title: Analysis of the autism chromosome 2 linkage region: GAD1 and other candidate genes.
abstract: Autism has a strong and complex genetic component, involving several genes. Genomic screens, including our own, have shown suggestive evidence for linkage over a 20-30 cM region on chromosome 2q31-q33. Two subsequent reports showed that the linkage evidence increased in the subset of families with phrase speech delay (PSD), defined as onset of phrase speech later than 3 years of age. To further investigate the linkage in the presumptive candidate region, microsatellite markers in a 2 cM grid covering the interval from 164 to 203 cM were analyzed in 110 multiplex (2 or more sampled autism patients) families. A maximum heterogeneity LOD (HLOD) score of 1.54 was detected at D2S1776 (173 cM) in the overall dataset (dominant model), increasing to 1.71 in the PSD subset. While not conclusive, these data continue to provide suggestive evidence for linkage, particularly considering replication by multiple independent groups. Positive LOD scores extended over the entire region, continuing to define a broad candidate interval. Association studies were performed on several functional candidates mapping within the region. These included GAD1, encoding GAD67, whose levels are reduced in autopsy brain material from autistic subjects, and STK17B, ABI2, CTLA4, CD28, NEUROD1, PDE1A, HOXD1 and DLX2. We found no evidence for significant allelic association between autism and any of these candidates, suggesting that they do not play a major role in the genetics of autism or that substantial allelic heterogeneity at any one of these loci dilutes potential disease-allele association.
authors.affiliation: Department of Medicine, Center for Human Genetics, 595 LaSalle St., Box 3445, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Raquel
authors.initials: R
authors.lastname: Rabionet
authors.forename: James M
authors.initials: JM
authors.lastname: Jaworski
authors.forename: Allison E
authors.initials: AE
authors.lastname: Ashley-Koch
authors.forename: Eden R
authors.initials: ER
authors.lastname: Martin
authors.forename: James S
authors.initials: JS
authors.lastname: Sutcliffe
authors.forename: Jonathan L
authors.initials: JL
authors.lastname: Haines
authors.forename: G Robert
authors.initials: GR
authors.lastname: Delong
authors.forename: Ruth K
authors.initials: RK
authors.lastname: Abramson
authors.forename: Harry H
authors.initials: HH
authors.lastname: Wright
authors.forename: Michael L
authors.initials: ML
authors.lastname: Cuccaro
authors.forename: John R
authors.initials: JR
authors.lastname: Gilbert
authors.forename: Margaret A
authors.initials: MA
authors.lastname: Pericak-Vance
mesh_terms: D001321:Autistic Disorder / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D002889:Chromosomes, Human, Pair 2 / Q000235:genetics*; D005190:Family; D008040:Genetic Linkage / Q000235:genetics*; D005968:Glutamate Decarboxylase / Q000235:genetics*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics*; D007805:Language Development Disorders / Q000235:genetics; D018895:Microsatellite Repeats / Q000235:genetics; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D011786:Quality Control
chemical_list: D007527:Isoenzymes; D005968:Glutamate Decarboxylase; C402565:glutamate decarboxylase 1