Showing papers by "Lauren A. Weiss published in 2009"

A genome-wide linkage and association scan reveals novel loci for autism

Abstract: 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.

Microdeletion/duplication at 15q13.2q13.3 among individuals with features of autism and other neuropsychiatric disorders

Abstract: Background: Segmental duplications at breakpoints (BP4-BP5) of chromosome 15q13.2q13.3 mediate a recurrent genomic imbalance syndrome associated with mental retardation, epilepsy, and/or EEG abnormalities. Patients: DNA samples from 1,445 unrelated patients submitted consecutively for clinical array comparative genomic hybridisation (CGH) testing at Children’s Hospital Boston and DNA samples from 1,441 individuals with Autism from 751 families in the Autism Genetic Resource Exchange (AGRE) repository. Results: We report the clinical features of five patients with a BP4-BP5 deletion, 3 with a BP4-BP5 duplication, and 2 with an overlapping but smaller duplication identified by whole genome high resolution oligonucleotide array CGH. These BP4-BP5 deletion cases exhibit minor dysmorphic features, significant expressive language deficits, and a spectrum of neuropsychiatric impairments that include autism spectrum disorder, ADHD, anxiety disorder, and mood disorder. Cognitive impairment varied from moderate mental retardation to normal IQ with learning disability. BP4-BP5 covers ~1.5Mb (chr15:28.719-30.298Mb) and includes 6 reference genes and 1 miRNA gene, while the smaller duplications cover ~500 kb (chr15:28.902-29.404 Mb and contain 3 reference genes and one miRNA gene. The BP4-BP5 deletion and duplication events span CHRNA7, a candidate gene for seizures. However, none of these individuals reported here has epilepsy, although one has an abnormal EEG. Conclusions: The phenotype of chromosome 15q13.2q13.3 BP4-BP5 microdeletion/duplication syndrome may include features of autism spectrum disorder, a variety of neuropsychiatric disorders, and cognitive impairment. Recognition of this broader phenotype has implications for clinical diagnostic testing and efforts to understand the underlying etiology of this syndrome.

Autism genetics: emerging data from genome-wide copy-number and single nucleotide polymorphism scans

Abstract: Autism and related traits are highly heritable but cannot be explained by currently known genetic risk factors. Therefore, the advent of genome-wide single nucleotide polymorphism (SNP) and copy number variant (CNV) microarray technologies heralded identification of additional autism loci. CNVs associated with autism seem to show variable expressivity, also leading to other phenotypes, such as schizophrenia, mental retardation/developmental delay and epilepsy. Initial genome-wide SNP-association studies have each identified a single novel associated locus with modest effect. Based on the lessons from other complex common disease, larger sample sizes and meta-analyses are likely to identify additional SNP loci, and the genes implicated may act on multiple related disorders. Even if common alleles or rare variants hold little predictive value, neurodevelopmental pathways disrupted in autism may be identified. Future research might yet uncover common CNV risk loci and rare single nucleotide risk alleles, which are currently difficult to detect. The genetic architecture and phenotypic heterogeneity identified so far suggest additional approaches, such as population-based research and study of relevant neurobiological endophenotypes.

Polymorphisms of the Scavenger Receptor Class B Member 1 Are Associated with Insulin Resistance with Evidence of Gene by Sex Interaction

Abstract: Background: Genetic variation in diabetes-associated genes cumulatively explain little of the overall heritability of this trait. We sought to determine whether polymorphisms of the scavenger receptor class B, member I (SCARB1), an estrogen-regulated chromosome 12q24 positional candidate diabetes gene, were associated with type 2 diabetes or insulin resistance in a sex-specific fashion. Methods: We evaluated 34 haplotype-tagged single-nucleotide polymorphisms (SNPs) of SCARB1 for their association with type 2 diabetes and measures of insulin resistance in two populations: a clinic-based sample of 444 Mexican-American women from Proyecto SALSA and a community-based sample of 830 white women from the Rancho Bernardo Study. Results: We identified significant associations between a tagged SNP in intron 9, rs9919713, and fasting glucose in the SALSA population (P = 2.3 × 10−4). In the Rancho Bernardo Study, the same SNP also showed significant association with the related traits homeostasis model assessment for insulin resistance (P = 3.0 × 10−4), fasting glucose (P = 1.1 × 10−3), and type 2 diabetes (P = 9.0 × 10−3). In men from the Rancho Bernardo population, the opposite effect was found (genotype by sex interaction in the Rancho Bernardo population P < 10−3 for insulin resistance). Conclusions: Our data support an association between SCARB1 variants and insulin resistance, especially in women, with evidence of significant gene by sex interaction. These findings warrant further investigation in additional populations and prompt exploration of a role for SR-BI in the development of insulin resistance.