Analysis of the RELN gene as a genetic risk factor for autism

Characterization of neonatal vocal and motor repertoire of reelin mutant mice

Reelin is a large secreted extracellular matrix glycoprotein playing an important role in early neurodevelopment. Several genetic studies found an association between RELN gene and increased risk of autism suggesting that reelin deficiency may be a vulnerability factor in its etiology. Moreover, a reduced reelin expression has been observed in several brain regions of subjects with Autism Spectrum Disorders. Since a number of reports have documented presence of vocal and neuromotor abnormalities in patients with autism and suggested that these dysfunctions predate the onset of the syndrome, we performed a fine-grain characterization of the neonatal vocal and motor repertoire in reelin mutant mice to explore the developmental precursors of the disorder. Our findings evidence a general delay in motor and vocal development in heterozygous (50% reduced reelin) and reeler (lacking reelin gene) mutant mice. As a whole, an increased number of calls characterized heterozygous pup's emission. Furthermore, the typical ontogenetic peak in the number of calls characterizing wild-type pups on postnatal day 4 appeared slightly delayed in heterozygous pups (to day 6) and was quite absent in reeler littermates, which exhibited a flat profile during development. We also detected a preferential use of a specific call category (two-components) by heterozygous and reeler mice at postnatal days 6 and 8 as compared to their wild-type littermates. With regard to the analysis of spontaneous movements, a differential profile emerged early in development among the three genotypes. While only slight coordination difficulties are exhibited by heterozygous pups, all indices of motor development appear delayed in reeler mice. Overall, our results evidence a genotype-dependent deviation in ultrasonic vocal repertoire and a general delay in motor development in reelin mutant pups.

The involvement of Reelin in neurodevelopmental disorders

Reelin is a glycoprotein that serves important roles both during development (regulation of neuronal migration and brain lamination) and in adulthood (maintenance of synaptic function). A number of neuropsychiatric disorders including autism, schizophrenia, bipolar disorder, major depression, Alzheimer's disease and lissencephaly share a common feature of abnormal Reelin expression in the brain. Altered Reelin expression has been hypothesized to impair neuronal connectivity and synaptic plasticity, leading ultimately to the cognitive deficits present in these disorders. The mechanisms for abnormal Reelin expression in some of these disorders are currently unknown although possible explanations include early developmental insults, mutations, hypermethylation of the promoter for the Reelin gene (RELN), miRNA silencing of Reelin mRNA, FMRP underexpression and Reelin processing abnormalities. Increasing Reelin expression through pharmacological therapies may help ameliorate symptoms resulting from Reelin deficits. This article is part of the Special Issue entitled 'Neurodevelopmental Disorders'.

Prenatal diagnosis and molecular cytogenetic characterization of a de novo interstitial deletion of 7q (7q22.1→q31.1)

We present prenatal diagnosis and molecular cytogenetic characterization of de novo interstitial deletion of 7q (7q22.1→q31.1) by aCGH, FISH and QF-PCR in a fetus with an abnormal maternal serum screening result and ultrasound findings of facial cleft and hypogenitalism. We discuss the genotype-phenotype correlation and the consequence of haploinsufficiency of ZKSCAN5, ARPC1A, CYP3A43, RELN, LAMB1, IMMP2L and DOCK4 in this case.

Epigenetic factors and autism spectrum disorders

Autism is a complex neurodevelopmental disorder that has significant phenotypic overlap with several diseases, many of which fall within the broader category of autism spectrum disorders (ASDs). The etiology of the disorder is unclear and seems to involve a complex interplay of polygenic as well as environmental factors. We discuss evidence that suggests that epigenetic dysregulation is highly implicated as a contributing cause of ASDs and autism. Specifically, we examine neurodevelopmental disorders that share significant phenotypic overlap with ASDs and feature the dysregulation of epigenetically modified genes including UBE3A, GABA receptor genes, and RELN. We then look at the dysregulated expression of implicated epigenetic modifiers, namely MeCP2, that yield complex and varied downstream pleiotropic effects. Finally, we examine epigenetically mediated parent-of-origin effects through which paternal gene expression dominates that of maternal contributing to contrasting phenotypes implicated in ASDs. Such preliminary evidence suggests that elucidating the complex role of epigenetic regulations involved in ASDs could prove vital in furthering our understanding of the complex etiology of autism and ASDs.

Genomics and autism spectrum disorder

PURPOSE

To present the current state of the evidence regarding translation of genetics (the study of single genes) and genomics (the study of all genes and gene-gene or gene-environment interactions) into health care of children with autism spectrum disorder (ASD).

METHODS

This article presents an overview of ASD as an international health challenge, the emerging science related to broad diagnostic criteria, and the role of the nurse in research, education, and practice.

FINDINGS

Much progress is being made in the understanding of genetics and genomics of ASD. Environmental factors are thought to contribute to the risk of developing ASD by interacting with a number of genes in different ways, thus suggesting causal heterogeneity. The rising identified prevalence of ASD, the changing diagnostic criteria for ASD, and the complexity of the core and associated features have made it difficult to define the ASD phenotype (observable behaviors that result from gene-environment interaction). Because early identification improves opportunities for intervention, researchers are looking for a useful biomarker to detect ASD. This search is complicated by the likelihood that there are multiple causes for multiple expressions that are defined as the autism spectrum.

CONCLUSIONS

To date, genetic and genomic research on ASD have underscored the complexity of the causes of ASD indicating that there are very complex genetic processes involved that are still not well understood.

CLINICAL RELEVANCE

Nurses will benefit from new knowledge related to early identification, diagnosis, and implications for the family to promote early intervention. Families who have a child with ASD will require nursing support for advocacy for optimal health outcomes.

Neuronal connectivity as a convergent target of gene × environment interactions that confer risk for Autism Spectrum Disorders

Evidence implicates environmental factors in the pathogenesis of Autism Spectrum Disorders (ASD). However, the identity of specific environmental chemicals that influence ASD risk, severity or treatment outcome remains elusive. The impact of any given environmental exposure likely varies across a population according to individual genetic substrates, and this increases the difficulty of identifying clear associations between exposure and ASD diagnoses. Heritable genetic vulnerabilities may amplify adverse effects triggered by environmental exposures if genetic and environmental factors converge to dysregulate the same signaling systems at critical times of development. Thus, one strategy for identifying environmental risk factors for ASD is to screen for environmental factors that modulate the same signaling pathways as ASD susceptibility genes. Recent advances in defining the molecular and cellular pathology of ASD point to altered patterns of neuronal connectivity in the developing brain as the neurobiological basis of these disorders. Studies of syndromic ASD and rare highly penetrant mutations or CNVs in ASD suggest that ASD risk genes converge on several major signaling pathways linked to altered neuronal connectivity in the developing brain. This review briefly summarizes the evidence implicating dysfunctional signaling via Ca(2+)-dependent mechanisms, extracellular signal-regulated kinases (ERK)/phosphatidylinositol-3-kinases (PI3K) and neuroligin-neurexin-SHANK as convergent molecular mechanisms in ASD, and then discusses examples of environmental chemicals for which there is emerging evidence of their potential to interfere with normal neuronal connectivity via perturbation of these signaling pathways.

Complex epigenetic regulation of engrailed-2 (EN-2) homeobox gene in the autism cerebellum

The elucidation of epigenetic alterations in the autism brain has potential to provide new insights into the molecular mechanisms underlying abnormal gene expression in this disorder. Given strong evidence that engrailed-2 (EN-2) is a developmentally expressed gene relevant to cerebellar abnormalities and autism, the epigenetic evaluation of this candidate gene was undertaken in 26 case and control post-mortem cerebellar samples. Assessments included global DNA methylation, EN-2 promoter methylation, EN-2 gene expression and EN-2 protein levels. Chromatin immunoprecipitation was used to evaluate trimethylation status of histone H3 lysine 27 (H3K27) associated with gene downregulation and histone H3 lysine 4 (H3K4) associated with gene activation. The results revealed an unusual pattern of global and EN-2 promoter region DNA hypermethylation accompanied by significant increases in EN-2 gene expression and protein levels. Consistent with EN-2 overexpression, histone H3K27 trimethylation mark in the EN-2 promoter was significantly decreased in the autism samples relative to matched controls. Supporting a link between reduced histone H3K27 trimethylation and increased EN-2 gene expression, the mean level of histone H3K4 trimethylation was elevated in the autism cerebellar samples. Together, these results suggest that the normal EN-2 downregulation that signals Purkinje cell maturation during late prenatal and early-postnatal development may not have occurred in some individuals with autism and that the postnatal persistence of EN-2 overexpression may contribute to autism cerebellar abnormalities.

Association analysis of two single-nucleotide polymorphisms of the RELN gene with autism in the South African population

BACKGROUND

Autism (MIM209850) is a neurodevelopmental disorder characterized by a triad of impairments, namely impairment in social interaction, impaired communication skills, and restrictive and repetitive behavior. A number of family and twin studies have demonstrated that genetic factors play a pivotal role in the etiology of autistic disorder. Various reports of reduced levels of reelin protein in the brain and plasma in autistic patients highlighted the role of the reelin gene (RELN) in autism. There is no such published study on the South African (SA) population.

AIMS

The aim of the present study was to find the genetic association of intronic rs736707 and exonic rs362691 (single-nucleotide polymorphisms [SNPs] of the RELN gene) with autism in a SA population.

METHODS

Genomic DNA was isolated from cheek cell swabs from autistic (136) as well as control (208) subjects. The TaqMan(®) Real-Time polymerase chain reaction and genotyping assay was utilized to determine the genotypes.

RESULTS

A significant association of SNP rs736707, but not for SNP rs362691, with autism in the SA population is observed.

CONCLUSION

There might be a possible role of RELN in autism, especially for SA populations. The present study represents the first report on genetic association studies on the RELN gene in the SA population.

Transcriptional dysregulation of neocortical circuit assembly in ASD

Autism spectrum disorders (ASDs) impair social cognition and communication, key higher-order functions centered in the human neocortex. The assembly of neocortical circuitry is a precisely regulated developmental process susceptible to genetic alterations that can ultimately affect cognitive abilities. Because ASD is an early onset neurodevelopmental disorder that disrupts functions executed by the neocortex, miswiring of neocortical circuits has been hypothesized to be an underlying mechanism of ASD. This possibility is supported by emerging genetic findings and data from imaging studies. Recent research on neocortical development has identified transcription factors as key determinants of neocortical circuit assembly, mediating diverse processes including neuronal specification, migration, and wiring. Many of these TFs (TBR1, SOX5, FEZF2, and SATB2) have been implicated in ASD. Here, I will discuss the functional roles of these transcriptional programs in neocortical circuit development and their neurobiological implications for the emerging etiology of ASD.

Genes associated with autism spectrum disorder

Autism spectrum disorder (ASD) is a heterogeneous grouping of neurodevelopmental disorders characterized by impairment in social interaction, verbal communication and repetitive/stereotypic behaviors. Much evidence suggests that ASD is multifactorial with a strong genetic basis, but the underlying mechanisms are far from clear. Recent advances in genetic technologies are beginning to shed light on possible etiologies of ASD. This review discusses current evidence for several widely studied candidate ASD genes, as well as various rare genes that supports their relationship to the etiology of ASD. The majority of the data are based on molecular, cytogenetic, linkage and association studies of autistic subjects, but newer methods, including whole-exome sequencing, are also beginning to make significant contributions to our understanding of autism.

The role of immune dysfunction in the pathophysiology of autism

Autism spectrum disorders (ASD) are a complex group of neurodevelopmental disorders encompassing impairments in communication, social interactions and restricted stereotypical behaviors. Although a link between altered immune responses and ASD was first recognized nearly 40 years ago, only recently has new evidence started to shed light on the complex multifaceted relationship between immune dysfunction and behavior in ASD. Neurobiological research in ASD has highlighted pathways involved in neural development, synapse plasticity, structural brain abnormalities, cognition and behavior. At the same time, several lines of evidence point to altered immune dysfunction in ASD that directly impacts some or all these neurological processes. Extensive alterations in immune function have now been described in both children and adults with ASD, including ongoing inflammation in brain specimens, elevated pro-inflammatory cytokine profiles in the CSF and blood, increased presence of brain-specific auto-antibodies and altered immune cell function. Furthermore, these dysfunctional immune responses are associated with increased impairments in behaviors characteristic of core features of ASD, in particular, deficits in social interactions and communication. This accumulating evidence suggests that immune processes play a key role in the pathophysiology of ASD. This review will discuss the current state of our knowledge of immune dysfunction in ASD, how these findings may impact on underlying neuro-immune mechanisms and implicate potential areas where the manipulation of the immune response could have an impact on behavior and immunity in ASD.

Triggers for autism: genetic and environmental factors

This report reviews the research on the factors that cause autism. In several studies, these factors have been verified by reproducing them in autistic animal models. Clinical research has demonstrated that genetic and environmental factors play a major role in the development of autism. However, most cases are idiopathic, and no single factor can explain the trends in the pathology and prevalence of autism. At the time of this writing, autism is viewed more as a multi-factorial disorder. However, the existence of an unknown factor that may be common in all autistic cases cannot be ruled out. It is hoped that future biological studies of autism will help construct a new theory that can interpret the pathology of autism in a coherent manner. To achieve this, large-scale epidemiological research is essential.

Behavioural genetics of childhood disorders

After a general introduction into genetic risk factors for child psychiatric disorders, four specific child psychiatric disorders with a strong genetic component, namely, Autism Spectrum Disorders, Attention Deficit / Hyperactivity Disorder, Nocturnal Enuresis, and obesity, are discussed in detail. Recent evidence of linkage, candidate gene, and genome-wide association studies are presented. This chapter ends with a prospectus on further research needs.

Autism spectrum disorders: from immunity to behavior

Autism spectrum disorders (ASD) are complex and heterogeneous with a spectrum of diverse symptoms. Mounting evidence from a number of disciplines suggests a link between immune function and ASD. Although the causes of ASD have yet to be identified, genetic studies have uncovered a host of candidate genes relating to immune regulation that are altered in ASD, while epidemiological studies have shown a relationship with maternal immune disturbances during pregnancy and ASD. Moreover, decades of research have identified numerous systemic and cellular immune abnormalities in individuals with ASD and their families. These include changes in immune cell number, differences in cytokine and chemokine production, and alterations of cellular function at rest and in response to immunological challenge. Many of these changes in immune responses are associated with increasing impairment in behaviors that are core features of ASD. Despite this evidence, much remains to be understood about the precise mechanism by which the immune system alters neurodevelopment and to what extent it is involved in the pathogenesis of ASD. With estimates of ASD as high as 1% of children, ASD is a major public health issue. Improvements in our understanding of the interactions between the nervous and immune system during early neurodevelopment and how this interaction is different in ASD will have important therapeutic implications with wide ranging benefits.

No association of polymorphisms in the CDK5, NDEL1, and LIS1 with autism in Chinese Han population

Autism is a pervasive neurodevelopmental disorder. CDK5 (cyclin-dependent kinase 5) and its interacting molecules are involved in neurodevelopment. We performed a family-based association analysis between CDK5, NDEL1, and LIS1 polymorphisms and autism in a Chinese Han population. Our study did not detect a significant association. It indicated that common genetic variations in these genes might not play a role in the genetic predisposition to autism.

A brain region-specific predictive gene map for autism derived by profiling a reference gene set

Molecular underpinnings of complex psychiatric disorders such as autism spectrum disorders (ASD) remain largely unresolved. Increasingly, structural variations in discrete chromosomal loci are implicated in ASD, expanding the search space for its disease etiology. We exploited the high genetic heterogeneity of ASD to derive a predictive map of candidate genes by an integrated bioinformatics approach. Using a reference set of 84 Rare and Syndromic candidate ASD genes (AutRef84), we built a composite reference profile based on both functional and expression analyses. First, we created a functional profile of AutRef84 by performing Gene Ontology (GO) enrichment analysis which encompassed three main areas: 1) neurogenesis/projection, 2) cell adhesion, and 3) ion channel activity. Second, we constructed an expression profile of AutRef84 by conducting DAVID analysis which found enrichment in brain regions critical for sensory information processing (olfactory bulb, occipital lobe), executive function (prefrontal cortex), and hormone secretion (pituitary). Disease specificity of this dual AutRef84 profile was demonstrated by comparative analysis with control, diabetes, and non-specific gene sets. We then screened the human genome with the dual AutRef84 profile to derive a set of 460 potential ASD candidate genes. Importantly, the power of our predictive gene map was demonstrated by capturing 18 existing ASD-associated genes which were not part of the AutRef84 input dataset. The remaining 442 genes are entirely novel putative ASD risk genes. Together, we used a composite ASD reference profile to generate a predictive map of novel ASD candidate genes which should be prioritized for future research.

Links between genetics and pathophysiology in the autism spectrum disorders

Autism spectrum disorders (ASD) are important neuropsychiatric disorders, currently estimated to affect approximately 1% of children, with considerable emotional and financial costs. Significant collaborative effort has been made over the last 15 years in an attempt to unravel the genetic mechanisms underlying these conditions. This has led to important discoveries, both of the roles of specific genes, as well as larger scale chromosomal copy number changes. Here, we summarize some of the latest genetic findings in the field of ASD and attempt to link them with the results of pathophysiological studies to provide an overall picture of at least one of the mechanisms by which ASD may develop.

Casting a net on dendritic spines: the extracellular matrix and its receptors

Dendritic spines are dynamic structures that accommodate the majority of excitatory synapses in the brain and are influenced by extracellular signals from presynaptic neurons, glial cells, and the extracellular matrix (ECM). The ECM surrounds dendritic spines and extends into the synaptic cleft, maintaining synapse integrity as well as mediating trans-synaptic communications between neurons. Several scaffolding proteins and glycans that compose the ECM form a lattice-like network, which serves as an attractive ground for various secreted glycoproteins, lectins, growth factors, and enzymes. ECM components can control dendritic spines through the interactions with their specific receptors or by influencing the functions of other synaptic proteins. In this review, we focus on ECM components and their receptors that regulate dendritic spine development and plasticity in the normal and diseased brain.

Autism risk assessment in siblings of affected children using sex-specific genetic scores

Background

The inheritance pattern in most cases of autism is complex. The risk of autism is increased in siblings of children with autism and previous studies have indicated that the level of risk can be further identified by the accumulation of multiple susceptibility single nucleotide polymorphisms (SNPs) allowing for the identification of a higher-risk subgroup among siblings. As a result of the sex difference in the prevalence of autism, we explored the potential for identifying sex-specific autism susceptibility SNPs in siblings of children with autism and the ability to develop a sex-specific risk assessment genetic scoring system.

Methods

SNPs were chosen from genes known to be associated with autism. These markers were evaluated using an exploratory sample of 480 families from the Autism Genetic Resource Exchange (AGRE) repository. A reproducibility index (RI) was proposed and calculated in all children with autism and in males and females separately. Differing genetic scoring models were then constructed to develop a sex-specific genetic score model designed to identify individuals with a higher risk of autism. The ability of the genetic scores to identify high-risk children was then evaluated and replicated in an independent sample of 351 affected and 90 unaffected siblings from families with at least 1 child with autism.

Results

We identified three risk SNPs that had a high RI in males, two SNPs with a high RI in females, and three SNPs with a high RI in both sexes. Using these results, genetic scoring models for males and females were developed which demonstrated a significant association with autism (P = 2.2 × 10^-6 and 1.9 × 10^-5, respectively).

Conclusions

Our results demonstrate that individual susceptibility associated SNPs for autism may have important differential sex effects. We also show that a sex-specific risk score based on the presence of multiple susceptibility associated SNPs allow for the identification of subgroups of siblings of children with autism who have a significantly higher risk of autism.

Autism: a "critical period" disorder?

Cortical circuits in the brain are refined by experience during critical periods early in postnatal life. Critical periods are regulated by the balance of excitatory and inhibitory (E/I) neurotransmission in the brain during development. There is now increasing evidence of E/I imbalance in autism, a complex genetic neurodevelopmental disorder diagnosed by abnormal socialization, impaired communication, and repetitive behaviors or restricted interests. The underlying cause is still largely unknown and there is no fully effective treatment or cure. We propose that alteration of the expression and/or timing of critical period circuit refinement in primary sensory brain areas may significantly contribute to autistic phenotypes, including cognitive and behavioral impairments. Dissection of the cellular and molecular mechanisms governing well-established critical periods represents a powerful tool to identify new potential therapeutic targets to restore normal plasticity and function in affected neuronal circuits.

Gender-specific effect of Mthfr genotype and neonatal vigabatrin interaction on synaptic proteins in mouse cortex

The enzyme methylenetetrahydrofolate reductase (MTHFR) is a part of the homocysteine and folate metabolic pathways, affecting the methylations of DNA, RNA, and proteins. Mthfr deficiency was reported as a risk factor for neurodevelopmental disorders such as autism spectrum disorder and schizophrenia. Neonatal disruption of the GABAergic system is also associated with behavioral outcomes. The interaction between the epigenetic influence of Mthfr deficiency and neonatal exposure to the GABA potentiating drug vigabatrin (GVG) in mice has been shown to have gender-dependent effects on mice anxiety and to have memory impairment effects in a gender-independent manner. Here we show that Mthfr deficiency interacts with neonatal GABA potentiation to alter social behavior in female, but not male, mice. This impairment was associated with a gender-dependent enhancement of proteins implicated in excitatory synapse plasticity in the female cortex. Reelin and fragile X mental retardation 1 protein (FMRP) levels and membrane GluR1/GluR2 ratios were elevated in wild-type mice treated neonatally with GVG and in Mthfr+/- mice treated with saline, but not in Mthfr+/- mice treated with GVG, compared with control groups (wild type treated with saline). A minor influence on the levels of these proteins was observed in male mice cortices, possibly due to high basal protein levels. Interaction between gender, genotype, and treatment was also observed in the GABA pathway. In female mice, GABA Aα2/gephyrin ratios were suppressed in all test groups; in male mice, a genotype-specific enhancement of GABA Aα2/gephyrin was observed. The lack of an effect on either reln or Fmr1 transcription suggests post-transcriptional regulation of these genes. Taken together, these findings suggest that Mthfr deficiency may interact with neonatal GABA potentiation in a gender-dependent manner to interrupt synaptic function. This may illustrate a possible mechanism for the epigenetic involvement of Mthfr deficiency in neurodevelopmental disorders.

Altered T cell responses in children with autism

Autism spectrum disorders (ASD) are characterized by impairment in social interactions, communication deficits, and restricted repetitive interests and behaviors. A potential etiologic role for immune dysfunction in ASD has been suggested. Dynamic adaptive cellular immune function was investigated in 66 children with a confirmed diagnosis of ASD and 73 confirmed typically developing (TD) controls 2-5 years-of-age. In vitro stimulation of peripheral blood mononuclear cells with PHA and tetanus was used to compare group-associated cellular responses. The production of GM-CSF, TNFα, and IL-13 were significantly increased whereas IL-12p40 was decreased following PHA stimulation in ASD relative to TD controls. Induced cytokine production was associated with altered behaviors in ASD children such that increased pro-inflammatory or T(H)1 cytokines were associated with greater impairments in core features of ASD as well as aberrant behaviors. In contrast, production of GM-CSF and T(H)2 cytokines were associated with better cognitive and adaptive function. Following stimulation, the frequency of CD3(+), CD4(+) and CD8(+) T cells expressing activation markers CD134 and CD25 but not CD69, HLA-DR or CD137 were significantly reduced in ASD, and suggests an altered activation profile for T cells in ASD. Overall these data indicate significantly altered adaptive cellular immune function in children with ASD that may reflect dysfunctional immune activation, along with evidence that these perturbations may be linked to disturbances in behavior and developmental functioning. Further longitudinal analyzes of cellular immunity profiles would delineate the relationship between immune dysfunction and the progression of behavioral and developmental changes throughout the course of this disorder.

Altered posterior cingulate cortical cyctoarchitecture, but normal density of neurons and interneurons in the posterior cingulate cortex and fusiform gyrus in autism

Autism is a developmental disorder with prenatal origins, currently estimated to affect 1 in 91 children in the United States. Social-emotional deficits are a hallmark of autism and early neuropathology studies have indicated involvement of the limbic system. Imaging studies demonstrate abnormal activation of the posterior cingulate cortex (PCC), a component of the limbic system. Abnormal activation has also been noted in the fusiform gyrus (FFG), a region important for facial recognition and a key element in social interaction. A potential imbalance between excitatory and inhibitory interneurons in the cortex may contribute to altered information processing in autism. Furthermore, reduced numbers of GABA receptors have previously been reported in the autistic brain. Thionin-stained sections were used to qualitatively assess cytoarchitectonic patterning and quantitatively determine the density of neurons and immunohistochemistry was used to determine the densities of a subset of GABAergic interneurons utilizing parvalbumin-and calbindin-immunoreactivity. In autism, the PCC displayed altered cytoarchitecture with irregularly distributed neurons, poorly demarcated layers IV and V, and increased presence of white matter neurons. In contrast, no neuropathology was observed in the FFG. There was no significant difference in the density of thionin, parvalbumin, or calbindin interneurons in either region and there was a trend towards a reduced density of calbindin neurons in the PCC. This study highlights the presence of abnormal findings in the PCC, which appear to be developmental in nature and could affect the local processing of social-emotional behaviors as well as functioning of interrelated areas.

No significant association between RELN polymorphism and autism in case-control and family-based association study in Chinese Han population

The present study genotyped four SNPs (rs736707, rs2229864, rs362691, and rs2073559) of the Reelin gene (RELN) in 165 autistic trios, 67 sporadic autistic children and 283 healthy controls with Chinese Han pedigree. Both case-control analysis and transmission disequilibrium test (TDT) found no evidence of significant association. The results do not support previous positive findings and suggest that the four single-nucleotide polymorphisms (SNP) of RELN are unlikely to be associated with childhood autism in Chinese Han population.

Analysis of 9p24 and 11p12-13 regions in autism spectrum disorders: rs1340513 in the JMJD2C gene is associated with ASDs in Finnish sample

OBJECTIVE

Autism spectrum disorders (ASD) often show obsessive repetitive symptoms that are characteristic to obsessive-compulsive disorder (OCD). Aberrant glutamate function has been suggested to a risk for both ASDs and OCD. Considering the common metabolic pathway and recent results from association studies both in OCD and ASDs, a question, whether there is common molecular background in ASDs and OCD, was raised.

METHODS

Ten single nucleotide polymorphisms (SNPs) at 9p24 and 11p12-p13 containing glutamate transporter genes SLC1A1 and SLC1A2 and their neighboring regions in 175 patients with ASDs and 216 controls of Finnish origin were analyzed using real-time-PCR or direct sequencing.

RESULTS

The strongest association was detected with rs1340513 in the JMJD2C gene at 9p24.1 (P=0.007; corrected P=0.011) that is the same SNP associated with infantile autism (P=0.0007) in the autism genome project consortium (2007). No association was detected at 11p12-p13 with ASD. Interestingly, the strongest association in OCD has been found at rs301443 (P=0.000067) residing between SLC1A1 and JMJD2C at 9p24.

CONCLUSION

In summary, our results give evidence for a possible common locus for OCD and ASDs at 9p24. We speculate that the area may represent a special candidate region for obsessive repetitive symptoms in ASDs.

Genome-wide linkage in Utah autism pedigrees

Genetic studies of autism over the past decade suggest a complex landscape of multiple genes. In the face of this heterogeneity, studies that include large extended pedigrees may offer valuable insights, as the relatively few susceptibility genes within single large families may be more easily discerned. This genome-wide screen of 70 families includes 20 large extended pedigrees of 6-9 generations, 6 moderate-sized families of 4-5 generations and 44 smaller families of 2-3 generations. The Center for Inherited Disease Research (CIDR) provided genotyping using the Illumina Linkage Panel 12, a 6K single-nucleotide polymorphism (SNP) platform. Results from 192 subjects with an autism spectrum disorder (ASD) and 461 of their relatives revealed genome-wide significance on chromosome 15q, with three possibly distinct peaks: 15q13.1-q14 (heterogeneity LOD (HLOD)=4.09 at 29 459 872 bp); 15q14-q21.1 (HLOD=3.59 at 36 837 208 bp); and 15q21.1-q22.2 (HLOD=5.31 at 55 629 733 bp). Two of these peaks replicate earlier findings. There were additional suggestive results on chromosomes 2p25.3-p24.1 (HLOD=1.87), 7q31.31-q32.3 (HLOD=1.97) and 13q12.11-q12.3 (HLOD=1.93). Affected subjects in families supporting the linkage peaks found in this study did not reveal strong evidence for distinct phenotypic subgroups.

Pentapeptide sharing between Corynebacterium diphtheria toxin and the human neural protein network

We describe the pentapeptides shared between the Corynebacterium diphtheria toxin and the human proteins associated with fundamental neural functions. We report that diphtheria toxin pentapeptides are spread among human antigens such as tuberous sclerosis proteins 1 and 2, reelin, contactin-4, neuroligins, semaphorin-5A, sodium channel protein type 1 subunit α, Williams-Beuren syndrome chromosomal region 1 protein, Williams-Beuren syndrome chromosomal region 20A protein. Williams-Beuren syndrome chromosomal region 8 protein, Bardet-Biedl syndrome 9 protein, Bardet-Biedl syndrome 10 protein, oligodendrocyte-myelin glycoprotein, neurofibromin-2, and periaxin. The data are discussed in relation to the bacterial immune escape phenomenon, and in the context of potential cross-reactions in diagnostic tests and immune therapies.

Abnormal cell patterning at the cortical gray-white matter boundary in autism spectrum disorders

Previous research on neuronal spacing and columnar organization indicates the presence of cell patterning alterations within the cerebral cortex of individuals with autism spectrum disorders (ASD). These patterning abnormalities include irregularities at the gray-white matter boundary and may implicate early neurodevelopmental events such as migration in altering cortical organization in ASD. The present study utilized a novel method to quantify the gray-white matter boundary in eight ASD and eight typically developing control subjects. Digital photomicrographs of the gray-white matter boundary were acquired from multiple positions within the superior temporal gyrus (BA21), dorsolateral frontal lobe (BA9), and dorsal parietal lobe (BA7) of each case. A sigmoid curve was fitted to the transition zone between layer VI and underlying white matter (subplate), and the slope of the resulting curve was used as a measure of the spatial extent of the transition zone. For all three cortical regions examined, ASD subjects showed "shallower" sigmoid curves compared to neurotypicals, indicating the presence of an indistinct boundary between cortical layer VI and the underlying white matter. These results may reflect the presence of supernumerary neurons beneath the cortical plate that could be the result of migration deficits or failed apoptosis in the subplate region. Furthermore, these findings raise questions regarding the validity of cortical measures that rely on gray-white matter parcellation, since an indistinct transition zone could lead to a misplaced cortical boundary and errors in both thickness and volume measures.

The Reelin (RELN) gene is associated with executive function in healthy individuals

Executive functions such as set-shifting and maintenance are cognitive processes that rely on complex neurodevelopmental processes. Although neurodevelopmental processes are mainly studied in animal models and in neuropsychiatric disorders, the underlying genetic basis for these processes under physiological conditions is poorly understood. We aimed to investigate the association between genetic variants of the Reelin (RELN) gene and cognitive set-shifting in healthy young individuals. The relationship between 12 selected single nucleotide polymorphisms (SNPs) of the RELN gene and cognitive set-shifting as measured by perseverative errors using the modified card sorting test (MCST) was analysed in a sample of N=98 young healthy individuals (mean age in years: 22.7 ± 0.19). Results show that in individual MANCOVA analyses two of five significant SNPs (rs2711870: F(2,39)=7.14; p=0.0019; rs2249372: F(2,39)=6.97; p=0.002) withstood Bonferroni correction for multiple testing (corrected p-value: p=0.004). While haplotype analyses of the RELN gene showed significant associations between three haplotypes and perseverative error processing in various models of inheritance (adjusted for age, gender, BDI, MWTB IQ), the GCT haplotype showed the most robust finding with a recessive model of inheritance (p=2.32 × 10(-5)) involving the functional SNP rs362691 (Leu-Val amino acid change). Although our study strongly suggests the involvement of the RELN gene in cognitive set-shifting and maintenance, our study requires further exploration as well as replication of the findings in larger samples of healthy individuals and in clinical samples with neuropsychiatric disorders.

Autism spectrum disorders and epigenetics

OBJECTIVE

Current research suggests that the causes of autism spectrum disorders (ASD) are multifactorial and include both genetic and environmental factors. Several lines of evidence suggest that epigenetics also plays an important role in ASD etiology and that it might, in fact, integrate genetic and environmental influences to dysregulate neurodevelopmental processes. The objective of this review is to illustrate how epigenetic modifications that are known to alter gene expression without changing primary DNA sequence may play a role in the etiology of ASD.

METHOD

In this review, we summarize current knowledge about epigenetic modifications to genes and genomic regions possibly involved in the etiology of ASD.

RESULTS

Several genetic syndromes comorbid with ASD, which include Rett, Fragile X, Prader-Willi, Angelman, and CHARGE (Coloboma of the eye, Heart defects, Atresia of the nasal choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and deafness), all demonstrate dysregulation of epigenetic marks or epigenetic mechanisms. We report also on genes or genomic regions exhibiting abnormal epigenetic regulation in association with either syndromic (15q11-13 maternal duplication) or nonsyndromic forms of ASD. Finally, we discuss the state of current knowledge regarding the etiologic role of environmental factors linked to both the development of ASD and epigenetic dysregulation.

CONCLUSION

Data reviewed in this article highlight a variety of situations in which epigenetic dysregulation is associated with the development of ASD, thereby supporting a role for epigenetics in the multifactorial etiologies of ASD.

Key role for gene dosage and synaptic homeostasis in autism spectrum disorders

Autism spectrum disorders (ASD) are characterized by impairments in reciprocal social communication, and repetitive, stereotyped verbal and non-verbal behaviors. Genetic studies have provided a relatively large number of genes that constitute a comprehensive framework to better understand this complex and heterogeneous syndrome. Based on the most robust findings, three observations can be made. First, genetic contributions to ASD are highly heterogeneous and most probably involve a combination of alleles with low and high penetrance. Second, the majority of the mutations apparently affect a single allele, suggesting a key role for gene dosage in susceptibility to ASD. Finally, the broad expression and function of the causative genes suggest that alteration of synaptic homeostasis could be a common biological process associated with ASD. Understanding the mechanisms that regulate synaptic homeostasis should shed new light on the causes of ASD and could provide a means to modulate the severity of the symptoms.

Immune dysfunction in autism: a pathway to treatment

Autism is a complex and clinically heterogeneous disorder with a spectrum of symptoms. Clinicians, schools, and service agencies worldwide have reported a dramatic increase in the number of children identified with autism. Despite expanding research, the etiology and underlying biological processes of autism remain poorly understood, and the relative contribution from genetic, epigenetic, and environmental factors remains unclear. Although autism affects primarily brain function (especially affect, social functioning, and cognition), it is unknown to what extent other organs and systems are disrupted. Published findings have identified widespread changes in the immune systems of children with autism, at both systemic and cellular levels. Brain specimens from autism subjects exhibit signs of active, ongoing inflammation, as well as alterations in gene pathways associated with immune signaling and immune function. Moreover, many genetic studies have indicated a link between autism and genes that are relevant to both the nervous system and the immune system. Alterations in these pathways can affect function in both systems. Together, these reports suggest that autism may in fact be a systemic disorder with connections to abnormal immune responses. Such immune system dysfunction may represent novel targets for treatment. A better understanding of the involvement of the immune response in autism, and of how early brain development is altered, may have important therapeutic implications.

Identification of chromosome 7 inversion breakpoints in an autistic family narrows candidate region for autism susceptibility

Chromosomal breaks and rearrangements have been observed in conjunction with autism and autistic spectrum disorders. A chromosomal inversion has been previously reported in autistic siblings, spanning the region from approximately 7q22.1 to 7q31. This family is distinguished by having multiple individuals with autism and associated disabilities. The region containing the inversion has been strongly implicated in autism by multiple linkage studies, and has been particularly associated with language defects in autism as well as in other disorders with language components. Mapping of the inversion breakpoints by FISH has localized the inversion to the region spanning approximately 99-108.75 Mb of chromosome 7. The proximal breakpoint has the potential to disrupt either the coding sequence or regulatory regions of a number of cytochrome P450 genes while the distal region falls in a relative gene desert. Copy number variant analysis of the breakpoint regions detected no duplication or deletion that could clearly be associated with disease status. Association analysis in our autism data set using single nucleotide polymorphisms located near the breakpoints showed no significant association with proximal breakpoint markers, but has identified markers near the distal breakpoint ( approximately 108-110 Mb) with significant associations to autism. The chromosomal abnormality in this family strengthens the case for an autism susceptibility gene in the chromosome 7q22-31 region and targets a candidate region for further investigation.

Genetics of autistic disorders: review and clinical implications

Twin and family studies in autistic disorders (AD) have elucidated a high heritability of AD. In this literature review, we will present an overview on molecular genetic studies in AD and highlight the most recent findings of an increased rate of copy number variations in AD. An extensive literature search in the PubMed database was performed to obtain English published articles on genetic findings in autism. Results of linkage, (genome wide) association and cytogenetic studies are presented, and putative aetiopathological pathways are discussed. Implications of the different genetic findings for genetic counselling and genetic testing at present will be described. The article ends with a prospectus on future directions.

Differential monocyte responses to TLR ligands in children with autism spectrum disorders

Autism spectrum disorders (ASD) are characterized by impairment in social interactions, communication deficits, and restricted repetitive interests and behaviors. Recent evidence has suggested that impairments of innate immunity may play an important role in ASD. To test this hypothesis, we isolated peripheral blood monocytes from 17 children with ASD and 16 age-matched typically developing (TD) controls and stimulated these cell cultures in vitro with distinct toll-like receptors (TLR) ligands: TLR 2 (lipoteichoic acid; LTA), TLR 3 (poly I:C), TLR 4 (lipopolysaccharide; LPS), TLR 5 (flagellin), and TLR 9 (CpG-B). Supernatants were harvested from the cell cultures and pro-inflammatory cytokine responses for IL-1beta, IL-6, IL-8, TNFalpha, MCP-1, and GM-CSF were determined by multiplex Luminex analysis. After in vitro challenge with TLR ligands, differential cytokine responses were observed in monocyte cultures from children with ASD compared with TD control children. In particular, there was a marked increase in pro-inflammatory IL-1beta, IL-6, and TNFalpha responses following TLR 2, and IL-1beta response following TLR 4 stimulation in monocyte cultures from children with ASD (p<0.04). Conversely, following TLR 9 stimulation there was a decrease in IL-1beta, IL-6, GM-CSF, and TNFalpha responses in monocyte cell cultures from children with ASD compared with controls (p<0.05). These data indicate that, monocyte cultures from children with ASD are more responsive to signaling via select TLRs. As monocytes are key regulators of the immune response, dysfunction in the response of these cells could result in long-term immune alterations in children with ASD that may lead to the development of adverse neuroimmune interactions and could play a role in the pathophysiology observed in ASD.

Preliminary evidence of the in vitro effects of BDE-47 on innate immune responses in children with autism spectrum disorders

Autism spectrum disorders (ASD) are complex neurodevelopmental disorders that manifest in childhood. Immune dysregulation and autoimmune reactivity may contribute to the etiology of ASD and are likely the result of both genetic and environmental susceptibilities. A common environmental contaminant, 2,2',4,4'-tetrabrominated biphenyl (BDE-47), was tested for differential effects on the immune response of peripheral blood mononuclear cells (PBMC) isolated from children with ASD (n=19) and age-matched typically developing controls (TD, n=18). PBMC were exposed in vitro to either 100 nM or 500 nM BDE-47, before challenge with bacterial lipopolysaccharide (LPS), an innate immune activator, with resultant cytokine production measured using the Luminex multiplex platform. The cytokine responses of LPS stimulated PBMC from ASD and TD subjects diverged in the presence of 100 nM BDE. For example, cells cultured from the TD group demonstrated significantly decreased levels of the cytokines IL-12p40, GM-CSF, IL-6, TNFalpha, and the chemokines MIP-1alpha and MIP-1beta following LPS stimulation of PBMC pretreated with 100 nM BDE-47 compared with samples treated with vehicle control (p<0.05). In contrast, cells cultured from subjects with ASD demonstrated an increased IL-1beta response to LPS (p=0.033) when pretreated with 100 nM BDE-47 compared with vehicle control. Preincubation with 500 nM BDE-47 significantly increased the stimulated release of the inflammatory chemokine IL-8 (p<0.04) in cells cultured from subjects with ASD but not in cells from TD controls. These data suggest that in vitro exposure of PBMC to BDE-47 affects cell cytokine production in a pediatric population. Moreover, PBMC from the ASD subjects were differentially affected when compared with the TD controls suggesting a biological basis for altered sensitivity to BDE-47 in the ASD population.

Increased IgG4 levels in children with autism disorder

Accumulating evidence indicates that immune dysfunction is associated with autism disorders in a significant subset of children. Previous reports have shown abnormal immunoglobulin (Ig) levels, including an increased presence of autoreactive antibodies in the circulation of individuals with autism. As IgG is the predominant antibody isotype in circulation, we expected that an altered immune response could result in an abnormal IgG subclass profile in children with autism. We examined circulating plasma levels of IgG1, IgG2, IgG3, and IgG4 in 241 children from the CHARGE (Childhood Autism Risks from Genetics and the Environment) study, a large epidemiologic case-control investigation, including 114 children who meet full criteria for autism disorder (AU), 96 typically developing control children (TD) from a randomly selected sample of the general population, and 31 children with developmental delays (DD). We report significantly increased levels of the IgG4 subclass in children with AU compared with TD control children (p=0.016) and compared with DD controls (p=0.041). These results may suggest an underlying immunological abnormality in AU subjects resulting in elevated IgG4 production. Further investigation is necessary to elucidate the relationship between immunological findings and behavioral impairments in autism.

Autism spectrum disorders and childhood-onset schizophrenia: clinical and biological contributions to a relation revisited

OBJECTIVE

To highlight emerging evidence for clinical and biological links between autism/pervasive developmental disorder (PDD) and schizophrenia, with particular attention to childhood-onset schizophrenia (COS).

METHOD

Clinical, demographic, and brain developmental data from the National Institute of Mental Health (and other) COS studies and selected family, imaging, and genetic data from studies of autism, PDD, and schizophrenia were reviewed.

RESULTS

In the two large studies that have examined this systematically, COS is preceded by and comorbid with PDD in 30% to 50% of cases. Epidemiological and family studies find association between the disorders. Both disorders have evidence of accelerated trajectories of anatomic brain development at ages near disorder onset. A growing number of risk genes and/or rare small chromosomal variants (microdeletions or duplications) are shared by schizophrenia and autism.

CONCLUSIONS

Biological risk does not closely follow DSM phenotypes, and core neurobiological processes are likely common for subsets of these two heterogeneous clinical groups. Long-term prospective follow-up of autistic populations and greater diagnostic distinction between schizophrenia spectrum and autism spectrum disorders in adult relatives are needed.

Altered gene expression and function of peripheral blood natural killer cells in children with autism

Immune related abnormalities have repeatedly been reported in autism spectrum disorders (ASD), including evidence of immune dysregulation and autoimmune phenomena. NK cells may play an important role in neurodevelopmental disorders such as ASD. Here we performed a gene expression screen and cellular functional analysis on peripheral blood obtained from 52 children with ASD and 27 typically developing control children enrolled in the case-control CHARGE study. RNA expression of NK cell receptors and effector molecules were significantly upregulated in ASD. Flow cytometric analysis of NK cells demonstrated increased production of perforin, granzyme B, and interferon gamma (IFNgamma) under resting conditions in children with ASD (p<0.01). Following NK cell stimulation in the presence of K562 target cells, the cytotoxicity of NK cells was significantly reduced in ASD compared with controls (p<0.02). Furthermore, under similar stimulation conditions the presence of perforin, granzyme B, and IFNgamma in NK cells from ASD children was significantly lower compared with controls (p<0.001). These findings suggest possible dysfunction of NK cells in children with ASD. Abnormalities in NK cells may represent a susceptibility factor in ASD and may predispose to the development of autoimmunity and/or adverse neuroimmune interactions during critical periods of development.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

The Reelin signaling pathway promotes dendritic spine development in hippocampal neurons

The development of distinct cellular layers and precise synaptic circuits is essential for the formation of well functioning cortical structures in the mammalian brain. The extracellular protein Reelin, through the activation of a core signaling pathway, including the receptors ApoER2 and VLDLR (very low density lipoprotein receptor) and the adapter protein Dab1 (Disabled-1), controls the positioning of radially migrating principal neurons, promotes the extension of dendritic processes in immature forebrain neurons, and affects synaptic transmission. Here we report for the first time that the Reelin signaling pathway promotes the development of postsynaptic structures such as dendritic spines in hippocampal pyramidal neurons. Our data underscore the importance of Reelin as a factor that promotes the maturation of target neuronal populations and the development of excitatory circuits in the postnatal hippocampus. These findings may have implications for understanding the origin of cognitive disorders associated with Reelin deficiency.

Genetic analysis of reelin gene (RELN) SNPs: no association with autism spectrum disorder in the Indian population

Involvement of reelin with Autism spectrum disorder (ASD) has been implicated through several biochemical as well as genetic studies. Reelin is an extracellular signaling protein, which plays a significant role in cytoarchitectonic pattern formation of different brain areas during development. Reelin gene (RELN) is located on chromosome 7q22; an important autism critical region identified through several genome-wide scans. A number of genetic studies have been carried out to investigate the association of reelin with autism. Recently we reported possible paternal effect in the transmission of CGG repeat alleles of RELN in the susceptibility towards autism. Further analysis on other polymorphisms is warranted to validate the status of RELN as a candidate for autism. Therefore in the present study, we have investigated six more SNPs (rs727531, rs2072403, rs2072402, rs362691, rs362719, rs736707) in 102 patients, 182 parents and 101 healthy controls. We have followed DSM-IV criteria and the screening for autism was carried out using CARS. Genomic DNA isolated from blood was used for PCR and subsequent RFLP analysis. Finally, case-control and family-based association studies were carried out to examine the genetic association of these SNP markers with ASD in the Indian population. But, we failed to detect either preferential parental transmission of any alleles of the markers to affected offspring or any biased allelic or genotypic distribution between the cases and controls. Thus the present study suggests that these SNPs of RELN are unlikely to be associated with ASD in the Indian population.

Advances in autism genetics: on the threshold of a new neurobiology

Autism is a heterogeneous syndrome defined by impairments in three core domains: social interaction, language and range of interests. Recent work has led to the identification of several autism susceptibility genes and an increased appreciation of the contribution of de novo and inherited copy number variation. Promising strategies are also being applied to identify common genetic risk variants. Systems biology approaches, including array-based expression profiling, are poised to provide additional insights into this group of disorders, in which heterogeneity, both genetic and phenotypic, is emerging as a dominant theme.

The association analysis of RELN and GRM8 genes with autistic spectrum disorder in Chinese Han population

The region on chromosome 7q stands out as the region of suggestive linkage to aetiology of autism with the greatest concordance in many independent genome-wide scans. RELN and GRM8, the two genes selected in this study, are located within this region. The protein products of both genes are considered to play a pivotal role in the development of the central nervous system. In addition, biochemical and neuroanatomical data indicated that RELN and GRM8 genes are likely involved in the pathogenesis of autistic disorder. Therefore, both RELN and GRM8 genes are considered to be not only the positional but also the functional candidate genes to autism for association research. In this study, we genotyped 12 single nucleotide polymorphisms (SNPs) located within the RELN and GRM8 genes in 213 children with autistic spectrum disorder (ASD) and 160 controls. A significant genetic association between SNP2 (located in intron 59 of RELN) and ASD was observed, and the log-additive model was accepted as the best inheritance model fitting this data (OR: 0.72, 95% CI: 0.54-0.97, P = 0.03). Haplotype-specific association analysis revealed that the result was consistent with the individual SNP study; the combination of SNP1/SNP2/SNP3/SNP4 which are in strong linkage disequilibrium (LD) (D' > 0.75) showed significant association with ASD (P = 0.027). Neither the single SNP nor the haplotype analysis showed significant association between ASD and the markers of GRM8 gene. Hence, our study suggested the possible involvement of RELN gene in the susceptibility to ASD. Future replications are warranted before definitive conclusion can be drawn.

Peripheral Blood Leukocyte Production of BDNF following Mitogen Stimulation in Early Onset and Regressive Autism

Brain-derived neurotrophic factor (BDNF) is critical for neuronal differentiation and synaptic development. BDNF is also implicated in the development of psychological disorders including depression, bipolar disorder and schizophrenia. Previously, elevated BDNF levels were observed in neonatal blood samples from infants who were later diagnosed with autism when compared with children who developed normally, suggesting that BDNF may be involved in the development of autism. BDNF is produced by activated brain microglial cells, a cellular phenotype that shares several features with peripheral macrophages, suggesting an important role for the immune system in BDNF production. We hypothesized that under mitogenic stimulation, peripheral blood mononuclear cells obtained from children with autism may have altered BDNF production compared with age-matched typically developing control subjects. In addition, we examined the differences between the production of BDNF in classic/early-onset autism and children who had a regressive form of autism. We show here that plasma levels of BDNF levels are increased in children with autism, especially in early onset autism subjects. Furthermore, under mitogenic stimulation with PHA and LPS, BDNF production is significantly increased in children with autism compared with typically developing subjects. However, stimulation with tetanus toxoid results in a decreased response in children with autism. This data suggest that immune cell-derived production of BDNF could be an important source for the increased BDNF that is detected in some subjects with autism. As a neurotrophic factor produced by immune cells, BDNF could help elucidate the role of the immune system in neurodevelopment and neuronal maintenance, which may be dysregulated in autism.

Lissencephaly 1 linking to multiple diseases: mental retardation, neurodegeneration, schizophrenia, male sterility, and more

Lissencephaly 1 (LIS1) was the first gene implicated in the pathogenesis of type-1 lissencephaly. More than a decade of research by multiple laboratories has revealed that LIS1 is a key node protein, which participates in several pathways, including association with the molecular motor cytoplasmic dynein, the reelin signaling pathway, and the platelet-activating factor pathway. Mutations in LIS1-interacting proteins, either in human, or in mouse models has suggested that LIS1 might play a role in the pathogenesis of numerous diseases such as male sterility, schizophrenia, neuronal degeneration, and viral infections.

Advances in behavioral genetics: mouse models of autism

Autism is a neurodevelopmental syndrome with markedly high heritability. The diagnostic indicators of autism are core behavioral symptoms, rather than definitive neuropathological markers. Etiology is thought to involve complex, multigenic interactions and possible environmental contributions. In this review, we focus on genetic pathways with multiple members represented in autism candidate gene lists. Many of these pathways can also be impinged upon by environmental risk factors associated with the disorder. The mouse model system provides a method to experimentally manipulate candidate genes for autism susceptibility, and to use environmental challenges to drive aberrant gene expression and cell pathology early in development. Mouse models for fragile X syndrome, Rett syndrome and other disorders associated with autistic-like behavior have elucidated neuropathology that might underlie the autism phenotype, including abnormalities in synaptic plasticity. Mouse models have also been used to investigate the effects of alterations in signaling pathways on neuronal migration, neurotransmission and brain anatomy, relevant to findings in autistic populations. Advances have included the evaluation of mouse models with behavioral assays designed to reflect disease symptoms, including impaired social interaction, communication deficits and repetitive behaviors, and the symptom onset during the neonatal period. Research focusing on the effect of gene-by-gene interactions or genetic susceptibility to detrimental environmental challenges may further understanding of the complex etiology for autism.