Postdoctoral Research Fellow, Columbia University Medical Center
We have identified cognitive, behavioral, and autism phenotype in Old-Order Amish children.
Autism spectrum disorder (ASD) is a continuum of neurodevelopmental disorders characterized by deficits in social behavior and communication, accompanied by restricted interests and repetitive behaviors. Currently, between 10-20% of ASD cases are associated with known genetic mutations or syndromes. Therefore, the study of specific ASD endophenotypes, (such as ASD associated with CNTNAP2 mutations), may yield breakthroughs in our understanding of underlying biological pathways and pathophysiology, and to identification of biomarkers and potential treatments, that are of relevance to a broader ASD population.
Strauss et al. (2006) identified a mutation of CNTNAP2 in a group of Old Order Amish children with cortical dysplasia-focal epilepsy (CDFE) syndrome, a disorder of neuronal migration causing epilepsy and global developmental delay. Subsequent deterioration in language, cognitive ability and social behavior occurs, with significant global developmental delay in all cases and ASD in two-thirds of cases. Oxytocin is a naturally occurring neuropeptide, which acts as a neurotransmitter, neuromodulator, and a hormone throughout the body. In animal models including primates, oxytocin has been demonstrated to increase eye contact, social interest, social recognition, and generosity, and to reduce stress responses (Takayanagi et al., 2005; Liu et al., 2008; Insel, 2010). Animal models of autism related to CNTNAP2 mutations have demonstrated dysregulation in the oxytocin system, which can be restored with exogenous oxytocin administration (Peñagarikano et al. 2015). Like their human counterparts, CNTNAP2 knockout mice display seizures and decreased social behaviors. An in vivo screen for pharmacological treatments identified oxytocin as having therapeutic benefit in CNTNAP2 mutant mice, in terms of amelioration of abnormal social behaviors (Peñagarikano et al. 2015). The benefit observed in CNTNAP2 mutant mice following oxytocin administration lead us to investigate its potential usage for Old-Order Amish Children with CNTNAP-2 mutations.
Abstract: Autism is a genetically complex neurodevelopmental syndrome in which language deficits are a core feature. We describe results from two complimentary approaches used to identify risk variants on chromosome 7 that likely contribute to the etiology of autism. A two-stage association study tested 2758 SNPs across a 10 Mb 7q35 language-related autism QTL in AGRE (Autism Genetic Resource Exchange) trios and found significant association with Contactin Associated Protein-Like 2 (CNTNAP2), a strong a priori candidate. Male-only containing families were identified as primarily responsible for this association signal, consistent with the strong male affection bias in ASD and other language-based disorders. Gene-expression analyses in developing human brain further identified CNTNAP2 as enriched in circuits important for language development. Together, these results provide convergent evidence for involvement of CNTNAP2, a Neurexin family member, in autism, and demonstrate a connection between genetic risk for autism and specific brain structures.
Pub.: 09 Jan '08, Pinned: 25 Aug '17
Abstract: Contactin-associated protein-like 2 (CNTNAP2) is a large multi-domain neuronal adhesion molecule implicated in a number of neurological disorders, including epilepsy, schizophrenia, autistic spectrum disorder (ASD), intellectual disability, and language delay. We reveal here by electron microscopy that the architecture of CNTNAP2 is composed of a large, medium, and small lobe that flex with respect to each other. Using epitope labeling and fragments, we assign the F58C, L1, and L2 domains to the large lobe, the FBG and L3 domains to the middle lobe, and the L4 domain to the small lobe of the CNTNAP2 molecular envelop. Our data reveal that CNTNAP2 has a very different architecture compared to neurexin 1alpha, a fellow member of the neurexin superfamily and a prototype, suggesting that CNTNAP2 uses a different strategy to integrate into the synaptic protein network. We show that the ectodomains of CNTNAP2 and contactin 2 (CNTN2) bind directly and specifically, with low nanomolar affinity. We show further that mutations in CNTNAP2 implicated in ASD are not segregated, but are distributed over the whole ectodomain. The molecular shape and dimensions of CNTNAP2 place constraints on how CNTNAP2 integrates in the cleft of axo-glial and neuronal contact sites and how it functions as an organizing and adhesive molecule.
Pub.: 14 Sep '16, Pinned: 25 Aug '17
Abstract: The role of some genes and their single nucleotide polymorphisms (SNPs) as genetic contributors of complex diseases is still a topic of much investigation. Research on genes related to autism susceptibility has been somewhat challenging, but also promising. Common genomic variants of CNTNAP2 have been associated with autism, and a range of autistic phenotypes such as impaired language function, abnormal social behavior, intellectual deficiency, epilepsy, and schizophrenia have been associated with this gene. Earlier findings have suggested that SNPs in the CNTNAP2 gene may be used as genetic markers for predisposition to autism spectrum disorder (ASD). We analyzed the SNPs (rs7794745 and rs2710102) in the CNTNAP2 gene of 210 individuals with idiopathic ASD and 200 non-autistic individuals by polymerase chain reaction-restriction fragment length polymorphism. The results revealed higher frequency distributions statistically significant (P = 0.034) of the homozygous SNP rs7794745 (presumed risk genotype) in ASD patients as compared with control subjects. The results also showed an association (OR = 1.802, 95%CI = 1.054-3.083, P = 0.042) between the same homozygous genotype and ASD, suggesting that it is a susceptibility factor for autism in this Brazilian population.
Pub.: 26 Feb '16, Pinned: 25 Aug '17
Abstract: CNTNAP2, one of the largest genes in the human genome, has been linked to human-specific language abilities and neurodevelopmental disorders. Our hypothesis is that epigenetic rather than genetic changes have accelerated the evolution of the human brain. To compare the cortex DNA methylation patterns of human and chimpanzee CNTNAP2 at ultra-high resolution, we combined methylated DNA immunoprecipitation (MeDIP) with NimbleGen tiling arrays for the orthologous gene and flanking sequences. Approximately 1.59 Mb of the 2.51 Mb target region could be aligned and analyzed with a customized algorithm in both species. More than one fifth (0.34 Mb) of the analyzed sequence throughout the entire gene displayed significant methylation differences between six human and five chimpanzee cortices. One of the most striking interspecies differences with 28% methylation in human and 59% in chimpanzee cortex (by bisulfite pyrosequencing) lies in a region 300 bp upstream of human SNP rs7794745 which has been associated with autism and parent-of-origin effects. Quantitative real-time RT PCR revealed that the protein-coding splice variant CNTNAP2-201 is 1.6-fold upregulated in human cortex, compared with the chimpanzee. Transcripts CNTNAP2-001, -002, and -003 did not show skewed allelic expression, which argues against CNTNAP2 imprinting, at least in adult human brain. Collectively, our results suggest widespread cortex DNA methylation changes in CNTNAP2 since the human-chimpanzee split, supporting a role for CNTNAP2 fine-regulation in human-specific language and communication traits.
Pub.: 18 Jan '14, Pinned: 25 Aug '17
Abstract: The CNTNAP2 (contactin associated protein-like 2) gene, highly expressed in the human prefrontal cortex, has been linked with autism and language impairment. Potential relationships between CNTNAP2, dorsolateral prefrontal cortex (DLPFC), and cognition have been suggested by previous clinical studies, but have not been directly examined in the same study. The current study collected structural MRI, genetic, and behavioral data in 317 healthy Chinese adults, and examined associations between CNTNAP2 variants, DLPFC, and cognitive performance (measured by the Stroop task). After controlling for intracranial volume, sex, and age, the CNTNAP2 genetic polymorphism at SNP rs7809486 had the strongest association with bilateral DLPFC volume (p = 0.00015 and 0.00014 for left and right DLPFC volumes, respectively), with GG homozygotes having greater bilateral DLPFC volumes and surface areas than the other genotypes. Furthermore, TT homozygotes of CNTNAP2 rs4726946 (a nearby SNP that had moderate linkage disequilibrium with rs7809486) had greater left DLPFC volume and surface area, and better cognitive performance than the other genotypes. Subjects with greater left DLPFC surface area had better cognitive performance. Importantly, the left DLPFC surface area mediated the association between the CNTNAP2 rs4726946 genotype and cognitive performance. This study provides the first evidence for associations among the CNTNAP2 gene, left DLPFC structure, and cognitive control.
Pub.: 01 Dec '16, Pinned: 25 Aug '17
Abstract: Although genetic variations in several genes encoding for synaptic adhesion proteins have been found to be associated with autism spectrum disorders, one of the most consistently replicated genes has been CNTNAP2, encoding for contactin-associated protein-like 2 (CASPR2), a multidomain transmembrane protein of the neurexin superfamily. Using immunofluorescence confocal microscopy and complementary biochemical techniques, we compared wild-type CASPR2 to 12 point mutations identified in individuals with autism. In contrast to the wild-type protein, localized to the cell surface, some of the mutants show altered cellular disposition. In particular, CASPR2-D1129H is largely retained in the endoplasmic reticulum (ER) in HEK-293 cells and in hippocampal neurons. BiP/Grp78, Calnexin and ERp57, key ER chaperones, appear to be responsible for retention of this mutant and activation of one signaling pathway of the unfolded protein response (UPR). The presence of this mutation also lowers expression and activates proteosomal degradation. A frame-shift mutation that causes a form of syndromic epilepsy (CASPR2-1253*), results in a secreted protein with seemingly normal folding and oligomerization. Taken together, these data indicate that CASPR2-D1129H has severe trafficking abnormalities and CASPR2-1253* is a secreted soluble protein, suggesting that the structural or signaling functions of the membrane tethered form are lost. Our data support a complex genetic architecture in which multiple distinct risk factors interact with others to shape autism risk and presentation.
Pub.: 09 Aug '12, Pinned: 25 Aug '17
Abstract: Recently, carriers of a common variant in the autism risk gene, CNTNAP2, were found to have altered functional brain connectivity using functional MRI. Here, we scanned 328 young adults with high-field (4-Tesla) diffusion imaging, to test the hypothesis that carriers of this gene variant would have altered structural brain connectivity. All participants (209 women, 119 men, age: 23.4±2.17 SD years) were scanned with 105-gradient high-angular-resolution diffusion imaging (HARDI) at 4 Tesla. After performing a whole-brain fiber tractography using the full angular resolution of the diffusion scans, 70 cortical surface-based regions of interest were created from each individual's co-registered anatomical data to compute graph metrics for all pairs of cortical regions. In graph theory analyses, subjects homozygous for the risk allele (CC) had lower characteristic path length, greater small-worldness and global efficiency in whole-brain analyses, and lower [corrected] eccentricity (maximum path length) in 60 of the 70 nodes in regional analyses. These results were not reducible to differences in more commonly studied traits such as fiber density or fractional anisotropy. This is the first study that links graph theory metrics of brain structural connectivity to a common genetic variant linked with autism and will help us understand the neurobiology of the circuits implicated in the risk for autism.
Pub.: 01 Jan '11, Pinned: 25 Aug '17
Abstract: Speech sound disorder is the most common communication disorder. Some investigations support the possibility that the CNTNAP2 gene might be involved in the pathogenesis of speech-related diseases. To investigate single-nucleotide polymorphisms in the CNTNAP2 gene, 300 unrelated speech sound disorder patients and 200 normal controls were included in the study. Five single-nucleotide polymorphisms were amplified and directly sequenced. Significant differences were found in the genotype (P = .0003) and allele (P = .0056) frequencies of rs2538976 between patients and controls. The excess frequency of the A allele in the patient group remained significant after Bonferroni correction (P = .0280). A significant haplotype association with rs2710102T/+rs17236239A/+2538976A/+2710117A (P = 4.10e-006) was identified. A neighboring single-nucleotide polymorphism, rs10608123, was found in complete linkage disequilibrium with rs2538976, and the genotypes exactly corresponded to each other. The authors propose that these CNTNAP2 variants increase the susceptibility to speech sound disorder. The single-nucleotide polymorphisms rs10608123 and rs2538976 may merge into one single-nucleotide polymorphism.
Pub.: 22 Apr '15, Pinned: 25 Aug '17
Abstract: The genetic basis of complex neurological disorders involving language are poorly understood, partly due to the multiple additive genetic risk factors that are thought to be responsible. Furthermore, these conditions are often syndromic in that they have a range of endophenotypes that may be associated with the disorder and that may be present in different combinations in patients. However, the emergence of individual genes implicated across multiple disorders has suggested that they might share similar underlying genetic mechanisms. The CNTNAP2 gene is an excellent example of this, as it has recently been implicated in a broad range of phenotypes including autism spectrum disorder (ASD), schizophrenia, intellectual disability, dyslexia and language impairment. This review considers the evidence implicating CNTNAP2 in these conditions, the genetic risk factors and mutations that have been identified in patient and population studies and how these relate to patient phenotypes. The role of CNTNAP2 is examined in the context of larger neurogenetic networks during development and disorder, given what is known regarding the regulation and function of this gene. Understanding the role of CNTNAP2 in diverse neurological disorders will further our understanding of how combinations of individual genetic risk factors can contribute to complex conditions.
Pub.: 30 May '13, Pinned: 25 Aug '17
Abstract: A homozygous mutation of the CNTNAP2 gene has been associated with a syndrome of focal epilepsy, mental retardation, language regression and other neuropsychiatric problems in children of the Old Order Amish community. Here we report genomic rearrangements resulting in haploinsufficiency of the CNTNAP2 gene in association with epilepsy and schizophrenia. Genomic deletions of varying sizes affecting the CNTNAP2 gene were identified in three non-related Caucasian patients. In contrast, we did not observe any dosage variation for this gene in 512 healthy controls. Moreover, this genomic region has not been identified as showing large-scale copy number variation. Our data thus confirm an association of CNTNAP2 to epilepsy outside the Old Order Amish population and suggest that dosage alteration of this gene may lead to a complex phenotype of schizophrenia, epilepsy and cognitive impairment.
Pub.: 25 Jul '07, Pinned: 25 Aug '17
Abstract: Genome-wide association studies and copy number variation analyses have linked contactin associated protein 2 (Caspr2, gene name Cntnap2) with autism spectrum disorder (ASD). In line with these findings, mice lacking Caspr2 (Cntnap2(-/-)) were shown to have core autism-like deficits including abnormal social behavior and communication, and behavior inflexibility. However the role of Caspr2 in ASD pathogenicity remains unclear. Here we have generated a new Caspr2:tau-LacZ knock-in reporter line (Cntnap2(tlacz/tlacz)), which enabled us to monitor the neuronal circuits in the brain expressing Caspr2. We show that Caspr2 is expressed in many brain regions and produced a comprehensive report of Caspr2 expression. Moreover, we found that Caspr2 marks all sensory modalities: it is expressed in distinct brain regions involved in different sensory processings and is present in all primary sensory organs. Olfaction-based behavioral tests revealed that mice lacking Caspr2 exhibit abnormal response to sensory stimuli and lack preference for novel odors. These results suggest that loss of Caspr2 throughout the sensory system may contribute to the sensory manifestations frequently observed in ASD.
Pub.: 10 Dec '15, Pinned: 25 Aug '17
Abstract: Autism spectrum disorder (ASD) is a phenotypically and genetically heterogeneous condition characterized by the presence of repetitive/restrictive behaviors and variable deficits in language and social behavior. Many genes predisposing an individual to ASD have been identified, and understanding the causal disease mechanism(s) is critical to be able to develop treatments. Neurobiological, genetic, and imaging data provide strong evidence for the CNTNAP2 gene as a risk factor for ASD and related neurodevelopmental disorders. This review discusses the clinical genetics and current understanding of the biology of CNTNAP2 as related to ASD and illustrates how the integration of multiple research approaches, from human studies to animal models, converge to inform functional biology focused on novel treatment development.
Pub.: 01 Mar '12, Pinned: 25 Aug '17
Abstract: Early language development is known to be under genetic influence, but the genes affecting normal variation in the general population remain largely elusive. Recent studies of disorder reported that variants of the CNTNAP2 gene are associated both with language deficits in specific language impairment (SLI) and with language delays in autism. We tested the hypothesis that these CNTNAP2 variants affect communicative behavior, measured at 2 years of age in a large epidemiological sample, the Western Australian Pregnancy Cohort (Raine) Study. Singlepoint analyses of 1149 children (606 males and 543 females) revealed patterns of association which were strikingly reminiscent of those observed in previous investigations of impaired language, centered on the same genetic markers and with a consistent direction of effect (rs2710102, P = 0.0239; rs759178, P = 0.0248). On the basis of these findings, we performed analyses of four-marker haplotypes of rs2710102-rs759178-rs17236239-rs2538976 and identified significant association (haplotype TTAA, P = 0.049; haplotype CGAG, [corrected] P = .0014). Our study suggests that common variants in the exon 13-15 region of CNTNAP2 influence early language acquisition, as assessed at age 2, in the general population. We propose that these CNTNAP2 variants increase susceptibility to SLI or autism when they occur together with other risk factors.
Pub.: 12 Feb '11, Pinned: 25 Aug '17
Abstract: Multiple lines of genetic evidence suggest a role for CNTNAP2 in autism. To assess its population impact we studied 2148 common single nucleotide polymorphisms (SNPs) using transmission disequilibrium test (TDT) across the entire ~3.3 Mb CNTNAP2 locus in 186 (408 trios) multiplex and 323 simplex families with autistic spectrum disorder (ASD). This analysis yielded two SNPs with nominal statistical significance (rs17170073, p = 2.0 x 10(-4); rs2215798, p = 1.6 x 10(-4)) that did not survive multiple testing. In a combined analysis of all families, two highly correlated (r (2) = 0.99) SNPs in intron 14 showed significant association with autism (rs2710093, p = 9.0 x 10(-6); rs2253031, p = 2.5 x 10(-5)). To validate these findings and associations at SNPs from previous autism studies (rs7794745, rs2710102 and rs17236239) we genotyped 2051 additional families (572 multiplex and 1479 simplex). None of these variants were significantly associated with ASD after corrections for multiple testing. The analysis of Mendelian errors within each family did not indicate any segregating deletions. Nevertheless, a study of CNTNAP2 gene expression in brains of autistic patients and of normal controls, demonstrated altered expression in a subset of patients (p = 1.9 x10(-5)). Consequently, this study suggests that although CNTNAP2 dysregulation plays a role in some cases, its population contribution to autism susceptibility is limited.
Pub.: 23 Oct '13, Pinned: 25 Aug '17
Abstract: Intragenic deletions of the contactin-associated protein-like 2 gene (CNTNAP2) have been found in patients with Gilles de la Tourette syndrome, intellectual disability (ID), obsessive compulsive disorder, cortical dysplasia-focal epilepsy syndrome, autism, schizophrenia, Pitt-Hopkins syndrome, stuttering, and attention deficit hyperactivity disorder. A variety of molecular mechanisms, such as loss of transcription factor binding sites and perturbation of penetrance and expressivity, have been proposed to account for the phenotypic variability resulting from CNTNAP2 mutations. Deletions of both CNTNAP2 alleles produced truncated proteins lacking the transmembrane or some of the extracellular domains, or no protein at all. This observation can be extended to heterozygous intragenic deletions by assuming that such deletion-containing alleles lead to expression of a Caspr2 protein lacking one or several extracellular domains. Such altered forms of Capr2 proteins will lack the ability to bridge the intercellular space between neurons by binding to partners, such as CNTN1, CNTN2, DLG1, and DLG4. This presumed effect of intragenic deletions of CNTNAP2, and possibly other genes involved in connecting neuronal cells, represents a molecular basis for the postulated neuronal hypoconnectivity in autism and probably other neurodevelopmental disorders, including epilepsy, ID, language impairments and schizophrenia. Thus, CNTNAP2 may represent a paradigmatic case of a gene functioning as a node in a genetic and cellular network governing brain development and acquisition of higher cognitive functions.
Pub.: 08 Jun '17, Pinned: 25 Aug '17
Abstract: Based on genomic rearrangements and copy number variations, the contactin-associated protein-like 2 gene (CNTNAP2) has been implicated in neurodevelopmental disorders such as Gilles de la Tourette syndrome, intellectual disability, obsessive compulsive disorder, cortical dysplasia-focal epilepsy syndrome, autism, schizophrenia, Pitt-Hopkins syndrome, and attention deficit hyperactivity disorder. To explain the phenotypic pleiotropy of CNTNAP2 alterations, several hypotheses have been put forward. Those include gene disruption, loss of a gene copy by a heterozygous deletion, altered regulation of gene expression due to loss of transcription factor binding and DNA methylation sites, and mutations in the amino acid sequence of the encoded protein which may provoke altered interactions of the CNTNAP2-encoded protein, Caspr2, with other proteins. Also exome sequencing, which covers <0.2% of the CNTNAP2 genomic DNA, has revealed numerous single nucleotide variants in healthy individuals and in patients with neurodevelopmental disorders. In some of these disorders, disruption of CNTNAP2 may be interpreted as a susceptibility factor rather than a directly causative mutation. In addition to being associated with impaired development of language, CNTNAP2 may turn out to be a central node in the molecular networks controlling neurodevelopment. This review discusses the impact of CNTNAP2 mutations on its functioning at multiple levels of the combinatorial genetic networks that govern brain development. In addition, recommendations for genomic testing in the context of clinical genetic management of patients with neurodevelopmental disorders and their families are put forward.
Pub.: 09 Apr '15, Pinned: 25 Aug '17
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