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NAAR-Funded Researcher Co-Authors Publication

Trinity College Study Focuses on Autism Genetics in Ireland
April 23, 2007

Louise Gallagher, MB, MRC, Psych., of Trinity College in Dublin, has recently co-authored a genetics study in the journal, Molecular Psychiatry, that was made possible in part by funding from NAAR.

The study examines the role of the gene 5-HTT in the genetically homogenous population of Ireland. The study, titled “Serotonin Transporter Gene and Autism: A Haplotype Analysis In An Irish Autistic Population,” was published in the January 6, 2004 edition of Molecular Psychiatry.

The project was supported in part by NAAR through a $99,101 grant awarded to Dr. Gallagher in 2001 for her pilot study, The Molecular Genetics of Autism: Linkage Disequilibrium Screen in the Irish Population.

Dr. Gallagher said her NAAR-funded research has helped inspire the work she does that focuses on autism and families that live with the disorder.

“In relation to the sort of people involved with NAAR, very often I find those who have family members with autism have such drive, enthusiasm and a focus for research,” she said. “This is a wonderful thing that inspires research and affects us as researchers.”

The abstract of the study is listed below:

Serotonin Transporter Gene And Autism: A Haplotype Analysis In An Irish Autistic Population.

Conroy J, Meally E, Kearney G, Fitzgerald M, Gill M, Gallagher L. Department of Genetics, Smurfit Institute, Trinity College, Dublin, Ireland.

The role of the serotonin transporter (5-HTT) in the development of neuropsychiatric disorders has been widely investigated. Two polymorphisms, an insertion/deletion in the promoter region and a 12 repeat allele in a variable nucleotide tandem repeat (VNTR) in intron 2, drive higher expression of the 5-HTT gene. Four studies have shown nominally significant excess transmission of alleles of the 5-HTT gene in autism, while three studies have reported no excess transmission.

This present study investigates the role of 5-HTT in the genetically homogenous Irish population.

In all, 84 families were genotyped for five polymorphisms (three SNPs, a VNTR and an in/del).

The analysis of allele transmissions using the transmission disequilibrium test (TDT) was undertaken and indicated preferential transmission of the short promoter allele (TDT P-value=0.0334).

Linkage disequilibrium between markers was calculated and haplotypes were assessed for excess transmission and odds ratios (ORs) to affected children.

A number of haplotypes, especially those involving and surrounding SNP10, showed evidence of association.

The ORs ranged from 1.2 to 2.4.

The most significant haplotype associated with transmission to affected probands was the SNP10-VNTR-SNP18 haplotype (chi(2)=7.3023, P=0.0069, odds ratio=1.8).

This haplotype included the 12 repeat allele of the VNTR, which is associated with increased expression and may play a subtle role in the early development of the brain in affected probands.