Examples and outlook of family-based cohort study / 한국역학회지

Family-based designs are commonly used in genetic association studies to identify and to locate genes that underlie complex diseases. In this paper, we review two examples of genome-wide association studies using family-based cohort studies, including the Framingham Heart Study and International Multi-Center ADHD Genetics Project. We also review statistical methods of family-based designs, including the transmission disequilibrium test (TDT), linkage analysis, and imprinting effect analysis. In addition, we evaluate the strengths and limitations of the family-based cohort design. Despite the costs and difficulties in carrying out this type of study, a family-based cohort study can play avery important role in genome wide studies. First, the design will be free from biases due to population heterogeneity or stratification. Moreover, family-based designs provide the opportunity to conduct joint tests of linkage and association. Finally, family-based designs also allow access to epigenetic phenomena like imprinting. The family-based cohort design should be given careful consideration in planning new studies for genome-wide strategies.

Family-Based Association Study of Tryptophan-2,3 Dioxygenase (TDO2) Gene and Autism Spectrum Disorder in the Korean Population

OBJECTIVES: Autism is a complex neurodevelopmental spectrum disorder with a strong genetic component. Previous neurochemical and genetic studies have suggested the possible involvement of the serotonin system in autism. Tryptophan 2,3-dioxygenase(TDO2) is the rate-limiting enzyme in the catabolism of tryptophan, which is the precursor of serotonin synthesis. The aim of this study was to investigate the association between the TDO2 gene and autism spectrum disorders(ASD) in a Korean population. METHODS: The patients were diagnosed with ASD on the basis of the DSM-IV diagnostic classification outlined in the Korean version of the Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule. The present study included the detection of four single nucleotide polymorphisms(SNPs) in the TDO2 gene(rs2292536, rs6856558, rs6830072, rs6830800) and the family-based association analysis of the single nucleotide polymorphisms in Korean ASD trios using a transmission disequilibrium test(TDT) and haplotype analysis. The family trios of 136 probands were included in analysis. 87.5% were male and 86.0% were diagnosed with autism. The mean age of the probands was 78.5+/-35.8 months(range: 26-264 months). RESULTS: Two SNPs showed no polymorphism, and there was no significant difference in transmission in the other two SNPs. We also could not find any significant transmission in the haplotype analysis(p>.05). CONCLUSION: We could not find any significant statistical association between the transmission of SNPs in the TDO2 gene and ASD in a Korean population. This result may not support the possible involvement of the TDO2 gene in the development of ASD, and further exploration might be needed to investigate other plausible SNP sites.

Polymorphisms in Glutamate Receptor, Ionotropic, N-methyl-D-aspartate 2B(GRIN2B) Genes of Autism Spectrum Disorders in Korean Population: Family-based Association Study

OBJECTIVES: Autism is a complex neurodevelopmental spectrum disorder with a strong genetic component. Previous neurochemical and genetic studies suggested the possible involvement of glutamate N-methyl-D-aspartate(NMDA) receptor in autism. The aim of study was to investigate the association between the NMDA2B receptor gene(GRIN2B) and autism spectrum disorders(ASD) in the Korean population. METHODS: The patients with ASD were diagnosed with Autism Diagnostic Interview-Revised and Autism Diagnostic Observation Schedule based on DSM-IV diagnostic classification. The present study was conducted with the detection of four single nucleotide polymorphisms(SNPs) in GRIK2 and family-based association analysis of the single nucleotide polymorphisms in Korean ASD trios using transmission disequilibrium test (TDT). RESULTS: One hundred twenty six patients with ASD and their biological parents were analyzed. 86.5% were male and 85.1% were diagnosed as autistic disorder. The mean age was 71.9+/-31.6 months(range : 26-185 months). We found that rs1805247 showed significantly preferential transmission(TDT chi-square=12.8, p < 0.001) in ASD. CONCLUSION: One SNP in GRIN2B gene was significantly associated with ASD in the Korean population. This result suggests the possible involvement of glutamate NMDA receptor gene in the development of ASD.