spectrum disorder (ASD) results from interactions of genetic and environmental factors. The MET proto-oncogene has been identified as a candidate gene for autism susceptibility, and is implicated in neurodevelopment and social brain circuitry. Here, we describe the first case of a familial mutation of MET, consisting of an interstitial genomic deletion removing exons 12 through 15, causing a frameshift and premature stop codon, with evidence of nonsense-mediated mRNA decay. On the other allele, patients carried the C allele of the MET promoter rs1858830 polymorphism, known to decrease MET expression and previously associated with autism susceptibility. The heterozygous mutation was associated with autism in one patient, and language and social impairment in a sibling. Our observations delineate the phenotypic spectrum associated with a clearly defined, very likely complete loss of function mutation of MET. Incomplete penetrance in this family was consistent with MET as a partial susceptibility gene for ASD. Implication of MET in normal and pathological brain development opens new perspectives for understanding the pathophysiology of autism and for eventual therapeutical clues. Autism Res 2014, ●●: ●●-●●. © 2014 International Society for Autism Research, Wiley Periodicals, Inc.

PMID: 24909855 [PubMed - as supplied by publisher]

Epigenetics, autism spectrum, and neurodevelopmental disorders.

June 10, 2014 - 6:13am
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Epigenetics, autism spectrum, and neurodevelopmental disorders.

Neurotherapeutics. 2013 Oct;10(4):742-56

Authors: Rangasamy S, D'Mello SR, Narayanan V

Abstract
Epigenetic marks are modifications of DNA and histones. They are considered to be permanent within a single cell during development, and are heritable across cell division. Programming of neurons through epigenetic mechanisms is believed to be critical in neural development. Disruption or alteration in this process causes an array of neurodevelopmental disorders, including autism spectrum disorders (ASDs). Recent studies have provided evidence for an altered epigenetic landscape in ASDs and demonstrated the central role of epigenetic mechanisms in their pathogenesis. Many of the genes linked to the ASDs encode proteins that are involved in transcriptional regulation and chromatin remodeling. In this review we highlight selected neurodevelopmental disorders in which epigenetic dysregulation plays an important role. These include Rett syndrome, fragile X syndrome, Prader-Willi syndrome, Angelman syndrome, and Kabuki syndrome. For each of these disorders, we discuss how advances in our understanding of epigenetic mechanisms may lead to novel therapeutic approaches.

PMID: 24104594 [PubMed - indexed for MEDLINE]

Transcriptional Consequences of 16p11.2 Deletion and Duplication in Mouse Cortex and Multiplex Autism Families.

June 7, 2014 - 8:35am

Transcriptional Consequences of 16p11.2 Deletion and Duplication in Mouse Cortex and Multiplex Autism Families.

Am J Hum Genet. 2014 Jun 5;94(6):870-883

Authors: Blumenthal I, Ragavendran A, Erdin S, Klei L, Sugathan A, Guide JR, Manavalan P, Zhou JQ, Wheeler VC, Levin JZ, Ernst C, Roeder K, Devlin B, Gusella JF, Talkowski ME

Abstract
Reciprocal copy-number variation (CNV) of a 593 kb region of 16p11.2 is a common genetic cause of autism spectrum disorder (ASD), yet it is not completely penetrant and can manifest in a wide array of phenotypes. To explore its molecular consequences, we performed RNA sequencing of cerebral cortex from mouse models with CNV of the syntenic 7qF3 region and lymphoblast lines from 34 members of 7 multiplex ASD-affected families harboring the 16p11.2 CNV. Expression of all genes in the CNV region correlated well with their DNA copy number, with no evidence of dosage compensation. We observed effects on gene expression outside the CNV region, including apparent positional effects in cis and in trans at genomic segments with evidence of physical interaction in Hi-C chromosome conformation data. One of the most significant positional effects was telomeric to the 16p11.2 CNV and includes the previously described "distal" 16p11.2 microdeletion. Overall, 16p11.2 CNV was associated with altered expression of genes and networks that converge on multiple hypotheses of ASD pathogenesis, including synaptic function (e.g., NRXN1, NRXN3), chromatin modification (e.g., CHD8, EHMT1, MECP2), transcriptional regulation (e.g., TCF4, SATB2), and intellectual disability (e.g., FMR1, CEP290). However, there were differences between tissues and species, with the strongest effects being consistently within the CNV region itself. Our analyses suggest that through a combination of indirect regulatory effects and direct effects on nuclear architecture, alteration of 16p11.2 genes disrupts expression networks that involve other genes and pathways known to contribute to ASD, suggesting an overlap in mechanisms of pathogenesis.

PMID: 24906019 [PubMed - as supplied by publisher]

Open questions: What has genetics told us about autism spectrum disorders?

June 7, 2014 - 8:35am

Open questions: What has genetics told us about autism spectrum disorders?

BMC Biol. 2014;12(1):45

Authors: Raff M

Abstract
Some of the most interesting questions in biology today, in my view, derive from the real advances in neuropsychiatry that have come largely from human genetics. Research in autism spectrum disorders (ASDs) has been leading the way, mainly because it has become especially well funded and has recently attracted many outstanding scientists. (I must make it clear that I am an outsider in this field, as I have never worked on any neuropsychiatric disorder).

PMID: 24903674 [PubMed - in process]

Blocking metabotropic glutamate receptor subtype 7 (mGlu7) via the Venus flytrap domain (VFTD) inhibits amygdala plasticity, stress, and anxiety-related behavior.

June 5, 2014 - 11:17am
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Blocking metabotropic glutamate receptor subtype 7 (mGlu7) via the Venus flytrap domain (VFTD) inhibits amygdala plasticity, stress, and anxiety-related behavior.

J Biol Chem. 2014 Apr 18;289(16):10975-87

Authors: Gee CE, Peterlik D, Neuhäuser C, Bouhelal R, Kaupmann K, Laue G, Uschold-Schmidt N, Feuerbach D, Zimmermann K, Ofner S, Cryan JF, van der Putten H, Fendt M, Vranesic I, Glatthar R, Flor PJ

Abstract
The metabotropic glutamate receptor subtype 7 (mGlu7) is an important presynaptic regulator of neurotransmission in the mammalian CNS. mGlu7 function has been linked to autism, drug abuse, anxiety, and depression. Despite this, it has been difficult to develop specific blockers of native mGlu7 signaling in relevant brain areas such as amygdala and limbic cortex. Here, we present the mGlu7-selective antagonist 7-hydroxy-3-(4-iodophenoxy)-4H-chromen-4-one (XAP044), which inhibits lateral amygdala long term potentiation (LTP) in brain slices from wild type mice with a half-maximal blockade at 88 nm. There was no effect of XAP044 on LTP of mGlu7-deficient mice, indicating that this pharmacological effect is mGlu7-dependent. Unexpectedly and in contrast to all previous mGlu7-selective drugs, XAP044 does not act via the seven-transmembrane region but rather via a binding pocket localized in mGlu7's extracellular Venus flytrap domain, a region generally known for orthosteric agonist binding. This was shown by chimeric receptor studies in recombinant cell line assays. XAP044 demonstrates good brain exposure and wide spectrum anti-stress and antidepressant- and anxiolytic-like efficacy in rodent behavioral paradigms. XAP044 reduces freezing during acquisition of Pavlovian fear and reduces innate anxiety, which is consistent with the phenotypes of mGlu7-deficient mice, the results of mGlu7 siRNA knockdown studies, and the inhibition of amygdala LTP by XAP044. Thus, we present an mGlu7 antagonist with a novel molecular mode of pharmacological action, providing significant application potential in psychiatry. Modeling the selective interaction between XAP044 and mGlu7's Venus flytrap domain, whose three-dimensional structure is already known, will facilitate future drug development supported by computer-assisted drug design.

PMID: 24596089 [PubMed - indexed for MEDLINE]

Brain MRI abnormalities and spectrum of neurological and clinical findings in three patients with proximal 16p11.2 microduplication.

June 4, 2014 - 7:47am

Brain MRI abnormalities and spectrum of neurological and clinical findings in three patients with proximal 16p11.2 microduplication.

Am J Med Genet A. 2014 May 28;

Authors: Filges I, Sparagana S, Sargent M, Selby K, Schlade-Bartusiak K, Lueder GT, Robichaux-Viehoever A, Schlaggar BL, Shimony JS, Shinawi M

Abstract
The phenotype of recurrent ∼600 kb microdeletion and microduplication on proximal 16p11.2 is characterized by a spectrum of neurodevelopmental impairments including developmental delay and intellectual disability, epilepsy, autism and psychiatric disorders which are all subject to incomplete penetrance and variable expressivity. A variety of brain MRI abnormalities were reported in patients with 16p11.2 rearrangements, but no systematic correlation has been studied among patients with similar brain anomalies, their neurodevelopmental and clinical phenotypes. We present three patients with the proximal 16p11.2 microduplication exhibiting significant developmental delay, anxiety disorder and other variable clinical features. Our patients have abnormal brain MRI findings of cerebral T2 hyperintense foci (3/3) and ventriculomegaly (2/3). The neuroradiological or neurological findings in two cases prompted an extensive diagnostic work-up. One patient has exhibited neurological regression and progressive vision impairment and was diagnosed with juvenile neuronal ceroid-lipofuscinosis. We compare the clinical course and phenotype of these patients in regard to the clinical significance of the cerebral lesions and the need for MRI surveillance. We conclude that in all three patients the lesions were not progressive, did not show any sign of malignant transformation and could not be correlated to specific clinical features. We discuss potential etiologic mechanisms that may include overexpression of genes within the duplicated region involved in control of cell proliferation and complex molecular mechanisms such as the MAPK/ERK pathway. Systematic studies in larger cohorts are needed to confirm our observation and to establish the prevalence and clinical significance of these neuroanatomical abnormalities in patients with 16p11.2 duplications. © 2014 Wiley Periodicals, Inc.

PMID: 24891046 [PubMed - as supplied by publisher]

Pathogenic rare copy number variants in community-based schizophrenia suggest a potential role for clinical microarrays.

June 4, 2014 - 7:47am
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Pathogenic rare copy number variants in community-based schizophrenia suggest a potential role for clinical microarrays.

Hum Mol Genet. 2013 Nov 15;22(22):4485-501

Authors: Costain G, Lionel AC, Merico D, Forsythe P, Russell K, Lowther C, Yuen T, Husted J, Stavropoulos DJ, Speevak M, Chow EW, Marshall CR, Scherer SW, Bassett AS

Abstract
Individually rare, large copy number variants (CNVs) contribute to genetic vulnerability for schizophrenia. Unresolved questions remain, however, regarding the anticipated yield of clinical microarray testing in schizophrenia. Using high-resolution genome-wide microarrays and rigorous methods, we investigated rare CNVs in a prospectively recruited community-based cohort of 459 unrelated adults with schizophrenia and estimated the minimum prevalence of clinically significant CNVs that would be detectable on a clinical microarray. A blinded review by two independent clinical cytogenetic laboratory directors of all large (>500 kb) rare CNVs in cases and well-matched controls showed that those deemed to be clinically significant were highly enriched in schizophrenia (16.4-fold increase, P < 0.0001). In a single community catchment area, the prevalence of individuals with these CNVs was 8.1%. Rare 1.7 Mb CNVs at 2q13 were found to be significantly associated with schizophrenia for the first time, compared with the prevalence in 23 838 population-based controls (42.9-fold increase, P = 0.0002). Additional novel findings that will facilitate the future clinical interpretation of smaller CNVs in schizophrenia include: (i) a greater proportion of individuals with two or more rare exonic CNVs >10 kb in size (1.5-fold increase, P = 0.0109) in schizophrenia; (ii) the systematic discovery of new candidate genes for schizophrenia; and, (iii) functional gene enrichment mapping highlighting a differential impact in schizophrenia of rare exonic deletions involving diverse functions, including neurodevelopmental and synaptic processes (4.7-fold increase, P = 0.0060). These findings suggest consideration of a potential role for clinical microarray testing in schizophrenia, as is now the suggested standard of care for related developmental disorders like autism.

PMID: 23813976 [PubMed - indexed for MEDLINE]

Family-based association study of microsatellites in the 5' flanking region of AVPR1A with autism spectrum disorder in the Korean population.

June 4, 2014 - 7:47am
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Family-based association study of microsatellites in the 5' flanking region of AVPR1A with autism spectrum disorder in the Korean population.

Psychiatry Res. 2010 Jun 30;178(1):199-201

Authors: Yang SY, Cho SC, Yoo HJ, Cho IH, Park M, Yoe J, Kim SA

Abstract
This study evaluated the association between autism spectrum disorders (ASDs) and microsatellites (RS3 and RS1) in the 5' flanking region of AVPR1A in 148 Korean trios comprising children with ASDs. In the transmission equilibrium test and haplotype analysis, we found a statistically significant association between microsatellites and Korean ASDs.

PMID: 20452058 [PubMed - indexed for MEDLINE]

The involvement of serotonin polymorphisms in autistic spectrum symptomatology.

June 3, 2014 - 7:15am

The involvement of serotonin polymorphisms in autistic spectrum symptomatology.

Psychiatr Genet. 2014 Jun 2;

Authors: Hervás A, Toma C, Romarís P, Ribasés M, Salgado M, Bayes M, Balmaña N, Cormand B, Maristany M, Guijarro S, Arranz MJ

Abstract
BACKGROUND: Autism spectrum disorders (ASD) are highly inherited developmental syndromes, resulting from a complex interaction between environmental and genetic factors. To date, only a limited number of genetic variants have been discovered with respect to autism, and their contribution to the development of the disorder has not been clearly determined. Investigation of specific autistic symptomatology may improve the chances of identifying related genes and may help to better understand these disorders.
MATERIALS AND METHODS: We investigated the contribution of 80 genetic variants in 15 serotonin genes to ASD phenotypes [intelligence quotation (IQ), intellectual disability (ID) and language onset delay (LD)] in a cohort of 141 children and young adults (121 male patients and 20 female patients, average age 14.5±5.1 years).
RESULTS: Two polymorphisms in the HTR2B gene, rs10194776 and rs16827801, were associated with IQ (P=0.0004 and 0.003, respectively), ID (P=0.02 and 0.03) and LD (P=0.04 and 0.004). Nominal associations were also detected between the ASD phenotypes investigated and 5-HT2A, 5-HT4 and 5-HT6 genetic variants.
CONCLUSION: Our study provides evidence of the contribution of serotonergic variants to IQ, ID and LD in ASD patients.

PMID: 24887447 [PubMed - as supplied by publisher]

Cartography of neurexin alternative splicing mapped by single-molecule long-read mRNA sequencing.

June 3, 2014 - 7:15am
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Cartography of neurexin alternative splicing mapped by single-molecule long-read mRNA sequencing.

Proc Natl Acad Sci U S A. 2014 Apr 1;111(13):E1291-9

Authors: Treutlein B, Gokce O, Quake SR, Südhof TC

Abstract
Neurexins are evolutionarily conserved presynaptic cell-adhesion molecules that are essential for normal synapse formation and synaptic transmission. Indirect evidence has indicated that extensive alternative splicing of neurexin mRNAs may produce hundreds if not thousands of neurexin isoforms, but no direct evidence for such diversity has been available. Here we use unbiased long-read sequencing of full-length neurexin (Nrxn)1α, Nrxn1β, Nrxn2β, Nrxn3α, and Nrxn3β mRNAs to systematically assess how many sites of alternative splicing are used in neurexins with a significant frequency, and whether alternative splicing events at these sites are independent of each other. In sequencing more than 25,000 full-length mRNAs, we identified a novel, abundantly used alternatively spliced exon of Nrxn1α and Nrxn3α (referred to as alternatively spliced sequence 6) that encodes a 9-residue insertion in the flexible hinge region between the fifth LNS (laminin-α, neurexin, sex hormone-binding globulin) domain and the third EGF-like sequence. In addition, we observed several larger-scale events of alternative splicing that deleted multiple domains and were much less frequent than the canonical six sites of alternative splicing in neurexins. All of the six canonical events of alternative splicing appear to be independent of each other, suggesting that neurexins may exhibit an even larger isoform diversity than previously envisioned and comprise thousands of variants. Our data are consistent with the notion that α-neurexins represent extracellular protein-interaction scaffolds in which different LNS and EGF domains mediate distinct interactions that affect diverse functions and are independently regulated by independent events of alternative splicing.

PMID: 24639501 [PubMed - indexed for MEDLINE]

Current progress and challenges in the search for autism biomarkers.

June 3, 2014 - 7:15am
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Current progress and challenges in the search for autism biomarkers.

Dis Markers. 2013;35(1):55-65

Authors: Voineagu I, Yoo HJ

Abstract
Autism spectrum disorders (ASD) encompass a range of neurodevelopmental conditions that are clinically and etiologically very heterogeneous. ASD is currently diagnosed entirely on behavioral criteria, but intensive research efforts are focused on identifying biological markers for disease risk and early diagnosis. Here, we discuss recent progress toward identifying biological markers for ASD and highlight specific challenges as well as ethical aspects of translating ASD biomarker research into the clinic.

PMID: 24167349 [PubMed - indexed for MEDLINE]

Genetic diagnosis of autism spectrum disorders: The opportunity and challenge in the genomics era.

June 1, 2014 - 6:45am

Genetic diagnosis of autism spectrum disorders: The opportunity and challenge in the genomics era.

Crit Rev Clin Lab Sci. 2014 May 30;:1-14

Authors: Jiang YH, Wang Y, Xiu X, Choy KW, Pursley AN, Cheung SW

Abstract
Abstract A genetic etiology for autism spectrum disorders (ASDs) was first suggested from twin studies reported in the 1970s. The identification of gene mutations in syndromic ASDs provided evidence to support a genetic cause of ASDs. More recently, genome-wide copy number variant and sequence analyses have uncovered a list of rare and highly penetrant copy number variants (CNVs) or single nucleotide variants (SNVs) associated with ASDs, which has strengthened the claim of a genetic etiology for ASDs. Findings from research studies in the genetics of ASD now support an important role for molecular diagnostics in the clinical genetics evaluation of ASDs. Various molecular diagnostic assays including single gene tests, targeted multiple gene panels and copy number analysis should all be considered in the clinical genetics evaluation of ASDs. Whole exome sequencing could also be considered in selected clinical cases. However, the challenge that remains is to determine the causal role of genetic variants identified through molecular testing. Variable expressivity, pleiotropic effects and incomplete penetrance associated with CNVs and SNVs also present significant challenges for genetic counseling and prenatal diagnosis.

PMID: 24878448 [PubMed - as supplied by publisher]

Chromosome microarrays in diagnostic testing: interpreting the genomic data.

May 30, 2014 - 8:42am

Chromosome microarrays in diagnostic testing: interpreting the genomic data.

Methods Mol Biol. 2014;1168:117-55

Authors: Peters GB, Pertile MD

Abstract
DNA-based Chromosome MicroArrays (CMAs) are now well established as diagnostic tools in clinical genetics laboratories. Over the last decade, the primary application of CMAs has been the genome-wide detection of a particular class of mutation known as copy number variants (CNVs). Since 2010, CMA testing has been recommended as a first-tier test for detection of CNVs associated with intellectual disability, autism spectrum disorders, and/or multiple congenital anomalies…in the post-natal setting. CNVs are now regarded as pathogenic in 14-18 % of patients referred for these (and related) disorders.Through consideration of clinical examples, and several microarray platforms, we attempt to provide an appreciation of microarray diagnostics, from the initial inspection of the microarray data, to the composing of the patient report. In CMA data interpretation, a major challenge comes from the high frequency of clinically irrelevant CNVs observed within "patient" and "normal" populations. As might be predicted, the more common and clinically insignificant CNVs tend to be the smaller ones <100 kb in length, involving few or no known genes. However, this relationship is not at all straightforward: CNV length and gene content are only very imperfect indicators of CNV pathogenicity. Presently, there are no reliable means of separating, a priori, the benign from the pathological CNV classes.This chapter also considers sources of technical "noise" within CMA data sets. Some level of noise is inevitable in diagnostic genomics, given the very large number of data points generated in any one test. Noise further limits CMA resolution, and some miscalling of CNVs is unavoidable. In this, there is no ideal solution, but various strategies for handling noise are available. Even without solutions, consideration of these diagnostic problems per se is informative, as they afford critical insights into the biological and technical underpinnings of CNV discovery. These are indispensable to any clinician or scientist practising within the field of genome diagnostics.

PMID: 24870134 [PubMed - in process]

Disruption of the non-canonical Wnt gene PRICKLE2 leads to autism-like behaviors with evidence for hippocampal synaptic dysfunction.

May 30, 2014 - 8:42am
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Disruption of the non-canonical Wnt gene PRICKLE2 leads to autism-like behaviors with evidence for hippocampal synaptic dysfunction.

Mol Psychiatry. 2013 Oct;18(10):1077-89

Authors: Sowers LP, Loo L, Wu Y, Campbell E, Ulrich JD, Wu S, Paemka L, Wassink T, Meyer K, Bing X, El-Shanti H, Usachev YM, Ueno N, Manak JR, Manak RJ, Shepherd AJ, Ferguson PJ, Darbro BW, Richerson GB, Mohapatra DP, Wemmie JA, Bassuk AG

Abstract
Autism spectrum disorders (ASDs) have been suggested to arise from abnormalities in the canonical and non-canonical Wnt signaling pathways. However, a direct connection between a human variant in a Wnt pathway gene and ASD-relevant brain pathology has not been established. Prickle2 (Pk2) is a post-synaptic non-canonical Wnt signaling protein shown to interact with post-synaptic density 95 (PSD-95). Here, we show that mice with disruption in Prickle2 display behavioral abnormalities including altered social interaction, learning abnormalities and behavioral inflexibility. Prickle2 disruption in mouse hippocampal neurons led to reductions in dendrite branching, synapse number and PSD size. Consistent with these findings, Prickle2 null neurons show decreased frequency and size of spontaneous miniature synaptic currents. These behavioral and physiological abnormalities in Prickle2 disrupted mice are consistent with ASD-like phenotypes present in other mouse models of ASDs. In 384 individuals with autism, we identified two with distinct, heterozygous, rare, non-synonymous PRICKLE2 variants (p.E8Q and p.V153I) that were shared by their affected siblings and inherited paternally. Unlike wild-type PRICKLE2, the PRICKLE2 variants found in ASD patients exhibit deficits in morphological and electrophysiological assays. These data suggest that these PRICKLE2 variants cause a critical loss of PRICKLE2 function. The data presented here provide new insight into the biological roles of Prickle2, its behavioral importance, and suggest disruptions in non-canonical Wnt genes such as PRICKLE2 may contribute to synaptic abnormalities underlying ASDs.

PMID: 23711981 [PubMed - indexed for MEDLINE]

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