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Although the BCL6 transcriptional repressor is frequently expressed in human follicular lymphomas (FL), its biological role in this disease remains unknown. Herein, we comprehensively identify the set of gene promoters directly targeted by BCL6 in primary human FLs. We noted that BCL6 binds and represses NOTCH2 and NOTCH pathway genes. Moreover, BCL6 and NOTCH2 pathway gene expression is inversely correlated in FL. Notably, BCL6 upregulation is associated with repression of NOTCH2 and its target genes in primary human and murine germinal center (GC) cells. Repression of NOTCH2 is an essential function of BCL6 in FL and GC B cells because inducible expression of Notch2 abrogated GC formation in mice and killed FL cells. Indeed, BCL6-targeting compounds or gene silencing leads to the induction of NOTCH2 activity and compromises survival of FL cells, whereas NOTCH2 depletion or pathway antagonists rescue FL cells from such effects. Moreover, BCL6 inhibitors induced NOTCH2 expression and suppressed growth of human FL xenografts in vivo and primary human FL specimens ex vivo. These studies suggest that established FLs are thus dependent on BCL6 through its suppression of NOTCH2. Significance: We show that human FLs are dependent on BCL6, and primary human FLs can be killed using specific BCL6 inhibitors. Integrative genomics and functional studies of BCL6 in primary FL cells point toward a novel mechanism whereby BCL6 repression of NOTCH2 drives the survival and growth of FL cells as well as GC B cells, which are the FL cell of origin. Cancer Discov; 7(5); 506–21. ©2017 AACR. This article is highlighted in the In This Issue feature, p. 443

A promoter-linked insertion/deletion polymorphism of the serotonin transporter gene (SLC6A4) has been implicated in autism spectrum disorders (ASDs) in numerous family based association studies. However, the results of these investigations have been inconsistent in that both the long and short alleles have been shown to be over-transmitted to affected offspring. In order to further elucidate the relationship between the 5-HTTLPR variant and autism risk, we undertook a thorough study of parent-of-origin effects, maternal genotype effects, and offspring genotype effects in a sample of affected offspring from the Autism Genetic Resource Exchange (AGRE). Both the overall autism phenotype and measures of autism behaviors from the Autism Diagnostic Interview-Revised [Lord et al. (1994); J Autism Dev Disord 24(5): 659–685] were considered. We found evidence of over-transmission (risk allele short, P = 0.012), maternal effects (risk allele long, P = 0.035), and parent-of-origin effects (risk allele short from mother, P = 0.018) of the 5-HTTLPR variant in the AGRE sample. Population- and gender-specific effects were also explored as associations may be heterogeneous across populations and sexes. Parent-of-origin effects of the variant were associated with maternally inherited copies of the short allele that resulted in more impaired overall level of language (P = 0.04). Our study was conducted to further investigate the 5-HTTLPR risk variants by identifying allelic associations that may be population-specific, phenotype-specific, or conferred by maternal or parent-of-origin effects. In light of conflicting observations from previous studies, these are just a few of the possible explanations that deserve attention. © 2010 Wiley-Liss, Inc.

Maternal 15q11-q13 duplication is the most common copy number variant in autism, accounting for ∼1-3% of cases. The 15q11-q13 region is subject to epigenetic regulation, and genomic copy number losses and gains cause genomic disorders in a parent-of-origin-specific manner. One 15q11-q13 locus encodes the GABA(A) receptor β3 subunit gene (GABRB3), which has been implicated by several studies in both autism and absence epilepsy, and the co-morbidity of epilepsy in autism is well established. We report that maternal transmission of a GABRB3 signal peptide variant (P11S), previously implicated in childhood absence epilepsy, is associated with autism. An analysis of wild-type and mutant β3 subunit-containing α1β3γ2 or α3β3γ2 GABA(A) receptors shows reduced whole-cell current and decreased β3 subunit protein on the cell surface due to impaired intracellular β3 subunit processing. We thus provide the first evidence of an association between a specific GABA(A) receptor defect and autism, direct evidence that this defect causes synaptic dysfunction that is autism relevant and the first maternal risk effect in the 15q11-q13 autism duplication region that is linked to a coding variant.

Autism spectrum disorders (ASDs) are childhood neurodevelopmental disorders with complex genetic origins. Previous studies focusing on candidate genes or genomic regions have identified several copy number variations (CNVs) that are associated with an increased risk of ASDs. Here we present the results from a whole-genome CNV study on a cohort of 859 ASD cases and 1,409 healthy children of European ancestry who were genotyped with approximately 550,000 single nucleotide polymorphism markers, in an attempt to comprehensively identify CNVs conferring susceptibility to ASDs. Positive findings were evaluated in an independent cohort of 1,336 ASD cases and 1,110 controls of European ancestry. Besides previously reported ASD candidate genes, such as NRXN1 (ref. 10) and CNTN4 (refs 11, 12), several new susceptibility genes encoding neuronal cell-adhesion molecules, including NLGN1 and ASTN2, were enriched with CNVs in ASD cases compared to controls (P = 9.5 x 10(-3)). Furthermore, CNVs within or surrounding genes involved in the ubiquitin pathways, including UBE3A, PARK2, RFWD2 and FBXO40, were affected by CNVs not observed in controls (P = 3.3 x 10(-3)). We also identified duplications 55 kilobases upstream of complementary DNA AK123120 (P = 3.6 x 10(-6)). Although these variants may be individually rare, they target genes involved in neuronal cell-adhesion or ubiquitin degradation, indicating that these two important gene networks expressed within the central nervous system may contribute to the genetic susceptibility of ASD.

Background One genetic mechanism known to be associated with autism spectrum disorders (ASD) is chromosomal abnormalities. The identification of copy number variants (CNV), i.e., microdeletions and microduplications that are undetectable at the level of traditional cytogenetic analysis, allows the potential association of submicroscopic chromosomal imbalances and human disease. Methods We performed array comparative genomic hybridization (aCGH) utilizing a 19K whole genome tiling path bacterial artificial chromosome (BAC) microarray on 397 unrelated subjects with autism spectrum disorder. Common CNV were excluded using a control group comprised of 372 individuals from the National Institute of Mental Health (NIMH) Genetics Initiative Control samples. Confirmation studies were performed on all remaining CNV using fluorescence in situ hybridization (FISH), microsatellite analysis, and/or quantitative polymerase chain reaction (PCR) analysis. Results A total of 51 CNV were confirmed in 46 ASD subjects. Three maternal interstitial duplications of 15q11-q13 known to be associated with ASD were identified. The other 48 CNV ranged in size from 189 kilobase (kb) to 5.5 megabase (Mb) and contained from 0 to ∼40 National Center for Biotechnology Information (NCBI) Reference Sequence (RefSeq) genes. Seven CNV were de novo and 44 were inherited. Conclusions Fifty-one autism-specific CNV were identified in 46 of 397 ASD patients using a 19K BAC microarray for an overall rate of 11.6%. These microdeletions and microduplications cause gene dosage imbalance in 272 genes, many of which could be considered as candidate genes for autism.

Autism is a childhood neurodevelopmental disorder with a strong genetic component, yet the identification of autism susceptibility loci remains elusive. We investigated 180 autism probands and 372 control subjects by array comparative genomic hybridization (aCGH) using a 19K whole-genome tiling path bacterial artificial chromosome microarray to identify submicroscopic chromosomal rearrangements specific to autism. We discovered a recurrent 16p11.2 microdeletion in two probands with autism and none in controls. The deletion spans approximately 500-kb and is flanked by approximately 147-kb segmental duplications (SDs) that are99% identical, a common characteristic of genomic disorders. We assessed the frequency of this new autism genomic disorder by screening an additional 532 probands and 465 controls by quantitative PCR and identified two more patients but no controls with the microdeletion, indicating a combined frequency of 0.6% (4/712 autism versus 0/837 controls; Fisher exact test P = 0.044). We confirmed all 16p11.2 deletions using fluorescence in situ hybridization, microsatellite analyses and aCGH, and mapped the approximate deletion breakpoints to the edges of the flanking SDs using a custom-designed high-density oligonucleotide microarray. Bioinformatic analysis localized 12 of the 25 genes within the microdeletion to nodes in one interaction network. We performed phenotype analyses and found no striking features that distinguish patients with the 16p11.2 microdeletion as a distinct autism subtype. Our work reports the first frequency, breakpoint, bioinformatic and phenotypic analyses of a de novo 16p11.2 microdeletion that represents one of the most common recurrent genomic disorders associated with autism to date.

The Epstein-Barr virus (EBV) encoded oncoprotein Latent Membrane Protein 1 (LMP1) signals through two C-terminal tail domains to drive cell growth, survival and transformation. The LMP1 membrane-proximal TES1/CTAR1 domain recruits TRAFs to activate MAP kinase, non-canonical and canonical NF-kB pathways, and is critical for EBV-mediated B-cell transformation. TRAF1 is amongst the most highly TES1-induced target genes and is abundantly expressed in EBV-associated lymphoproliferative disorders. We found that TRAF1 expression enhanced LMP1 TES1 domain-mediated activation of the p38, JNK, ERK and canonical NF-kB pathways, but not non-canonical NF-kB pathway activity. To gain insights into how TRAF1 amplifies LMP1 TES1 MAP kinase and canonical NF-kB pathways, we performed proteomic analysis of TRAF1 complexes immuno-purified from cells uninduced or induced for LMP1 TES1 signaling. Unexpectedly, we found that LMP1 TES1 domain signaling induced an association between TRAF1 and the linear ubiquitin chain assembly complex (LUBAC), and stimulated linear (M1)-linked polyubiquitin chain attachment to TRAF1 complexes. LMP1 or TRAF1 complexes isolated from EBV-transformed lymphoblastoid B cell lines (LCLs) were highly modified by M1-linked polyubiqutin chains. The M1-ubiquitin binding proteins IKK-gamma/NEMO, A20 and ABIN1 each associate with TRAF1 in cells that express LMP1. TRAF2, but not the cIAP1 or cIAP2 ubiquitin ligases, plays a key role in LUBAC recruitment and M1-chain attachment to TRAF1 complexes, implicating the TRAF1:TRAF2 heterotrimer in LMP1 TES1-dependent LUBAC activation. Depletion of either TRAF1, or the LUBAC ubiquitin E3 ligase subunit HOIP, markedly impaired LCL growth. Likewise, LMP1 or TRAF1 complexes purified from LCLs were decorated by lysine 63 (K63)-linked polyubiqutin chains. LMP1 TES1 signaling induced K63-polyubiquitin chain attachment to TRAF1 complexes, and TRAF2 was identified as K63-Ub chain target. Co-localization of M1- and K63-linked polyubiquitin chains on LMP1 complexes may facilitate downstream canonical NF-kB pathway activation. Our results highlight LUBAC as a novel potential therapeutic target in EBV-associated lymphoproliferative disorders., Author Summary The linear ubiquitin assembly complex (LUBAC) plays crucial roles in immune receptor-mediated NF-kB and MAP kinase pathway activation. Comparatively little is known about the extent to which microbial pathogens use LUBAC to activate downstream pathways. We demonstrate that TRAF1 enhances EBV oncoprotein LMP1 TES1/CTAR1 domain mediated MAP kinase and canonical NF-kB activation. LMP1 TES1 signaling induces association between TRAF1 and LUBAC, and triggers M1-polyubiquitin chain attachment to TRAF1 complexes. TRAF1 and LMP1 complexes are decorated by M1-polyubiquitin chains in LCL extracts. TRAF2 plays a key role in LMP1-induced LUBAC recruitment and M1-chain attachment to TRAF1 complexes. TRAF1 and LMP1 complexes are modified by lysine 63-linked polyubiquitin chains in LCL extracts, and TRAF2 is a target of LMP1-induced K63-ubiquitin chain attachment. Thus, the TRAF1:TRAF2 heterotrimer may coordinate ubiquitin signaling downstream of TES1. Depletion of TRAF1 or the LUBAC subunit HOIP impairs LCL growth and survival. Thus, although TRAF1 is the only TRAF without a RING finger ubiquitin ligase domain, TRAF1 nonetheless has important roles in ubiqutin-mediated signal transduction downstream of LMP1. Our work suggests that LUBAC is important for EBV-driven B-cell proliferation, and suggests that LUBAC may be a novel therapeutic target in EBV-associated lymphoproliferative disorders.

Glutamate transporters are critical for signaling and excitotoxicity because they regulate extracellular glutamate in the synapse. Four glutamate transporter genes, SLC1A1, SLC1A2, SLC1A3, and SLC1A6, are positional and functional candidates for autism. Studies have implicated SLC1A1 in obsessive compulsive disorder (Arnold et al. 2006) and autism spectrum disorder (ASD) (Brune et al. 2008). Up-regulation of SLC1A2 and SLC1A3 has been reported in brains of individuals with autism (Purcell et al. 2001). SLC1A2 is under the highest linkage peak in the Autism Genome Project scan (Szatmari et al. 2007). Both SLC1A3 and SLC1A6 are most abundantly expressed in cerebellum (Bridges and Esslinger 2005) where structural and functional deficits occur in autism. Based on these lines of evidence, we hypothesized that variations in these four glutamate transporter genes confer risk for autism susceptibility. Previously we tested the association between autism and SLC1A1 in a strictly defined sample (N=85) and a found nominally significant association with a SLC1A1 SNP (rs301979) (Brune et al. 2008). Subsequently, we recruited additional families (N= 68) with either “strict autism” (N=39) or “broad ASD” (N=29). “Strict” autism was defined as a proband with Autism Diagnostic Interview-Revised (ADI-R) and Autism Diagnostic Observation Schedule (ADOS) autism plus a best estimate diagnosis of autism by a clinical psychologist and/or child psychiatrist. The “broad ASD” probands had a best estimate diagnosis of any ASD (autism, Asperger’s disorder or PDD-NOS) plus combinations of ADI-R/ADOS criteria of Autism/ASD, ASD/Autism, or ASD/ASD. Altogether, 14 SNPs were genotyped in 153 trio families using TaqMan® SNP genotyping assay, including four SLC1A1 SNPs (rs301430, rs301979, rs301434, rs301443), three SLC1A2 SNPs (rs3088168, rs911562, rs1923291), three SLC1A3 SNPs (rs13173144, rs2269271, rs2301066), three SLC1A6 SNPs (rs10414225, rs873599, rs2285980), and one C9ORF68 (gene overlapping SLC1A1) SNP (rs384535). We dropped rs13173144 (SLC1A3, p=0.014) and rs384535 (C9ORF68, p=0.024) due to deviation from Hardy-Weinberg Equilibrium in founders; dropped four trio families because of Mendelian errors in remaining SNPs. Family-Based Association Test (FBAT) was performed on the new sample (N=68), strict combined sample (N=124) and overall combined sample (N=153) for both additive and recessive models. Only p < 0.05 uncorrected for multiple testing are reported. Association between rs301979 (SLC1A1) and autism was observed in the new samples (recessive model, Z=−2.778, p=0.005) as well as in the overall combined samples (additive, Z=−2.137, p=0.033; recessive, Z=−2.424, p=0.015). One SLC1A2 SNP (rs3088168) was nominally significant in the new sample under a recessive model (Z=−2.178, p=0.029), but not in the overall combined sample. Exploratory haplotype analyses revealed nominally significant associations between five SNP pairs including rs301979-rs301434 (p=0.04), rs301979-rs1923291 (p=0.02), rs1923291-rs911562 (p=0.03), rs911562-rs10414225 (p=0.01), rs301443-rs2285980 (p=0.01) under a recessive model. In summary, this study supported the previous association between SLC1A1 and autism, but failed to provide additional evidence for associations with three other glutamate transporter genes. However, given the small sample size and power, these genes require further investigation with denser markers and exploration of copy number variations in a larger sample set.

Member of the Autism Genome Project Consortium: Astrid M. Vicente Although autism is a highly heritable neurodevelopmental disorder, attempts to identify specific susceptibility genes have thus far met with limited success. Genome-wide association studies using half a million or more markers, particularly those with very large sample sizes achieved through meta-analysis, have shown great success in mapping genes for other complex genetic traits. Consequently, we initiated a linkage and association mapping study using half a million genome-wide single nucleotide polymorphisms (SNPs) in a common set of 1,031 multiplex autism families (1,553 affected offspring). We identified regions of suggestive and significant linkage on chromosomes 6q27 and 20p13, respectively. Initial analysis did not yield genome-wide significant associations; however, genotyping of top hits in additional families revealed an SNP on chromosome 5p15 (between SEMA5A and TAS2R1) that was significantly associated with autism (P = 2 x 10(-7)). We also demonstrated that expression of SEMA5A is reduced in brains from autistic patients, further implicating SEMA5A as an autism susceptibility gene. The linkage regions reported here provide targets for rare variation screening whereas the discovery of a single novel association demonstrates the action of common variants.

Background A child with autism and mild microcephaly was found to have a de novo 3.3 Mb microdeletion on chromosome 1p34.2p34.3. The hypothesis is tested that this microdeletion contains one or more genes that underlie the autism phenotype in this child and in other children with autism spectrum disorders. Methods To search for submicroscopic chromosomal rearrangements in the child, array comparative genomic hybridisation (aCGH) was performed using a 19 K whole genome human bacterial artificial chromosome (BAC) array and the Illumina 610-Quad BeadChip microarray. Ingenuity pathway analysis (IPA) was used to construct functional biological networks to identify candidate autism genes. To identify putative functional variants in candidate genes, mutation screening was performed using polymerase chain reaction (PCR) based Sanger sequencing in 512 unrelated autism patients and 462 control subjects. Results A de novo 3.3 Mb deletion containing ∼43 genes in chromosome 1p34.2p34.3 was identified and subsequently confirmed using fluorescence in situ hybridization (FISH). Literature review and bioinformatics analyses identified Regulating Synaptic Membrane Exocytosis 3 (RIMS3) as the most promising autism candidate gene. Mutation screening of this gene in autism patients identified five inherited coding variants, including one (p.E177A) that segregated with the autism phenotype in a sibship, was predicted to be deleterious, and was absent in 1161 controls. Conclusions This case report and mutation screening data suggest that RIMS3 is an autism causative or contributory gene. Functional studies of RIMS3 variants such as p.E177A should provide additional insight into the role of synaptic proteins in the pathophysiology of autism.

BackgroundAutism is a complex childhood neurodevelopmental disorder with a strong genetic basis. Microdeletion or duplication of a approximately 500-700-kb genomic rearrangement on 16p11.2 that contains 24 genes represents the second most frequent chromosomal disorder associated with autism. The role of common and rare 16p11.2 sequence variants in autism etiology is unknown.Methodology/principal findingsTo identify common 16p11.2 variants with a potential role in autism, we performed association studies using existing data generated from three microarray platforms: Affymetrix 5.0 (777 families), Illumina 550 K (943 families), and Affymetrix 500 K (60 families). No common variants were identified that were significantly associated with autism. To look for rare variants, we performed resequencing of coding and promoter regions for eight candidate genes selected based on their known expression patterns and functions. In total, we identified 26 novel variants in autism: 13 exonic (nine non-synonymous, three synonymous, and one untranslated region) and 13 promoter variants. We found a significant association between autism and a coding variant in the seizure-related gene SEZ6L2 (12/1106 autism vs. 3/1161 controls; p = 0.018). Sez6l2 expression in mouse embryos was restricted to the spinal cord and brain. SEZ6L2 expression in human fetal brain was highest in post-mitotic cortical layers, hippocampus, amygdala, and thalamus. Association analysis of SEZ6L2 in an independent sample set failed to replicate our initial findings.Conclusions/significanceWe have identified sequence variation in at least one candidate gene in 16p11.2 that may represent a novel genetic risk factor for autism. However, further studies are required to substantiate these preliminary findings.

Autism spectrum disorders (ASDs) represent a group of childhood neurodevelopmental and neuropsychiatric disorders characterized by deficits in verbal communication, impairment of social interaction, and restricted and repetitive patterns of interests and behaviour. To identify common genetic risk factors underlying ASDs, here we present the results of genome-wide association studies on a cohort of 780 families (3,101 subjects) with affected children, and a second cohort of 1,204 affected subjects and 6,491 control subjects, all of whom were of European ancestry. Six single nucleotide polymorphisms between cadherin 10 (CDH10) and cadherin 9 (CDH9)-two genes encoding neuronal cell-adhesion molecules-revealed strong association signals, with the most significant SNP being rs4307059 (P = 3.4 x 10(-8), odds ratio = 1.19). These signals were replicated in two independent cohorts, with combined P values ranging from 7.4 x 10(-8) to 2.1 x 10(-10). Our results implicate neuronal cell-adhesion molecules in the pathogenesis of ASDs, and represent, to our knowledge, the first demonstration of genome-wide significant association of common variants with susceptibility to ASDs.

Reports identified the neuronal glutamate transporter gene, SLC1A1 (OMIM 133550, chromosome 9p24), as a positional and functional candidate gene for obsessive–compulsive disorder (OCD). The presence of obsessions and compulsions similar to OCD in autism, the identification of this region in a genome-wide linkage analysis of individuals with autism spectrum disorders (ASDs), and the hypothesized role of glutamate in ASDs make SLC1A1 a candidate gene for ASD as well. To test for association between SLC1A1 and autism, we typed three single nucleotide polymorphisms (SNPs, rs301430, rs301979, rs301434) previously associated with OCD in 86 strictly defined trios with autism. Family-Based Association Tests (FBAT) with additive and recessive models were used to check for association. Additionally, an rs301430–rs301979 haplotype identified for OCD was investigated. FBAT revealed nominally significant association between autism and one SNP under a recessive model. The G allele of rs301979 was undertransmitted (equivalent to overtransmission of the C allele under a dominant model) to individuals with autism (Z = −2.47, P = 0.01). The G allele was also undertransmitted in the T–G haplotype under the recessive model (Z = −2.41, P = 0.02). Both findings were also observed in the male-only sample. However, they did not withstand correction for multiple comparisons.

Evidence implicates the serotonin transporter gene (SLC6A4) and the 15q11-q13 genes as candidates for autism as well as restricted repetitive behavior (RRB). We conducted dense transmission disequilibrium mapping of the 15q11-q13 region with 93 single nucleotide polymorphisms (SNPs) in 86 strictly defined autism trios and tested association between SNPs and autism using the transmission disequilibrium test (TDT). As exploratory analyses, parent-of-origin effects were examined using likelihood-ratio tests (LRTs) and genotype-phenotype associations for specific RRB using the Family-Based Association Test (FBAT). Additionally, gene-gene interactions between nominally associated 15q11-q13 variants and 5-HTTLPR, the common length polymorphism of SLC6A4, were examined using conditional logistic regression (CLR). TDT revealed nominally significant transmission disequilibrium between autism and five SNPs, three of which are located within close proximity of the GABA(A) receptor subunit gene clusters. Three SNPs in the SNRPN/UBE3A region had marginal imprinting effects. FBAT for genotype-phenotype relations revealed nominally significant association between two SNPs and one ADI-R subdomain item. However, both TDT and FBAT were not statistically significant after correcting for multiple comparisons. Gene-gene interaction analyses by CLR revealed additive genetic effect models, without interaction terms, fit the data best. Lack of robust association between the 15q11-q13 SNPs and RRB phenotypes may be due to a small sample size and absence of more specific RRB measurement. Further investigation of the 15q11-q13 region with denser genotyping in a larger sample set may be necessary to determine whether this region confers risk to autism, indicated by association, or to specific autism phenotypes.

Autism is a childhood neuropsychiatric disorder that, despite exhibiting high heritability, has largely eluded efforts to identify specific genetic variants underlying its etiology. We performed a two-stage genetic study in which genome-wide linkage and family-based association mapping was followed up by association and replication studies in an independent sample. We identified a common polymorphism in contactin-associated protein-like 2 (CNTNAP2), a member of the neurexin superfamily, that is significantly associated with autism susceptibility. Importantly, the genetic variant displays a parent-of-origin and gender effect recapitulating the inheritance of autism.

Autism is a neurodevelopmental disorder characterized by an early onset of abnormal social, communicative, and repetitive behavior. Engrailed-2 (EN2) was identified as an autism candidate gene because its influence on cerebellar development in mice parallels neurodevelopmental abnormalities seen in individuals with autism. Studies investigating association between markers at EN2 (chr7q36), a location associated with language disorders, and autism reveal mixed findings. Two positive reports revealed association with two intronic SNPs. Since the associated SNPs were in high linkage disequilibrium and shared similar minor allele frequencies, we chose to test whether one of the SNPs (rs1861972) was associated with autism in three recruiting sites from the NIH Collaborative Programs of Excellence in Autism (CPEA) network. A recessive model revealed significant association with broad autism spectrum disorder. Site specific analyses indicated differential allele transmission by site, despite similar ethnicity, and parental genotypes, suggesting the SNP may contribute to various risk haplotypes. No significant association with autism was found under an additive model for either a broad (autism spectrum disorder) or a narrow (autistic disorder) diagnostic group. Although our findings were not as robust as the previous studies, they suggest that rs1861972 may influence the risk for autism spectrum disorders. Future studies investigating EN2 should consider how the association of variants in this gene with autism could be influenced by differences in phenotype and possible interactions with genotypes at other autism candidate genes.

The oxytocin receptor gene (OXTR) has been studied in autism because of the role of oxytocin (OT) in social cognition. Linkage has also been demonstrated to the region of OXTR in a large sample. Two single nucleotide polymorphisms (SNPs) and a haplotype constructed from them in OXTR have been associated with autism in the Chinese Han population. We tested whether these associations replicated in a Caucasian sample with strictly defined autistic disorder. We genotyped the two previously associated SNPs (rs2254298, rs53576) in 57 Caucasian autism trios. Probands met clinical, ADI-R, and ADOS criteria for autistic disorder. Significant association was detected at rs2254298 (p=0.03) but not rs53576. For rs2254298, overtransmission of the G allele to probands with autistic disorder was found which contrasts with the overtransmission of A previously reported in the Chinese Han sample. In both samples, G was more frequent than A. However, in our Caucasian autism trios and the CEU Caucasian HapMap samples the frequency of A was less than that reported in the Chinese Han and Chinese in Bejing HapMap samples. The haplotype test of association did not reveal excess transmission from parents to affected offspring. These findings provide support for association of OXTR with autism in a Caucasian population. Overtransmission of different alleles in different populations may be due to a different pattern of linkage disequilibrium between the marker rs2254298 and an as yet undetermined susceptibility variant in OXTR.

The serotonin transporter gene (SLC6A4) is a strong autism candidate gene because of its association with anxiety, aggression and attention, and the effectiveness of selective serotonin reuptake inhibitors (SSRIs) in treating certain behavioral symptoms. In families with individuals with autism, several reports of biased transmission of both alleles (short, long) at the serotonin transporter gene promotor polymorphism (5-HTTLPR) locus of SLC6A4 now exist. The heterogeneity in these reports may be due to clinical heterogeneity. The authors hypothesized that 5-HTTLPR genotypes would be related to variation in specific symptoms in children with autism.The authors explored whether variants of two functional polymorphisms of SLC6A4 (5-HTTLPR, intron 2 variable number tandem repeat [2 VNTR]) were related to behavioral characteristics measured by the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule. Subjects (N=73, age 3-19 years old) met diagnostic criteria for autistic disorder based on both measures.Evidence of genotype-phenotype interactions on the Autism Diagnostic Interview-Revised was found with the 5-HTTLPR short group of HTTLPR (S/L or S/S genotypes) being rated as more severe on the subdomain "failure to use nonverbal communication to regulate social interaction," and the long group (L/L genotype) being more severe on the subdomain "stereotyped and repetitive motor mannerisms" and on an aggression measure. In contrast, on the Autism Diagnostic Observation Schedule, the long group was associated with greater severity on directed facial expressions and unusual sensory interests. There were no significant relationships between the intron 2 VNTR genotypes and subdomains or domains of symptoms on the Autism Diagnostic Interview-Revised or the Autism Diagnostic Observation Schedule.These findings provide initial support for genotype-specific phenotypes for 5-HTTLPR in autism based on ratings from the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule.