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Candidate genes and neuropsychological phenotypes in children with ADHD: review of association studies.

ABSTRACT: BACKGROUND: We reviewed systematically the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder (ADHD) and neuropsychological traits relevant for this disorder. METHODS: We identified papers for review through the PubMed database. RESULTS: Twenty-nine studies examined 10 genes (DRD4, DAT1, COMT, DBH, MAOA, DRD5, ADRA2A, GRIN2A, BDNF and TPH2) in relation to neuropsychological traits relevant for ADHD. For DRD4, the continuous performance test (CPT) and derived tasks were the most used tests. Association of high reaction time variability with the 7-repeat allele absence appears to be the most consistent result and seems to be specific to ADHD. Speed of processing, set-shifting and cognitive impulsiveness were less frequently investigated but seem to be altered in the 7-repeat allele carriers. No effect of genotype was found on response inhibition (the stop and go/no-go tasks). For DAT1, 4 studies provide conflicting results in relation to omission and commission errors from CPT and derived tasks. High reaction time variability seems to be the most replicated cognitive marker associated with the 10-repeat homozygosity. The other genes have attracted fewer studies, and the reported findings need to be replicated. LIMITATIONS: Although we aimed to perform a formal meta-analysis, this was not possible because the number of studies using the same neurocognitive endophenotypes was limited. We referred only minimally to the various theoretical frameworks in this field of research; more detail would have been beyond the scope of our systematic review. Finally, sample sizes in most of the studies we reviewed were small. Thus, some negative findings could be attributed to a lack of statistical power, and positive results should be considered preliminary until they are replicated in extended samples. CONCLUSION: Several methodological issues, including measurement errors, developmental changes in cognitive abilities, sex, psychostimulant effects and presence of comorbid conditions, represent confounding factors and may explain conflicting results.

SUBMITTER: Kebir O

PROVIDER: S-EPMC2647566 | biostudies-literature | 2009 Mar

REPOSITORIES: biostudies-literature

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Candidate genes and neuropsychological phenotypes in children with ADHD: review of association studies.

Kebir Oussama O Tabbane Karim K Sengupta Sarojini S Joober Ridha R

Journal of psychiatry & neuroscience : JPN 20090301 2

<h4>Background</h4>We reviewed systematically the results of genetic studies investigating associations between putative susceptibility genes for attention-deficit hyperactivity disorder (ADHD) and neuropsychological traits relevant for this disorder.<h4>Methods</h4>We identified papers for review through the PubMed database.<h4>Results</h4>Twenty-nine studies examined 10 genes (DRD4, DAT1, COMT, DBH, MAOA, DRD5, ADRA2A, GRIN2A, BDNF and TPH2) in relation to neuropsychological traits relevant fo ...[more]

PMID: 19270759

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Project description:Root system architecture plays a crucial role in nutrient and water absorption during rice production. Genetic improvement of the rice root system requires elucidating its genetic control. Genome-wide association studies (GWASs) have identified genomic regions responsible for rice root phenotypes. However, candidate gene prioritization around the peak region often suffers from low statistical power and resolution. Transcriptomics enables other statistical mappings, such as transcriptome-wide association study (TWAS) and expression GWAS (eGWAS), which improve candidate gene identification by leveraging the natural variation of the expression profiles. To explore the genes responsible for root phenotypes, we conducted GWAS, TWAS, and eGWAS for 12 root phenotypes in 57 rice accessions using 427,751 single nucleotide polymorphisms (SNPs) and the expression profiles of 16,901 genes expressed in the roots. The GWAS identified three significant peaks, of which the most significant peak responsible for seven root phenotypes (crown root length, crown root surface area, number of crown root tips, lateral root length, lateral root surface area, lateral root volume, and number of lateral root tips) was detected at 6,199,732 bp on chromosome 8. In the most significant GWAS peak region, OsENT1 was prioritized as the most plausible candidate gene because its expression profile was strongly negatively correlated with the seven root phenotypes. In addition to OsENT1, OsEXPA31, OsSPL14, OsDEP1, and OsDEC1 were identified as candidate genes responsible for root phenotypes using TWAS. Furthermore, a cis-eGWAS peak SNP was detected for OsDjA6, which showed the eighth strongest association with lateral root volume in the TWAS. The cis-eGWAS peak SNP for OsDjA6 was in strong linkage disequilibrium (LD) with a GWAS peak SNP on the same chromosome for lateral root volume and in perfect LD with another SNP variant in a putative cis-element at the 518 bp upstream of the gene. These candidate genes provide new insights into the molecular breeding of root system architecture.

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Candidate genes and neuropsychological phenotypes in children with ADHD: review of association studies.

Publications

Candidate genes and neuropsychological phenotypes in children with ADHD: review of association studies.

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