HLA-DR4 as a risk allele for autism acting in mothers of probands possibly during pregnancy.

OBJECTIVES: To test whether HLA-DR4 acts in the mother, possibly during pregnancy, to contribute to the phenotype of autistic disorder in her fetus. DESIGN: Transmission disequilibrium testing in case mothers and maternal grandparents. SETTING: Previous studies have consistently shown increased frequency of HLA-DR4 in probands with autism and their mothers, but not their fathers. However, this has been documented only in case-control studies and not by a more direct study design to determine whether HLA-DR4 acts in mothers during pregnancy to contribute to autism in their affected offspring. PARTICIPANTS: We genotyped for HLA-DR alleles in members of 31 families with parents and maternal grandparents. Probands with autism were tested using the Autism Diagnostic Observation Schedule-Western Psychological Services and Autism Diagnostic Interview, Revised. There was 80% power to detect an odds ratio of 3.6. Participants were all families from New Jersey and were similar in number to earlier studies of autism and HLA-DR4. OUTCOME MEASURES: Analysis was by standard transmission disequilibrium testing. As a secondary test we examined the possibility of maternal imprinting. RESULTS: Significant transmission disequilibrium for HLA-DR4 was seen (odds ratio, 4.67; 95% confidence interval, 1.34-16.24; P = .008) for transmissions from maternal grandparents to mothers of probands, supporting a role for HLA-DR4 as an autism risk factor acting in mothers during pregnancy. Transmission disequilibrium was not seen for HLA-DR4 transmissions from parents to probands or from mothers to probands. CONCLUSIONS: The HLA-DR4 gene may act in mothers of children with autism during pregnancy to contribute to autism in their offspring. Further studies are required to confirm these findings.

Risk of autistic disorder in affected offspring of mothers with a glutathione S-transferase P1 haplotype.

OBJECTIVE: To test whether polymorphisms of the glutathione S-transferase P1 gene (GSTP1) act in the mother during pregnancy to contribute to the phenotype of autistic disorder (AD) in her fetus. DESIGN: Transmission disequilibrium testing (TDT) in case mothers and maternal grandparents. SETTING: Autistic disorder may result from multiple genes and environmental factors acting during pregnancy and afterward. Teratogenic alleles act in mothers during pregnancy to contribute to neurodevelopmental disorders in their offspring; however, only a handful have been identified. GSTP1 is a candidate susceptibility gene for AD because of its tissue distribution and its role in oxidative stress, xenobiotic metabolism, and JNK regulation. PARTICIPANTS: We genotyped GSTP1*G313A and GSTP1*C341T polymorphisms in 137 members of 49 families with AD. All probands received a clinical diagnosis of AD by Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule-Generic testing. MAIN OUTCOME MEASURES: Association of haplotypes with AD was tested by the TDT-Phase program, using the expectation-maximization (EM) algorithm for uncertain haplotypes and for incomplete parental genotypes, with standard measures of statistical significance. RESULTS: The GSTP1*A haplotype was overtransmitted to case mothers (P = .01 [P = .03 using permutation testing]; odds ratio, 2.67 [95% confidence interval, 1.39-5.13]). Results of the combined haplotype and genotype analyses suggest that the GSTP1-313 genotype alone determined the observed haplotype effect. CONCLUSIONS: Overtransmission of the GSTP1*A haplotype to case mothers suggests that action in the mother during pregnancy likely increases the likelihood of AD in her fetus. If this is confirmed and is a result of a gene-environment interaction occurring during pregnancy, these findings could lead to the design of strategies for prevention or treatment.

Brief report: brain activation to social words in a sedated child with autism.

A functional magnetic resonance imaging (fMRI) study was performed on a 4-year-old girl with autism. While sedated, she listened to three utterances (numbers, hello, her own first name) played through headphones. Based on analyses of the fMRI data, the amount of total brain activation varied with the content of the utterance. The greatest volume of overall activation was in response to numbers, followed by the word 'hello', with the least activation to her name. Frontal cortex activation was greatest in response to her name, with less activation for numbers, and the least for the word 'hello.' These findings indicate that fMRI can identify and quantify the brain regions that are activated in response to words in children with autism under sedation.

Analysis of case-parent trios at a locus with a deletion allele: association of GSTM1 with autism.

BACKGROUND: Certain loci on the human genome, such as glutathione S-transferase M1 (GSTM1), do not permit heterozygotes to be reliably determined by commonly used methods. Association of such a locus with a disease is therefore generally tested with a case-control design. When subjects have already been ascertained in a case-parent design however, the question arises as to whether the data can still be used to test disease association at such a locus. RESULTS: A likelihood ratio test was constructed that can be used with a case-parents design but has somewhat less power than a Pearson's chi-squared test that uses a case-control design. The test is illustrated on a novel dataset showing a genotype relative risk near 2 for the homozygous GSTM1 deletion genotype and autism. CONCLUSION: Although the case-control design will remain the mainstay for a locus with a deletion, the likelihood ratio test will be useful for such a locus analyzed as part of a larger case-parent study design. The likelihood ratio test has the advantage that it can incorporate complete and incomplete case-parent trios as well as independent cases and controls. Both analyses support (p = 0.046 for the proposed test, p = 0.028 for the case-control analysis) an association of the homozygous GSTM1 deletion genotype with autism.