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Repeated positive fighting experience in male inbred mice.

June 24, 2015 - 8:59am
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Repeated positive fighting experience in male inbred mice.

Nat Protoc. 2014 Nov;9(11):2705-17

Authors: Kudryavtseva NN, Smagin DA, Kovalenko IL, Vishnivetskaya GB

Abstract
Repeated aggression is a frequent symptom of many psychiatric and neurological disorders, including obsessive-compulsive and attention deficit hyperactivity disorders, bipolar and post-traumatic stress disorders, epilepsy, autism, schizophrenia and drug abuse. However, repeated aggression is insufficiently studied because there is a lack of adequate models in animals. The sensory contact model (SCM), widely used to study the effects of chronic social defeat stress, can also be used to investigate the effects of repeated aggression. Mice with repeated positive fighting experience in daily agonistic interactions in this model develop pronounced aggressiveness, anxiety and impulsivity, disturbances in motivated and cognitive behaviors, and impairments of sociability; they also demonstrate hyperactivity, attention-deficit behavior, motor dysfunctions and repetitive stereotyped behaviors, such as jerks, rotations and head twitches. In this protocol, we describe how to apply the SCM to study repeated aggression in mice. Severe neuropathology develops in male mice after 20-21 d of agonistic interactions.

PMID: 25340443 [PubMed - indexed for MEDLINE]

Investigation of 15q11-q13, 16p11.2 and 22q13 CNVs in autism spectrum disorder Brazilian individuals with and without epilepsy.

June 24, 2015 - 8:59am
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Investigation of 15q11-q13, 16p11.2 and 22q13 CNVs in autism spectrum disorder Brazilian individuals with and without epilepsy.

PLoS One. 2014;9(9):e107705

Authors: Moreira DP, Griesi-Oliveira K, Bossolani-Martins AL, Lourenço NC, Takahashi VN, da Rocha KM, Moreira ES, Vadasz E, Meira JG, Bertola D, O'Halloran E, Magalhães TR, Fett-Conte AC, Passos-Bueno MR

Abstract
Copy number variations (CNVs) are an important cause of ASD and those located at 15q11-q13, 16p11.2 and 22q13 have been reported as the most frequent. These CNVs exhibit variable clinical expressivity and those at 15q11-q13 and 16p11.2 also show incomplete penetrance. In the present work, through multiplex ligation-dependent probe amplification (MLPA) analysis of 531 ethnically admixed ASD-affected Brazilian individuals, we found that the combined prevalence of the 15q11-q13, 16p11.2 and 22q13 CNVs is 2.1% (11/531). Parental origin could be determined in 8 of the affected individuals, and revealed that 4 of the CNVs represent de novo events. Based on CNV prediction analysis from genome-wide SNP arrays, the size of those CNVs ranged from 206 kb to 2.27 Mb and those at 15q11-q13 were limited to the 15q13.3 region. In addition, this analysis also revealed 6 additional CNVs in 5 out of 11 affected individuals. Finally, we observed that the combined prevalence of CNVs at 15q13.3 and 22q13 in ASD-affected individuals with epilepsy (6.4%) was higher than that in ASD-affected individuals without epilepsy (1.3%; p<0.014). Therefore, our data show that the prevalence of CNVs at 15q13.3, 16p11.2 and 22q13 in Brazilian ASD-affected individuals is comparable to that estimated for ASD-affected individuals of pure or predominant European ancestry. Also, it suggests that the likelihood of a greater number of positive MLPA results might be found for the 15q13.3 and 22q13 regions by prioritizing ASD-affected individuals with epilepsy.

PMID: 25255310 [PubMed - indexed for MEDLINE]

The applications of pharmacogenomics to neurological disorders.

June 24, 2015 - 8:59am
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The applications of pharmacogenomics to neurological disorders.

Curr Mol Med. 2014;14(7):880-90

Authors: Gilman C, McSweeney C, Mao Y

Abstract
The most common neurological disorders, including neurodegenerative diseases and psychiatric disorders, have received recent attention with regards to pharmacogenomics and personalized medicine. Here, we will focus on a neglected neurodegenerative disorder, cerebral ischemic stroke (CIS), and highlight recent advances in two disorders, Parkinson's disease (PD) and Alzheimer's diseases (AD), that possess both similar and distinct mechanisms in regards to potential therapeutic targets. In the first part of this review, we will focus primarily on mechanisms that are somewhat specific to each disorder which are involved in neurodegeneration (i.e., protease pathways, calcium homeostasis, reactive oxygen species regulation, DNA repair mechanisms, neurogenesis regulation, mitochondrial function, etc.). In the second part of this review, we will discuss the applications of the genome-wide technology on pharmacogenomics of mental illnesses including schizophrenia (SCZ), autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), and obsessive compulsive disorder (OCD).

PMID: 25109797 [PubMed - indexed for MEDLINE]

'What's up, (R)DoC?'--can identifying core dimensions of early functioning help us understand, and then reduce, developmental risk for mental disorders?

June 24, 2015 - 8:59am
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'What's up, (R)DoC?'--can identifying core dimensions of early functioning help us understand, and then reduce, developmental risk for mental disorders?

J Child Psychol Psychiatry. 2014 Aug;55(8):849-51

Authors: Sonuga-Barke EJ

Abstract
In the U.S. the National Institute of Mental Health (NIMH), the main funder of mental health research in the world, has recently changed its funding model to promote a radically new perspective for mental health science. This bold, and for some controversial, initiative, termed the Research Diagnostic Criteria (or RDoC for short), intends to shift the focus of research, and eventually clinical practice, away from existing diagnostic categories, as recently updated in the DSM-5, towards 'new ways of classifying psychopathology based on dimensions of observable behavior and neurobiological measures.' This reorientation from discrete categorical disorder manifestations to underlying cross-cutting dimensions of individual functioning has generated considerable debate across the community of mental health researchers and clinicians (with strong views voiced both pro and con). Given its pivotal role in defining the research agenda globally, there is little doubt that this US science funding initiative will also have ramifications for researchers and clinicians worldwide. In this Editorial we focus specifically on the translational potential of the dimensional RDoC approach, properly extended to developmental models of early risk, in terms of its value as a potential driver of early intervention/prevention models; in the current issue of the JCPP this is exemplified by a number of papers thata address the mapping of underlying dimensions of core functioning to disorder risk, providing evidence for their potential predictive power as early markers of later disorder processes.

PMID: 25039570 [PubMed - indexed for MEDLINE]

A familial heterozygous null mutation of MET in autism spectrum disorder.

June 24, 2015 - 8:59am
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A familial heterozygous null mutation of MET in autism spectrum disorder.

Autism Res. 2014 Oct;7(5):617-22

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.

PMID: 24909855 [PubMed - indexed for MEDLINE]

Brief report: impact of child problem behaviors and parental broad autism phenotype traits on substance use among parents of children with ASD.

June 24, 2015 - 8:59am
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Brief report: impact of child problem behaviors and parental broad autism phenotype traits on substance use among parents of children with ASD.

J Autism Dev Disord. 2014 Oct;44(10):2621-7

Authors: Wade JL, Cox NB, Reeve RE, Hull M

Abstract
Using data from the Simons Simplex Collection, the present study examined the impact of child externalizing behavior and parental broad autism phenotype traits on substance use among parents of children with autism spectrum disorder (n = 2,388). For both fathers and mothers, child externalizing behaviors predicted tobacco use (OR = 1.01 and OR = 1.02, respectively), whereas rigidity increased risk of tobacco use for fathers (OR = 1.29) but not mothers. Additionally, among mothers, child externalizing behaviors increased risk of illegal substance use (OR = 1.04), whereas maternal rigidity decreased risk of alcohol use (OR = .83). Collectively, results suggest that child externalizing behaviors and parental rigidity may have differing impacts on the types of substances used by parents.

PMID: 24805795 [PubMed - indexed for MEDLINE]

Developing with ring 14 syndrome: a survey in different countries.

June 24, 2015 - 8:59am
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Developing with ring 14 syndrome: a survey in different countries.

Clin Linguist Phon. 2014 Nov;28(11):844-56

Authors: Zampini L, Zanchi P, D'Odorico L

Abstract
This study aimed to assess the communicative skills of children and young adults with ring 14 syndrome and linear 14q deletions, investigating the relationships among their language development and their genetic, clinical, psychomotor and behavioural characteristics. Participants were 36 individuals with chromosome 14 aberrations whose parents completed a questionnaire, specifically developed in five languages, to assess their son's/daughter's development. Data analysis showed that chronological age does not account for the high individual variability found in the participants' skills. The comparison between participants with ring 14 syndrome and participants with 14q linear deletions showed that the former were characterised by a higher occurrence of epilepsy, abnormalities of the retina and autism. The participants with smaller amounts of deleted genetic material were those who had a higher level of language development. Because ring 14 syndrome is a rare genetic disease, the collection of data from a large group of individuals could be helpful to create expectations about the possible developmental outcomes of these children.

PMID: 24779649 [PubMed - indexed for MEDLINE]

Brief report: functional MRI of a patient with 7q11.23 duplication syndrome and autism spectrum disorder.

June 24, 2015 - 8:59am
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Brief report: functional MRI of a patient with 7q11.23 duplication syndrome and autism spectrum disorder.

J Autism Dev Disord. 2014 Oct;44(10):2608-13

Authors: Prontera P, Serino D, Caldini B, Scarponi L, Merla G, Testa G, Muti M, Napolioni V, Mazzotta G, Piccirilli M, Donti E

Abstract
The duplication of the Williams-Beuren syndrome (WBS) region (7q11.23) is a copy number variant associated with autism spectrum disorder (ASD). One of the most intriguing aspects is that the reciprocal microdeletion causes WBS, characterized by hypersociability, marked empathy, and a relative capacity in verbal short-term memory and language. Herein, we studied, by using functional morphological and volumetric magnetic resonance, a 17-year-old male patient who displays a de novo 7q11.23 duplication and ASD. The limbic system of the patient appeared hypo-functional, while the total brain volume was increased, thus contrasting, in an opposite and intriguing manner, with the global brain volume reduction reported in WBS. Even if these findings come from the analysis of a single patient and, therefore, have to be considered preliminary results, they encourage carrying on further functional and volumetric studies in patients with 7q11.23 duplication, to fully elucidate the role of this gene-dosage alteration on brain development and limbic system function.

PMID: 24722762 [PubMed - indexed for MEDLINE]

X-linked focal epilepsy with reflex bathing seizures: Characterization of a distinct epileptic syndrome.

June 23, 2015 - 6:42am
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X-linked focal epilepsy with reflex bathing seizures: Characterization of a distinct epileptic syndrome.

Epilepsia. 2015 Jun 19;

Authors: Nguyen DK, Rouleau I, Sénéchal G, Ansaldo AI, Gravel M, Benfenati F, Cossette P

Abstract
OBJECTIVE: We recently reported a Q555X mutation of synapsin 1 (SYN1) on chromosome Xp11-q21 in a family segregating partial epilepsy and autistic spectrum disorder. Herein, we provide a detailed description of the epileptic syndrome in the original family.
METHODS: A total of 34 members from a large French-Canadian family were evaluated. Family members with seizures or epilepsy underwent (when possible) clinical, neuropsychological, electrophysiologic, and neuroimaging assessments.
RESULTS: Epilepsy was diagnosed in 10 family members (4 deceased, 6 living). In addition to occasional spontaneous complex partial seizures, seven family members clearly had reflex seizures triggered by bathing or showering. Hippocampal atrophy was found in two of five epileptic family members family members who underwent magnetic resonance (MR) imaging. Video-electroencephalography (EEG) recordings of three triggered seizures in two affected members showed rhythmic theta activity over temporal head regions. Ictal single-photon emission computed tomography (SPECT) showed temporoinsular perfusion changes. Detailed neuropsychological assessments revealed that SYN1 Q555X male mutation carriers showed specific language impairment and mild autistic spectrum disorder. Female carriers also exhibited reading impairments and febrile seizures but no chronic epilepsy.
SIGNIFICANCE: Available evidence suggests that impaired SYN1 function is associated with hyperexcitability of the temporoinsular network and disturbance of high mental functions such as language and social interaction. The presence of reflex bathing seizures, a most peculiar clinical feature, could be helpful in identifying other patients with this syndrome.

PMID: 26096837 [PubMed - as supplied by publisher]

The Human Clinical Phenotypes of Altered CHRNA7 Copy Number.

June 23, 2015 - 6:42am
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The Human Clinical Phenotypes of Altered CHRNA7 Copy Number.

Biochem Pharmacol. 2015 Jun 18;

Authors: Gillentine M, Schaaf C

Abstract
Copy number variants (CNVs) have been implicated in multiple neuropsychiatric conditions, including autism spectrum disorder (ASD), schizophrenia, and intellectual disability (ID). Chromosome 15q13 is a hotspot for such CNVs due to the presence of low copy repeat (LCR) elements, which facilitate non-allelic homologous recombination (NAHR). Several of these CNVs have been overrepresented in individuals with neuropsychiatric disorders; yet variable expressivity and incomplete penetrance are commonly seen. Dosage sensitivity of the CHRNA7 gene, which encodes for the α7 nicotinic acetylcholine receptor in the human brain, has been proposed to have a major contribution to the observed cognitive and behavioral phenotypes, as it represents the smallest region of overlap to all the 15q13.3 deletions and duplications. Individuals with zero to four copies of CHRNA7 have been reported in the literature, and represent a range of clinical severity, with deletions causing generally more severe and more highly penetrant phenotypes. Potential mechanisms to account for the variable expressivity within each group of 15q13.3 CNVs will be discussed.

PMID: 26095975 [PubMed - as supplied by publisher]

Paired-Duplication Signatures Mark Cryptic Inversions and Other Complex Structural Variation.

June 23, 2015 - 6:42am
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Paired-Duplication Signatures Mark Cryptic Inversions and Other Complex Structural Variation.

Am J Hum Genet. 2015 Jun 17;

Authors: Brand H, Collins RL, Hanscom C, Rosenfeld JA, Pillalamarri V, Stone MR, Kelley F, Mason T, Margolin L, Eggert S, Mitchell E, Hodge JC, Gusella JF, Sanders SJ, Talkowski ME

Abstract
Copy-number variants (CNVs) have been the predominant focus of genetic studies of structural variation, and chromosomal microarray (CMA) for genome-wide CNV detection is the recommended first-tier genetic diagnostic screen in neurodevelopmental disorders. We compared CNVs observed by CMA to the structural variation detected by whole-genome large-insert sequencing in 259 individuals diagnosed with autism spectrum disorder (ASD) from the Simons Simplex Collection. These analyses revealed a diverse landscape of complex duplications in the human genome. One remarkably common class of complex rearrangement, which we term dupINVdup, involves two closely located duplications ("paired duplications") that flank the breakpoints of an inversion. This complex variant class is cryptic to CMA, but we observed it in 8.1% of all subjects. We also detected other paired-duplication signatures and duplication-mediated complex rearrangements in 15.8% of all ASD subjects. Breakpoint analysis showed that the predominant mechanism of formation of these complex duplication-associated variants was microhomology-mediated repair. On the basis of the striking prevalence of dupINVdups in this cohort, we explored the landscape of all inversion variation among the 235 highest-quality libraries and found abundant complexity among these variants: only 39.3% of inversions were canonical, or simple, inversions without additional rearrangement. Collectively, these findings indicate that dupINVdups, as well as other complex duplication-associated rearrangements, represent relatively common sources of genomic variation that is cryptic to population-based microarray and low-depth whole-genome sequencing. They also suggest that paired-duplication signatures detected by CMA warrant further scrutiny in genetic diagnostic testing given that they might mark complex rearrangements of potential clinical relevance.

PMID: 26094575 [PubMed - as supplied by publisher]

A critical role of RBM8a in proliferation and differentiation of embryonic neural progenitors.

June 22, 2015 - 6:52am

A critical role of RBM8a in proliferation and differentiation of embryonic neural progenitors.

Neural Dev. 2015 Jun 21;10(1):18

Authors: Zou D, McSweeney C, Sebastian A, Reynolds DJ, Dong F, Zhou Y, Deng D, Wang Y, Liu L, Zhu J, Zou J, Shi Y, Albert I, Mao Y

Abstract
BACKGROUND: Nonsense mediated mRNA decay (NMD) is an RNA surveillance mechanism that controls RNA stability and ensures the speedy degradation of erroneous and unnecessary transcripts. This mechanism depends on several core factors in the exon junction complex (EJC), eIF4A3, RBM8a, Magoh, and BTZ, as well as peripheral factors to distinguish premature stop codons (PTCs) from normal stop codons in transcripts. Recently, emerging evidence has indicated that NMD factors are associated with neurodevelopmental disorders such as autism spectrum disorder (ASD) and intellectual disability (ID). However, the mechanism in which these factors control embryonic brain development is not clear.
RESULT: We found that RBM8a is critical for proliferation and differentiation in cortical neural progenitor cells (NPCs). RBM8a is highly expressed in the subventricular zone (SVZ) of the early embryonic cortex, suggesting that RBM8a may play a role in regulating NPCs. RBM8a overexpression stimulates embryonic NPC proliferation and suppresses neuronal differentiation. Conversely, knockdown of RBM8a in the neocortex reduces NPC proliferation and promotes premature neuronal differentiation. Moreover, overexpression of RBM8a suppresses cell cycle exit and keeps cortical NPCs in a proliferative state. To uncover the underlying mechanisms of this phenotype, genome-wide RNAseq was used to identify potential downstream genes of RBM8a in the brain, which have been implicated in autism and neurodevelopmental disorders. Interestingly, autism and schizophrenia risk genes are highly represented in downstream transcripts of RBM8a. In addition, RBM8a regulates multiple alternative splicing genes and NMD targets that are implicated in ASD. Taken together, this data suggests a novel role of RBM8a in the regulation of neurodevelopment.
CONCLUSIONS: Our studies provide some insight into causes of mental illnesses and will facilitate the development of new therapeutic strategies for neurodevelopmental illnesses.

PMID: 26094033 [PubMed - as supplied by publisher]

Current controversies in the relationships between autism and epilepsy.

June 21, 2015 - 8:31am
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Current controversies in the relationships between autism and epilepsy.

Epilepsy Behav. 2015 Jun;47:143-6

Authors: Besag FM

Abstract
The controversies that have arisen in endeavoring to establish the nature of the relationships between autism and epilepsy might be summarized in a few simple questions, most of which do not yet have clear, complete answers. Does epilepsy cause autism? Does autism cause epilepsy? Are there underlying brain mechanisms that predispose to both conditions? What is the role of genetics in this regard? What is the importance of prenatal, perinatal, and postnatal environmental factors? Do any of the proposed relationships between autism and epilepsy provide insight into useful management or treatment? Is the prognosis of either autism or epilepsy different when the other condition is also present? What is the role of additional comorbidities, such as intellectual impairment or attention deficit hyperactivity disorder, in the relationship between the two conditions and in influencing treatment choices? From the evidence currently available, it would appear that epilepsy can rarely be the cause of autistic features but is not the cause of autism in most cases. There is currently no credible mechanism for suggesting that autism might cause epilepsy. There is strong evidence for an underlying predisposition for both conditions, particularly arising from genetic investigations. However, many issues remain unresolved. Considering the amount of research that has been published in this area, it is surprising that so few definitive answers have been established. The papers in this issue's special section provide additional insights into the relationships between autism and epilepsy; while they do not provide answers to all the questions, they represent considerable progress in this area and, at the very least, give some strong indication of what research might, in the future, provide such answers.

PMID: 26091860 [PubMed - in process]

Transient DNMT1 suppression reveals hidden heritable marks in the genome.

June 19, 2015 - 8:01am
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Transient DNMT1 suppression reveals hidden heritable marks in the genome.

Nucleic Acids Res. 2015 Feb 18;43(3):1485-97

Authors: McGraw S, Zhang JX, Farag M, Chan D, Caron M, Konermann C, Oakes CC, Mohan KN, Plass C, Pastinen T, Bourque G, Chaillet JR, Trasler JM

Abstract
Genome-wide demethylation and remethylation of DNA during early embryogenesis is essential for development. Imprinted germline differentially methylated domains (gDMDs) established by sex-specific methylation in either male or female germ cells, must escape these dynamic changes and sustain precise inheritance of both methylated and unmethylated parental alleles. To identify other, gDMD-like sequences with the same epigenetic inheritance properties, we used a modified embryonic stem (ES) cell line that emulates the early embryonic demethylation and remethylation waves. Transient DNMT1 suppression revealed gDMD-like sequences requiring continuous DNMT1 activity to sustain a highly methylated state. Remethylation of these sequences was also compromised in vivo in a mouse model of transient DNMT1 loss in the preimplantation embryo. These novel regions, possessing heritable epigenetic features similar to imprinted-gDMDs are required for normal physiological and developmental processes and when disrupted are associated with disorders such as cancer and autism spectrum disorders. This study presents new perspectives on DNA methylation heritability during early embryo development that extend beyond conventional imprinted-gDMDs.

PMID: 25578964 [PubMed - indexed for MEDLINE]

Exposure to serotonin adversely affects oligodendrocyte development and myelination in vitro.

June 19, 2015 - 8:01am
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Exposure to serotonin adversely affects oligodendrocyte development and myelination in vitro.

J Neurochem. 2015 May;133(4):532-43

Authors: Fan LW, Bhatt A, Tien LT, Zheng B, Simpson KL, Lin RC, Cai Z, Kumar P, Pang Y

Abstract
Serotonin (5-hydroxytryptamine, 5-HT) has been implicated to play critical roles in early neural development. Recent reports have suggested that perinatal exposure to selective serotonin reuptake inhibitors (SSRIs) resulted in cortical network miswiring, abnormal social behavior, callosal myelin malformation, as well as oligodendrocyte (OL) pathology in rats. To gain further insight into the cellular and molecular mechanisms underlying SSRIs-induced OL and myelin abnormalities, we investigated the effect of 5-HT exposure on OL development, cell death, and myelination in cell culture models. First, we showed that 5-HT receptor 1A and 2A subtypes were expressed in OL lineages, using immunocytochemistry, Western blot, as well as intracellular Ca(2+) measurement. We then assessed the effect of serotonin exposure on the lineage development, expression of myelin proteins, cell death, and myelination, in purified OL and neuron-OL myelination cultures. For pure OL cultures, our results showed that 5-HT exposure led to disturbance of OL development, as indicated by aberrant process outgrowth and reduced myelin proteins expression. At higher doses, such exposure triggered a development-dependent cell death, as immature OLs exhibited increasing susceptibility to 5-HT treatment compared to OL progenitor cells (OPC). We showed further that 5-HT-induced immature OL death was mediated at least partially via 5-HT2A receptor, since cell death could be mimicked by 5-HT2A receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane hydrochloride, (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride, but atten-uated by pre-treatment with 5-HT2A receptor antagonist ritanserin. Utilizing a neuron-OL myelination co-culture model, our data showed that 5-HT exposure significantly reduced the number of myelinated internodes. In contrast to cell injury observed in pure OL cultures, 5-HT exposure did not lead to OL death or reduced OL density in neuron-OL co-cultures. However, abnormal patterns of contactin-associated protein (Caspr) clustering were observed at the sites of Node of Ranvier, suggesting that 5-HT exposure may affect other axon-derived factors for myelination. In summary, this is the first study to demonstrate that manipulation of serotonin levels affects OL development and myelination, which may contribute to altered neural connectivity noted in SSRIs-treated animals. The current in vitro study demonstrated that exposure to high level of serotonin (5-HT) led to aberrant oligodendrocyte (OL) development, cell injury, and myelination deficit. We propose that elevated extracellular serotonin levels in the fetal brain, such as upon the use of selective serotonin reuptake inhibitors (SSRIs) during pregnancy, may adversely affect OL development and/or myelination, thus contributing to altered neural connectivity seen in Autism Spectrum Disorders. OPC = oligodendrocyte progenitor cell.

PMID: 25382136 [PubMed - indexed for MEDLINE]

A novel ribosomopathy caused by dysfunction of RPL10 disrupts neurodevelopment and causes X-linked microcephaly in humans.

June 18, 2015 - 6:23am
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A novel ribosomopathy caused by dysfunction of RPL10 disrupts neurodevelopment and causes X-linked microcephaly in humans.

Genetics. 2014 Oct;198(2):723-33

Authors: Brooks SS, Wall AL, Golzio C, Reid DW, Kondyles A, Willer JR, Botti C, Nicchitta CV, Katsanis N, Davis EE

Abstract
Neurodevelopmental defects in humans represent a clinically heterogeneous group of disorders. Here, we report the genetic and functional dissection of a multigenerational pedigree with an X-linked syndromic disorder hallmarked by microcephaly, growth retardation, and seizures. Using an X-linked intellectual disability (XLID) next-generation sequencing diagnostic panel, we identified a novel missense mutation in the gene encoding 60S ribosomal protein L10 (RPL10), a locus associated previously with autism spectrum disorders (ASD); the p.K78E change segregated with disease under an X-linked recessive paradigm while, consistent with causality, carrier females exhibited skewed X inactivation. To examine the functional consequences of the p.K78E change, we modeled RPL10 dysfunction in zebrafish. We show that endogenous rpl10 expression is augmented in anterior structures, and that suppression decreases head size in developing morphant embryos, concomitant with reduced bulk translation and increased apoptosis in the brain. Subsequently, using in vivo complementation, we demonstrate that p.K78E is a loss-of-function variant. Together, our findings suggest that a mutation within the conserved N-terminal end of RPL10, a protein in close proximity to the peptidyl transferase active site of the 60S ribosomal subunit, causes severe defects in brain formation and function.

PMID: 25316788 [PubMed - indexed for MEDLINE]

Opposite risk patterns for autism and schizophrenia are associated with normal variation in birth size: phenotypic support for hypothesized diametric gene-dosage effects.

June 18, 2015 - 6:23am
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Opposite risk patterns for autism and schizophrenia are associated with normal variation in birth size: phenotypic support for hypothesized diametric gene-dosage effects.

Proc Biol Sci. 2014 Nov 7;281(1794):20140604

Authors: Byars SG, Stearns SC, Boomsma JJ

Abstract
Opposite phenotypic and behavioural traits associated with copy number variation and disruptions to imprinted genes with parent-of-origin effects have led to the hypothesis that autism and schizophrenia share molecular risk factors and pathogenic mechanisms, but a direct phenotypic comparison of how their risks covary has not been attempted. Here, we use health registry data collected on Denmark's roughly 5 million residents between 1978 and 2009 to detect opposing risks of autism and schizophrenia depending on normal variation (mean ± 1 s.d.) in adjusted birth size, which we use as a proxy for diametric gene-dosage variation in utero. Above-average-sized babies (weight, 3691-4090 g; length, 52.8-54.3 cm) had significantly higher risk for autism spectrum (AS) and significantly lower risk for schizophrenia spectrum (SS) disorders. By contrast, below-average-sized babies (2891-3290 g; 49.7-51.2 cm) had significantly lower risk for AS and significantly higher risk for SS disorders. This is the first study directly comparing autism and schizophrenia risks in the same population, and provides the first large-scale empirical support for the hypothesis that diametric gene-dosage effects contribute to these disorders. Only the kinship theory of genomic imprinting predicts the opposing risk patterns that we discovered, suggesting that molecular research on mental disease risk would benefit from considering evolutionary theory.

PMID: 25232142 [PubMed - indexed for MEDLINE]

High diagnostic yield of clinical exome sequencing in Middle Eastern patients with Mendelian disorders.

June 17, 2015 - 7:35am

High diagnostic yield of clinical exome sequencing in Middle Eastern patients with Mendelian disorders.

Hum Genet. 2015 Jun 16;

Authors: Yavarna T, Al-Dewik N, Al-Mureikhi M, Ali R, Al-Mesaifri F, Mahmoud L, Shahbeck N, Lakhani S, AlMulla M, Nawaz Z, Vitazka P, Alkuraya FS, Ben-Omran T

Abstract
Clinical exome sequencing (CES) has become an increasingly popular diagnostic tool in patients with heterogeneous genetic disorders, especially in those with neurocognitive phenotypes. Utility of CES in consanguineous populations has not yet been determined on a large scale. A clinical cohort of 149 probands from Qatar with suspected Mendelian, mainly neurocognitive phenotypes, underwent CES from July 2012 to June 2014. Intellectual disability and global developmental delay were the most common clinical presentations but our cohort displayed other phenotypes, such as epilepsy, dysmorphism, microcephaly and other structural brain anomalies and autism. A pathogenic or likely pathogenic mutation, including pathogenic CNVs, was identified in 89 probands for a diagnostic yield of 60 %. Consanguinity and positive family history predicted a higher diagnostic yield. In 5 % (7/149) of cases, CES implicated novel candidate disease genes (MANF, GJA9, GLG1, COL15A1, SLC35F5, MAGE4, NEUROG1). CES uncovered two coexisting genetic disorders in 4 % (6/149) and actionable incidental findings in 2 % (3/149) of cases. Average time to diagnosis was reduced from 27 to 5 months. CES, which already has the highest diagnostic yield among all available diagnostic tools in the setting of Mendelian disorders, appears to be particularly helpful diagnostically in the highly consanguineous Middle Eastern population.

PMID: 26077850 [PubMed - as supplied by publisher]

Detection of Chromosomal Aberrations in Clinical Practice: From Karyotype to Genome Sequence.

June 17, 2015 - 7:35am

Detection of Chromosomal Aberrations in Clinical Practice: From Karyotype to Genome Sequence.

Annu Rev Genomics Hum Genet. 2015 May 6;

Authors: Martin CL, Warburton D

Abstract
Since the inception of clinical cytogenetics in the late 1950s, the field has witnessed the evolution of multiple methodologies for the evaluation of chromosomal imbalances and rearrangements. From the replacement of solidly stained chromosomes by Giemsa banding (G-banding) to in situ hybridization and microarrays, each technique has sought to detect smaller and smaller chromosomal aberrations across the genome. Microarray analysis has revealed that copy-number variants-a class of mutation resulting from the loss (deletion) or gain (duplication) of genomic material that is >1 kb in size-are among the significant contributors to human disease and normal variation. Here, we evaluate the history and utility of various methodologies and their impact on the current practice of clinical cytogenetics. Expected final online publication date for the Annual Review of Genomics and Human Genetics Volume 16 is August 31, 2015. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.

PMID: 26077817 [PubMed - as supplied by publisher]

Disrupted intricacy of histone H3K4 methylation in neurodevelopmental disorders.

June 17, 2015 - 7:35am

Disrupted intricacy of histone H3K4 methylation in neurodevelopmental disorders.

Epigenomics. 2015 Jun;7(3):503-19

Authors: Vallianatos CN, Iwase S

Abstract
Methylation of histone H3 lysine 4 (H3K4me) is an intricately regulated posttranslational modification, which is broadly associated with enhancers and promoters of actively transcribed genomic loci. Recent advances in next-generation sequencing have identified a number of H3K4me regulators mutated in neurodevelopmental disorders including intellectual disabilities, autism spectrum disorders, and schizophrenia. Here, we aim to summarize the molecular function of H3K4me-regulating enzymes in brain development and function. We describe four H3K4me methyltransferases (KMT2A, KMT2C, KMT2D, KMT2F), four demethylases (KDM1A, KDM5A, KDM5B, KDM5C), and two reader proteins (PHF21A, PHF8) mutated in neurodevelopmental disorders. Understanding the role of these chromatin regulators in the development and maintenance of neural connections will advance therapeutic opportunities for prevention and treatment of these lifelong neurodevelopmental disorders.

PMID: 26077434 [PubMed - in process]

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