1. ¹Centre for Basic Psychiatric Research, Psychiatric Hospital in Aarhus, Aarhus University Hospital, Risskov, Denmark
2. ²Department of Clinical Biochemistry and Genetics, Odense University Hospital, Odense C, Denmark
3. ³Department of Psychiatry, Amager Hospital, Copenhagen University Hospital, Copenhagen S, Denmark
4. ⁴Department of Psychiatry, Landssjùkrahusid (National Hospital), Torshavn, Faroe Islands

Correspondence: Dr MB Lauritsen, Centre for Basic Psychiatric Research, Aarhus University Hospital, Skovagervej 2, DK-8240 Risskov, Denmark. E-mail: mbl@dadlnet.dk

⁵In respectful memory of Professor Henrik Ewald 1958–2004.

Received 9 November 2004; Revised 22 August 2005; Accepted 23 August 2005; Published online 4 October 2005.

Abstract

The involvement of genetic factors in the etiology of autism has been clearly established. We undertook a genome-wide search for regions containing susceptibility genes for autism in 12 subjects with childhood autism and related pervasive developmental disorders (PDDs) and 44 controls from the relatively isolated population of the Faroe Islands. In total, 601 microsatellite markers distributed throughout the human genome with an average distance of 5.80 cM were genotyped, including 502 markers in the initial scan. The Faroese population structure and genetic relatedness of cases and controls were also evaluated. Based on a combined approach, including an assumption-free test as implemented in CLUMP, Fisher's exact test for specific alleles and haplotypes, and IBD₀ probability calculations, we found association between autism and microsatellite markers in regions on 2q, 3p, 6q, 15q, 16p, and 18q. The most significant finding was on 3p25.3 (P_T1=0.00003 and P_T4=0.00007), which was also supported by other genetic studies. Furthermore, no evidence of population substructure was found, and a higher degree of relatedness among cases could not be detected, decreasing the risk of inflated P-values. Our data suggest that markers in these regions are in linkage disequilibrium with genes involved in the etiology of autism, and we hypothesize susceptibility genes for autism and related PDDs to be localized within these regions.