Autism is a neurodevelopmental disorder characterized by impaired social reciprocity, impaired communication and stereotypical behaviors. Despite strong evidence for a genetic basis, few susceptibility genes have been identified. Here, we describe the positional cloning of SCAMP5, CLIC4 and PPCDC as candidate genes for autism, starting from a person with idiopathic, sporadic autism carrying a de novo chromosomal translocation. One of these genes, SCAMP5 is silenced on the derivative chromosome, and encodes a brain-enriched protein involved in membrane trafficking, similar to the previously identified candidate genes NBEA and AMISYN. Gene silencing of Nbea, Amisyn and Scamp5 in mouse beta-TC3 cells resulted in a 2-fold increase in stimulated secretion of large dense-core vesicles (LDCVs), while overexpression suppressed secretion. Moreover, ultrastructural analysis of blood platelets from the patients with haploinsufficieny of one of the three candidate genes, showed morphological abnormalities of dense-core granules, which closely resemble LDCVs. Taken together, this study shows that in three independent patients with autism three different negative regulators of LDCV secretion are affected, respectively, suggesting that in at least a subgroup of patients the regulation of neuronal vesicle trafficking may be involved in the pathogenesis of autism.
Over a half of all proteins are glycosylated, and their proper glycosylation is essential for normal function. Unfortunately, because of structural complexity of nonlinear branched glycans and the absence of genetic template for their synthesis, the knowledge about glycans is lagging significantly behind the knowledge about proteins or DNA. Using a recently developed quantitative high throughput glycan analysis method we quantified components of the plasma N-glycome in 99 children with attention-deficit hyperactivity disorder (ADHD), 81 child and 5 adults with autism spectrum disorder, and a total of 340 matching healthy controls. No changes in plasma glycome were found to associate with autism spectrum disorder, but several highly significant associations were observed with ADHD. Further structural analysis of plasma glycans revealed that ADHD is associated with increased antennary fucosylation of biantennary glycans and decreased levels of some complex glycans with three or four antennas. The design of this study prevented any functional conclusions about the observed associations, but specific differences in glycosylation appears to be strongly associated with ADHD and warrants further studies in this direction. Molecular & Cellular Proteomics 10: 10.1074/mcp.M110.004200, 1-7, 2011. Attention-deficit hyperactivity disorder (ADHD)1 and autism spectrum disorders (ASDs) are both highly heritable multifactorial and clinically heterogeneous childhood-onset neurodevelopmental disorders (1, 2). The hallmarks of ADHD are severe inattention, hyperactivity, and impulsivity whereas the characteristic symptoms of ASD include impaired communication and social interaction skills as well as repetitive and restricted behavior and interests (3). Several pieces of evidence point toward some shared heritability and thus genetic factors contributing to the occurrence of both ADHD an ASD (4). Children with ADHD and ASD frequently share symptoms of impaired communication skills, impaired social interactions (4), and develop difficulties in familial, educational, and academic functioning (5, 6). The abnormal functioning of the dopaminergic and serotonergic systems (5, 7-9), among other neurotransmitters, were repeatedly found in ADHD and ASD, and therefore the candidate genes common for both disorders are the dopaminergic transporter gene, dopaminergic receptor type 3 and type 4 genes, serotonin transporter gene, and genes for catechol-o-methyl-transferase and monoamine oxidase type A (4), although genome-wide association studies did not confirm with certainty all these candidates (10). A shared genetic basis is further suggested by the higher frequency of ADHD and ASD traits in children with a defined genetic diagnosis such as 22q11 deletion syndrome, XXYY syndrome, and microdeletions or duplications in the chromosome 15q13.2-q13.3 region (11,12). However, the molecular agents related to various biological processes and interactions between different risk factors responsible for development of ADHD and ASD remain elusive (6).Prote...
We report a sporadic patient with Autism Spectrum Disorder (ASD), mild intellectual disability and attention deficit hyperactivity disorder (ADHD) with a de novo partial deletion of CADHERIN 11 (CDH11). The deletion is associated with one of the breakpoints of a de novo complex chromosomal rearrangement 46,XY,t(3;16;5)(q29;q22;q15)inv4(p14;q21) ins(4;5)(q21;q14.3q15). Cadherins are cell adhesion molecules involved in synaptic plasticity. Since genetic evidence points towards a role for cadherins in ASD, we studied the possible contribution of CDH11 to ASD. A case-control association study for 14 SNP variants in 519 ASD cases and 1,192 controls showed significant overrepresentation of rs7187376C/C genotypes in the patient group [P ¼ 0.0049 (Chi-square ¼ 7.90 1 df) and O.R. 3.88 C.I. ¼ 1.403-10.733]. There was no association for C/T versus T/T [P ¼ 0.6772 (Chisquare ¼ 0.17 1 df)] nor was there association at the allelic level [P ¼ 0.4373 (Chi-square ¼ 0.6 1 df)]. In addition to the association of common variants in CDH11 with ASD, we studied the possible contribution of rare variants by sequencing CDH11 in 247 patients, and found three novel variants in the coding region of CDH1, of which two variants were unlikely to be causal. Targeted CNV screening in these 247 patients did not reveal copy number variation in CDH11. In conclusion, the data provide evidence for the involvement of CDH11 in ASD which is consistent with the association of other cadherins with ASD and neuropsychiatric diseases.
We describe the identification and delineation of an inherited 2.07 Mb microduplication in 1q42.2 in two brothers with autism and mild mental retardation. Since this duplication was not present in 1577 Belgian persons, we consider this as an extremely rare variant which has the potential to provide further insight into the genetics of autism. The duplication contains seven genes including the DISC1 gene, an interesting candidate gene that has been associated to schizophrenia, bipolar disorder, autism and Asperger syndrome. In this report we describe additional analyses undertaken to investigate the causal relationship of the duplication to the autism phenotype. We conclude that the 1q42.2 microduplication probably confers susceptibility to autism in the current family. This study is a typical illustration of the difficult interpretation of causality of a very rare variant in neuropsychiatric disease and the challenge of genetic counselling in a particular family.
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