Partial deletion of ANKRD11 results in the KBG phenotype distinct from the 16q24.3 microdeletion syndrome.

Am J Med Genet A. 2013 Mar 12;

Authors: Khalifa M, Stein J, Grau L, Nelson V, Meck J, Aradhya S, Duby J

Abstract
KBG syndrome (OMIM 148050) is a very rare genetic disorder characterized by macrodontia, distinctive craniofacial abnormalities, short stature, intellectual disability, skeletal, and neurologic involvement. Approximately 60 patients have been reported since it was first described in 1975. Recently mutations in ANKRD11 have been documented in patients with KBG syndrome, and it has been proposed that haploinsufficiency of ANKRD11 is the cause of this syndrome. In addition, copy number variation in the 16q24.3 region that includes ANKRD11 results in a variable phenotype that overlaps with KBG syndrome and also includes autism spectrum disorders and other dysmorphic facial features. In this report we present a 2½-year-old African American male with features highly suggestive of KBG syndrome. Genomic microarray identified an intragenic 154 kb deletion at 16q24.3 within ANKRD11. This child's mother was mosaic for the same deletion (present in approximately 38% of cells) and exhibited a milder phenotype including macrodontia, short stature and brachydactyly. This family provides additional evidence that ANKRD11 causes KBG syndrome, and the mild phenotype in the mosaic form suggests that KBG phenotypes might be dose dependent, differentiating it from the more variable 16q24.3 microdeletion syndrome. This family has additional features that might expand the phenotype of KBG syndrome. © 2013 Wiley Periodicals, Inc.

PMID: 23494856 [PubMed - as supplied by publisher]

Modeling socially anhedonic syndromes: genetic and pharmacological manipulation of opioid neurotransmission in mice.

Transl Psychiatry. 2012;2:e155

Authors: Cinque C, Pondiki S, Oddi D, Di Certo MG, Marinelli S, Troisi A, Moles A, D'Amato FR

Abstract
Social anhedonia, or the diminished capacity to experience pleasure and reward from social affiliation, is a major symptom of different psychiatric disorders, including some forms of infantile autism and schizophrenia spectrum disorders. The brain opioid hypothesis of social attachment is a promising model for achieving insights into how neurobiological and developmental factors contribute to the regulation of social reward. In this study, genetic knocking-out and naltrexone (NTRX) treatment during the first 4 days of life were used to disrupt opioid neurotransmission in mouse pups and their attachment relationships with the mother. Both permanent (genetic) and transient (pharmacological) manipulations of opioid neurotransmission exerted long-term effects on social affiliation. When juveniles, both μ-opioid receptor knockout mice and NTRX-treated pups showed reduced interest in peers and no preference for socially rewarding environment. These results demonstrate that sociability in juvenile mice is highly dependent on the establishment during infancy of a positive affective relationship with their mothers and that opioid neurotransmission has a major role in the regulation of social hedonic capacity. If the validity of this animal model will be confirmed by future research, translational studies focusing on the interaction between early experience and opioid neurotransmission could provide useful insights for identifying endophenotypes of human psychiatric disorders associated with social anhedonia.

PMID: 22929597 [PubMed - indexed for MEDLINE]

Dosage effects of X and Y chromosomes on language and social functioning in children with supernumerary sex chromosome aneuploidies: implications for idiopathic language impairment and autism spectrum disorders.

J Child Psychol Psychiatry. 2012 Oct;53(10):1072-81

Authors: Lee NR, Wallace GL, Adeyemi EI, Lopez KC, Blumenthal JD, Clasen LS, Giedd JN

Abstract
BACKGROUND:  Supernumerary sex chromosome aneuploidies (X/Y-aneuploidies), the presence of extra X and/or Y chromosomes, are associated with heightened rates of language impairments and social difficulties. However, no single study has examined different language domains and social functioning in the same sample of children with tri-, tetra-, and pentasomy X/Y-aneuploidy. The current research sought to fill this gap in the literature and to examine dosage effects of X and Y chromosomes on language and social functioning.
METHODS: Participants included 110 youth with X/Y-aneuploidies (32 female) and 52 with typical development (25 female) matched on age (mean ∼12 years; range 4-22) and maternal education. Participants completed the Wechsler intelligence scales, and parents completed the children's communication checklist-2 and the social responsiveness scale to assess language skills and autistic traits, respectively.
RESULTS: Both supernumerary X and Y chromosomes were related to depressed structural and pragmatic language skills and increased autistic traits. The addition of a Y chromosome had a disproportionately greater impact on pragmatic language; the addition of one or more X chromosomes had a disproportionately greater impact on structural language.
CONCLUSIONS: Given that we link extra X chromosomes with structural language impairments and an extra Y chromosome with pragmatic language impairments, X/Y-aneuploidies may provide clues to genetic mechanisms contributing to idiopathic language impairment and autism spectrum disorders.

PMID: 22827287 [PubMed - indexed for MEDLINE]

GABAB-mediated rescue of altered excitatory-inhibitory balance, gamma synchrony and behavioral deficits following constitutive NMDAR-hypofunction.

Transl Psychiatry. 2012;2:e142

Authors: Gandal MJ, Sisti J, Klook K, Ortinski PI, Leitman V, Liang Y, Thieu T, Anderson R, Pierce RC, Jonak G, Gur RE, Carlson G, Siegel SJ

Abstract
Reduced N-methyl-D-aspartate-receptor (NMDAR) signaling has been associated with schizophrenia, autism and intellectual disability. NMDAR-hypofunction is thought to contribute to social, cognitive and gamma (30-80 Hz) oscillatory abnormalities, phenotypes common to these disorders. However, circuit-level mechanisms underlying such deficits remain unclear. This study investigated the relationship between gamma synchrony, excitatory-inhibitory (E/I) signaling, and behavioral phenotypes in NMDA-NR1(neo-/-) mice, which have constitutively reduced expression of the obligate NR1 subunit to model disrupted developmental NMDAR function. Constitutive NMDAR-hypofunction caused a loss of E/I balance, with an increase in intrinsic pyramidal cell excitability and a selective disruption of parvalbumin-expressing interneurons. Disrupted E/I coupling was associated with deficits in auditory-evoked gamma signal-to-noise ratio (SNR). Gamma-band abnormalities predicted deficits in spatial working memory and social preference, linking cellular changes in E/I signaling to target behaviors. The GABA(B)-receptor agonist baclofen improved E/I balance, gamma-SNR and broadly reversed behavioral deficits. These data demonstrate a clinically relevant, highly translatable neural-activity-based biomarker for preclinical screening and therapeutic development across a broad range of disorders that share common endophenotypes and disrupted NMDA-receptor signaling.

PMID: 22806213 [PubMed - indexed for MEDLINE]

Excess variants in AFF2 detected by massively parallel sequencing of males with autism spectrum disorder.

Hum Mol Genet. 2012 Oct 1;21(19):4356-64

Authors: Mondal K, Ramachandran D, Patel VC, Hagen KR, Bose P, Cutler DJ, Zwick ME

Abstract
Autism spectrum disorder (ASD) is a heterogeneous disorder with substantial heritability, most of which is unexplained. ASD has a population prevalence of one percent and affects four times as many males as females. Patients with fragile X E (FRAXE) intellectual disability, which is caused by a silencing of the X-linked gene AFF2, display a number of ASD-like phenotypes. Duplications and deletions at the AFF2 locus have also been reported in cases with moderate intellectual disability and ASD. We hypothesized that other rare X-linked sequence variants at the AFF2 locus might contribute to ASD. We sequenced the AFF2 genomic region in 202 male ASD probands and found that 2.5% of males sequenced had missense mutations at highly conserved evolutionary sites. When compared with the frequency of missense mutations in 5545 X chromosomes from unaffected controls, we saw a statistically significant enrichment in patients with ASD (OR: 4.9; P < 0.014). In addition, we identified rare AFF2 3' UTR variants at conserved sites which alter gene expression in a luciferase assay. These data suggest that rare variation in AFF2 may be a previously unrecognized ASD susceptibility locus and may help explain some of the male excess of ASD.

PMID: 22773736 [PubMed - indexed for MEDLINE]

RBFOX1 regulates both splicing and transcriptional networks in human neuronal development.

Hum Mol Genet. 2012 Oct 1;21(19):4171-86

Authors: Fogel BL, Wexler E, Wahnich A, Friedrich T, Vijayendran C, Gao F, Parikshak N, Konopka G, Geschwind DH

Abstract
RNA splicing plays a critical role in the programming of neuronal differentiation and, consequently, normal human neurodevelopment, and its disruption may underlie neurodevelopmental and neuropsychiatric disorders. The RNA-binding protein, fox-1 homolog (RBFOX1; also termed A2BP1 or FOX1), is a neuron-specific splicing factor predicted to regulate neuronal splicing networks clinically implicated in neurodevelopmental disease, including autism spectrum disorder (ASD), but only a few targets have been experimentally identified. We used RNA sequencing to identify the RBFOX1 splicing network at a genome-wide level in primary human neural stem cells during differentiation. We observe that RBFOX1 regulates a wide range of alternative splicing events implicated in neuronal development and maturation, including transcription factors, other splicing factors and synaptic proteins. Downstream alterations in gene expression define an additional transcriptional network regulated by RBFOX1 involved in neurodevelopmental pathways remarkably parallel to those affected by splicing. Several of these differentially expressed genes are further implicated in ASD and related neurodevelopmental diseases. Weighted gene co-expression network analysis demonstrates a high degree of connectivity among these disease-related genes, highlighting RBFOX1 as a key factor coordinating the regulation of both neurodevelopmentally important alternative splicing events and clinically relevant neuronal transcriptional programs in the development of human neurons.

PMID: 22730494 [PubMed - indexed for MEDLINE]

Chromosome microarray in Australia: a guide for paediatricians.

J Paediatr Child Health. 2012 Feb;48(2):E59-67

Authors: Palmer EE, Peters GB, Mowat D

Abstract
Chromosomal microarray or molecular karyotype has become the first-line genetic investigation for children with intellectual disability, autistic spectrum disorder or multiple congenital anomalies. Chromosomal microarray increases the detection rate of pathogenic chromosome imbalances including submicroscopic deletions or duplications in patients with undiagnosed intellectual disability to approximately 15% compared with 3% with conventional cytogenetics. This review article summarises the diagnostic technique and highlights the advantages and limitations of chromosomal microarray. Our aim is to assist clinicians in providing pretest counselling and with interpretation of the result.

PMID: 22320280 [PubMed - indexed for MEDLINE]

[RETT syndrome is not an autistic disorder].

Perspect Infirm. 2013 Jan-Feb;10(1):54

Authors: Gagné L

PMID: 23379050 [PubMed - indexed for MEDLINE]

Brain transcriptional and epigenetic associations with autism.

PLoS One. 2012;7(9):e44736

Authors: Ginsberg MR, Rubin RA, Falcone T, Ting AH, Natowicz MR

Abstract
BACKGROUND: Autism is a common neurodevelopmental syndrome. Numerous rare genetic etiologies are reported; most cases are idiopathic.
METHODOLOGY/PRINCIPAL FINDINGS: To uncover important gene dysregulation in autism we analyzed carefully selected idiopathic autistic and control cerebellar and BA19 (occipital) brain tissues using high resolution whole genome gene expression and whole genome DNA methylation microarrays. No changes in DNA methylation were identified in autistic brain but gene expression abnormalities in two areas of metabolism were apparent: down-regulation of genes of mitochondrial oxidative phosphorylation and of protein translation. We also found associations between specific behavioral domains of autism and specific brain gene expression modules related to myelin/myelination, inflammation/immune response and purinergic signaling.
CONCLUSIONS/SIGNIFICANCE: This work highlights two largely unrecognized molecular pathophysiological themes in autism and suggests differing molecular bases for autism behavioral endophenotypes.

PMID: 22984548 [PubMed - indexed for MEDLINE]

Understanding sex bias in autism spectrum disorder.

Proc Natl Acad Sci U S A. 2013 Mar 8;

Authors: Werling DM, Geschwind DH

Abstract

PMID: 23476067 [PubMed - as supplied by publisher]

Genome-wide scan of healthy human connectome discovers SPON1 gene variant influencing dementia severity.

Proc Natl Acad Sci U S A. 2013 Mar 5;

Authors: Jahanshad N, Rajagopalan P, Hua X, Hibar DP, Nir TM, Toga AW, Jack CR, Saykin AJ, Green RC, Weiner MW, Medland SE, Montgomery GW, Hansell NK, McMahon KL, de Zubicaray GI, Martin NG, Wright MJ, Thompson PM, the Alzheimer’s Disease Neuroimaging Initiative

Abstract
Aberrant connectivity is implicated in many neurological and psychiatric disorders, including Alzheimer's disease and schizophrenia. However, other than a few disease-associated candidate genes, we know little about the degree to which genetics play a role in the brain networks; we know even less about specific genes that influence brain connections. Twin and family-based studies can generate estimates of overall genetic influences on a trait, but genome-wide association scans (GWASs) can screen the genome for specific variants influencing the brain or risk for disease. To identify the heritability of various brain connections, we scanned healthy young adult twins with high-field, high-angular resolution diffusion MRI. We adapted GWASs to screen the brain's connectivity pattern, allowing us to discover genetic variants that affect the human brain's wiring. The association of connectivity with the SPON1 variant at rs2618516 on chromosome 11 (11p15.2) reached connectome-wide, genome-wide significance after stringent statistical corrections were enforced, and it was replicated in an independent subsample. rs2618516 was shown to affect brain structure in an elderly population with varying degrees of dementia. Older people who carried the connectivity variant had significantly milder clinical dementia scores and lower risk of Alzheimer's disease. As a posthoc analysis, we conducted GWASs on several organizational and topological network measures derived from the matrices to discover variants in and around genes associated with autism (MACROD2), development (NEDD4), and mental retardation (UBE2A) significantly associated with connectivity. Connectome-wide, genome-wide screening offers substantial promise to discover genes affecting brain connectivity and risk for brain diseases.

PMID: 23471985 [PubMed - as supplied by publisher]

Revealing the complexity of a monogenic disease: rett syndrome exome sequencing.

PLoS One. 2013;8(2):e56599

Authors: Grillo E, Lo Rizzo C, Bianciardi L, Bizzarri V, Baldassarri M, Spiga O, Furini S, De Felice C, Signorini C, Leoncini S, Pecorelli A, Ciccoli L, Mencarelli MA, Hayek J, Meloni I, Ariani F, Mari F, Renieri A

Abstract
Rett syndrome (OMIM#312750) is a monogenic disorder that may manifest as a large variety of phenotypes ranging from very severe to mild disease. Since there is a weak correlation between the mutation type in the Xq28 disease-gene /X-inactivation status and phenotypic variability, we used this disease as a model to unveil the complex nature of a monogenic disorder. Whole exome sequencing was used to analyze the functional portion of the genome of two pairs of sisters with Rett syndrome. Although each pair of sisters had the same OMIM*300005) mutation and balanced X-inactivation, one individual from each pair could not speak or walk, and had a profound intellectual deficit (classical Rett syndrome), while the other individual could speak and walk, and had a moderate intellectual disability (Zappella variant). In addition to the mutation, each patient has a group of variants predicted to impair protein function. The classical Rett girls, but not their milder affected sisters, have an enrichment of variants in genes related to oxidative stress, muscle impairment and intellectual disability and/or autism. On the other hand, a subgroup of variants related to modulation of immune system, exclusive to the Zappella Rett patients are driving toward a milder phenotype. We demonstrate that genome analysis has the potential to identify genetic modifiers of Rett syndrome, providing insight into disease pathophysiology. Combinations of mutations that affect speaking, walking and intellectual capabilities may represent targets for new therapeutic approaches. Most importantly, we demonstrated that monogenic diseases may be more complex than previously thought.

PMID: 23468869 [PubMed - in process]

Psychiatric disorder-related abnormal behavior and habenulointerpeduncular pathway defects in Wnt1-cre and Wnt1-GAL4 double transgenic mice.

J Neurochem. 2013 Jan;124(2):241-9

Authors: Nakajima M, Mori H, Nishikawa C, Tsuruta M, Okuyama S, Furukawa Y

Abstract
The neural crest is a unique structure in vertebrates. Wnt1-cre and Wnt1-GAL4 double transgenic (dTg) mice have been used in a variety of studies concerning neural crest cell lineages in which the Cre/loxP or GAL4/UAS system was applied. Here, we show psychiatric disorder-related behavioral abnormalities and histologic alterations in a neural crest-derived brain region in dTg mice. The dTg mice exhibited increased locomotor activity, decreased social interaction, and impaired short-term spatial memory and nesting behavior. The choline acetyltransferase- and vesicular glutamate transporter 2-immunoreactive habenulointerpeduncular fiber tracts that project from the medial habenular nucleus of the epithalamus to the interpeduncular nucleus of the midbrain tegmentum appeared irregular in the dTg mice. Both the medial habenula nucleus and the interpeduncular nucleus were confirmed to be derived from the neural crest. The findings of this study suggest that neural crest-derived cells have pathogenic roles in the development of psychiatric disorders and that the dTg mouse could be a useful animal model for studying the pathophysiology of mental illness such as autism and schizophrenia. Scientists that use the dTg mice as a cre-transgenic deleter line should be cautious in its possible toxicity, especially if behavioral analyses are to be performed.

PMID: 23134367 [PubMed - indexed for MEDLINE]

Autworks: a cross-disease network biology application for Autism and related disorders.

BMC Med Genomics. 2012;5:56

Authors: Nelson TH, Jung JY, Deluca TF, Hinebaugh BK, St Gabriel KC, Wall DP

Abstract
BACKGROUND: The genetic etiology of autism is heterogeneous. Multiple disorders share genotypic and phenotypic traits with autism. Network based cross-disorder analysis can aid in the understanding and characterization of the molecular pathology of autism, but there are few tools that enable us to conduct cross-disorder analysis and to visualize the results.
DESCRIPTION: We have designed Autworks as a web portal to bring together gene interaction and gene-disease association data on autism to enable network construction, visualization, network comparisons with numerous other related neurological conditions and disorders. Users may examine the structure of gene interactions within a set of disorder-associated genes, compare networks of disorder/disease genes with those of other disorders/diseases, and upload their own sets for comparative analysis.
CONCLUSIONS: Autworks is a web application that provides an easy-to-use resource for researchers of varied backgrounds to analyze the autism gene network structure within and between disorders.Availability: http://autworks.hms.harvard.edu/

PMID: 23190929 [PubMed - indexed for MEDLINE]

Correlations of gene expression with ratings of inattention and hyperactivity/impulsivity in Tourette syndrome: a pilot study.

BMC Med Genomics. 2012;5:49

Authors: Tian Y, Stamova B, Ander BP, Jickling GC, Gunther JR, Corbett BA, Bos-Veneman NG, Hoekstra PJ, Schweitzer JB, Sharp FR

Abstract
BACKGROUND: Inattentiveness, impulsivity and hyperactivity are the primary behaviors associated with attention-deficit hyperactivity disorder (ADHD). Previous studies showed that peripheral blood gene expression signatures can mirror central nervous system disease. Tourette syndrome (TS) is associated with inattention (IA) and hyperactivity/impulsivity (HI) symptoms over 50% of the time. This study determined if gene expression in blood correlated significantly with IA and/or HI rating scale scores in participants with TS.
METHODS: RNA was isolated from the blood of 21 participants with TS, and gene expression measured on Affymetrix human U133 Plus 2.0 arrays. To identify the genes that correlated with Conners' Parents Ratings of IA and HI ratings of symptoms, an analysis of covariance (ANCOVA) was performed, controlling for age, gender and batch.
RESULTS: There were 1201 gene probesets that correlated with IA scales, 1625 that correlated with HI scales, and 262 that correlated with both IA and HI scale scores (P<0.05, |Partial correlation (r(p))|>0.4). Immune, catecholamine and other neurotransmitter pathways were associated with IA and HI behaviors. A number of the identified genes (n=27) have previously been reported in ADHD genetic studies. Many more genes correlated with either IA or HI scales alone compared to those that correlated with both IA and HI scales.
CONCLUSIONS: These findings support the concept that the pathophysiology of ADHD and/or its subtypes in TS may involve the interaction of multiple genes. These preliminary data also suggest gene expression may be useful for studying IA and HI symptoms that relate to ADHD in TS and perhaps non-TS participants. These results will need to be confirmed in future studies.

PMID: 23110997 [PubMed - indexed for MEDLINE]

Activity-dependent neuronal signalling and autism spectrum disorder.

Nature. 2013 Jan 17;493(7432):327-37

Authors: Ebert DH, Greenberg ME

Abstract
Neuronal activity induces the post-translational modification of synaptic molecules, promotes localized protein synthesis within dendrites and activates gene transcription, thereby regulating synaptic function and allowing neuronal circuits to respond dynamically to experience. Evidence indicates that many of the genes that are mutated in autism spectrum disorder are crucial components of the activity-dependent signalling networks that regulate synapse development and plasticity. Dysregulation of activity-dependent signalling pathways in neurons may, therefore, have a key role in the aetiology of autism spectrum disorder.

PMID: 23325215 [PubMed - indexed for MEDLINE]

Enhanced recruitment of endosomal Na+/H+ exchanger NHE6 into Dendritic spines of hippocampal pyramidal neurons during NMDA receptor-dependent long-term potentiation.

J Neurosci. 2013 Jan 9;33(2):595-610

Authors: Deane EC, Ilie AE, Sizdahkhani S, Das Gupta M, Orlowski J, McKinney RA

Abstract
Postsynaptic endosomal trafficking has emerged as a principal regulatory mechanism of structural and functional plasticity of glutamatergic synapses. Recycling endosomes perform activity-dependent transport of AMPA receptors (AMPARs) and lipids to the postsynaptic membrane, activities that are known to contribute to long-term synaptic potentiation and hypothesized to subserve learning and memory processes in the brain. Recently, genetic defects in a widely expressed vesicular pH-regulating transporter, the Na(+)/H(+) exchanger NHE6 isoform, have been implicated in neurodevelopmental disorders including severe X-linked mental retardation and autism. However, little information is available regarding the cellular properties of this transporter in the CNS. Here, we show by quantitative light microscopy that the protein abundance of NHE6 is developmentally regulated in area CA1 of the mouse hippocampus. Within pyramidal neurons, NHE6 was found to localize to discrete puncta throughout the soma and neurites, with noticeable accumulation at dendritic spines and presynaptic terminals. Dual immunolabeling of dendritic spines revealed that NHE6 partially colocalizes with typical markers of early and recycling endosomes as well as with the AMPAR subunit GluA1. Significantly, NHE6-containing vesicles exhibited enhanced translocation to dendritic spine heads during NMDA receptor (NMDAR)-dependent long-term potentiation. These data suggest that NHE6 may play a unique, previously unrecognized, role at glutamatergic synapses that are important for learning and memory.

PMID: 23303939 [PubMed - indexed for MEDLINE]

Exaggerated translation causes synaptic and behavioural aberrations associated with autism.

Nature. 2013 Jan 17;493(7432):411-5

Authors: Santini E, Huynh TN, MacAskill AF, Carter AG, Pierre P, Ruggero D, Kaphzan H, Klann E

Abstract
Autism spectrum disorders (ASDs) are an early onset, heterogeneous group of heritable neuropsychiatric disorders with symptoms that include deficits in social interaction skills, impaired communication abilities, and ritualistic-like repetitive behaviours. One of the hypotheses for a common molecular mechanism underlying ASDs is altered translational control resulting in exaggerated protein synthesis. Genetic variants in chromosome 4q, which contains the EIF4E locus, have been described in patients with autism. Importantly, a rare single nucleotide polymorphism has been identified in autism that is associated with increased promoter activity in the EIF4E gene. Here we show that genetically increasing the levels of eukaryotic translation initiation factor 4E (eIF4E) in mice results in exaggerated cap-dependent translation and aberrant behaviours reminiscent of autism, including repetitive and perseverative behaviours and social interaction deficits. Moreover, these autistic-like behaviours are accompanied by synaptic pathophysiology in the medial prefrontal cortex, striatum and hippocampus. The autistic-like behaviours displayed by the eIF4E-transgenic mice are corrected by intracerebroventricular infusions of the cap-dependent translation inhibitor 4EGI-1. Our findings demonstrate a causal relationship between exaggerated cap-dependent translation, synaptic dysfunction and aberrant behaviours associated with autism.

PMID: 23263185 [PubMed - indexed for MEDLINE]

Autism-related deficits via dysregulated eIF4E-dependent translational control.

Nature. 2013 Jan 17;493(7432):371-7

Authors: Gkogkas CG, Khoutorsky A, Ran I, Rampakakis E, Nevarko T, Weatherill DB, Vasuta C, Yee S, Truitt M, Dallaire P, Major F, Lasko P, Ruggero D, Nader K, Lacaille JC, Sonenberg N

Abstract
Hyperconnectivity of neuronal circuits due to increased synaptic protein synthesis is thought to cause autism spectrum disorders (ASDs). The mammalian target of rapamycin (mTOR) is strongly implicated in ASDs by means of upstream signalling; however, downstream regulatory mechanisms are ill-defined. Here we show that knockout of the eukaryotic translation initiation factor 4E-binding protein 2 (4E-BP2)-an eIF4E repressor downstream of mTOR-or eIF4E overexpression leads to increased translation of neuroligins, which are postsynaptic proteins that are causally linked to ASDs. Mice that have the gene encoding 4E-BP2 (Eif4ebp2) knocked out exhibit an increased ratio of excitatory to inhibitory synaptic inputs and autistic-like behaviours (that is, social interaction deficits, altered communication and repetitive/stereotyped behaviours). Pharmacological inhibition of eIF4E activity or normalization of neuroligin 1, but not neuroligin 2, protein levels restores the normal excitation/inhibition ratio and rectifies the social behaviour deficits. Thus, translational control by eIF4E regulates the synthesis of neuroligins, maintaining the excitation-to-inhibition balance, and its dysregulation engenders ASD-like phenotypes.

PMID: 23172145 [PubMed - indexed for MEDLINE]

Effects of maternal immune activation on gene expression patterns in the fetal brain.

Transl Psychiatry. 2012;2:e98

Authors: Garbett KA, Hsiao EY, Kálmán S, Patterson PH, Mirnics K

Abstract
We are exploring the mechanisms underlying how maternal infection increases the risk for schizophrenia and autism in the offspring. Several mouse models of maternal immune activation (MIA) were used to examine the immediate effects of MIA induced by influenza virus, poly(I:C) and interleukin IL-6 on the fetal brain transcriptome. Our results indicate that all three MIA treatments lead to strong and common gene expression changes in the embryonic brain. Most notably, there is an acute and transient upregulation of the α, β and γ crystallin gene family. Furthermore, levels of crystallin gene expression are correlated with the severity of MIA as assessed by placental weight. The overall gene expression changes suggest that the response to MIA is a neuroprotective attempt by the developing brain to counteract environmental stress, but at a cost of disrupting typical neuronal differentiation and axonal growth. We propose that this cascade of events might parallel the mechanisms by which environmental insults contribute to the risk of neurodevelopmental disorders such as schizophrenia and autism.

PMID: 22832908 [PubMed - indexed for MEDLINE]