A genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p.
ABSTRACT: Autism is characterized by impairments in reciprocal communication and social interaction and by repetitive and stereotyped patterns of activities and interests. Evidence for a strong underlying genetic predisposition comes from twin and family studies, although susceptibility genes have not yet been identified. A whole-genome screen for linkage, using 83 sib pairs with autism, has been completed, and 119 markers have been genotyped in 13 candidate regions in a further 69 sib pairs. The addition of new families and markers provides further support for previous reports of linkages on chromosomes 7q and 16p. Two new regions of linkage have also been identified on chromosomes 2q and 17q. The most significant finding was a multipoint maximum LOD score (MLS) of 3.74 at marker D2S2188 on chromosome 2; this MLS increased to 4.80 when only sib pairs fulfilling strict diagnostic criteria were included. The susceptibility region on chromosome 7 was the next most significant, generating a multipoint MLS of 3.20 at marker D7S477. Chromosome 16 generated a multipoint MLS of 2.93 at D16S3102, whereas chromosome 17 generated a multipoint MLS of 2.34 at HTTINT2. With the addition of new families, there was no increased allele sharing at a number of other loci originally showing some evidence of linkage. These results support the continuing collection of multiplex sib-pair families to identify autism-susceptibility genes.
SUBMITTER: International Molecular Genetic Study of Autism Consortium (IMGSAC)
Project description:We previously reported a genomewide scan to identify autism-susceptibility loci in 110 multiplex families, showing suggestive evidence (P <.01) for linkage to autism-spectrum disorders (ASD) on chromosomes 5, 8, 16, 19, and X and showing nominal evidence (P <.05) on several additional chromosomes (2, 3, 4, 10, 11, 12, 15, 18, and 20). In this follow-up analysis we have increased the sample size threefold, while holding the study design constant, so that we now report 345 multiplex families, each with at least two siblings affected with autism or ASD phenotype. Along with 235 new multiplex families, 73 new microsatellite markers were also added in 10 regions, thereby increasing the marker density at these strategic locations from 10 cM to approximately 2 cM and bringing the total number of markers to 408 over the entire genome. Multipoint maximum LOD scores (MLS) obtained from affected-sib-pair analysis of all 345 families yielded suggestive evidence for linkage on chromosomes 17, 5, 11, 4, and 8 (listed in order by MLS) (P <.01). The most significant findings were an MLS of 2.83 (P =.00029) on chromosome 17q, near the serotonin transporter (5-hydroxytryptamine transporter [5-HTT]), and an MLS of 2.54 (P =.00059) on 5p. The present follow-up genome scan, which used a consistent research design across studies and examined the largest ASD sample collection reported to date, gave either equivalent or marginally increased evidence for linkage at several chromosomal regions implicated in our previous scan but eliminated evidence for linkage at other regions.
Project description:Gilles de la Tourette syndrome is a neuropsychiatric disorder characterized by waxing and waning multiple motor and phonic tics with a complex mode of inheritance. Previous attempts, which used large multigenerational families to localize susceptibility loci, have been unsuccessful. In this report, the results of the first systematic genome scan, using 76 affected-sib-pair families with a total of 110 sib pairs, are summarized. While no results reached acceptable statistical significance, the multipoint maximum-likelihood scores (MLS) for two regions (4q and 8p) were suggestive (MLS > 2.0). Four additional genomic regions also gave multipoint MLS scores between 1.0 and 2.0.
Project description:We report the analysis of 335 microsatellite markers genotyped in 110 multiplex families with autism. All families include at least two "affected" siblings, at least one of whom has autism; the remaining affected sibs carry diagnoses of either Asperger syndrome or pervasive developmental disorder. Affected sib-pair analysis yielded multipoint maximum LOD scores (MLS) that reach the accepted threshold for suggestive linkage on chromosomes 5, X, and 19. Nominal evidence for linkage (point-wise P<.05) was obtained on chromosomes 2, 3, 4, 8, 10, 11, 12, 15, 16, 18, and 20, and secondary loci were found on chromosomes 5 and 19. Analysis of families sharing alleles at the putative X chromosomal linked locus and one or more other putative linked loci produced an MLS of 3.56 for the DXS470-D19S174 marker combination. In an effort to increase power to detect linkage, scan statistics were used to evaluate the significance of peak LOD scores based on statistical evidence at adjacent marker loci. This analysis yielded impressive evidence for linkage to autism and autism-spectrum disorders with significant genomewide P values <.05 for markers on chromosomes 5 and 8 and with suggestive linkage evidence for a marker on chromosome 19.
Project description:We are conducting a genome scan at an average resolution of 10 centimorgans (cM) for type 2 diabetes susceptibility genes in 716 affected sib pairs from 477 Finnish families. To date, our best evidence for linkage is on chromosome 20 with potentially separable peaks located on both the long and short arms. The unweighted multipoint maximum logarithm of odds score (MLS) was 3.08 on 20p (location, chi = 19.5 cM) under an additive model, whereas the weighted MLS was 2.06 on 20q (chi = 57 cM, recurrence risk,lambda(s) = 1. 25, P = 0.009). Weighted logarithm of odds scores of 2.00 (chi = 69.5 cM, P = 0.010) and 1.92 (chi = 18.5 cM, P = 0.013) were also observed. Ordered subset analyses based on sibships with extreme mean values of diabetes-related quantitative traits yielded sets of families who contributed disproportionately to the peaks. Two-hour glucose levels in offspring of diabetic individuals gave a MLS of 2. 12 (P = 0.0018) at 9.5 cM. Evidence from this and other studies suggests at least two diabetes-susceptibility genes on chromosome 20. We have also screened the gene for maturity-onset diabetes of the young 1, hepatic nuclear factor 4-a (HNF-4alpha) in 64 affected sibships with evidence for high chromosomal sharing at its location on chromosome 20q. We found no evidence that sequence changes in this gene accounted for the linkage results we observed.
Project description:BACKGROUND: Allergic diseases such as asthma and rhinitis have closely related phenotypes and often occur with atopy. They show strong familial and intra-individual clustering, suggesting overlapping disease aetiology. Various loci and candidate genes have been suggested to underlie allergy. Many or all are still inconclusive. Following genome-wide scans on multiple phenotypes, we previously suggested that chromosome 3q13.12-q21.2 harbours an allergy locus. OBJECTIVE: To identify candidate loci in the Danish population, two additional independent sets of sib-pair families were fine-scale mapped in candidate regions showing maximum likelihood scores (MLS) > or =1.5 in the genome-wide scans. RESULTS: Twenty eight microsatellite markers in a denser map on chromosome 3q were analysed in 236 allergy sib-pair families including 125 sib pairs with rhinitis. We report significant evidence for linkage to chromosome 3q13.31 for rhinitis (MLS 5.55, identity by descent (IBD) 63.9%) and atopy (increased specific immunoglobulin E) (MLS 3.71, IBD 61.7%). We obtained an MLS of 5.1 (IBD 67.3%) at 3q13.31 when sib pairs with both rhinitis and atopy were analysed. CONCLUSION: This study reports the first statistically significant evidence for a genetic susceptibility locus for rhinitis and to our knowledge shows the most significant evidence to date of linkage for any allergy phenotype.
Project description:Despite recent advances in the molecular genetics of type 2 diabetes, the majority of susceptibility genes in humans remain to be identified. We therefore conducted a 10-cM genomewide search (401 microsatellite markers) for type 2 diabetes-related traits in 637 members of 143 French pedigrees ascertained through multiple diabetic siblings, to map such genes in the white population. Nonparametric two-point and multipoint linkage analyzes-using the MAPMAKER-SIBS (MLS) and MAXIMUM-BINOMIAL-LIKELIHOOD (MLB) programs for autosomal markers and the ASPEX program for chromosome X markers-were performed with six diabetic phenotypes: diabetes and diabetes or glucose intolerance (GI), as well as with each of the two phenotypes associated with normal body weight (body-mass index<27 kg/m(2)) or early age at diagnosis (<45 years). In a second step, high-resolution genetic mapping ( approximately 2 cM) was performed in regions on chromosomes 1 and 3 loci showing the strongest linkage to diabetic traits. We found evidence for linkage with diabetes or GI diagnosed at age <45 years in 92 affected sib pairs from 55 families at the D3S1580 locus on chromosome 3q27-qter using MAPMAKER-SIBS (MLS = 4.67, P=.000004), supported by the MLB statistic (MLB-LOD=3.43, P=.00003). We also found suggestive linkage between the lean diabetic status and markers APOA2-D1S484 (MLS = 3. 04, P=.00018; MLB-LOD=2.99, P=.00010) on chromosome 1q21-q24. Several other chromosomal regions showed indication of linkage with diabetic traits, including markers on chromosome 2p21-p16, 10q26, 20p, and 20q. These results (a) showed evidence for a novel susceptibility locus for type 2 diabetes in French whites on chromosome 3q27-qter and (b) confirmed the previously reported diabetes-susceptibility locus on chromosome 1q21-q24. Saturation on both chromosomes narrowed the regions of interest down to an interval of <7 cM.
Project description:Autism is a syndrome characterized by deficits in language and social skills and by repetitive behaviors. We hypothesized that potential quantitative trait loci (QTLs) related to component autism endophenotypes might underlie putative or significant regions of autism linkage. We performed nonparametric multipoint linkage analyses, in 152 families from the Autism Genetic Resource Exchange, focusing on three traits derived from the Autism Diagnostic Interview: "age at first word," "age at first phrase," and a composite measure of "repetitive and stereotyped behavior." Families were genotyped for 335 markers, and multipoint sib pair linkage analyses were conducted. Using nonparametric multipoint linkage analysis, we found the strongest QTL evidence for age at first word on chromosome 7q (nonparametric test statistic [Z] 2.98; P=.001), and subsequent linkage analyses of additional markers and association analyses in the same region supported the initial result (Z=2.85, P=.002; chi(2)=18.84, df 8, P=.016). Moreover, the peak fine-mapping result for repetitive behavior (Z=2.48; P=.007) localized to a region overlapping this language QTL. The putative autism-susceptibility locus on chromosome 7 may be the result of separate QTLs for the language and repetitive or stereotyped behavior deficits that are associated with the disorder.
Project description:Autistic disorder (AutD) is a neurodevelopmental disorder characterized by significant disturbances in social, communicative, and behavioral functioning. A two-stage genomic screen analysis of 99 families with AutD revealed suggestive evidence for linkage to chromosome 2q (D2S116 nonparametric sib-pair LOD score [MLS] 1.12 at 198 cM). In addition, analysis of linkage disequilibrium for D2S116 showed an allele-specific P value of <.01. Recently, linkage to the same region of 2q was reported in an independent genome screen. This evidence for linkage increased when analysis was restricted to the subset of patients with AutD who had delayed onset (>36 mo) of phrase speech (PSD). We similarly classified our data set of 82 sib pairs with AutD, identifying 45 families with AutD and PSD. Analysis of this PSD subset increased our support for linkage to 2q (MLS 2.86 and HLOD 2.12 for marker D2S116). These data support evidence for a gene on chromosome 2 contributing to risk of AutD, and they suggest that phenotypic homogeneity increases the power to find susceptibility genes for AutD.
Project description:To identify genetic loci for autism-spectrum disorders, we have performed a two-stage genomewide scan in 38 Finnish families. The detailed clinical examination of all family members revealed infantile autism, but also Asperger syndrome (AS) and developmental dysphasia, in the same set of families. The most significant evidence for linkage was found on chromosome 3q25-27, with a maximum two-point LOD score of 4.31 (Z(max )(dom)) for D3S3037, using infantile autism and AS as an affection status. Six markers flanking over a 5-cM region on 3q gave Z(max dom) >3, and a maximum parametric multipoint LOD score (MLS) of 4.81 was obtained in the vicinity of D3S3715 and D3S3037. Association, linkage disequilibrium, and haplotype analyses provided some evidence for shared ancestor alleles on this chromosomal region among affected individuals, especially in the regional subisolate. Additional potential susceptibility loci with two-point LOD scores >2 were observed on chromosomes 1q21-22 and 7q. The region on 1q21-22 overlaps with the previously reported candidate region for infantile autism and schizophrenia, whereas the region on chromosome 7q provided evidence for linkage 58 cM distally from the previously described autism susceptibility locus (AUTS1).
Project description:A genome scan was performed on 164 Dutch affected sib pairs (ASPs) with attention-deficit/hyperactivity disorder (ADHD). All subjects were white and of Dutch descent and were phenotyped according to criteria set out in the Diagnostic and Statistical Manual Of Mental Disorders, 4th edition. Initially, a narrow phenotype was defined, in which all the sib pairs met the full ADHD criteria (117 ASPs). In a broad phenotype, additional sib pairs were included, in which one child had an autistic-spectrum disorder but also met the full ADHD criteria (164 ASPs). A set of 402 polymorphic microsatellite markers with an average intermarker distance of 10 cM was genotyped and analyzed using the Mapmaker/sibs program. Regions with multipoint maximum likelihood scores (MLSs) >1.5 in both phenotypes were fine mapped with additional markers. This genome scan indicated several regions of interest, two of which showed suggestive evidence for linkage. The most promising chromosome region was located at 15q, with an MLS of 3.54 under the broad phenotype definition. This region was previously implicated in reading disability and autism. In addition, MLSs of 3.04 and 2.05 were found for chromosome regions 7p and 9q in the narrow phenotype. Except for a region on chromosome 5, no overlap was found with regions mentioned in the only other independent genome scan in ADHD reported to date.