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Additional post-natal diagnoses following antenatal diagnosis of isolated cleft lip +/- palate.

March 16, 2014 - 9:10pm
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Additional post-natal diagnoses following antenatal diagnosis of isolated cleft lip +/- palate.

Arch Dis Child Fetal Neonatal Ed. 2014 Mar 13;

Authors: Burnell L, Verchere C, Pugash D, Loock C, Robertson S, Lehman A

Abstract
INTRODUCTION: Cleft lip with or without palate (CLP) can be diagnosed antenatally through ultrasound, and may be categorised as apparently isolated versus associated with other malformations. Limited data exist on the long-term outcomes following antenatal diagnosis of apparently isolated CLP.
AIM: This study examined the long-term post-natal outcomes of CLP when found in isolation antenatally, in order to determine the rates of unexpected additional anomalies, developmental delay or genetic syndromes.
PATIENTS AND METHODS: A retrospective chart review of antenatal and post-natal medical charts was completed for a ten-year period between January 2000 and December 2009. At least 2 years of available post-natal clinical information was required for inclusion in the study.
RESULTS: A total of 97 cases of antenatally isolated CLP were ascertained. Fifteen pregnancies were terminated. Follow-up data were available for 81 liveborns, though 4 were lost to follow-up prior to 2 years of age. Twelve of the 77 children meeting study criteria were identified to have other major malformations and/or developmental disability either later in the pregnancy or post-natally. Findings included familial clefting syndromes, trisomy 21, autism spectrum disorders, brain malformations, fetal alcohol syndrome and Kabuki syndrome, among other findings. Another 11 children had additional anomalies of minor impact. Examples of findings include a perimembranous ventricular septal defect, mild unilateral optic nerve hypoplasia, mild pulmonary artery stenosis with a small atrial septal defect, and transient delays in fine and gross motor skills. No children with clefting of the lip only had major additional diagnoses.
CONCLUSIONS: The frequency of an associated complex developmental disorder following an otherwise reassuring fetal ultrasound is around 15%. A few diagnoses could be suspected at the antenatal assessment based on family history or exposures. Our study is lacking comprehensive assessment on the yield of genomic microarray testing for this population.

PMID: 24625434 [PubMed - as supplied by publisher]

Genetic aspects of autism spectrum disorders: insights from animal models.

March 10, 2014 - 2:35am
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Genetic aspects of autism spectrum disorders: insights from animal models.

Front Cell Neurosci. 2014;8:58

Authors: Banerjee S, Riordan M, Bhat MA

Abstract
Autism spectrum disorders (ASDs) are a complex neurodevelopmental disorder that display a triad of core behavioral deficits including restricted interests, often accompanied by repetitive behavior, deficits in language and communication, and an inability to engage in reciprocal social interactions. ASD is among the most heritable disorders but is not a simple disorder with a singular pathology and has a rather complex etiology. It is interesting to note that perturbations in synaptic growth, development, and stability underlie a variety of neuropsychiatric disorders, including ASD, schizophrenia, epilepsy, and intellectual disability. Biological characterization of an increasing repertoire of synaptic mutants in various model organisms indicates synaptic dysfunction as causal in the pathophysiology of ASD. Our understanding of the genes and genetic pathways that contribute toward the formation, stabilization, and maintenance of functional synapses coupled with an in-depth phenotypic analysis of the cellular and behavioral characteristics is therefore essential to unraveling the pathogenesis of these disorders. In this review, we discuss the genetic aspects of ASD emphasizing on the well conserved set of genes and genetic pathways implicated in this disorder, many of which contribute to synapse assembly and maintenance across species. We also review how fundamental research using animal models is providing key insights into the various facets of human ASD.

PMID: 24605088 [PubMed - as supplied by publisher]

Diagnosing Young Children with Autism.

March 10, 2014 - 2:35am
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Diagnosing Young Children with Autism.

Int J Dev Neurosci. 2014 Mar 3;

Authors: Matson JL, Goldin RL

Abstract
The starting point for any research on Autism Spectrum Disorder (ASD) involves the identification of people who evince the condition. From this point flows research on symptom presentation, genetics, epidemiology, animal models, treatment efficacy, and many other important topics. Major advances have been made in differential diagnosis, particularly with young children. This fact is particularly important since ASD is a life long condition. This review documents recent advances and the current state of research on this topic.

PMID: 24603281 [PubMed - as supplied by publisher]

DAWN: A framework to identify autism genes and subnetworks using gene expression and genetics.

March 10, 2014 - 2:35am
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DAWN: A framework to identify autism genes and subnetworks using gene expression and genetics.

Mol Autism. 2014 Mar 6;5(1):22

Authors: Liu L, Lei J, Sanders SJ, Willsey AJ, Kou Y, Cicek AE, Klei L, Lu C, He X, Li M, Muhle RA, Ma'ayan A, Noonan JP, Sestan N, McFadden KA, State MW, Buxbaum JD, Devlin B, Roeder K

Abstract
BACKGROUND: \emph{De novo} loss-of-function (dnLoF) mutations are found twofold more often in autism spectrum disorder (ASD) probands than their unaffected siblings. Multiple independent dnLoF mutations in the same gene implicate the gene in risk and hence provide a systematic, albeit arduous, path forward for ASD genetics. It is likely that using additional non-genetic data will enhance the ability to identify ASD genes.
METHODS: To accelerate the search for ASD genes, we developed a novel algorithm, DAWN, to model two kinds of data: rare variations from exome sequencing and gene co-expression in the mid-fetal prefrontal and motor-somatosensory neocortex, a critical nexus for risk. The algorithm casts the ensemble data as a hidden Markov random field in which the graph structure is determined by gene co-expression and it combines these interrelationships with node-specific observations, namely gene identity, expression, genetic data and the estimated effect on risk.
RESULTS: Using currently available genetic data and a specific developmental time period for gene co-expression, DAWN identified 127 genes that plausibly affect risk, and a set of likely ASD subnetworks. Validation experiments making use of published targeted resequencing results demonstrate its efficacy in reliably predicting ASD genes. DAWN also successfully predicts known ASD genes, not included in the genetic data used to create the model.
CONCLUSIONS: Validation studies demonstrate that DAWN is effective in predicting ASD genes and subnetworks by leveraging genetic and gene expression data. The findings reported here implicate neurite extension and neuronal arborization as risks for ASD. Using DAWN on emerging ASD sequence data and gene expression data from other brain regions and tissues would likely identify novel ASD genes. DAWN can also be used for other complex disorders to identify genes and subnetworks in those disorders.

PMID: 24602502 [PubMed - as supplied by publisher]

Dendritic arborization and spine dynamics are abnormal in the mouse model of MECP2 duplication syndrome.

March 10, 2014 - 2:35am
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Dendritic arborization and spine dynamics are abnormal in the mouse model of MECP2 duplication syndrome.

J Neurosci. 2013 Dec 11;33(50):19518-33

Authors: Jiang M, Ash RT, Baker SA, Suter B, Ferguson A, Park J, Rudy J, Torsky SP, Chao HT, Zoghbi HY, Smirnakis SM

Abstract
MECP2 duplication syndrome is a childhood neurological disorder characterized by intellectual disability, autism, motor abnormalities, and epilepsy. The disorder is caused by duplications spanning the gene encoding methyl-CpG-binding protein-2 (MeCP2), a protein involved in the modulation of chromatin and gene expression. MeCP2 is thought to play a role in maintaining the structural integrity of neuronal circuits. Loss of MeCP2 function causes Rett syndrome and results in abnormal dendritic spine morphology and decreased pyramidal dendritic arbor complexity and spine density. The consequences of MeCP2 overexpression on dendritic pathophysiology remain unclear. We used in vivo two-photon microscopy to characterize layer 5 pyramidal neuron spine turnover and dendritic arborization as a function of age in transgenic mice expressing the human MECP2 gene at twice the normal levels of MeCP2 (Tg1; Collins et al., 2004). We found that spine density in terminal dendritic branches is initially higher in young Tg1 mice but falls below control levels after postnatal week 12, approximately correlating with the onset of behavioral symptoms. Spontaneous spine turnover rates remain high in older Tg1 animals compared with controls, reflecting the persistence of an immature state. Both spine gain and loss rates are higher, with a net bias in favor of spine elimination. Apical dendritic arbors in both simple- and complex-tufted layer 5 Tg1 pyramidal neurons have more branches of higher order, indicating that MeCP2 overexpression induces dendritic overgrowth. P70S6K was hyperphosphorylated in Tg1 somatosensory cortex, suggesting that elevated mTOR signaling may underlie the observed increase in spine turnover and dendritic growth.

PMID: 24336718 [PubMed - indexed for MEDLINE]

Identification of two novel Shank3 transcripts in the developing mouse neocortex.

March 10, 2014 - 2:35am
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Identification of two novel Shank3 transcripts in the developing mouse neocortex.

J Neurochem. 2014 Jan;128(2):280-93

Authors: Waga C, Asano H, Sanagi T, Suzuki E, Nakamura Y, Tsuchiya A, Itoh M, Goto Y, Kohsaka S, Uchino S

Abstract
SHANK3 is a synaptic scaffolding protein enriched in the post-synaptic density of excitatory synapses. Since several SHANK3 mutations have been identified in a particular phenotypic group of patients with autism spectrum disorder (ASD), SHANK3 is strongly suspected of being involved in the pathogenesis and neuropathology of ASD. Several SHANK3 isoforms are known to be produced in the developing brain, but they have not been fully investigated. Here, we identified two different amino-terminus truncated Shank3 transcripts. One transcript, designated as Shank3c-3, produces an isoform that contains the entire carboxyl-terminus, but the other transcript, designated as Shank3c-4, produces a carboxyl-terminus truncated isoform. During development, expression of the novel Shank3 transcripts increased after birth, transiently decreased at P14 and then gradually increased again thereafter. We also determined that methyl CpG-binding protein 2 (MeCP2) is involved in regulating expression of the novel Shank3 transcripts. MeCP2 is a transcriptional regulator that has been identified as the causative molecule of Rett syndrome, a neurodevelopmental disorder that includes autistic behavior. We demonstrated a difference between the expression of the novel Shank3 transcripts in wild-type mice and Mecp2-deficient mice. These findings suggest that the SHANK3 isoforms may be implicated in the synaptic abnormality in Rett syndrome. SHANK3 is a synaptic scaffolding protein and is suspected of being implicated in the pathogenesis and neuropathology of ASD. We here identified two different amino-terminus truncated Shank3 transcripts, Shank3c-3 and Shank3c-4, expressed from the intron 10 of the Shank3 gene, and also suggested the epigenetic regulation of their expression via methyl CpG-binding protein 2 (MeCP2) that has been identified as the causative molecule of Rett syndrome.

PMID: 24164323 [PubMed - indexed for MEDLINE]

Brain Region-Specific Expression of MeCP2 Isoforms Correlates with DNA Methylation within Mecp2 Regulatory Elements.

March 7, 2014 - 4:12pm
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Brain Region-Specific Expression of MeCP2 Isoforms Correlates with DNA Methylation within Mecp2 Regulatory Elements.

PLoS One. 2014;9(3):e90645

Authors: Olson CO, Zachariah RM, Ezeonwuka CD, Liyanage VR, Rastegar M

Abstract
MeCP2 is a critical epigenetic regulator in brain and its abnormal expression or compromised function leads to a spectrum of neurological disorders including Rett Syndrome and autism. Altered expression of the two MeCP2 isoforms, MeCP2E1 and MeCP2E2 has been implicated in neurological complications. However, expression, regulation and functions of the two isoforms are largely uncharacterized. Previously, we showed the role of MeCP2E1 in neuronal maturation and reported MeCP2E1 as the major protein isoform in the adult mouse brain, embryonic neurons and astrocytes. Recently, we showed that DNA methylation at the regulatory elements (REs) within the Mecp2 promoter and intron 1 impact the expression of Mecp2 isoforms in differentiating neural stem cells. This current study is aimed for a comparative analysis of temporal, regional and cell type-specific expression of MeCP2 isoforms in the developing and adult mouse brain. MeCP2E2 displayed a later expression onset than MeCP2E1 during mouse brain development. In the adult female and male brain hippocampus, both MeCP2 isoforms were detected in neurons, astrocytes and oligodendrocytes. Furthermore, MeCP2E1 expression was relatively uniform in different brain regions (olfactory bulb, striatum, cortex, hippocampus, thalamus, brainstem and cerebellum), whereas MeCP2E2 showed differential enrichment in these brain regions. Both MeCP2 isoforms showed relatively similar distribution in these brain regions, except for cerebellum. Lastly, a preferential correlation was observed between DNA methylation at specific CpG dinucleotides within the REs and Mecp2 isoform-specific expression in these brain regions. Taken together, we show that MeCP2 isoforms display differential expression patterns during brain development and in adult mouse brain regions. DNA methylation patterns at the Mecp2 REs may impact this differential expression of Mecp2/MeCP2 isoforms in brain regions. Our results significantly contribute towards characterizing the expression profiles of Mecp2/MeCP2 isoforms and thereby provide insights on the potential role of MeCP2 isoforms in the developing and adult brain.

PMID: 24594659 [PubMed - in process]

Heterogeneous Pattern of Selective Pressure for PRRT2 in Human Populations, but No Association with Autism Spectrum Disorders.

March 7, 2014 - 4:12pm
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Heterogeneous Pattern of Selective Pressure for PRRT2 in Human Populations, but No Association with Autism Spectrum Disorders.

PLoS One. 2014;9(3):e88600

Authors: Huguet G, Nava C, Lemière N, Patin E, Laval G, Ey E, Brice A, Leboyer M, Szepetowski P, Gillberg C, Depienne C, Delorme R, Bourgeron T

Abstract
Inherited and de novo genomic imbalances at chromosome 16p11.2 are associated with autism spectrum disorders (ASD), but the causative genes remain unknown. Among the genes located in this region, PRRT2 codes for a member of the synaptic SNARE complex that allows the release of synaptic vesicles. PRRT2 is a candidate gene for ASD since homozygote mutations are associated with intellectual disability and heterozygote mutations cause benign infantile seizures, paroxysmal dyskinesia, or hemiplegic migraine. Here, we explored the contribution of PRRT2 mutations in ASD by screening its coding part in a large sample of 1578 individuals including 431 individuals with ASD, 186 controls and 961 individuals from the human genome Diversity Panel. We detected 24 nonsynonymous variants, 1 frameshift (A217PfsX8) and 1 in-frame deletion of 6 bp (p.A361_P362del). The frameshift mutation was observed in a control with no history of neurological or psychiatric disorders. The p.A361_P362del was observed in two individuals with autism from sub-Saharan African origin. Overall, the frequency of PRRT2 deleterious variants was not different between individuals with ASD and controls. Remarkably, PRRT2 displays a highly significant excess of nonsynonymous (pN) vs synonymous (pS) mutations in Asia (pN/pS = 4.85) and Europe (pN/pS = 1.62) compared with Africa (pN/pS = 0.26; Asia vs Africa: P = 0.000087; Europe vs Africa P = 0.00035; Europe vs Asia P = P = 0.084). We also showed that whole genome amplification performed through rolling cycle amplification could artificially introduce the A217PfsX8 mutation indicating that this technology should not be performed prior to PRRT2 mutation screening. In summary, our results do not support a role for PRRT2 coding sequence variants in ASD, but provide an ascertainment of its genetic variability in worldwide populations that should help researchers and clinicians to better investigate the role of PRRT2 in human diseases.

PMID: 24594579 [PubMed - in process]

Autism and specific language impairment: to know what we see, or how your sample determines what you observe.

March 7, 2014 - 4:12pm
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Autism and specific language impairment: to know what we see, or how your sample determines what you observe.

Am J Psychiatry. 2014 Jan 1;171(1):5-8

Authors: Kim YS

PMID: 24399420 [PubMed - indexed for MEDLINE]

A genome scan for loci shared by autism spectrum disorder and language impairment.

March 7, 2014 - 4:12pm
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A genome scan for loci shared by autism spectrum disorder and language impairment.

Am J Psychiatry. 2014 Jan 1;171(1):72-81

Authors: Bartlett CW, Hou L, Flax JF, Hare A, Cheong SY, Fermano Z, Zimmerman-Bier B, Cartwright C, Azaro MA, Buyske S, Brzustowicz LM

Abstract
OBJECTIVE: The authors conducted a genetic linkage study of families that have both autism spectrum disorder (ASD) and language-impaired probands to find common communication impairment loci. The hypothesis was that these families have a high genetic loading for impairments in language ability, thus influencing the language and communication deficits of the family members with ASD. Comprehensive behavioral phenotyping of the families also enabled linkage analysis of quantitative measures, including normal, subclinical, and disordered variation in all family members for the three general autism symptom domains: social, communication, and compulsive behaviors.
METHOD: The primary linkage analysis coded persons with either ASD or specific language impairment as "affected." The secondary linkage analysis consisted of quantitative metrics of autism-associated behaviors capturing normal to clinically severe variation, measured in all family members.
RESULTS: Linkage to language phenotypes was established at two novel chromosomal loci, 15q23-26 and 16p12. The secondary analysis of normal and disordered quantitative variation in social and compulsive behaviors established linkage to two loci for social behaviors (at 14q and 15q) and one locus for repetitive behaviors (at 13q).
CONCLUSION: These data indicate shared etiology of ASD and specific language impairment at two novel loci. Additionally, nonlanguage phenotypes based on social aloofness and rigid personality traits showed compelling evidence for linkage in this study group. Further genetic mapping is warranted at these loci.

PMID: 24170272 [PubMed - indexed for MEDLINE]

Reduced juvenile long-term depression in tuberous sclerosis complex is mitigated in adults by compensatory recruitment of mGluR5 and Erk signaling.

March 7, 2014 - 4:12pm
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Reduced juvenile long-term depression in tuberous sclerosis complex is mitigated in adults by compensatory recruitment of mGluR5 and Erk signaling.

PLoS Biol. 2013;11(8):e1001627

Authors: Potter WB, Basu T, O'Riordan KJ, Kirchner A, Rutecki P, Burger C, Roopra A

Abstract
Tuberous sclerosis complex (TSC) is a multisystem genetic disease that manifests with mental retardation, tumor formation, autism, and epilepsy. Heightened signaling through the mammalian target of rapamycin (mTOR) pathway is involved in TSC pathology, however it remains unclear how other signaling pathways are perturbed and contribute to disease symptoms. Reduced long-term depression (LTD) was recently reported in TSC mutant mice. We find that although reduced LTD is a feature of the juvenile mutant hippocampus, heightened expression of metabotropic glutamate receptor 5 and constitutively activated Erk signaling in the adult hippocampus drives wild-type levels of LTD. Increased mGluR5 and Erk results in a novel mTOR-independent LTD in CA1 hippocampus of adult mice, and contributes to the development of epileptiform bursting activity in the TSC2(+/-) CA3 region of the hippocampus. Inhibition of mGluR5 or Erk signaling restores appropriate mTOR-dependence to LTD, and significantly reduces epileptiform bursting in TSC2(+/-) hippocampal slices. We also report that adult TSC2(+/-) mice exhibit a subtle perseverative behavioral phenotype that is eliminated by mGluR5 antagonism. These findings highlight the potential of modulating the mGluR5-Erk pathway in a developmental stage-specific manner to treat TSC.

PMID: 23966835 [PubMed - indexed for MEDLINE]

mGluR5 ablation in cortical glutamatergic neurons increases novelty-induced locomotion.

March 7, 2014 - 4:12pm
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mGluR5 ablation in cortical glutamatergic neurons increases novelty-induced locomotion.

PLoS One. 2013;8(8):e70415

Authors: Jew CP, Wu CS, Sun H, Zhu J, Huang JY, Yu D, Justice NJ, Lu HC

Abstract
The group I metabotropic glutamate receptor 5 (mGluR5) has been implicated in the pathology of various neurological disorders including schizophrenia, ADHD, and autism. mGluR5-dependent synaptic plasticity has been described at a variety of neural connections and its signaling has been implicated in several behaviors. These behaviors include locomotor reactivity to novel environment, sensorimotor gating, anxiety, and cognition. mGluR5 is expressed in glutamatergic neurons, inhibitory neurons, and glia in various brain regions. In this study, we show that deleting mGluR5 expression only in principal cortical neurons leads to defective cannabinoid receptor 1 (CB1R) dependent synaptic plasticity in the prefrontal cortex. These cortical glutamatergic mGluR5 knockout mice exhibit increased novelty-induced locomotion, and their locomotion can be further enhanced by treatment with the psychostimulant methylphenidate. Despite a modest reduction in repetitive behaviors, cortical glutamatergic mGluR5 knockout mice are normal in sensorimotor gating, anxiety, motor balance/learning and fear conditioning behaviors. These results show that mGluR5 signaling in cortical glutamatergic neurons is required for precisely modulating locomotor reactivity to a novel environment but not for sensorimotor gating, anxiety, motor coordination, several forms of learning or social interactions.

PMID: 23940572 [PubMed - indexed for MEDLINE]

Post-axial polydactyly type A2, overgrowth and autistic traits associated with a chromosome 13q31.3 microduplication encompassing miR-17-92 and GPC5.

March 7, 2014 - 4:12pm
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Post-axial polydactyly type A2, overgrowth and autistic traits associated with a chromosome 13q31.3 microduplication encompassing miR-17-92 and GPC5.

Eur J Med Genet. 2013 Aug;56(8):452-7

Authors: Kannu P, Campos-Xavier AB, Hull D, Martinet D, Ballhausen D, Bonafé L

Abstract
Genomic rearrangements at chromosome 13q31.3q32.1 have been associated with digital anomalies, dysmorphic features, and variable degree of mental disability. Microdeletions leading to haploinsufficiency of miR17∼92, a cluster of micro RNA genes closely linked to GPC5 in both mouse and human genomes, has recently been associated with digital anomalies in the Feingold like syndrome. Here, we report on a boy with familial dominant post-axial polydactyly (PAP) type A, overgrowth, significant facial dysmorphisms and autistic traits who carries the smallest germline microduplication known so far in that region. The microduplication encompasses the whole miR17∼92 cluster and the first 5 exons of GPC5. This report supports the newly recognized role of miR17∼92 gene dosage in digital developmental anomalies, and suggests a possible role of GPC5 in growth regulation and in cognitive development.

PMID: 23792790 [PubMed - indexed for MEDLINE]

Synaptic and extrasynaptic location of the receptor tyrosine kinase met during postnatal development in the mouse neocortex and hippocampus.

March 7, 2014 - 4:12pm
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Synaptic and extrasynaptic location of the receptor tyrosine kinase met during postnatal development in the mouse neocortex and hippocampus.

J Comp Neurol. 2013 Oct 1;521(14):3241-59

Authors: Eagleson KL, Milner TA, Xie Z, Levitt P

Abstract
MET, a replicated autism risk gene, encodes a pleiotropic receptor tyrosine kinase implicated in multiple cellular processes during development and following injury. Previous studies suggest that Met modulates excitatory synapse development in the neocortex and hippocampus, although the underlying mechanism is unknown. The peak of Met expression corresponds to the period of process outgrowth and synaptogenesis, with robust expression in hippocampal and neocortical neuropil. Resolving whether neuropil expression represents presynaptic, postsynaptic or glial localization provides insight into potential mechanisms of Met action. The subcellular distribution of Met was characterized using complementary ultrastructural, in situ proximity ligation assay (PLA), and biochemical approaches. At postnatal day (P) 7, immunoelectron microscopy revealed near-equivalent proportions of Met-immunoreactive pre- (axons and terminals) and postsynaptic (dendritic shafts and spines) profiles in the stratum radiatum in the hippocampal CA1 region. Staining was typically in elements in which the corresponding pre- or postsynaptic apposition was unlabeled. By P21, Met-immunoreactive presynaptic profiles predominated and ~20% of Met-expressing profiles were glial. A different distribution of Met-immunoreactive profiles was observed in layer V of somatosensory cortex: Met-labeled spines were rare and a smaller proportion of glial profiles expressed Met. Strikingly, Met-immunoreactive presynaptic profiles predominated over postsynaptic profiles as early as P7. PLA analysis of neurons in vitro and biochemical analysis of tissue subsynaptic fractions confirmed the localization of Met in specific synaptic subcompartments. The study demonstrates that Met is enriched at synapses during development and its activation may modulate synapse formation and stability through both pre- and postsynaptic mechanisms.

PMID: 23787772 [PubMed - indexed for MEDLINE]

Genotype-phenotype analysis of 18q12.1-q12.2 copy number variation in autism.

March 7, 2014 - 4:12pm
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Genotype-phenotype analysis of 18q12.1-q12.2 copy number variation in autism.

Eur J Med Genet. 2013 Aug;56(8):420-5

Authors: Wang P, Carrion P, Qiao Y, Tyson C, Hrynchak M, Calli K, Lopez-Rangel E, Andrieux J, Delobel B, Duban-Bedu B, Thuresson AC, Annerén G, Liu X, Rajcan-Separovic E, Suzanne Lewis ME

Abstract
Autism Spectrum Disorders (ASD) are complex neurodevelopmental conditions characterized by delays in social interactions and communication as well as displays of restrictive/repetitive interests. DNA copy number variants have been identified as a genomic susceptibility factor in ASDs and imply significant genetic heterogeneity. We report a 7-year-old female with ADOS-G and ADI-R confirmed autistic disorder harbouring a de novo 4 Mb duplication (18q12.1). Our subject displays severely deficient expressive language, stereotypic and repetitive behaviours, mild intellectual disability (ID), focal epilepsy, short stature and absence of significant dysmorphic features. Search of the PubMed literature and DECIPHER database identified 4 additional cases involving 18q12.1 associated with autism and/or ID that overlap our case: one duplication, two deletions and one balanced translocation. Notably, autism and ID are seen with genomic gain or loss at 18q12.1, plus epilepsy and short stature in duplication cases, and hypotonia and tall stature in deletion cases. No consistent dysmorphic features were noted amongst the reviewed cases. We review prospective ASD/ID candidate genes integral to 18q12.1, including those coding for the desmocollin/desmoglein cluster, ring finger proteins 125 and 138, trafficking protein particle complex 8 and dystrobrevin-alpha. The collective clinical and molecular features common to microduplication 18q12.1 suggest that dosage-sensitive, position or contiguous gene effects may be associated in the etiopathogenesis of this autism-ID-epilepsy syndrome.

PMID: 23727450 [PubMed - indexed for MEDLINE]

What's in the pipeline? Drugs in development for autism spectrum disorder.

March 5, 2014 - 6:22am

What's in the pipeline? Drugs in development for autism spectrum disorder.

Neuropsychiatr Dis Treat. 2014;10:371-381

Authors: Sung M, Chin CH, Lim CG, Liew HS, Lim CS, Kashala E, Weng SJ

Abstract
Autism Spectrum Disorder (ASD) is a complex neurodevelopmental disorder with both core symptoms and associated symptoms (eg, irritability, aggression, and comorbidities) that affect both the individual and the family/systems around them. There have been recent advances in the understanding of the underlying pathophysiology of ASD pertaining to genetics, epigenetics, neurological, hormonal, and environmental factors that contribute to the difficulties found in individuals with ASD. With this improved understanding, there has been a shift in the application of psychopharmacology in ASD and its related disorders. A literature review was conducted to examine research published in the last 5 years between different classes of psychotropic medications and ASD. The broad scope of the existing literature for the use of conventional medications is summarized and novel medications are discussed.

PMID: 24591832 [PubMed - as supplied by publisher]

A Higher Mutational Burden in Females Supports a "Female Protective Model" in Neurodevelopmental Disorders.

March 4, 2014 - 6:00am

A Higher Mutational Burden in Females Supports a "Female Protective Model" in Neurodevelopmental Disorders.

Am J Hum Genet. 2014 Feb 26;

Authors: Jacquemont S, Coe BP, Hersch M, Duyzend MH, Krumm N, Bergmann S, Beckmann JS, Rosenfeld JA, Eichler EE

Abstract
Increased male prevalence has been repeatedly reported in several neurodevelopmental disorders (NDs), leading to the concept of a "female protective model." We investigated the molecular basis of this sex-based difference in liability and demonstrated an excess of deleterious autosomal copy-number variants (CNVs) in females compared to males (odds ratio [OR] = 1.46, p = 8 × 10(-10)) in a cohort of 15,585 probands ascertained for NDs. In an independent autism spectrum disorder (ASD) cohort of 762 families, we found a 3-fold increase in deleterious autosomal CNVs (p = 7 × 10(-4)) and an excess of private deleterious single-nucleotide variants (SNVs) in female compared to male probands (OR = 1.34, p = 0.03). We also showed that the deleteriousness of autosomal SNVs was significantly higher in female probands (p = 0.0006). A similar bias was observed in parents of probands ascertained for NDs. Deleterious CNVs (>400 kb) were maternally inherited more often (up to 64%, p = 10(-15)) than small CNVs < 400 kb (OR = 1.45, p = 0.0003). In the ASD cohort, increased maternal transmission was also observed for deleterious CNVs and SNVs. Although ASD females showed higher mutational burden and lower cognition, the excess mutational burden remained, even after adjustment for those cognitive differences. These results strongly suggest that females have an increased etiological burden unlinked to rare deleterious variants on the X chromosome. Carefully phenotyped and genotyped cohorts will be required for identifying the symptoms, which show gender-specific liability to mutational burden.

PMID: 24581740 [PubMed - as supplied by publisher]

A genotype-first approach to defining the subtypes of a complex disease.

March 4, 2014 - 6:00am

A genotype-first approach to defining the subtypes of a complex disease.

Cell. 2014 Feb 27;156(5):872-7

Authors: Stessman HA, Bernier R, Eichler EE

Abstract
Medical genetics typically entails the detailed characterization of a patient's phenotypes followed by genotyping to discover the responsible gene or mutation. Here, we propose that the systematic discovery of genetic variants associated with complex diseases such as autism are progressing to a point where a reverse strategy may be fruitful in assigning the pathogenic effects of many different genes and in determining whether particular genotypes manifest as clinically recognizable phenotypes. This "genotype-first" approach for complex disease necessitates the development of large, highly integrated networks of researchers, clinicians, and patient families, with the promise of improved therapies for subsets of patients.

PMID: 24581488 [PubMed - in process]

Rit subfamily small GTPases: regulators in neuronal differentiation and survival.

March 4, 2014 - 6:00am
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Rit subfamily small GTPases: regulators in neuronal differentiation and survival.

Cell Signal. 2013 Oct;25(10):2060-8

Authors: Shi GX, Cai W, Andres DA

Abstract
Ras family small GTPases serve as binary molecular switches to regulate a broad array of cellular signaling cascades, playing essential roles in a vast range of normal physiological processes, with dysregulation of numerous Ras-superfamily G-protein-dependent regulatory cascades underlying the development of human disease. However, the physiological function for many "orphan" Ras-related GTPases remain poorly characterized, including members of the Rit subfamily GTPases. Rit is the founding member of a novel branch of the Ras subfamily, sharing close homology with the neuronally expressed Rin and Drosophila Ric GTPases. Here, we highlight recent studies using transgenic and knockout animal models which have begun to elucidate the physiological roles for the Rit subfamily, including emerging roles in the regulation of neuronal morphology and cellular survival signaling, and discuss new genetic data implicating Rit and Rin signaling in disorders such as cancer, Parkinson's disease, autism, and schizophrenia.

PMID: 23770287 [PubMed - indexed for MEDLINE]

Reorganization of circuits underlying cerebellar modulation of prefrontal cortical dopamine in mouse models of autism spectrum disorder.

March 4, 2014 - 6:00am
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Reorganization of circuits underlying cerebellar modulation of prefrontal cortical dopamine in mouse models of autism spectrum disorder.

Cerebellum. 2013 Aug;12(4):547-56

Authors: Rogers TD, Dickson PE, McKimm E, Heck DH, Goldowitz D, Blaha CD, Mittleman G

Abstract
Imaging, clinical, and pre-clinical studies have provided ample evidence for a cerebellar involvement in cognitive brain function including cognitive brain disorders, such as autism and schizophrenia. We previously reported that cerebellar activity modulates dopamine release in the mouse medial prefrontal cortex (mPFC) via two distinct pathways: (1) cerebellum to mPFC via dopaminergic projections from the ventral tegmental area (VTA) and (2) cerebellum to mPFC via glutamatergic projections from the mediodorsal and ventrolateral thalamus (ThN md and vl). The present study compared functional adaptations of cerebello-cortical circuitry following developmental cerebellar pathology in a mouse model of developmental loss of Purkinje cells (Lurcher) and a mouse model of fragile X syndrome (Fmr1 KO mice). Fixed potential amperometry was used to measure mPFC dopamine release in response to cerebellar electrical stimulation. Mutant mice of both strains showed an attenuation in cerebellar-evoked mPFC dopamine release compared to respective wildtype mice. This was accompanied by a functional reorganization of the VTA and thalamic pathways mediating cerebellar modulation of mPFC dopamine release. Inactivation of the VTA pathway by intra-VTA lidocaine or kynurenate infusions decreased dopamine release by 50 % in wildtype and 20-30 % in mutant mice of both strains. Intra-ThN vl infusions of either drug decreased dopamine release by 15 % in wildtype and 40 % in mutant mice of both strains, while dopamine release remained relatively unchanged following intra-ThN md drug infusions. These results indicate a shift in strength towards the thalamic vl projection, away from the VTA. Thus, cerebellar neuropathologies associated with autism spectrum disorders may cause a reduction in cerebellar modulation of mPFC dopamine release that is related to a reorganization of the mediating neuronal pathways.

PMID: 23436049 [PubMed - indexed for MEDLINE]

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