Prioritization of Copy Number Variation Loci Associated with Autism from AutDB-An Integrative Multi-Study Genetic Database

Saliva DNA: An alternative biospecimen for single nucleotide polymorphism chromosomal microarray analysis in autism

Chromosomal microarray analysis (CMA) is typically performed for investigation of autism using blood DNA. However, blood collection poses significant challenges for autistic children with repetitive behaviors and sensory and communication issues, often necessitating physical restraint or sedation. Noninvasive saliva collection offers an alternative, however, no published studies to date have evaluated saliva DNA for CMA in autism. Furthermore, previous reports suggest that saliva is suboptimal for detecting copy number variation. We therefore aimed to evaluate saliva DNA for single nucleotide polymorphism (SNP) CMA in autistic children. Saliva DNA from 48 probands and parents (n = 133) was obtained with a mean concentration of 141.7 ng/μL. SNP CMA was successful in 131/133 (98.5%) patients from which we correlated the size and accuracy of a copy number variant(s) called between a proband and carrier parent, and for a subgroup (n = 17 probands) who had a previous CMA using blood sample. There were no discordant copy number variant results between the proband and carrier parent, or the subgroup, however, there was an acceptable mean size difference of 0.009 and 0.07 Mb, respectively. Our findings demonstrate that saliva DNA can be an alternative for SNP CMA in autism, which avoids blood collection with significant implications for clinical practice guidelines.

Molecular Dysregulation in Autism Spectrum Disorder

Autism Spectrum Disorder (ASD) comprises a heterogeneous group of neurodevelopmental disorders with a strong heritable genetic component. At present, ASD is diagnosed solely by behavioral criteria. Advances in genomic analysis have contributed to numerous candidate genes for the risk of ASD, where rare mutations and s common variants contribute to its susceptibility. Moreover, studies show rare de novo variants, copy number variation and single nucleotide polymorphisms (SNPs) also impact neurodevelopment signaling. Exploration of rare and common variants involved in common dysregulated pathways can provide new diagnostic and therapeutic strategies for ASD. Contributions of current innovative molecular strategies to understand etiology of ASD will be explored which are focused on whole exome sequencing (WES), whole genome sequencing (WGS), microRNA, long non-coding RNAs and CRISPR/Cas9 models. Some promising areas of pharmacogenomic and endophenotype directed therapies as novel personalized treatment and prevention will be discussed.

Factors Affecting Family Compliance with Genetic Testing of Children Diagnosed with Autism Spectrum Disorder

There is broad consensus about the importance of post-diagnostic genetic testing for children with ASD. However, the extent of compliance with these tests and the factors affecting compliance have rarely been examined. We surveyed a sample of 114 families with a child with ASD in Israel, where such genetic testing is funded by the government. We found that only one-third of these families completed post-diagnosis genetic testing for their child. The main factor influencing compliance was the doctor's recommendation (OR 11.6; 95% CI 3.2-42.4; p < 0.001). Furthermore, > 50% of the non-compliant families reported that genetic testing was irrelevant to them. Our findings highlight the importance of providing clear recommendations and explanations regarding the benefits and relevance of post-diagnosis genetic testing for children with ASD.

Neuropsychopathology of Autism Spectrum Disorder: Complex Interplay of Genetic, Epigenetic, and Environmental Factors

Autism spectrum disorder (ASD) is a complex heterogeneous consortium of pervasive development disorders (PDD) which ranges from atypical autism, autism, and Asperger syndrome affecting brain in the developmental stage. This debilitating neurodevelopmental disorder results in both core as well as associated symptoms. Core symptoms observed in autistic patients are lack of social interaction, pervasive, stereotyped, and restricted behavior while the associated symptoms include irritability, anxiety, aggression, and several comorbid disorders.ASD is a polygenic disorder and is multifactorial in origin. Copy number variations (CNVs) of several genes that regulate the synaptogenesis and signaling pathways are one of the major factors responsible for the pathogenesis of autism. The complex integration of various CNVs cause mutations in the genes which code for molecules involved in cell adhesion, voltage-gated ion-channels, scaffolding proteins as well as signaling pathways (PTEN and mTOR pathways). These mutated genes are responsible for affecting synaptic transmission by causing plasticity dysfunction responsible, in turn, for the expression of ASD.Epigenetic modifications affecting DNA transcription and various pre-natal and post-natal exposure to a variety of environmental factors are also precipitating factors for the occurrence of ASD. All of these together cause dysregulation of glutamatergic signaling as well as imbalance in excitatory: inhibitory pathways resulting in glial cell activation and release of inflammatory mediators responsible for the aberrant social behavior which is observed in autistic patients.In this chapter we review and provide insight into the intricate integration of various genetic, epigenetic, and environmental factors which play a major role in the pathogenesis of this disorder and the mechanistic approach behind this integration.

Clinical and molecular characterization of three genomic rearrangements at chromosome 22q13.3 associated with autism spectrum disorder

OBJECTIVES

Chromosome 22q13 is a hot region of genomic rearrangements that may result in deletion, duplication, and translocation, and that may lead to neurodevelopmental disorders in affected patients.

MATERIALS AND METHODS

We carried out an array-based comparative genomic hybridization analysis to detect copy number variations (CNVs) of genomic DNA in patients with autism spectrum disorders (ASD) who were consecutively recruited into our molecular genetic study of ASD. Karyotyping, fluorescent in-situ hybridization analysis, and real time-quantitative PCR were used for validation tests.

RESULTS

We completed a genome-wide CNV analysis of 335 patients with ASD from Taiwan. Three unrelated male patients were found to carry three different CNVs at 22q13.3, respectively, including a de novo terminal deletion of ∼106 kb at 22q13.33, a de novo interstitial duplication of ∼1.8 Mb at 22q13.32-q13.33, and a microdeletion of ∼147 kb at 22q13.33. These three CNVs all involved the dosage change of the SHANK3 gene. The last patient also carried a genomic duplication of ∼3.86 Mb at 19q13.42-q13.4 in addition to a microdeletion of ∼147 kb at 22q13.33. His younger sister also carried these two CNVs, but she had developmental delay and other neurological deficits without ASD. These two CNVs were transmitted from their unaffected father, who carried a balanced translocation between chromosome 22q and 19q.

CONCLUSION

Our data support that recurrent genomic rearrangements at 22q13.3 are part of the genetic landscape of ASD in our patients and changes in SHANK3 dosage are associated with neurodevelopmental disorders. However, the clinical symptoms of patients with 22q13.3 rearrangements can vary depending on other genetic and nongenetic factors, not limited to genes involved in CNVs in this region.

Contribution of maternal hypertension to autism etiology in a murine model; cerebellar gene expression

Aim: To study the contribution of maternal hypertension to autism spectrum disorders’ (ASD) phenotype, and gene expression, in a murine model. Materials & methods: To examine the effects of maternal hypertension, we used a well-described transgenic mouse model lacking functional endothelial nitric oxide synthase (eNOS or NOS3). Behavioral testing was performed on male offspring between 8 and 10 weeks of age. Cerebella underwent shotgun transcriptome RNA sequencing. Differentially expressed genes were examined for Gene Ontology enrichment. 2-way-RM-ANOVA, 1-way-ANOVA and Student's t-test were used for statistical analysis. Results & conclusion: Our findings revealed that a deficit in social behavior, the hallmark of ASD, is differentially present in offspring born to hypertensive mothers. Novel ASD-related genes were differentially expressed in the cerebellum, implicating its possible role in ASD etiology. Condensation: Altered uterine environment resulting from maternal hypertension contributes to ASD phenotype, and modifies expression of novel ASD-related genes in cerebella of eNOS heterozygous offspring.

Genome-wide analysis of copy number variations identifies PARK2 as a candidate gene for autism spectrum disorder

BACKGROUND

Autism spectrum disorder (ASD) is an early-onset neurodevelopmental disorder with complex genetic underpinning in its etiology. Copy number variations (CNVs) as one of the genetic factors associated with ASD have been addressed in recent genome-wide association studies (GWAS). However, the significance of CNV has not been well investigated in non-Caucasian ASD population.

METHODS

To identify the pathogenic CNVs responsible for ASD in Han Chinese, we performed a segment-based GWAS of CNV in 335 ASD cases and 1093 healthy controls using Affymetrix single nucleotide polymorphism (SNP) array by focusing on case-specific CNVs. PARK2 was one of the important genes with several case-specific regions overlapped on it. The findings were validated in the initial screen sample set and replicated in another sample set by real-time quantitative PCR (qPCR).

RESULTS

A total of six CNVs at 6q26 that spanned different exons of PARK2 were identified. The PARK2 expression level was down-regulated at exon-dependent manner in cases with either deletion or duplication. The result revealed that the gene function might be disrupted by exonic deletion and duplication. We also observed that the ASD case with exonic duplication demonstrated a more severe interference of PARK2 expression and the clinical feature than the ones with deletion at the exons 2-4 of the PARK2 gene.

CONCLUSIONS

Our finding provides evidence to support that CNVs affecting PARK2 function might contribute to genetic etiology of a proportion of cases with ASD. The intriguing results of this work warrant further study on characterizing the functional impact of various exonic CNVs on the PARK2 gene.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00494754.

Association of Copy Number Variations in Autism Spectrum Disorders: A Systematic Review

Autism spectrum disorders (ASDs) are characterized by language impairments, social deficits, and repetitive behaviors. The onset of symptoms occurs by the age of 3 and shows a lifelong persistence. Genetics plays a major role in the etiology of ASD. Except genetics, several potential risk factors (environmental factors and epigenetics) may contribute to ASD. Copy number variations (CNVs) are the most widespread structural variations in the human genome. These variations can alter the genome structure either by deletion or by duplication. CNVs can be de novo or inherited. Chromosomal rearrangements have been detected in 5–10% of the patients with ASD and recently copy number changes ranging from a few kilobases (kb) to several megabases (Mb) in size have been reported. Recent data have also revealed that submicroscopic CNVs can have a role in ASD, and de novo CNVs seem to be a more common risk factor in sporadic compared with inherited forms of ASD. CNVs are being implicated as a contributor to the pathophysiology of complex neurodevelopmental disorders and they can affect a wide range of human phenotypes including mental retardation (MR), autism, neuropsychiatric disorders, and susceptibility to other complex traits such as HIV, Crohn’s disease, and psoriasis. This review emphasizes the major CNVs reported to date in ASD.

Intragenic deletions affecting two alternative transcripts of the IMMP2L gene in patients with Tourette syndrome

Tourette syndrome is a neurodevelopmental disorder characterized by multiple motor and vocal tics, and the disorder is often accompanied by comorbidities such as attention-deficit hyperactivity-disorder and obsessive compulsive disorder. Tourette syndrome has a complex etiology, but the underlying environmental and genetic factors are largely unknown. IMMP2L (inner mitochondrial membrane peptidase, subunit 2) located on chromosome 7q31 is one of the genes suggested as a susceptibility factor in disease pathogenesis. Through screening of a Danish cohort comprising 188 unrelated Tourette syndrome patients for copy number variations, we identified seven patients with intragenic IMMP2L deletions (3.7%), and this frequency was significantly higher (P=0.0447) compared with a Danish control cohort (0.9%). Four of the seven deletions identified did not include any known exons of IMMP2L, but were within intron 3. These deletions were found to affect a shorter IMMP2L mRNA species with two alternative 5'-exons (one including the ATG start codon). We showed that both transcripts (long and short) were expressed in several brain regions, with a particularly high expression in cerebellum and hippocampus. The current findings give further evidence for the role of IMMP2L as a susceptibility factor in Tourette syndrome and suggest that intronic changes in disease susceptibility genes should be investigated further for presence of alternatively spliced exons.

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

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

Genetic targeting of the amphetamine and methylphenidate-sensitive dopamine transporter: on the path to an animal model of attention-deficit hyperactivity disorder

Alterations in dopamine (DA) signaling underlie the most widely held theories of molecular and circuit level perturbations that lead to risk for attention-deficit hyperactivity disorder (ADHD). The DA transporter (DAT), a presynaptic reuptake protein whose activity provides critical support for DA signaling by limiting DA action at pre- and postsynaptic receptors, has been consistently associated with ADHD through pharmacological, behavioral, brain imaging and genetic studies. Currently, the animal models of ADHD exhibit significant limitations, stemming in large part from their lack of construct validity. To remedy this situation, we have pursued the creation of a mouse model derived from a functional nonsynonymous variant in the DAT gene (SLC6A3) of ADHD probands. We trace our path from the identification of these variants to in vitro biochemical and physiological studies to the production of the DAT Val559 mouse model. We discuss our initial findings with these animals and their promise in the context of existing rodent models of ADHD.