Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-12-02T19:18:55.283Z Has data issue: false hasContentIssue false

Autism: the quest for the genes

Published online by Cambridge University Press:  03 September 2007

Nuala H. Sykes
Affiliation:
Wellcome Trust Centre for Human Genetics, University of Oxford, UK.
Janine A. Lamb*
Affiliation:
Centre for Integrated Genomic Medical Research, The University of Manchester, UK.
*
*Corresponding author: Janine A. Lamb, Centre for Integrated Genomic Medical Research (CIGMR), Stopford Building, The University of Manchester, Oxford Road, Manchester, M13 9PT, UK. Tel: +44 (0)161 275 1619; Fax: +44 (0)161 275 1617; E-mail: [email protected]

Abstract

Autism, at its most extreme, is a severe neurodevelopmental disorder, and recent studies have indicated that autism spectrum disorders are considerably more common than previously supposed. However, although one of the most heritable neuropsychiatric syndromes, autism has so far eluded attempts to discover its genetic origins in the majority of cases. Several whole-genome scans for autism-susceptibility loci have identified specific chromosomal regions, but the results have been inconclusive and fine mapping and association studies have failed to identify the underlying genes. Recent advances in knowledge from the Human Genome and HapMap Projects, and progress in technology and bioinformatic resources, have aided study design and made data generation more efficient and cost-effective. Broadening horizons about the landscape of structural genetic variation and the field of epigenetics are indicating new possible mechanisms underlying autism aetiology, while endophenotypes are being used in an attempt to break down the complexity of the syndrome and refine genetic data. Although the genetic variants underlying idiopathic autism have proven elusive so far, the future for this field looks promising.

Type
Review Article
Copyright
Copyright © Cambridge University Press 2007

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

References

1Kanner, L. (1943) Autistic disturbances of affective contact. Nervous Child, 217-250Google Scholar
2Asperger, H. (1949) Die ‘Autistischen Psychopathen’ im Kindesalter. Archiv fur Psychiatrie und Nervenkrankheiten 177, 76-136Google Scholar
3Jarbrink, K. and Knapp, M. (2001) The economic impact of autism in Britain. Autism 5, 7-22CrossRefGoogle ScholarPubMed
4Baird, G. et al. (2006) Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: the Special Needs and Autism Project (SNAP). Lancet 368, 210-215CrossRefGoogle Scholar
5Lord, C. et al. (2000) The autism diagnostic observation schedule-generic: a standard measure of social and communication deficits associated with the spectrum of autism. J Autism Dev Disord 30, 205-223CrossRefGoogle ScholarPubMed
6Lord, C., Rutter, M. and Le, C.A. (1994) Autism Diagnostic Interview-Revised: a revised version of a diagnostic interview for caregivers of individuals with possible pervasive developmental disorders. J Autism Dev Disord 24, 659-685CrossRefGoogle ScholarPubMed
7Bryson, S.E., Rogers, S.J. and Fombonne, E. (2003) Autism spectrum disorders: early detection, intervention, education, and psychopharmacological management. Can J Psychiatry 48, 506-516CrossRefGoogle ScholarPubMed
8Folstein, S. and Rutter, M. (1977) Infantile autism: a genetic study of 21 twin pairs. J Child Psychol Psychiatry 18, 297-321CrossRefGoogle ScholarPubMed
9Bailey, A. et al. (1995) Autism as a strongly genetic disorder: evidence from a British twin study. Psychol Med 25, 63-77CrossRefGoogle ScholarPubMed
10Steffenburg, S. et al. (1989) A twin study of autism in Denmark, Finland, Iceland, Norway and Sweden. J Child Psychol Psychiatry 30, 405-416CrossRefGoogle ScholarPubMed
11Hurley, R.S. et al. (2006) The Broad Autism Phenotype Questionnaire. J Autism Dev Disord, Dec 5 [Epub ahead of print]Google ScholarPubMed
12Rutter, M. et al. (1999) Genetics and child psychiatry: II Empirical research findings. J Child Psychol Psychiatry 40, 19-55CrossRefGoogle ScholarPubMed
13Pickles, A. et al. (1995) Latent-class analysis of recurrence risks for complex phenotypes with selection and measurement error: a twin and family history study of autism. Am J Hum Genet 57, 717-726Google ScholarPubMed
14Risch, N. et al. (1999) A genomic screen of autism: evidence for a multilocus etiology. Am J Hum Genet 65, 493-507CrossRefGoogle ScholarPubMed
15Bailey, A. et al. (1998) Autism: the phenotype in relatives. J Autism Dev Disord 28, 369-392CrossRefGoogle ScholarPubMed
16Juul-Dam, N., Townsend, J. and Courchesne, E. (2001) Prenatal, perinatal, and neonatal factors in autism, pervasive developmental disorder-not otherwise specified, and the general population. Pediatrics 107, E63CrossRefGoogle ScholarPubMed
17Miyazaki, K., Narita, N. and Narita, M. (2005) Maternal administration of thalidomide or valproic acid causes abnormal serotonergic neurons in the offspring: implication for pathogenesis of autism. Int J Dev Neurosci 23, 287-297CrossRefGoogle ScholarPubMed
18Stromland, K. et al. (1994) Autism in thalidomide embryopathy: a population study. Dev Med Child Neurol 36, 351-356CrossRefGoogle ScholarPubMed
19Patterson, P.H. (2002) Maternal infection: window on neuroimmune interactions in fetal brain development and mental illness. Curr Opin Neurobiol 12, 115-118CrossRefGoogle ScholarPubMed
20Smeeth, L. et al. (2004) MMR vaccination and pervasive developmental disorders: a case-control study. Lancet 364, 963-969CrossRefGoogle ScholarPubMed
21Uchiyama, T., Kurosawa, M. and Inaba, Y. (2007) MMR-vaccine and regression in autism spectrum disorders: negative results presented from Japan. J Autism Dev Disord 37, 210-217CrossRefGoogle ScholarPubMed
22International Molecular Genetic Study of Autism Consortium (IMGSAC) (2001) A genomewide screen for autism: strong evidence for linkage to chromosomes 2q, 7q, and 16p. Am J Hum Genet 69, 570-581CrossRefGoogle Scholar
23International Molecular Genetic Study of Autism Consortium (IMGSAC) (1998) A full genome screen for autism with evidence for linkage to a region on chromosome 7q. International Molecular Genetic Study of Autism Consortium. Hum Mol Genet 7, 571-578CrossRefGoogle Scholar
24Lamb, J.A. et al. (2005) Analysis of IMGSAC autism susceptibility loci: evidence for sex limited and parent of origin specific effects. J Med Genet 42, 132-137CrossRefGoogle ScholarPubMed
25Barrett, S. et al. (1999) An autosomal genomic screen for autism. Collaborative linkage study of autism. Am J Med Genet 88, 609-615Google ScholarPubMed
26Philippe, A. et al. (1999) Genome-wide scan for autism susceptibility genes. Paris Autism Research International Sibpair Study. Hum Mol Genet 8, 805-812CrossRefGoogle ScholarPubMed
27Buxbaum, J.D. et al. (2001) Evidence for a susceptibility gene for autism on chromosome 2 and for ge netic heterogeneity. Am J Hum Genet 68, 1514-1520CrossRefGoogle Scholar
28Liu, J. et al. (2001) A genomewide screen for autism susceptibility loci. Am J Hum Genet 69, 327-340CrossRefGoogle ScholarPubMed
29Yonan, A.L. et al. (2003) A genomewide screen of 345 families for autism-susceptibility loci. Am J Hum Genet 73, 886-897CrossRefGoogle ScholarPubMed
30Buxbaum, J.D. et al. (2004) Linkage analysis for autism in a subset families with obsessive-compulsive behaviors: evidence for an autism susceptibility gene on chromosome 1 and further support for susceptibility genes on chromosome 6 and 19. Mol Psychiatry 9, 144-150CrossRefGoogle Scholar
31Shao, Y. et al. (2002) Genomic screen and follow-up analysis for autistic disorder. Am J Med Genet 114, 99-105CrossRefGoogle ScholarPubMed
32Auranen, M. et al. (2002) A genomewide screen for autism-spectrum disorders: evidence for a major susceptibility locus on chromosome 3q25-27. Am J Hum Genet 71, 777-790CrossRefGoogle Scholar
33Cantor, R.M. et al. (2005) Replication of autism linkage: fine-mapping peak at 17q21. Am J Hum Genet 76, 1050-1056CrossRefGoogle Scholar
34Schellenberg, G.D. et al. (2006) Evidence for multiple loci from a genome scan of autism kindreds. Mol Psychiatry 11, 1049–60, 979CrossRefGoogle ScholarPubMed
35McCauley, J.L. et al. (2005) Genome-wide and Ordered-Subset linkage analyses provide support for autism loci on 17q and 19p with evidence of phenotypic and interlocus genetic correlates. BMC Med Genet 6, 1CrossRefGoogle ScholarPubMed
36Bacchelli, E. and Maestrini, E. (2006) Autism spectrum disorders: molecular genetic advances. Am J Med Genet C Semin Med Genet 142, 13-23CrossRefGoogle Scholar
37Shao, Y. et al. (2002) Phenotypic homogeneity provides increased support for linkage on chromosome 2 in autistic disorder. Am J Hum Genet 70, 1058-1061CrossRefGoogle ScholarPubMed
38Badner, J.A. and Gershon, E.S. (2002) Regional meta-analysis of published data supports linkage of autism with markers on chromosome 7. Mol Psychiatry 7, 56-66CrossRefGoogle ScholarPubMed
39Collaborative Linkage Study of Autism (2001) An autosomal genomic screen for autism. Am J Med Genet 105, 609-615Google Scholar
40Trikalinos, T.A. et al. (2006) A heterogeneity-based genome search meta-analysis for autism-spectrum disorders. Mol Psychiatry 11, 29-36CrossRefGoogle ScholarPubMed
41Stone, J.L. et al. (2004) Evidence for sex-specific risk alleles in autism spectrum disorder. Am J Hum Genet 75, 1117-1123CrossRefGoogle ScholarPubMed
42Cook, E.H. and Leventhal, B.L. (1996) The serotonin system in autism. Curr Opin Pediatr 8, 348-354CrossRefGoogle ScholarPubMed
43Lam, K.S., Aman, M.G. and Arnold, L.E. (2006) Neurochemical correlates of autistic disorder: a review of the literature. Res Dev Disabil 27, 254-289CrossRefGoogle ScholarPubMed
44The Autism Genome Project (AGP) Consortium et al. (2007) Mapping autism risk loci using genetic linkage and chromosomal rearrangements. Nat Genet 39, 319-328CrossRefGoogle Scholar
45Bartlett, C.W. and Vieland, V.J. (2007) Accumulating quantitative trait linkage evidence across multiple datasets using the posterior probability of linkage. Genet Epidemiol 31, 91-102CrossRefGoogle ScholarPubMed
46Vieland, V.J., Wang, K. and Huang, J. (2001) Power to detect linkage based on multiple sets of data in the presence of locus heterogeneity: comparative evaluation of model-based linkage methods for affected sib pair data. Hum Hered 51, 199-208CrossRefGoogle ScholarPubMed
47Carlson, C.S. et al. (2004) Mapping complex disease loci in whole-genome association studies. Nature 429, 446-452CrossRefGoogle ScholarPubMed
48Del, A.A. and Satrustegui, J. (1998) Molecular cloning of Aralar, a new member of the mitochondrial carrier superfamily that binds calcium and is present in human muscle and brain. J Biol Chem 273, 23327-23334Google Scholar
49Ramoz, N. et al. (2004) Linkage and association of the mitochondrial aspartate/glutamate carrier SLC25A12 gene with autism. Am J Psychiatry 161, 662-669CrossRefGoogle ScholarPubMed
50Segurado, R. et al. (2005) Confirmation of association between autism and the mitochondrial aspartate/glutamate carrier SLC25A12 gene on chromosome 2q31. Am J Psychiatry 162, 2182-2184CrossRefGoogle ScholarPubMed
51Blasi, F. et al. (2006) SLC25A12 and CMYA3 gene variants are not associated with autism in the IMGSAC multiplex family sample. Eur J Hum Genet 14, 123-126CrossRefGoogle Scholar
52Rabionet, R. et al. (2006) Lack of association between autism and SLC25A12. Am J Psychiatry 163, 929-931CrossRefGoogle ScholarPubMed
53Persico, A.M. et al. (2001) Reelin gene alleles and haplotypes as a factor predisposing to autistic disorder. Mol Psychiatry 6, 150-159CrossRefGoogle ScholarPubMed
54Skaar, D.A. et al. (2005) Analysis of the RELN gene as a genetic risk factor for autism. Mol Psychiatry 10, 563-571CrossRefGoogle ScholarPubMed
55Li, J. et al. (2004) Lack of evidence for an association between WNT2 and RELN polymorphisms and autism. Am J Med Genet B Neuropsychiatr Genet 126, 51-57CrossRefGoogle Scholar
56Bonora, E. et al. (2003) Analysis of reelin as a candidate gene for autism. Mol Psychiatry 8, 885-892CrossRefGoogle ScholarPubMed
57Devlin, B. et al. (2004) Alleles of a reelin CGG repeat do not convey liability to autism in a sample from the CPEA network. Am J Med Genet B Neuropsychiatr Genet 126, 46-50CrossRefGoogle Scholar
58Krebs, M.O. et al. (2002) Absence of association between a polymorphic GGC repeat in the 5 untranslated region of the reelin gene and autism. Mol Psychiatry 7, 801-804CrossRefGoogle ScholarPubMed
59Zhang, H. et al. (2002) Reelin gene alleles and susceptibility to autism spectrum disorders. Mol Psychiatry 7, 1012-1017CrossRefGoogle ScholarPubMed
60Persico, A.M., Levitt, P. and Pimenta, A.F. (2006) Polymorphic GGC repeat differentially regulates human reelin gene expression levels. J Neural Transm 113, 1373-1382CrossRefGoogle ScholarPubMed
61Fatemi, S.H. et al. (2005) Reelin signaling is impaired in autism. Biol Psychiatry 57, 777-787CrossRefGoogle ScholarPubMed
62Cook, E.H. Jr. et al. (1997) Evidence of linkage between the serotonin transporter and autistic disorder. Mol Psychiatry 2, 247-250Google ScholarPubMed
63McCauley, J.L. et al. (2004) Linkage and association analysis at the serotonin transporter (SLC6A4) locus in a rigid-compulsive subset of autism. Am J Med Genet B Neuropsychiatr Genet 127, 104-112CrossRefGoogle Scholar
64Conroy, J. et al. (2004) Serotonin transporter gene and autism: a haplotype analysis in an Irish autistic population. Mol Psychiatry 9, 587-593CrossRefGoogle Scholar
65Devlin, B. et al. (2005) Autism and the serotonin transporter: the long and short of it. Mol Psychiatry 10, 1110-1116CrossRefGoogle Scholar
66Klauck, S.M. et al. (1997) Serotonin transporter (5-HTT) gene variants associated with autism? Hum Mol Genet 6, 2233-2238CrossRefGoogle ScholarPubMed
67Yirmiya, N. et al. (2001) Evidence for an association with the serotonin transporter promoter region polymorphism and autism. Am J Med Genet 105, 381-386CrossRefGoogle ScholarPubMed
68Maestrini, E. et al. (1999) Serotonin transporter (5-HTT) and gamma-aminobutyric acid receptor subunit beta3 (GABRB3) gene polymorphisms are not associated with autism in the IMGSA families. The International Molecular Genetic Study of Autism Consortium. Am J Med Genet 88, 492-4963.0.CO;2-X>CrossRefGoogle Scholar
69Persico, A.M. et al. (2000) Lack of association between serotonin transporter gene promoter variants and autistic disorder in two ethnically distinct samples. Am J Med Genet 96, 123-1273.0.CO;2-N>CrossRefGoogle ScholarPubMed
70Ramoz, N. et al. (2006) Lack of evidence for association of the serotonin transporter gene SLC6A4 with autism. Biol Psychiatry 60, 186-191CrossRefGoogle ScholarPubMed
71Zhong, N. et al. (1999) 5-HTTLPR variants not associated with autistic spectrum disorders. Neurogenetics 2, 129-131CrossRefGoogle Scholar
72Brune, C.W. et al. (2006) 5-HTTLPR Genotype-Specific Phenotype in Children and Adolescents With Autism. Am J Psychiatry 163, 2148-2156CrossRefGoogle ScholarPubMed
73Sutcliffe, J.S. et al. (2005) Allelic heterogeneity at the serotonin transporter locus (SLC6A4) confers susceptibility to autism and rigid-compulsive behaviors. Am J Hum Genet 77, 265-279CrossRefGoogle ScholarPubMed
74Zondervan, K.T. and Cardon, L.R. (2004) The complex interplay among factors that influence allelic association. Nat Rev Genet 5, 89-100CrossRefGoogle ScholarPubMed
75Trikalinos, T.A. et al. (2004) Establishment of genetic associations for complex diseases is independent of early study findings. Eur J Hum Genet 12, 762-769CrossRefGoogle ScholarPubMed
76Zollner, S. and Pritchard, J.K. (2007) Overcoming the winner's curse: estimating penetrance parameters from case-control data. Am J Hum Genet 80, 605-615CrossRefGoogle ScholarPubMed
77Jamain, S. et al. (2003) Mutations of the X-linked genes encoding neuroligins NLGN3 and NLGN4 are associated with autism. Nat Genet 34, 27-29CrossRefGoogle ScholarPubMed
78Durand, C.M. et al. (2007) Mutations in the gene encoding the synaptic scaffolding protein SHANK3 are associated with autism spectrum disorders. Nat Genet 39, 25-27CrossRefGoogle ScholarPubMed
79International Human Genome Sequencing Consortium (2004) Finishing the euchromatic sequence of the human genome. Nature 431, 931-945CrossRefGoogle Scholar
80The International HapMap Consortium (2003) The International HapMap Project. Nature 426, 789-796CrossRefGoogle Scholar
81Fan, J.B., Chee, M.S. and Gunderson, K.L. (2006) Highly parallel genomic assays. Nat Rev Genet 7, 632-644CrossRefGoogle ScholarPubMed
82Todd, J.A. et al. (2007) Robust associations of four new chromosome regions from genome-wide analyses of type 1 diabetes. Nat Genet 39, 857-864CrossRefGoogle ScholarPubMed
83The Wellcome Trust Case Control Consortium (2007) Genome-wide association study of 14,000 cases of seven common diseases and 3,000 shared controls. Nature 447, 661-678CrossRefGoogle Scholar
84Feuk, L., Carson, A.R. and Scherer, S.W. (2006) Structural variation in the human genome. Nat Rev Genet 7, 85-97CrossRefGoogle ScholarPubMed
85Eichler, E.E. et al. (2007) Completing the map of human genetic variation. Nature 447, 161-165Google ScholarPubMed
86Redon, R. et al. (2006) Global variation in copy number in the human genome. Nature 444, 444-454CrossRefGoogle ScholarPubMed
87Wong, K.K. et al. (2007) A comprehensive analysis of common copy-number variations in the human genome. Am J Hum Genet 80, 91-104CrossRefGoogle ScholarPubMed
88Leekam, S.R. et al. (2006) Describing the Sensory Abnormalities of Children and Adults with Autism. J Autism Dev DisordGoogle Scholar
89Rogers, S.J., Hepburn, S. and Wehner, E. (2003) Parent reports of sensory symptoms in toddlers with autism and those with other developmental disorders. J Autism Dev Disord 33, 631-642CrossRefGoogle ScholarPubMed
90Feng, J. et al. (2006) High frequency of neurexin 1beta signal peptide structural variants in patients with autism. Neurosci Lett 409, 10-13CrossRefGoogle ScholarPubMed
91Sebat, J. et al. (2007) Strong association of de novo copy number mutations with autism. Science 316, 445-449CrossRefGoogle ScholarPubMed
92Eckhardt, F. et al. (2006) DNA methylation profiling of human chromosomes 6, 20 and 22. Nat Genet 38, 1378-1385CrossRefGoogle Scholar
93Cook, E.H. Jr. et al. (1997) Autism or atypical autism in maternally but not paternally derived proximal 15q duplication. Am J Hum Genet 60, 928-934Google ScholarPubMed
94Badcock, C. and Crespi, B. (2006) Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism. J Evol Biol 19, 1007-1032CrossRefGoogle ScholarPubMed
95Skuse, D.H. (2000) Imprinting, the X-chromosome, and the male brain: explaining sex differences in the liability to autism. Pediatr Res 47, 9-16CrossRefGoogle ScholarPubMed
96Amir, R.E. et al. (1999) Rett syndrome is caused by mutations in X-linked MECP2, encoding methyl-CpG-binding protein 2. Nat Genet 23, 185-188CrossRefGoogle ScholarPubMed
97Girard, M. et al. (2001) Parental origin of de novo MECP2 mutations in Rett syndrome. Eur J Hum Genet 9, 231-236CrossRefGoogle ScholarPubMed
98Trappe, R. et al. (2001) MECP2 mutations in sporadic cases of Rett syndrome are almost exclusively of paternal origin. Am J Hum Genet 68, 1093-1101CrossRefGoogle ScholarPubMed
99Nishimura, Y. et al. (2007) Genome-wide expression profiling of lymphoblastoid cell lines distinguishes different forms of autism and reveals shared pathways. Hum Mol Genet 16, 1682-1698CrossRefGoogle ScholarPubMed
100Junaid, M.A. and Pullarkat, R.K. (2001) Proteomic approach for the elucidation of biological defects in autism. J Autism Dev Disord 31, 557-560CrossRefGoogle ScholarPubMed
101Corbett, B.A. et al. (2007) A proteomic study of serum from children with autism showing differential expression of apolipoproteins and complement proteins. Mol Psychiatry 12, 292-306CrossRefGoogle ScholarPubMed
102Flint, J. and Munafo, M.R. (2007) The endophenotype concept in psychiatric genetics. Psychol Med 37, 163-180CrossRefGoogle ScholarPubMed
103Happe, F., Ronald, A. and Plomin, R. (2006) Time to give up on a single explanation for autism. Nat Neurosci 9, 1218-1220CrossRefGoogle ScholarPubMed
104Alarcon, M. et al. (2002) Evidence for a language quantitative trait locus on chromosome 7q in multiplex autism families. Am J Hum Genet 70, 60-71CrossRefGoogle ScholarPubMed
105Buxbaum, J.D. et al. (2004) Linkage analysis for autism in a subset families with obsessive-compulsive behaviors: evidence for an autism susceptibility gene on chromosome 1 and further support for susceptibility genes on chromosome 6 and 19. Mol Psychiatry 9, 144-150CrossRefGoogle Scholar
106Buxbaum, J.D. et al. (2007) Mutation screening of the PTEN gene in patients with autism spectrum disorders and macrocephaly. Am J Med Genet B Neuropsychiatr Genet 144, 484-491CrossRefGoogle Scholar
107Butler, M.G. et al. (2005) Subset of individuals with autism spectrum disorders and extreme macrocephaly associated with germline PTEN tumour suppressor gene mutations. J Med Genet 42, 318-321CrossRefGoogle ScholarPubMed
108Herman, G.E. et al. (2007) Increasing knowledge of PTEN germline mutations: Two additional patients with autism and macrocephaly. Am J Med Genet A 143, 589-593CrossRefGoogle Scholar

Further reading, resources and contacts

The University of California Santa Cruz Genome Browser allows access to the annotated reference human genome sequence as well as a large collection of other genomes, together with information on genes and gene expression, genetic variation and comparative genomics:

Belmonte, M.K. et al. (2004) Autism as a disorder of neural information processing: directions for research and targets for therapy. Mol Psychiatry 9, 646-663CrossRefGoogle ScholarPubMed
Baron-Cohen, S. (2006) The hyper-systemizing, assortative mating theory of autism. Prog Neuropsychopharmacol Biol Psychiatry 30, 865-872CrossRefGoogle ScholarPubMed
Rakyan, V.K. and Beck, S. (2006) Epigenetic variation and inheritance in mammals. Curr Opin Genet Dev 16, 573-577CrossRefGoogle ScholarPubMed
Palmer, L.J. and Cardon, L.R. (2005) Shaking the tree: mapping complex disease genes with linkage disequilibrium. Lancet 366, 1223-1234CrossRefGoogle ScholarPubMed
Belmonte, M.K. et al. (2004) Autism as a disorder of neural information processing: directions for research and targets for therapy. Mol Psychiatry 9, 646-663CrossRefGoogle ScholarPubMed
Baron-Cohen, S. (2006) The hyper-systemizing, assortative mating theory of autism. Prog Neuropsychopharmacol Biol Psychiatry 30, 865-872CrossRefGoogle ScholarPubMed
Rakyan, V.K. and Beck, S. (2006) Epigenetic variation and inheritance in mammals. Curr Opin Genet Dev 16, 573-577CrossRefGoogle ScholarPubMed
Palmer, L.J. and Cardon, L.R. (2005) Shaking the tree: mapping complex disease genes with linkage disequilibrium. Lancet 366, 1223-1234CrossRefGoogle ScholarPubMed