Fine mapping of the 2p11 dyslexia locus and exclusion of TACR1 as a candidate gene.
Developmental dyslexia, or reading disability, is a multigenic complex disease for which at least five loci, i.e. DYX1-3 and DYX5-6, have been clearly identified from the human genome. To date, DYX1C1 is the only dyslexia candidate gene cloned. We have previously reported linkage to 2p11 and 7q32 in 11 Finnish pedigrees. Here, we report the fine mapping of the approximately 40-cM linked region from chromosome 2 as we increased marker density to one per 1.8 cM. Linkage was supported with the highest NPL score of 3.0 (P=0.001) for marker D2S2216. Association analysis using the six pedigrees showing linkage pointed to marker D2S286/rs3220265 (P value0.001) in the near vicinity of D2S2216. We w…
Genome-wide association study reveals new insights into the heritability and genetic correlates of developmental dyslexia
Developmental dyslexia (DD) is a learning disorder affecting the ability to read, with a heritability of 40–60%. A notable part of this heritability remains unexplained, and large genetic studies are warranted to identify new susceptibility genes and clarify the genetic bases of dyslexia. We carried out a genome-wide association study (GWAS) on 2274 dyslexia cases and 6272 controls, testing associations at the single variant, gene, and pathway level, and estimating heritability using single-nucleotide polymorphism (SNP) data. We also calculated polygenic scores (PGSs) based on large-scale GWAS data for different neuropsychiatric disorders and cortical brain measures, educational attainment,…
A genome scan for developmental dyslexia confirms linkage to chromosome 2p11 and suggests a new locus on 7q32
Developmental dyslexia is a distinct learning disability with unexpected difficulty in learning to read despite adequate intelligence, education, and environment, and normal senses. The genetic aetiology of dyslexia is heterogeneous and loci on chromosomes 2, 3, 6, 15, and 18 have been repeatedly linked to it. We have conducted a genome scan with 376 markers in 11 families with 38 dyslexic subjects ascertained in Finland. Linkage of dyslexia to the vicinity of DYX3 on 2p was confirmed with a non-parametric linkage (NPL) score of 2.55 and a lod score of 3.01 for a dominant model, and a novel locus on 7q32 close to the SPCH1 locus was suggested with an NPL score of 2.77. The SPCH1 locus has p…
Genome-wide association scan identifies new variants associated with a cognitive predictor of dyslexia
Developmental dyslexia (DD) is one of the most prevalent learning disorders, with high impact on school and psychosocial development and high comorbidity with conditions like attention-deficit hyperactivity disorder (ADHD), depression, and anxiety. DD is characterized by deficits in different cognitive skills, including word reading, spelling, rapid naming, and phonology. To investigate the genetic basis of DD, we conducted a genome-wide association study (GWAS) of these skills within one of the largest studies available, including nine cohorts of reading-impaired and typically developing children of European ancestry (N = 2562–3468). We observed a genome-wide significant effect (p < 1 × 10…
Polymorphisms in DCDC2 and S100B associate with developmental dyslexia
Genetic studies of complex traits have become increasingly successful as progress is made in next-generation sequencing. We aimed at discovering single nucleotide variation present in known and new candidate genes for developmental dyslexia: CYP19A1, DCDC2, DIP2A, DYX1C1, GCFC2 (also known as C2orf3), KIAA0319, MRPL19, PCNT, PRMT2, ROBO1 and S100B. We used next-generation sequencing to identify single-nucleotide polymorphisms in the exons of these 11 genes in pools of 100 DNA samples of Finnish individuals with developmental dyslexia. Subsequent individual genotyping of those 100 individuals, and additional cases and controls from the Finnish and German populations, validated 92 out of 111 …
A locus on 2p12 containing the co-regulated MRPL19 and C2ORF3 genes is associated to dyslexia.
DYX3, a locus for dyslexia, resides on chromosome 2p11-p15. We have refined its location on 2p12 to a 157 kb region in two rounds of linkage disequilibrium (LD) mapping in a set of Finnish families. The observed association was replicated in an independent set of 251 German families. Two overlapping risk haplotypes spanning 16 kb were identified in both sample sets separately as well as in a joint analysis. In the German sample set, the odds ratio for the most significantly associated haplotype increased with dyslexia severity from 2.2 to 5.2. The risk haplotypes are located in an intergenic region between FLJ13391 and MRPL19/C2ORF3. As no novel genes could be cloned from this region, we hy…
The Aromatase Gene CYP19A1: Several Genetic and Functional Lines of Evidence Supporting a Role in Reading, Speech and Language
Inspired by the localization, on 15q21.2 of the CYP19A1 gene in the linkage region of speech and language disorders, and a rare translocation in a dyslexic individual that was brought to our attention, we conducted a series of studies on the properties of CYP19A1 as a candidate gene for dyslexia and related conditions. The aromatase enzyme is a member of the cytochrome P450 super family, and it serves several key functions: it catalyzes the conversion of androgens into estrogens; during early mammalian development it controls the differentiation of specific brain areas (e.g. local estrogen synthesis in the hippocampus regulates synaptic plasticity and axonal growth); it is involved in sexua…
DNA methylation in childhood asthma
Background: DNA methylation profiles associated with childhood asthma might provide novel insights into disease pathogenesis. We did an epigenome-wide association study to assess methylation profiles associated with childhood asthma. Methods: We did a large-scale epigenome-wide association study (EWAS) within the Mechanisms of the Development of ALLergy (MeDALL) project. We examined epigenome-wide methylation using Illumina Infinium Human Methylation450 BeadChips (450K) in whole blood in 207 children with asthma and 610 controls at age 4–5 years, and 185 children with asthma and 546 controls at age 8 years using a cross-sectional case-control design. After identification of differentially m…
Familial dyslexia: neurocognitive and genetic correlation in a large Finnish family.
Neuropsychological findings of individuals with dyslexia (n=24) from a large, three-generation Finnish family are presented. We have previously performed whole genome linkage scanning in this family and found that dyslexia in this kindred segregates with a single locus in the pericentromeric area of chromosome 3. Those included in the analyses were carefully evaluated for general cognitive ability, reading and spelling skills, and reading-related neurocognitive skills. The neurocognitive type of dyslexia segregating in this family consisted of deficits in phonological awareness, verbal short-term memory, and rapid naming. Severe dyslexia also seemed to be connected with a general language d…
Genetic analysis of dyslexia candidate genes in the European cross-linguistic NeuroDys cohort
The work conducted at the WTCHG was supported by Wellcome Trust grants [076566/Z/05/Z] and [075491/Z/04]; the work in Zurich partly by an SNSF grant [32-108130]. We also thank MAF (Mutation Analysis core Facility) at the Karolinska Institute, Novum, Huddinge. The French part of the project was funded by Agence Nationale de la Recherche (ANR-06-NEURO-019-01 GENEDYS) and Ville de Paris. S Paracchini is a Royal Society University Research Fellow. D Czamara was supported by the Deutsche Forschungsgemeinschaft (German Research Foundation) within the framework of the Munich Cluster for Systems Neurology (EXC 1010 SyNergy). Dyslexia is one of the most common childhood disorders with a prevalence o…
Genome Wide Association Scan identifies new variants associated with a cognitive predictor of dyslexia
AbstractDevelopmental dyslexia (DD) is one of the most prevalent learning disorders among children and is characterized by deficits in different cognitive skills, including reading, spelling, short term memory and others. To help unravel the genetic basis of these skills, we conducted a Genome Wide Association Study (GWAS), including nine cohorts of reading-impaired and typically developing children of European ancestry, recruited across different countries (N=2,562-3,468).We observed a genome-wide significant effect (p<1×10−8) on rapid automatized naming of letters (RANlet) for variants on 18q12.2 withinMIR924HG (micro-RNA 924 host gene;p= 4.73×10−9), and a suggestive association on 8q1…
A dominant gene for developmental dyslexia on chromosome 3.
Developmental dyslexia is a neurofunctional disorder characterised by an unexpected difficulty in learning to read and write despite adequate intelligence, motivation, and education. Previous studies have suggested mostly quantitative susceptibility loci for dyslexia on chromosomes 1, 2, 6, and 15, but no genes have been identified yet. We studied a large pedigree, ascertained from 140 families considered, segregating pronounced dyslexia in an autosomal dominant fashion. Affected status and the subtype of dyslexia were determined by neuropsychological tests. A genome scan with 320 markers showed a novel dominant locus linked to dyslexia in the pericentromeric region of chromosome 3 with a m…
Genome-wide association study reveals new insights into the heritability and genetic correlates of developmental dyslexia
Developmental dyslexia (DD) is a learning disorder affecting the ability to read, with a heritability of 40–60%. A notable part of this heritability remains unexplained, and large genetic studies are warranted to identify new susceptibility genes and clarify the genetic bases of dyslexia. We carried out a genome-wide association study (GWAS) on 2274 dyslexia cases and 6272 controls, testing associations at the single variant, gene, and pathway level, and estimating heritability using single-nucleotide polymorphism (SNP) data. We also calculated polygenic scores (PGSs) based on large-scale GWAS data for different neuropsychiatric disorders and cortical brain measures, educational attainment,…