Dataset Information

Investigation of the DCDC2 intron 2 deletion/compound short tandem repeat polymorphism in a large German dyslexia sample.

ABSTRACT: Dyslexia is a complex disorder manifested by difficulties in learning to read and spell despite conventional instruction, adequate intelligence and sociocultural opportunity. It is among the most common neurodevelopmental disorders with a prevalence of 5-12%. The dyslexia susceptibility locus 2 on chromosome 6p21-p22 is one of the best-replicated linkage regions in dyslexia. On the basis of systematic linkage disequilibrium studies, the doublecortin domain containing protein 2 gene (DCDC2) was identified as a strong candidate gene in this region. Data from a US study have suggested a complex deletion/compound short tandem repeat (STR) polymorphism in intron 2 of DCDC2 as the causative mutation. In this study, we analyzed this polymorphism in 396 German dyslexia trios which included 376 trios previously providing strong support for the DCDC2 locus. We observed no significant deviation from random transmission, neither for the deletion nor for the alleles of the compound STR. We also did not find the deletion or any of the STR alleles to be in linkage disequilibrium with the 2-marker haplotype, which was associated with dyslexia in our sample. We thus conclude that the causative variant/s in DCDC2 conferring susceptibility to dyslexia in our sample remain/s to be identified.

SUBMITTER: Ludwig KU

PROVIDER: S-EPMC9748830 | biostudies-literature | 2008 Dec

REPOSITORIES: biostudies-literature

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Investigation of the DCDC2 intron 2 deletion/compound short tandem repeat polymorphism in a large German dyslexia sample.

Ludwig Kerstin U KU Schumacher Johannes J Schulte-Körne Gerd G König Inke R IR Warnke Andreas A Plume Ellen E Anthoni Heidi H Peyrard-Janvid Myriam M Meng Haiying H Ziegler Andreas A Remschmidt Helmut H Kere Juha J Gruen Jeffrey R JR Müller-Myhsok Bertram B Nöthen Markus M MM Hoffmann Per P

Psychiatric genetics 20081201 6

Dyslexia is a complex disorder manifested by difficulties in learning to read and spell despite conventional instruction, adequate intelligence and sociocultural opportunity. It is among the most common neurodevelopmental disorders with a prevalence of 5-12%. The dyslexia susceptibility locus 2 on chromosome 6p21-p22 is one of the best-replicated linkage regions in dyslexia. On the basis of systematic linkage disequilibrium studies, the doublecortin domain containing protein 2 gene (DCDC2) was i ...[more]

PMID: 19018237

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Project description:IntroductionThe DCDC2 gene is involved in neuronal migration. Heterotopias have been found within the white matter of DCDC2-knockdown rats. A deletion in DCDC2/intron 2 (DCDC2d), which encompasses a regulatory region named 'regulatory element associated with dyslexia 1' (READ1), increases the risk for dyslexia. We hypothesized that DCDC2d can be associated to alterations of the white matter structure in general and in dyslexic brains.MethodsBased on a full-factorial analysis of covariance (ANCOVA) model, we investigated voxel-based diffusion tensor imaging (VB-DTI) data of four groups of subjects: dyslexia with/without DCDC2d, and normal readers with/without DCDC2d. We also tested DCDC2d effects upon correlation patterns between fractional anisotropy (FA) and reading scores.ResultsWe found that FA was reduced in the left arcuate fasciculus and splenium of the corpus callosum in subjects with versus without DCDC2d, irrespective of dyslexia. Subjects with dyslexia and DCDC2d showed reduced FA, mainly in the left hemisphere and in the corpus callosum; their counterpart without DCDC2d showed similar FA alterations. Noteworthy, a conjunction analysis in impaired readers revealed common regions with lower FA mainly in the left hemisphere. When we compared subjects with dyslexia with versus without DCDC2d, we found lower FA in the inferior longitudinal fasciculus and genu of the corpus callosum, bilaterally. Normal readers with versus without DCDC2d had FA increases and decreases in both the right and left hemisphere.DiscussionThe major contribution of our study was to provide evidence relating genes, brain and behaviour. Overall, our findings support the hypothesis that DCDC2d is associated with altered FA. In normal readers, DCDC2-related anatomical patterns may mark some developmental cognitive vulnerability to learning disabilities. In subjects with dyslexia, DCDC2d accounted for both common - mainly located in the left hemisphere - and unique - a more severe and extended pattern - alterations of white matter fibre tracts.

Project description:Developmental dyslexia is a complex reading and writing disorder with strong genetic components. In previous genetic studies about dyslexia, a number of candidate genes have been identified. These include DCDC2, which has repeatedly been associated with developmental dyslexia in various European and American populations. However, data regarding this relationship are varied according to population. The Uyghur people of China represent a Eurasian population with an interesting genetic profile. Thus, this group may provide useful information about the association between DCDC2 gene polymorphisms and dyslexia. In the current study, we examined genetic data from 392 Uyghur children aged 8-12 years old from the Xinjiang Uyghur Autonomous Region of China. Participants included 196 children with dyslexia and 196 grade-, age-, and gender-matched controls. DNA was isolated from oral mucosal cell samples and fourteen single nucleotide polymorphisms (rs6456593, rs1419228, rs34647318, rs9467075, rs793862, rs9295619, rs807701, rs807724, rs2274305, rs7765678, rs4599626, rs6922023, rs3765502, and rs1087266) in DCDC2 were screened via the SNPscan method. We compared SNP frequencies in five models (Codominant, Dominant, Recessive, Heterozygote advantage, and Allele) between the two groups by means of the chi-squared test. A single-locus analysis indicated that, with regard to the allele frequency of these polymorphisms, three SNPs (rs807724, rs2274305, and rs4599626) were associated with dyslexia. rs9467075 and rs2274305 displayed significant associations with developmental dyslexia under the dominant model. rs6456593 and rs6922023 were significantly associated with developmental dyslexia under the dominant model and in the heterozygous genotype. Additionally, we discovered that the T-G-C-T of the four-marker haplotype (rs9295619-rs807701-rs807724-rs2274305) and the T-A of the two-marker haplotype (rs3765502-1087266) were significantly different between cases and controls. Thus, we conclude that DCDC2 gene polymorphisms are associated with developmental dyslexia in Chinese Uyghur children.

Project description:BACKGROUND: Multi-drug resistance and severe/complicated cases are the emerging phenotypes of vivax malaria, which may deteriorate current anti-malarial control measures. The emergence of these phenotypes could be associated with either of the two Plasmodium vivax lineages. The two lineages had been categorized as Old World and New World, based on geographical sub-division and genetic and phenotypical markers. This study revisited the lineage hypothesis of P. vivax by typing the distribution of lineages among global isolates and evaluated their genetic relatedness using a panel of new mini-satellite markers. METHODS: 18S SSU rRNA S-type gene was amplified from 420 Plasmodium vivax field isolates collected from different geographical regions of India, Thailand and Colombia as well as four strains each of P. vivax originating from Nicaragua, Panama, Thailand (Pak Chang), and Vietnam (ONG). A mini-satellite marker panel was then developed to understand the population genetic parameters and tested on a sample subset of both lineages. RESULTS: 18S SSU rRNA S-type gene typing revealed the distribution of both lineages (Old World and New World) in all geographical regions. However, distribution of Plasmodium vivax lineages was highly variable in every geographical region. The lack of geographical sub-division between lineages suggests that both lineages are globally distributed. Ten mini-satellites were scanned from the P. vivax genome sequence; these tandem repeats were located in eight of the chromosomes. Mini-satellites revealed substantial allelic diversity (7-21, AE = 14.6 ± 2.0) and heterozygosity (He = 0.697-0.924, AE = 0.857 ± 0.033) per locus. Mini-satellite comparison between the two lineages revealed high but similar pattern of genetic diversity, allele frequency, and high degree of allele sharing. A Neighbour-Joining phylogenetic tree derived from genetic distance data obtained from ten mini-satellites also placed both lineages together in every cluster. CONCLUSIONS: The global lineage distribution, lack of genetic distance, similar pattern of genetic diversity, and allele sharing strongly suggested that both lineages are a single species and thus new emerging phenotypes associated with vivax malaria could not be clearly classified as belonging to a particular lineage on basis of their geographical origin.

Dataset Information

Investigation of the DCDC2 intron 2 deletion/compound short tandem repeat polymorphism in a large German dyslexia sample.

Publications

Investigation of the DCDC2 intron 2 deletion/compound short tandem repeat polymorphism in a large German dyslexia sample.

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