Association of the rs3743205 variant of DYX1C1 with dyslexia in Chinese children

The Moderating Role of the DYX1C1 Gene in the Effect of Home Supervision on Chinese Children's Reading Achievements: Evidence from the Diathesis-Stress Model

The current study aimed to explore whether susceptible children (with differences in DYX1C1 (dyslexia susceptibility 1 candidate gene 1) gene) are more likely to be influenced by either supportive or adverse home supervision in their reading achievements. Home supervision, reading achievements, and genotype data were collected from a total of 745 fourth and fifth grade children and their parents in Chongqing, China. The results showed that there was a significant interaction between the rs11629841 polymorphism of the DYX1C1 gene and home supervision on children's reading achievements. A further analysis based on the re-parameterized regression model showed that the interaction best fit a weak diathesis-stress model, which indicated that the home supervision had a stronger predictive effect on children's reading achievements among children with the susceptible genotype than children with a non-susceptible genotype in a more adverse environment rather than in a supportive environment. These results suggested that children carrying different genotypes may need targeted interventions and that their parents should emphasize home supervision to develop their children's reading skills.

Dyslexia-Related Hearing Loss Occurs Mainly through the Abnormal Spontaneous Electrical Activity of Spiral Ganglion Neurons

Dyslexia is a reading and spelling disorder due to neurodevelopmental abnormalities and is occasionally found to be accompanied by hearing loss, but the reason for the associated deafness remains unclear. This study finds that knockout of the dyslexia susceptibility 1 candidate 1 gene (Dyx1c1^-/- ) in mice, the best gene for studying dyslexia, causes severe hearing loss, and thus it is a good model for studying the mechanism of dyslexia-related hearing loss (DRHL). This work finds that the Dyx1c1 gene is highly expressed in the mouse cochlea and that the spontaneous electrical activity of inner hair cells and type I spiral ganglion neurons is altered in the cochleae of Dyx1c1^-/- mice. In addition, primary ciliary dyskinesia-related phenotypes such as situs inversus and disrupted ciliary structure are seen in Dyx1c1^-/- mice. In conclusion, this study gives new insights into the mechanism of DRHL in detail and suggests that Dyx1c1 may serve as a potential target for the clinical diagnosis of DRHL.

Contributions of common genetic variants to specific languages and to when a language is learned

Research over the past two decades has identified a group of common genetic variants explaining a portion of variance in native language ability. The present study investigates whether the same group of genetic variants are associated with different languages and languages learned at different times in life. We recruited 940 young adults who spoke from childhood Chinese and English as their first (native) (L1) and second (L2) language, respectively, who were learners of a new, third (L3) language. For the variants examined, we found a general decrease of contribution of genes to language functions from native to foreign (L2 and L3) languages, with variance in foreign languages explained largely by non-genetic factors such as musical training and motivation. Furthermore, genetic variants that were found to contribute to traits specific to Chinese and English respectively exerted the strongest effects on L1 and L2. These results seem to speak against the hypothesis of a language- and time-universal genetic core of linguistic functions. Instead, they provide preliminary evidence that genetic contribution to language may depend at least partly on the intricate language-specific features. Future research including a larger sample size, more languages and more genetic variants is required to further explore these hypotheses.

Do Genes Associated with Dyslexia of Chinese Characters Evolve Neutrally?

Dyslexia, or reading disability, is found to have a genetic basis, and several related genes have been reported. We investigated whether natural selection has acted on single nucleotide polymorphisms (SNPs) that were reported to be associated with risk/non-risk for the reading disability of Chinese characters. We applied recently developed 2D SFS-based statistics to SNP data of East Asian populations to examine whether there is any sign of selective sweep. While neutrality was not rejected for most SNPs, significant signs of selection were detected for two linkage disequilibrium (LD) regions containing the reported SNPs of GNPTAB and DCDC2. Furthermore, we searched for a selection target site among the SNPs in these LD regions, because a causal site is not necessarily a reported SNP but could instead be a tightly linked site. In both LD regions, we found candidate target sites, which may have an effect on expression regulation and have been selected, although which genes these SNPs affect remains unknown. Because most people were not engaged in reading until recently, it is unlikely that there has been selective pressure on reading ability itself. Consistent with this, our results suggest a possibility of genetic hitchhiking, whereby alleles of the reported SNPs may have increased in frequency together with the selected target, which could have functions for other genes and traits apart from reading ability.

Neuroimaging genetics studies of specific reading disability and developmental language disorder: A review

Developmental disorders of spoken and written language are heterogeneous in nature with impairments observed across various linguistic, cognitive, and sensorimotor domains. These disorders are also associated with characteristic patterns of atypical neural structure and function that are observable early in development, often before formal schooling begins. Established patterns of heritability point toward genetic contributions, and molecular genetics approaches have identified genes that play a role in these disorders. Still, identified genes account for only a limited portion of phenotypic variance in complex developmental disorders, described as the problem of "missing heritability." The characterization of intermediate phenotypes at the neural level may fill gaps in our understanding of heritability patterns in complex disorders, and the emerging field of neuroimaging genetics offers a promising approach to accomplish this goal. The neuroimaging genetics approach is gaining prevalence in language- and reading-related research as it is well-suited to incorporate behavior, genetics, and neurobiology into coherent etiological models of complex developmental disorders. Here, we review research applying the neuroimaging genetics approach to the study of specific reading disability (SRD) and developmental language disorder (DLD), much of which links genes with known neurodevelopmental function to functional and structural abnormalities in the brain.

Associations of genetic variants in endocytic trafficking of epidermal growth factor receptor super pathway with risk of nonsyndromic cleft lip with or without cleft palate

BACKGROUND

The genetic etiology of nonsyndromic cleft lip with or without cleft palate (NSCL/P) has not been fully clarified to date. Epidermal growth factor receptor (EGFR) was reportedly involved in its biological establishment and regulation of cell migration during the embryonic stage.

METHODS

We selected a super pathway of endocytic trafficking of EGFR and investigated the associations of single-nucleotide polymorphisms (SNPs) in the super pathway with the risk of NSCL/P by analyzing our published genome-wide association study (GWAS) data from 504 NSCL/P individuals and 455 controls. After the false discovery rate (FDR) control, we conducted linkage disequilibrium (LD) analyses and conditional regression analyses to obtain independent lead SNPs. We performed LD analyses between the lead SNPs and the reported SNPs to find novel ones from our study. We annotated the lead SNPs and investigated their mapped genes in silico.

RESULTS

A total of 82 SNPs showed a statistical association with the risk of NSCL/P after FDR control. They contained three reported SNPs which were g.117068049G>A (rs7078160), g.117086783C>G (rs10886040), and g.117101266G>T (rs17095681). Four independent lead SNPs were obtained, including g.116979803 T>C (rs1905539) and g.117037960A>G (rs7902502) at 10q25.3, g.35720163G>C (rs75656820) at 17q12, and g.156864512G>A (rs1800877) at 1q23.1. Three of them were in low LD (r²  < 0.5) with the reported SNPs except g.117037960A>G (rs7902502), so these three were newly identified. Lead SNPs were mapped to three genes: SHTN1, AP2B1, and NTRK1. The three genes were relatively more highly expressed in the human craniofacial region and in the proximal maxillary location during the craniofacial development stage of the embryonic mouse.

CONCLUSION

Our results suggested that SHTN1, AP2B1, and NTRK1 might be associated with the development of NSCL/P.

Genetic association study of dyslexia and ADHD candidate genes in a Spanish cohort: Implications of comorbid samples

Dyslexia and attention deficit hyperactivity disorder (ADHD) are two complex neuro-behaviorally disorders that co-occur more often than expected, so that reading disability has been linked to inattention symptoms. We examined 4 SNPs located on genes previously associated to dyslexia (KIAA0319, DCDC2, DYX1C1 and FOXP2) and 3 SNPs within genes related to ADHD (COMT, MAOA and DBH) in a cohort of Spanish children (N = 2078) that met the criteria of having one, both or none of these disorders (dyslexia and ADHD). We used a case-control approach comparing different groups of samples based on each individual diagnosis. In addition, we also performed a quantitative trait analysis with psychometric measures on the general population (N = 3357). The results indicated that the significance values for some markers change depending on the phenotypic groups compared and/or when considering pair-wise marker interactions. Furthermore, our quantitative trait study showed significant genetic associations with specific cognitive processes. These outcomes advocate the importance of establishing rigorous and homogeneous criteria for the diagnosis of cognitive disorders, as well as the relevance of considering cognitive endophenotypes.

Unfolding the genetic pathways of dyslexia in Asian population: A review

Dyslexia also known as specific reading disorder is a complex heritable disorder with unexpected difficulty in learning to read and spell despite adequate intelligence, education, environment, and normal senses. Over past decades, researchers have attempted to characterize dyslexia neurobiological and genetic levels and unfold its pathophysiology. The genetic research on dyslexia has received attention in Asia from the last decade. Though limited by different constraints the studies from Asia have been able to gather significant evidence in this field. We present a review of studies of genetics in Asian population and suggest future directions.

Study of Genetic Association With DCDC2 and Developmental Dyslexia in Hong Kong Chinese Children

Background:

Doublecortin domain-containing 2 (DCDC2) is a doublecortin domain-containing gene family member and the doublecortin domain has been demonstrated to bind to tubulin and enhance microtubule polymerization. It has been associated with developmental dyslexia and this protein family member is thought to function in neuronal migration where it may affect the signaling of primary cilia.

Objectives:

The objective of the study is to find out if there is any association of genetic variants of DCDC2 with developmental dyslexia in Chinese children from Hong Kong.

Methods:

The dyslexic children were diagnosed as developmental dyslexia (DD) using the Hong Kong Test of Specific Learning Difficulties in Reading and Writing (HKT-SpLD) by the Department of Health, Hong Kong. Saliva specimens were collected and their genotypes of DCDC2 were studied by DNA sequencing or TaqMan Real Time PCR Assays.

Results:

The most significant marker is rs6940827 which is associated with DD with nominal p-value (0.011). However, this marker did not remain significant after multiple testing corrections and the adjusted p-value from permutation test was 0.1329. Using sliding window haplotype analysis, several haplotypes were found to be nominally associated with DD. The smallest nominal p values was 0.0036 (rs2996452-rs1318700, C-A). However, none of the p values could withstand the multiple testing corrections.

Conclusion:

Despite early findings that DCDC2 is a strong candidate for developmental dyslexia and that some of the genetic variants have been linked to brain structure and functions, our findings showed that DCDC2 is not strongly associated with dyslexia.

Genetic and environmental risk factors for developmental dyslexia in children: systematic review of the last decade

Despite advances in the characterization of developmental dyslexia (DD), several questions regarding the interplay between DD-susceptibility genes and environmental risk factors remain open. This systematic review aimed at answering the following questions: What has been the impact of new resources on the knowledge about DD? Which questions remain open? What is the investigative agenda for the short term? Forty-six studies were analyzed. Despite the growing literature on DD candidate genes, most studies have not been replicated. We found large effects on causative genes and smaller environmental contributions, involving maternal smoking during pregnancy, SES and the DYX1C1-1259C/G marker. Implications are discussed.

Visual motion and rapid auditory processing are solid endophenotypes of developmental dyslexia

Although a genetic component is known to have an important role in the etiology of developmental dyslexia (DD), we are far from understanding the molecular etiopathogenetic pathways. Reduced measures of neurobiological functioning related to reading (dis)ability, i.e. endophenotypes (EPs), are promising targets for gene finding and the elucidation of the underlying mechanisms. In a sample of 100 nuclear families with DD (229 offspring) and 83 unrelated typical readers, we tested whether a set of well-established, cognitive phenotypes related to DD [i.e. rapid auditory processing (RAP), rapid automatized naming (RAN), multisensory nonspatial attention and visual motion processing] fulfilled the criteria of the EP construct. Visual motion and RAP satisfied all testable criteria (i.e. they are heritable, associate with the disorder, co-segregate with the disorder within a family and represent reproducible measures) and are therefore solid EPs of DD. Multisensory nonspatial attention satisfied three of four criteria (i.e. it associates with the disorder, co-segregates with the disorder within a family and represents a reproducible measure) and is therefore a potential EP for DD. Rapid automatized naming is heritable but does not meet other criteria of the EP construct. We provide the first evidence of a methodologically and statistically sound approach for identifying EPs for DD to be exploited as a solid alternative basis to clinical phenotypes in neuroscience.

Deficits in learning and memory in mice with a mutation of the candidate dyslexia susceptibility gene Dyx1c1

Dyslexia is a learning disability characterized by difficulty learning to read and write. The underlying biological and genetic etiology remains poorly understood. One candidate gene, dyslexia susceptibility 1 candidate 1 (DYX1C1), has been shown to be associated with deficits in short-term memory in dyslexic populations. The purpose of the current study was to examine the behavioral phenotype of a mouse model with a homozygous conditional (forebrain) knockout of the rodent homolog Dyx1c1. Twelve Dyx1c1 conditional homozygous knockouts, 7 Dyx1c1 conditional heterozygous knockouts and 6 wild-type controls were behaviorally assessed. Mice with the homozygous Dyx1c1 knockout showed deficits on memory and learning, but not on auditory or motor tasks. These findings affirm existing evidence that DYX1C1 may play an underlying role in the development of neural systems important to learning and memory, and disruption of this function could contribute to the learning deficits seen in individuals with dyslexia.

Primary Cilia as a Possible Link between Left-Right Asymmetry and Neurodevelopmental Diseases

Cilia have multiple functions in the development of the entire organism, and participate in the development and functioning of the central nervous system. In the last decade, studies have shown that they are implicated in the development of the visceral left-right asymmetry in different vertebrates. At the same time, some neuropsychiatric disorders, such as schizophrenia, autism, bipolar disorder, and dyslexia, are known to be associated with lateralization failure. In this review, we consider possible links in the mechanisms of determination of visceral asymmetry and brain lateralization, through cilia. We review the functions of seven genes associated with both cilia, and with neurodevelopmental diseases, keeping in mind their possible role in the establishment of the left-right brain asymmetry.

Neurogenetics of developmental dyslexia: from genes to behavior through brain neuroimaging and cognitive and sensorial mechanisms

Developmental dyslexia (DD) is a complex neurodevelopmental deficit characterized by impaired reading acquisition, in spite of adequate neurological and sensorial conditions, educational opportunities and normal intelligence. Despite the successful characterization of DD-susceptibility genes, we are far from understanding the molecular etiological pathways underlying the development of reading (dis)ability. By focusing mainly on clinical phenotypes, the molecular genetics approach has yielded mixed results. More optimally reduced measures of functioning, that is, intermediate phenotypes (IPs), represent a target for researching disease-associated genetic variants and for elucidating the underlying mechanisms. Imaging data provide a viable IP for complex neurobehavioral disorders and have been extensively used to investigate both morphological, structural and functional brain abnormalities in DD. Performing joint genetic and neuroimaging studies in humans is an emerging strategy to link DD-candidate genes to the brain structure and function. A limited number of studies has already pursued the imaging-genetics integration in DD. However, the results are still not sufficient to unravel the complexity of the reading circuit due to heterogeneous study design and data processing. Here, we propose an interdisciplinary, multilevel, imaging-genetic approach to disentangle the pathways from genes to behavior. As the presence of putative functional genetic variants has been provided and as genetic associations with specific cognitive/sensorial mechanisms have been reported, new hypothesis-driven imaging-genetic studies must gain momentum. This approach would lead to the optimization of diagnostic criteria and to the early identification of 'biologically at-risk' children, supporting the definition of adequate and well-timed prevention strategies and the implementation of novel, specific remediation approach.

Gene-environment interaction on neural mechanisms of orthographic processing in Chinese children

The ability to process and identify visual words requires efficient orthographic processing of print, consisting of letters in alphabetic languages or characters in Chinese. The N170 is a robust neural marker for orthographic processes. Both genetic and environmental factors, such as home literacy, have been shown to influence orthographic processing at the behavioral level, but their relative contributions and interactions are not well understood. The present study aimed to reveal possible gene-by-environment interactions on orthographic processing at the behavioral and neural level in a normal children sample. Sixty 12 year old Chinese children from a 10-year longitudinal sample underwent an implicit visual-word color decision task on real words and stroke combinations. The ERP analysis focused on the increase of the occipito-temporal N170 to words compared to stroke combinations. The genetic analysis focused on two SNPs (rs1419228, rs1091047) in the gene DCDC2 based on previous findings linking these 2 SNPs to orthographic coding. Home literacy was measured previously as the number of children's books at home, when the children were at the age of 3. Relative to stroke combinations, real words evoked greater N170 in bilateral posterior brain regions. A significant interaction between rs1091047 and home literacy was observed on the changes of N170 comparing real words to stroke combinations in the left hemisphere. Particularly, children carrying the major allele "G" showed a similar N170 effect irrespective of their environment, while children carrying the minor allele "C" showed a smaller N170 effect in low home-literacy environment than those in good environment.

An informatics approach to integrating genetic and neurological data in speech and language neuroscience

A number of heritable disorders impair the normal development of speech and language processes and occur in large numbers within the general population. While candidate genes and loci have been identified, the gap between genotype and phenotype is vast, limiting current understanding of the biology of normal and disordered processes. This gap exists not only in our scientific knowledge, but also in our research communities, where genetics researchers and speech, language, and cognitive scientists tend to operate independently. Here we describe a web-based, domain-specific, curated database that represents information about genotype-phenotype relations specific to speech and language disorders, as well as neuroimaging results demonstrating focal brain differences in relevant patients versus controls. Bringing these two distinct data types into a common database ( http://neurospeech.org/sldb ) is a first step toward bringing molecular level information into cognitive and computational theories of speech and language function. One bridge between these data types is provided by densely sampled profiles of gene expression in the brain, such as those provided by the Allen Brain Atlases. Here we present results from exploratory analyses of human brain gene expression profiles for genes implicated in speech and language disorders, which are annotated in our database. We then discuss how such datasets can be useful in the development of computational models that bridge levels of analysis, necessary to provide a mechanistic understanding of heritable language disorders. We further describe our general approach to information integration, discuss important caveats and considerations, and offer a specific but speculative example based on genes implicated in stuttering and basal ganglia function in speech motor control.

Association of SNPs of DYX1C1 with developmental dyslexia in an Indian population

OBJECTIVE

DYX1C1 has been identified as a susceptible candidate gene for developmental dyslexia (DD); studies in various populations have yielded inconclusive results and the causal allele is unknown in the Indian population. On the basis of the initial association studies and the role of DYX1C1 in neuronal migration, we investigated the role of DYX1C1 in causing DD in an Indian population.

MATERIALS AND METHODS

Ten single-nucleotide polymorphisms (SNPs) of DYX1C1 were genotyped in 210 cases with DD and 256 age-matched nondyslexic controls. Genotyping of these SNPs was carried with the MassARRAY technique using SpectroCHIP and analysed with MALDI-TOF MS. Single-marker and two-marker haplotype analyses were carried out and the χ-test, odds ratios, 95% confidence intervals and Yates correction were applied to identify the significance of the genotyped SNPs.

RESULTS

A significant association was observed for the homozygous genotype (GG) of the SNP rs12899331 (3.12%) and individual allele frequency (P=0.039). Psycholinguistic tests showed an association between rs12899331 with dyslexic phenotypes such as word and nonword reading, syllable reversal task, spoonerism task and spelling. Two-marker haplotype analysis also showed a significant association for the markers G/C at rs12899331/rs1075938 (P=0.039) with the phenotypes rapid naming ability and phonological awareness, as well as with word reading, spelling and sentence repetition.

CONCLUSION

The promoter SNP rs12899331 of DYX1C1 may contribute towards the manifestation of DD. This study supports the association of DYX1C1 with DD in an Indian population.

A common haplotype of KIAA0319 contributes to the phonological awareness skill in Chinese children

BACKGROUND

Previous studies have shown that KIAA0319 is a candidate gene for dyslexia in western populations. In view of the different languages used in Caucasian and Chinese populations, the aim of the present study was to investigate whether there is also an association of KIAA0319 in Chinese children with dyslexia and/or to the language-related cognitive skills.

METHOD AND RESULTS

A total of twenty six single nucleotide polymorphisms (SNPs) were genotyped from three hundred and ninety three individuals from 131 Chinese families. Four of the SNPs have been reported in the literature and twenty two being tag SNPs at KIAA0319. Analysis for allelic and haplotypic associations was performed with the UNPHASED program and multiple testing was corrected using permutation. Results indicate that KIAA0319 is not associated with Chinese children with dyslexia but a haplotype consisting of rs2760157 and rs807507 SNPs were significantly associated with an onset detection test, a measure of phonological awareness (pnominal = 6.85 10-5 and pcorrected = 0.0029).

CONCLUSION

In conclusion, our findings suggest that KIAA0319 is associated with a reading-related cognitive skill.

The zebrafish orthologue of the dyslexia candidate gene DYX1C1 is essential for cilia growth and function

DYX1C1, a susceptibility gene for dyslexia, encodes a tetratricopeptide repeat domain containing protein that has been implicated in neuronal migration in rodent models. The developmental role of this gene remains unexplored. To understand the biological function(s) of zebrafish dyx1c1 during embryonic development, we cloned the zebrafish dyx1c1 and used morpholino-based knockdown strategy. Quantitative real-time PCR analysis revealed the presence of dyx1c1 transcripts in embryos, early larval stages and in a wide range of adult tissues. Using mRNA in situ hybridization, we show here that dyx1c1 is expressed in many ciliated tissues in zebrafish. Inhibition of dyx1c1 produced pleiotropic phenotypes characteristically associated with cilia defects such as body curvature, hydrocephalus, situs inversus and kidney cysts. We also demonstrate that in dyx1c1 morphants, cilia length is reduced in several organs including Kupffer’s vesicle, pronephros, spinal canal and olfactory placode. Furthermore, electron microscopic analysis of cilia in dyx1c1 morphants revealed loss of both outer (ODA) and inner dynein arms (IDA) that have been shown to be required for cilia motility. Considering all these results, we propose an essential role for dyx1c1 in cilia growth and function.

Altered brain structure in Chinese dyslexic children

Due to the logographic nature of the writing system, learning to read Chinese places heavy demands on encoding of orthographic forms through rote memorization. Moreover, phonology has to often be retrieved from memory during reading because of the inconsistent mapping between characters and their pronunciations. Using optimized voxel-based morphometry, we examined differences in volumetrics between children with reading disability (RD, 10-12 years old) and age-matched typically developing (TD) children. Our study shows reduced gray matter volume (GMV) for RD in right inferior occipital gyrus and left inferior frontal gyrus, consistent with previous studies suggesting that Chinese dyslexics have deficits in orthographic and phonological processing. The deficit in phonological processing was further supported by reductions in white matter volumes (WMV) in left precentral gyrus. Greater deficits in ortho-phonological processing may be associated with semantic compensation, as lower skill RD children showed greater GMV in anterior temporal cortex, even though as a group they showed less GMV in this region compared to TD. Perhaps most interestingly, we showed reduced GMV in bilateral ventromedial prefrontal cortices (vmPFC) and this was correlated with reductions in WMV within vmPFC, suggesting that RD have deficits in memory retrieval. Moreover, these GMV alterations in vmPFC for the RD were correlated with alterations in right parahippocampal gyrus, which also showed a reduced GMV, suggesting that RD have a correlated deficit in memory encoding. Our results are consistent with previous studies suggesting that Chinese dyslexics have deficits in visuo-orthographic and phonological processing, but our study importantly suggests deficits in memory encoding and retrieval, perhaps due to the unique demands of the Chinese writing system.

Molecular networks of DYX1C1 gene show connection to neuronal migration genes and cytoskeletal proteins

BACKGROUND

The dyslexia susceptibility 1 candidate 1 (DYX1C1) gene has recently been associated with dyslexia and reading scores in several population samples. The DYX1C1 has also been shown to affect neuronal migration and modulate estrogen receptor signaling.

METHODS

We have analyzed the molecular networks of DYX1C1 by gene expression and protein interaction profiling in a human neuroblastoma cell line.

RESULTS

We find that DYX1C1 can modulate the expression of nervous system development and neuronal migration genes such as RELN and associate with a number of cytoskeletal proteins. We also show by live cell imaging that DYX1C1 regulates cell migration of the human neuroblastoma cell line dependent on its tetratricopeptide repeat and DYX1 protein domains. The DYX1 domain is a novel highly conserved domain identified in this study by multiple sequence alignment of DYX1C1 proteins recovered from a wide range of eukaryotic species.

CONCLUSIONS

Our results contribute to the hypothesis that dyslexia has a developmental neurobiological basis by linking DYX1C1 with many genes involved in neuronal migration disorders.

The genetics of reading disabilities: from phenotypes to candidate genes

This article provides an overview of (a) issues in definition and diagnosis of specific reading disabilities at the behavioral level that may occur in different constellations of developmental and phenotypic profiles (patterns); (b) rapidly expanding research on genetic heterogeneity and gene candidates for dyslexia and other reading disabilities; (c) emerging research on gene-brain relationships; and (d) current understanding of epigenetic mechanisms whereby environmental events may alter behavioral expression of genetic variations. A glossary of genetic terms (denoted by bold font) is provided for readers not familiar with the technical terms.

Association of the DYX1C1 dyslexia susceptibility gene with orthography in the Chinese population

Several independent studies have supported the association of DYX1C1 with dyslexia, but its role in general reading development remains unclear. Here, we investigated the contribution of this gene to reading, with a focus on orthographic skills, in a sample of 284 unrelated Chinese children aged 5 to 11 years who were participating in the Chinese Longitudinal Study of Reading Development. We tested this association using a quantitative approach for Chinese character reading, Chinese character dictation, orthographic judgment, and visual skills. Significant or marginally significant associations were observed at the marker rs11629841 with children's orthographic judgments at ages 7 and 8 years (all P values<0.020). Significant associations with Chinese character dictation (all P values<0.013) were also observed for this single-nucleotide polymorphism (SNP) at ages 9, 10, and 11 years. Further analyses revealed that the association with orthographic skills was specific to the processing of specific components of characters (P values<0.046). No association was found at either SNP of rs3743205 or rs57809907. Our findings suggest that DYX1C1 influences reading development in the general Chinese population and supports a universal effect of this gene.

Integrated computational and experimental analysis of the neuroendocrine transcriptome in genetic hypertension identifies novel control points for the cardiometabolic syndrome

BACKGROUND

Essential hypertension, a common complex disease, displays substantial genetic influence. Contemporary methods to dissect the genetic basis of complex diseases such as the genomewide association study are powerful, yet a large gap exists between the fraction of population trait variance explained by such associations and total disease heritability.

METHODS AND RESULTS

We developed a novel, integrative method (combining animal models, transcriptomics, bioinformatics, molecular biology, and trait-extreme phenotypes) to identify candidate genes for essential hypertension and the metabolic syndrome. We first undertook transcriptome profiling on adrenal glands from blood pressure extreme mouse strains: the hypertensive BPH (blood pressure high) and hypotensive BPL (blood pressure low). Microarray data clustering revealed a striking pattern of global underexpression of intermediary metabolism transcripts in BPH. The MITRA algorithm identified a conserved motif in the transcriptional regulatory regions of the underexpressed metabolic genes, and we then hypothesized that regulation through this motif contributed to the global underexpression. Luciferase reporter assays demonstrated transcriptional activity of the motif through transcription factors HOXA3, SRY, and YY1. We finally hypothesized that genetic variation at HOXA3, SRY, and YY1 might predict blood pressure and other metabolic syndrome traits in humans. Tagging variants for each locus were associated with blood pressure in a human population blood pressure extreme sample with the most extensive associations for YY1 tagging single nucleotide polymorphism rs11625658 on systolic blood pressure, diastolic blood pressure, body mass index, and fasting glucose. Meta-analysis extended the YY1 results into 2 additional large population samples with significant effects preserved on diastolic blood pressure, body mass index, and fasting glucose.

CONCLUSIONS

The results outline an innovative, systematic approach to the genetic pathogenesis of complex cardiovascular disease traits and point to transcription factor YY1 as a potential candidate gene involved in essential hypertension and the cardiometabolic syndrome.

The rs3743205 SNP is important for the regulation of the dyslexia candidate gene DYX1C1 by estrogen receptor β and DNA methylation

Estrogen is involved in numerous physiological processes such as growth, differentiation, and function of the male and female reproductive tissues. In the developing brain, estrogen signaling has been linked to cognitive functions, such as learning and memory; however, the molecular mechanisms underlying this phenomenon are poorly understood. We have previously shown a link between developmental dyslexia and estrogen signaling, when we studied the functional interactions between the dyslexia candidate protein DYX1C1 and the estrogen receptors α (ERα) and β (ERβ). Here, we investigate the 17β-estradiol (E2)-dependent regulation of dyslexia susceptibility 1 candidate 1 (DYX1C1) expression. We demonstrate that ERβ, not ERα, binds to a transcriptionally active cis-regulatory region upstream of DYX1C1 transcriptional start site and that DYX1C1 expression is enhanced by E2 in a neuroblastoma cell line. This regulation is dependent on transcription factor II-I and liganded ERβ recruitment to this region. In addition, we describe that a single nucleotide polymorphism previously shown to be associated with dyslexia and located in the cis-regulatory region of DYX1C1 may alter the epigenetic and endocrine regulation of this gene. Our data provide important molecular insights into the relationship between developmental dyslexia susceptibility and estrogen signaling.

Approach to epigenetic analysis in language disorders

Language and learning disorders such as reading disability and language impairment are recognized to be subject to substantial genetic influences, but few causal mutations have been identified in the coding regions of candidate genes. Association analyses of single nucleotide polymorphisms have suggested the involvement of regulatory regions of these genes, and a few mutations affecting gene expression levels have been identified, indicating that the quantity rather than the quality of the gene product may be most relevant for these disorders. In addition, several of the candidate genes appear to be involved in neuronal migration, confirming the importance of early developmental processes. Accordingly, alterations in epigenetic processes such as DNA methylation and histone modification are likely to be important in the causes of language and learning disorders based on their functions in gene regulation. Epigenetic processes direct the differentiation of cells in early development when neurological pathways are set down, and mutations in genes involved in epigenetic regulation are known to cause cognitive disorders in humans. Epigenetic processes also regulate the changes in gene expression in response to learning, and alterations in histone modification are associated with learning and memory deficits in animals. Genetic defects in histone modification have been reversed in animals through therapeutic interventions resulting in rescue of these deficits, making it particularly important to investigate their potential contribution to learning disorders in humans.