1
|
Price KM, Wigg KG, Feng Y, Blokland K, Wilkinson M, He G, Kerr EN, Carter TC, Guger SL, Lovett MW, Strug LJ, Barr CL. Genome-wide association study of word reading: Overlap with risk genes for neurodevelopmental disorders. GENES BRAIN AND BEHAVIOR 2020; 19:e12648. [PMID: 32108986 DOI: 10.1111/gbb.12648] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 01/28/2020] [Accepted: 02/24/2020] [Indexed: 12/12/2022]
Abstract
Reading disabilities (RD) are the most common neurocognitive disorder, affecting 5% to 17% of children in North America. These children often have comorbid neurodevelopmental/psychiatric disorders, such as attention deficit/hyperactivity disorder (ADHD). The genetics of RD and their overlap with other disorders is incompletely understood. To contribute to this, we performed a genome-wide association study (GWAS) for word reading. Then, using summary statistics from neurodevelopmental/psychiatric disorders, we computed polygenic risk scores (PRS) and used them to predict reading ability in our samples. This enabled us to test the shared aetiology between RD and other disorders. The GWAS consisted of 5.3 million single nucleotide polymorphisms (SNPs) and two samples; a family-based sample recruited for reading difficulties in Toronto (n = 624) and a population-based sample recruited in Philadelphia [Philadelphia Neurodevelopmental Cohort (PNC)] (n = 4430). The Toronto sample SNP-based analysis identified suggestive SNPs (P ~ 5 × 10-7 ) in the ARHGAP23 gene, which is implicated in neuronal migration/axon pathfinding. The PNC gene-based analysis identified significant associations (P < 2.72 × 10-6 ) for LINC00935 and CCNT1, located in the region of the KANSL2/CCNT1/LINC00935/SNORA2B/SNORA34/MIR4701/ADCY6 genes on chromosome 12q, with near significant SNP-based analysis. PRS identified significant overlap between word reading and intelligence (R2 = 0.18, P = 7.25 × 10-181 ), word reading and educational attainment (R2 = 0.07, P = 4.91 × 10-48 ) and word reading and ADHD (R2 = 0.02, P = 8.70 × 10-6 ; threshold for significance = 7.14 × 10-3 ). Overlap was also found between RD and autism spectrum disorder (ASD) as top-ranked genes were previously implicated in autism by rare and copy number variant analyses. These findings support shared risk between word reading, cognitive measures, educational outcomes and neurodevelopmental disorders, including ASD.
Collapse
Affiliation(s)
- Kaitlyn M Price
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada.,Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Karen G Wigg
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Yu Feng
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
| | - Kirsten Blokland
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Margaret Wilkinson
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Gengming He
- Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Elizabeth N Kerr
- Department of Psychology, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Tasha-Cate Carter
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.,Holland Bloorview Rehabilitation Hospital, Toronto, Ontario, Canada
| | - Sharon L Guger
- Department of Psychology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Maureen W Lovett
- Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Pediatrics, University of Toronto, Toronto, Ontario, Canada
| | - Lisa J Strug
- Genetics and Genome Biology, Hospital for Sick Children, Toronto, Ontario, Canada.,Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - Cathy L Barr
- Genetics and Development Division, Krembil Research Institute, University Health Network, Toronto, Ontario, Canada.,Program in Neuroscience and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| |
Collapse
|
2
|
Vagge A, Cavanna M, Traverso CE, Iester M. Evaluation of ocular movements in patients with dyslexia. ANNALS OF DYSLEXIA 2015; 65:24-32. [PMID: 25804764 DOI: 10.1007/s11881-015-0098-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2014] [Accepted: 03/04/2015] [Indexed: 05/21/2023]
Abstract
The aims of this study were to analyze the relationship between dyslexia and eye movements and to assess whether this method can be added to the workup of dyslexic patients. The sample was comprised of 11 children with a diagnosis of dyslexia and 11 normal between 8 and 13 years of age. All subjects underwent orthoptic evaluation, ophthalmological examinations, and eye movement analysis, specifically, stability analysis on fixating a still target, tracking saccades, analysis of fixation pauses, speed reading, saccades, and regressions through the reading of a text. Stability analysis on fixating a still target showed a significant (p < 0.001) difference between the two groups showing an increased amount of loss of fixation among dyslexic subjects (5.36 ± 2.5 s and 0.82 ± 2.1, respectively). Tracking saccades (left and right horizontal axis) did not show a significant difference. When reading parameters were looked into (number of saccades, number of regressions, reading time through the reading of a text), a significant (p < 0.001) difference was found between the groups. This study supports the belief that the alteration of eye movement does not depend on oculo-motor dysfunction but is secondary to a defect in the visual processing of linguistic material. Inclusion of assessment of this defect might prove beneficial in determining the presence of dyslexia in young children at a younger age, and an earlier intervention could be initiated.
Collapse
Affiliation(s)
- Aldo Vagge
- Clinica Oculistica, DiNOGMI, University of Genoa, Viale Benedetto XV 5, 16132, Genoa, Italy
| | | | | | | |
Collapse
|
3
|
Carrion-Castillo A, Franke B, Fisher SE. Molecular genetics of dyslexia: an overview. DYSLEXIA (CHICHESTER, ENGLAND) 2013; 19:214-240. [PMID: 24133036 DOI: 10.1002/dys.1464] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 09/02/2013] [Indexed: 05/28/2023]
Abstract
Dyslexia is a highly heritable learning disorder with a complex underlying genetic architecture. Over the past decade, researchers have pinpointed a number of candidate genes that may contribute to dyslexia susceptibility. Here, we provide an overview of the state of the art, describing how studies have moved from mapping potential risk loci, through identification of associated gene variants, to characterization of gene function in cellular and animal model systems. Work thus far has highlighted some intriguing mechanistic pathways, such as neuronal migration, axon guidance, and ciliary biology, but it is clear that we still have much to learn about the molecular networks that are involved. We end the review by highlighting the past, present, and future contributions of the Dutch Dyslexia Programme to studies of genetic factors. In particular, we emphasize the importance of relating genetic information to intermediate neurobiological measures, as well as the value of incorporating longitudinal and developmental data into molecular designs.
Collapse
Affiliation(s)
- Amaia Carrion-Castillo
- Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, Netherlands
| | | | | |
Collapse
|
4
|
Tran C, Gagnon F, Wigg K, Feng Y, Gomez L, Cate-Carter T, Kerr E, Field L, Kaplan B, Lovett M, Barr C. A family-based association analysis and meta-analysis of the reading disabilities candidate gene DYX1C1. Am J Med Genet B Neuropsychiatr Genet 2013; 162B:146-56. [PMID: 23341075 PMCID: PMC5381964 DOI: 10.1002/ajmg.b.32123] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 11/07/2012] [Indexed: 11/11/2022]
Abstract
Reading disabilities (RD) have a significant genetic basis and have shown linkage to multiple regions including chromosome 15q. Dyslexia susceptibility 1 candidate gene 1 (DYX1C1) on chromosome 15q21 was originally proposed as a candidate gene with two potentially functional polymorphisms at the -3G/A and 1249G/T positions showing association with RD. However, subsequent studies have yielded mixed results. We performed a literature review and meta-analysis of the -3G/A and 1249G/T polymorphisms, including new unpublished data from two family-based samples. Ten markers in DYX1C1 were genotyped in the two independently ascertained samples. Single marker and -3G/A:1249G/T haplotype analyses were performed for RD in both samples, and quantitative trait analyses using standardized reading-related measures was performed in one of the samples. For the meta-analysis, we used a random-effects model to summarize studies that tested for association between -3G/A or 1249G/T and RD. No significant association was found between the DYX1C1 SNPs and RD or any of the reading-related measures tested after correction for the number of tests performed. The previously reported risk haplotype (-3A:1249T) was not biased in transmission. A total of 9 and 10 study samples were included in the meta-analysis of the -3G/A and 1249G/T polymorphisms, respectively. Neither polymorphism reached statistical significance, but the heterogeneity for the 1249G/T polymorphism was high. The results of this study do not provide evidence for association between the putatively functional SNPs -3G/A and 1249G/T and RD.
Collapse
Affiliation(s)
- C. Tran
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - F. Gagnon
- Division of Epidemiology, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
| | - K.G. Wigg
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Y. Feng
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - L. Gomez
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - T.D. Cate-Carter
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - E.N. Kerr
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - L.L. Field
- Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada
| | - B.J. Kaplan
- Alberta Children’s Hospital and Department of Paediatrics, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - M.W. Lovett
- Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - C.L. Barr
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada,Program in Neurosciences and Mental Health, The Hospital for Sick Children, Toronto, Ontario, Canada,Correspondence to: Dr. C.L. Barr, Genetics and Development Division, The Toronto Western Hospital, 399 Bathurst St., Room MP14-302, Toronto, ON, Canada M5T 2S8.
| |
Collapse
|
5
|
Raskind WH, Peter B, Richards T, Eckert MM, Berninger VW. The genetics of reading disabilities: from phenotypes to candidate genes. Front Psychol 2013; 3:601. [PMID: 23308072 PMCID: PMC3538356 DOI: 10.3389/fpsyg.2012.00601] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 12/18/2012] [Indexed: 12/19/2022] Open
Abstract
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.
Collapse
Affiliation(s)
- Wendy H Raskind
- Department of Medicine, University of Washington Seattle, WA, USA ; Department of Psychiatry and Behavioral Sciences, University of Washington Seattle, WA, USA
| | | | | | | | | |
Collapse
|
6
|
Affiliation(s)
| | - Dennis Drayna
- National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, Maryland 20892;
| |
Collapse
|
7
|
Saviour P, Kumar S, Kiran U, Ravuri RR, Rao VR, Ramachandra NB. Allelic variants of DYX1C1 are not associated with dyslexia in India. INDIAN JOURNAL OF HUMAN GENETICS 2011; 14:99-102. [PMID: 20300304 PMCID: PMC2840802 DOI: 10.4103/0971-6866.45002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Dyslexia is a hereditary neurological disorder that manifests as an unexpected difficulty in learning to read despite adequate intelligence, education, and normal senses. The prevalence of dyslexia ranges from 3 to 15% of the school aged children. Many genetic studies indicated that loci on 6p21.3, 15q15-21, and 18p11.2 have been identified as promising candidate gene regions for dyslexia. Recently, it has been suggested that allelic variants of gene, DYX1C1 influence dyslexia. In the present study, exon 2 and 10 of DYX1C1 has been analyzed to verify whether these single nucleotide polymorphisms (SNPs) influence dyslexia, in our population. Our study identified 4 SNPs however, none of these SNPS were found to be significantly associated with dyslexia suggesting DYX1C1 allelic variants are not associated with dyslexia.
Collapse
Affiliation(s)
- Pushpa Saviour
- Human Genetics Laboratory, Department of Studies in Zoology, University of Mysore, Manasagangothri, Mysore-570 006, India
| | | | | | | | | | | |
Collapse
|
8
|
Poelmans G, Buitelaar JK, Pauls DL, Franke B. A theoretical molecular network for dyslexia: integrating available genetic findings. Mol Psychiatry 2011; 16:365-82. [PMID: 20956978 DOI: 10.1038/mp.2010.105] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Developmental dyslexia is a common specific childhood learning disorder with a strong heritable component. Previous studies using different genetic approaches have identified several genetic loci and candidate genes for dyslexia. In this article, we have integrated the current knowledge on 14 dyslexia candidate genes suggested by cytogenetic findings, linkage and association studies. We found that 10 of the 14 dyslexia candidate genes (ROBO1, KIAA0319, KIAA0319L, S100B, DOCK4, FMR1, DIP2A, GTF2I, DYX1C1 and DCDC2) fit into a theoretical molecular network involved in neuronal migration and neurite outgrowth. Based on this, we also propose three novel dyslexia candidate genes (SLIT2, HMGB1 and VAPA) from known linkage regions, and we discuss the possible involvement of genes emerging from the two reported genome-wide association studies for reading impairment-related phenotypes in the identified network.
Collapse
Affiliation(s)
- G Poelmans
- Department of Cognitive Neuroscience, Donders Institute for Brain, Cognition and Behaviour, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | | | | | |
Collapse
|
9
|
Skiba T, Landi N, Wagner R, Grigorenko EL. In search of the perfect phenotype: an analysis of linkage and association studies of reading and reading-related processes. Behav Genet 2011; 41:6-30. [PMID: 21243420 PMCID: PMC3056345 DOI: 10.1007/s10519-011-9444-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Accepted: 12/22/2010] [Indexed: 01/15/2023]
Abstract
Reading ability and specific reading disability (SRD) are complex traits involving several cognitive processes and are shaped by a complex interplay of genetic and environmental forces. Linkage studies of these traits have identified several susceptibility loci. Association studies have gone further in detecting candidate genes that might underlie these signals. These results have been obtained in samples of mainly European ancestry, which vary in their languages, inclusion criteria, and phenotype assessments. Such phenotypic heterogeneity across samples makes understanding the relationship between reading (dis)ability and reading-related processes and the genetic factors difficult; in addition, it may negatively influence attempts at replication. In moving forward, the identification of preferable phenotypes for future sample collection may improve the replicability of findings. This review of all published linkage and association results from the past 15 years was conducted to determine if certain phenotypes produce more replicable and consistent results than others.
Collapse
Affiliation(s)
| | - Nicole Landi
- Yale University & Haskins Laboratories, New Haven, CT, USA
| | | | - Elena L. Grigorenko
- Yale University, New Heaven, CT, USA
- Moscow State University, Moscow, Russia
- Columbia University, New York, NY, USA
| |
Collapse
|
10
|
Abstract
The status of DYX1C1 (C15q21.3) as a susceptibility gene for dyslexia is unclear. We report the association of this gene with reading and spelling ability in a sample of adolescent twins and their siblings. Family-based association analyses were carried out on 13 single-nucleotide polymorphisms (SNPs) in DYX1C1, typed in 790 families with up to 5 offspring and tested on 6 validated measures of lexical processing (irregular word) and grapheme-phoneme decoding (pseudo-word) reading- and spelling-based measures of dyslexia, as well as a short-term memory measure. Significant association was observed at the misssense mutation rs17819126 for all reading measures and for spelling of lexical processing words, and at rs3743204 for both irregular and nonword reading. Verbal short-term memory was associated with rs685935. Support for association was not found at rs3743205 and rs61761345 as previously reported by Taipale et al., but these SNPs had very low (0.002 for rs3743205) minor allele frequencies in this sample. These results suggest that DYX1C1 influences reading and spelling ability with additional effects on short-term information storage or rehearsal. Missense mutation rs17819126 is a potential functional basis for the association of DYX1C1 with dyslexia.
Collapse
|
11
|
Benítez-Burraco A. Neurobiología y neurogenética de la dislexia. Neurologia 2010; 25:563-81. [DOI: 10.1016/j.nrl.2009.12.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Accepted: 12/22/2009] [Indexed: 01/12/2023] Open
|
12
|
Couto JM, Livne-Bar I, Huang K, Xu Z, Cate-Carter T, Feng Y, Wigg K, Humphries T, Tannock R, Kerr EN, Lovett MW, Bremner R, Barr CL. Association of reading disabilities with regions marked by acetylated H3 histones in KIAA0319. Am J Med Genet B Neuropsychiatr Genet 2010; 153B:447-462. [PMID: 19588467 PMCID: PMC5381965 DOI: 10.1002/ajmg.b.30999] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Reading disabilities (RDs) have been associated with chromosome 6p with recent studies pointing to two genes, DCDC2 and KIAA0319. In this study, markers across the 6p region were tested for association with RD. Our strongest findings were for association with markers in KIAA0319, although with the opposite alleles compared with a previous study. We also found association with markers in VMP, but not with DCDC2. Current evidence indicates that differential regulation of KIAA0319 and DCDC2 contributes to RD, thus we used chromatin immunoprecipitation coupled with genomic tiling arrays (ChIP-chip) to map acetylated histones, a molecular marker for regulatory elements, across a 500 kb genomic region covering the RD locus on 6p. This approach identified several regions marked by acetylated histones that mapped near associated markers, including intron 7 of DCDC2 and the 5' region of KIAA0319. The latter is located within the 70 kb region previously associated with differential expression of KIAA0319. Interestingly, five markers associated with RD in independent studies were also located within the 2.7 kb acetylated region, and six additional associated markers, including the most significant one in this study, were located within a 22 kb haplotype block that encompassed this region. Our data indicates that this putative regulatory region is a likely site of genetic variation contributing to RD in our sample, further narrowing the candidate region.
Collapse
Affiliation(s)
- Jillian M. Couto
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Izzy Livne-Bar
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Katherine Huang
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Zhaodong Xu
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Tasha Cate-Carter
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Yu Feng
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Karen Wigg
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Tom Humphries
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rosemary Tannock
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Elizabeth N. Kerr
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Maureen W. Lovett
- Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rod Bremner
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | - Cathy L. Barr
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada,Program in Neurosciences and Mental Health, Hospital for Sick Children, Toronto, Ontario, Canada,Correspondence to: Prof. Cathy L. Barr, Toronto Western Research Institute, Toronto Western Hospital, MP14-302, 399 Bathurst Street, Toronto, Ontario, Canada M5T 2S8.
| |
Collapse
|
13
|
Abstract
Developmental dyslexia is a highly heritable disorder with a prevalence of at least 5% in school-aged children. Linkage studies have identified numerous loci throughout the genome that are likely to harbour candidate dyslexia susceptibility genes. Association studies and the refinement of chromosomal translocation break points in individuals with dyslexia have resulted in the discovery of candidate genes at some of these loci. A key function of many of these genes is their involvement in neuronal migration. This complements anatomical abnormalities discovered in dyslexic brains, such as ectopias, that may be the result of irregular neuronal migration.
Collapse
|
14
|
Benítez-Burraco A. Neurobiology and neurogenetics of dyslexia. NEUROLOGÍA (ENGLISH EDITION) 2010. [DOI: 10.1016/s2173-5808(20)70105-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022] Open
|
15
|
Couto JM, Gomez L, Wigg K, Cate-Carter T, Archibald J, Anderson B, Tannock R, Kerr EN, Lovett MW, Humphries T, Barr CL. The KIAA0319-like (KIAA0319L) gene on chromosome 1p34 as a candidate for reading disabilities. J Neurogenet 2009; 22:295-313. [PMID: 19085271 DOI: 10.1080/01677060802354328] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
A locus on chromosome 1p34-36 (DYX8) has been linked to developmental dyslexia or reading disabilities (RD) in three independent samples. In the current study, we investigated a candidate gene KIAA0319-Like (KIAA0319L) within DYX8, as it is homologous to KIAA0319, a strong RD candidate gene on chromosome 6p (DYX2). Association was assessed by using five tagging single nucleotide polymorphisms in a sample of 291 nuclear families ascertained through a proband with reading difficulties. Evidence of association was found for a single marker (rs7523017; P=0.042) and a haplotype (P=0.031), with RD defined as a categorical trait in a subset of the sample (n=156 families) with a proband that made our criteria for RD. The same haplotype also showed evidence for association with quantitative measures of word-reading efficiency (i.e., a composite score of word identification and decoding; P=0.032) and rapid naming of objects and colors (P=0.047) when analyzed using the entire sample. Although the results from the current study are modestly significant and would not withstand a correction for multiple testing, KIAA0319L remains an intriguing positional and functional candidate for RD, especially when considered alongside the supporting evidence for its homolog KIAA0319 on chromosome 6p. Additional studies in independent samples are now required to confirm these findings.
Collapse
Affiliation(s)
- Jillian M Couto
- Genetics and Development Division, Toronto Western Research Institute, Toronto Western Hospital, University Health Network, Toronto, Ontario, Canada
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Abstract
Genetic factors contribute substantially to the development of reading disability (RD). Family linkage studies have implicated many chromosomal regions containing RD susceptibility genes, of which putative loci at 1p34-p36 (DYX8), 2p (DYX3), 6p21.3 (DYX2), and 15q21 (DYX1) have been frequently replicated, whereas those at 3p12-q12 (DYX5), 6q13-q16 (DYX4), 11p15 (DYX7), 18p11 (DYX6), and Xq27 (DYX9) have less evidence. Association studies of positional candidate genes have implicated DCDC2 and KIAA0319 in DYX2, as well as C2ORF3 and MRPL19 (DYX3), whereas DYX1C1/EKN1 (DYX1) and ROBO1 (DYX5) were found to be disrupted by rare translocation breakpoints in reading-disabled individuals. Four of the candidate genes (DYX1C1, KIAA0319, DCDC2, and ROBO1) appear to function in neuronal migration and guidance, suggesting the importance of early neurodevelopmental processes in RD. Future studies to help us understand the function of these and other RD candidate genes promise to yield enormous insight into the neurobiologic mechanisms underlying the pathophysiology of this disorder.
Collapse
|
17
|
Wigg KG, Feng Y, Crosbie J, Tannock R, Kennedy JL, Ickowicz A, Malone M, Schachar R, Barr CL. Association of ADHD and the Protogenin gene in the chromosome 15q21.3 reading disabilities linkage region. GENES BRAIN AND BEHAVIOR 2009; 7:877-86. [PMID: 19076634 DOI: 10.1111/j.1601-183x.2008.00425.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Twin studies indicate genetic overlap between symptoms of attention deficit hyperactivity disorder (ADHD) and reading disabilities (RD), and linkage studies identify several chromosomal regions possibly containing common susceptibility genes, including the 15q region. Based on a translocation finding and association to two specific alleles, the candidate gene, DYX1C1, has been proposed as the susceptibility gene for RD in 15q. Previously, we tested markers in DYX1C1 for association with ADHD. Although we identified association for haplotypes across the gene, we were unable to replicate the association to the specific alleles reported. Thus, the risk alleles for ADHD are yet to be identified. The susceptibility alleles may be in a remote regulatory element, or DYX1C1 may not be the risk gene. To continue study of 15q, we tested a coding region change in DYX1C1, followed by markers across the gene Protogenin (PRTG) in 253 ADHD nuclear families. PRTG was chosen based on its location and because it is closely related to DCC and Neogenin, two genes known to guide migratory cells and axons during development. The markers in DYX1C1 were not associated to ADHD when analyzed individually; however, six markers in PRTG showed significant association with ADHD as a categorical trait (P = 0.025-0.005). Haplotypes in both genes showed evidence for association. We identified association with ADHD symptoms measured as quantitative traits in PRTG, but no evidence for association with two key components of reading, word identification and decoding was observed. These findings, while preliminary, identify association of ADHD to a gene that potentially plays a role in cell migration and axon growth.
Collapse
Affiliation(s)
- K G Wigg
- Genetics and Development Division, The Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada
| | | | | | | | | | | | | | | | | |
Collapse
|
18
|
Platko JV, Wood FB, Pelser I, Meyer M, Gericke GS, O'Rourke J, Birns J, Purcell S, Pauls DL. Association of reading disability on chromosome 6p22 in the Afrikaner population. Am J Med Genet B Neuropsychiatr Genet 2008; 147B:1278-87. [PMID: 18452150 DOI: 10.1002/ajmg.b.30774] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The genetic basis of reading disability (RD) has long been established through family and twin studies. More recently genetic linkage studies have identified genomic regions that appear to harbor susceptibility genes for RD. Association studies have been shown to have greater power for detecting genes of modest effect, particularly in genetically isolated populations. Hence, a case control study of RD was undertaken in the Afrikaner population in South Africa. Sixty-eight microsatellite markers in regions where linkages had been reported in previous studies were genotyped on 122 children with reading disability and 112 typically reading controls drawn from the same school population. A single allele of marker D6S299 showed a highly significant association with the RD phenotype (D6S299[229], P-value 0.000014). Other markers on other chromosomes also showed suggestive associations. Of particular interest were markers on chromosomes 1 and 15. These two regions have been implicated in studies of populations that formed the founding population in the Afrikaner population.
Collapse
Affiliation(s)
- Jill V Platko
- Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts 02114, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Further evidence for a susceptibility locus contributing to reading disability on chromosome 15q15–q21. Psychiatr Genet 2008; 18:137-42. [PMID: 18496212 DOI: 10.1097/ypg.0b013e3282fb7fc6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
20
|
Tapia-Páez I, Tammimies K, Massinen S, Roy AL, Kere J. The complex of TFII-I, PARP1, and SFPQ proteins regulates the DYX1C1 gene implicated in neuronal migration and dyslexia. FASEB J 2008; 22:3001-9. [PMID: 18445785 DOI: 10.1096/fj.07-104455] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
DYX1C1 was first identified as a candidate gene for dyslexia susceptibility, and its role in controlling neuronal migration during embryogenesis and effect on learning in rodents have been verified. In contrast, genetic association studies have been ambiguous in replicating its effects on dyslexia. To better understand the regulation of DYX1C1 and the possible functional role of genetic variation in the promoter of DYX1C1, we selected three single-nucleotide polymorphisms (SNPs) with predicted functional consequences or suggested associations to dyslexia for detailed study. Electrophoretic mobility shift assays suggested the allele-specific binding of the transcription factors TFII-I (to rs3743205) and Sp1 (to rs16787 and rs12899331) that could be verified by competition assays. In addition, we purified a complex of protein factors binding to the previously suggested dyslexia-related SNP, -3G/A (rs3743205). Three proteins, TFII-I, PARP1, and SFPQ, were unambiguously identified by mass spectrometry and protein sequencing. Two SNPs, rs16787 and rs3743205, showed significant allelic differences in luciferase assays. Our results show that TFII-I, PARP1, and SFPQ proteins, each previously implicated in gene regulation, form a complex controlling transcription of DYX1C1. Furthermore, allelic differences in the promoter or 5' untranslated region of DYX1C1 may affect factor binding and thus regulation of the gene.
Collapse
Affiliation(s)
- Isabel Tapia-Páez
- Department of Biosciences and Nutrition, 141 57 Huddinge, Karolinska Institute, Stockholm, Sweden
| | | | | | | | | |
Collapse
|
21
|
Caylak E. A review of association and linkage studies for genetical analyses of learning disorders. Am J Med Genet B Neuropsychiatr Genet 2007; 144B:923-43. [PMID: 17510947 DOI: 10.1002/ajmg.b.30537] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Learning disorders (LD) commonly comprise of a heterogeneous group of disorders manifested by unexpected problems in some children's experiences in the academic performance arena. These problems especially comprise of a variety of disorders which may be subclassified to attention-deficit hyperactivity disorder (ADHD), reading disability (RD), specific language impairment (SLI), speech-sound disorder (SSD), and dyspraxia. The aim of this review is to summarize the current molecular studies and some of the most exciting recent developments in molecular genetic research on LD. The findings for the association and linkage of LD with candidate genes will help to set the research agendas for future studies to follow.
Collapse
Affiliation(s)
- Emrah Caylak
- Department of Biochemistry and Clinical Biochemistry, Firat University, School of Medicine, Elazig, Turkey.
| |
Collapse
|
22
|
Abstract
Reading abilities are acquired only through specific teaching and training. A significant proportion of children fail to achieve these skills despite normal intellectual abilities and an appropriate opportunity to learn. Difficulty in learning to read is attributable to specific dysfunctions of the brain, which so far remain poorly understood. However, it is recognized that the neurological basis for dyslexia, or reading disability, is caused in large part by genetic factors. Linkage studies have successfully identified several regions of the human genome that are likely to harbor susceptibility genes for dyslexia. In the past few years there have been exciting advances with the identification of four candidate genes located within three of these linked chromosome regions: DYX1C1 on chromosome 15, ROBO1 on chromosome 3, and KIAA0319 and DCDC2 on chromosome 6. Functional studies of these genes are offering new insights about the biological mechanisms underlying the development of dyslexia and, in general, of cognition.
Collapse
Affiliation(s)
- Silvia Paracchini
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, United Kingdom
| | | | | |
Collapse
|
23
|
Genetik der Lese- und Rechtschreibstörung. Monatsschr Kinderheilkd 2007. [DOI: 10.1007/s00112-007-1479-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
24
|
Baron IS, Litman FR, Ahronovich MD, Larson JCG. Neuropsychological Outcomes of Preterm Triplets Discordant for Birthweight: A Case Report. Clin Neuropsychol 2007; 21:338-62. [PMID: 17455022 DOI: 10.1080/13854040601052141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Multiple gestation is associated with a higher incidence of preterm birth and preterm birth often results in later neurocognitive and behavioral problems that persist into adulthood. The medical, neurobiological, familial, and socio-environmental factors determinant for an individual are unpredictable. We present neuropsychological data for fraternal triplets discordant for birthweight whose school-age outcome was inconsistent with the low birthweight literature and for whom neurobiological variables appeared especially pertinent. Preterm infants may achieve optimal outcomes, although etiological factors leading to such outcomes may depend heavily on care center variables that limit or avoid intracerebral and other medical complications of prematurity.
Collapse
Affiliation(s)
- Ida Sue Baron
- Department of Pediatrics, Inova Fairfax Hospital for Children, Falls Church, VA, USA.
| | | | | | | |
Collapse
|
25
|
Schumacher J, Hoffmann P, Schmäl C, Schulte-Körne G, Nöthen MM. Genetics of dyslexia: the evolving landscape. J Med Genet 2007; 44:289-97. [PMID: 17307837 PMCID: PMC2597981 DOI: 10.1136/jmg.2006.046516] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dyslexia is among the most common neurodevelopmental disorders, with a prevalence of 5-12%. At the phenotypic level, various cognitive components that enable reading and spelling and that are disturbed in affected individuals can be distinguished. Depending on the phenotype dimension investigated, inherited factors are estimated to account for up to 80%. Linkage findings in dyslexia are relatively consistent across studies in comparison to findings for other neuropsychiatric disorders. This is particularly true for chromosome regions 1p34-p36, 6p21-p22, 15q21 and 18q11. Four candidate genes have recently been identified through systematic linkage disequilibrium studies in linkage region 6p21-p22, and through cloning approaches at chromosomal breakpoints. Results indicate that a disturbance in neuronal migration is a pathological correlate of dyslexia at the functional level. This review presents a summary of the latest insights into the genetics of dyslexia and an overview of anticipated future developments.
Collapse
|
26
|
Marino C, Citterio A, Giorda R, Facoetti A, Menozzi G, Vanzin L, Lorusso ML, Nobile M, Molteni M. Association of short-term memory with a variant within DYX1C1 in developmental dyslexia. GENES BRAIN AND BEHAVIOR 2007; 6:640-6. [PMID: 17309662 DOI: 10.1111/j.1601-183x.2006.00291.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A substantial genetic contribution in the etiology of developmental dyslexia (DD) has been well documented with independent groups reporting a susceptibility locus on chromosome 15q. After the identification of the DYX1C1 gene as a potential candidate for DD, several independent association studies reported controversial results. We performed a family-based association study to determine whether the DYX1C1 single nucleotide polymorphisms (SNPs) that have been associated with DD before, that is SNPs '-3GA' and '1249GT', influence a broader phenotypic definition of DD. A significant linkage disequilibrium was observed with 'Single Letter Backward Span' (SLBS) in both single-marker and haplotype analyses. These results provide further support to the association between DD and DYX1C1 and it suggests that the linkage disequilibrium with DYX1C1 is more saliently explained in Italian dyslexics by short-term memory, as measured by 'SLBS', than by the categorical diagnosis of DD or other related phenotypes.
Collapse
Affiliation(s)
- C Marino
- Scientific Institute 'Eugenio Medea', Department of Child Psychiatry, Bosisio Parini, Italy.
| | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Abstract
Genetic factors are important contributors to language and learning disorders, and discovery of the underlying genes can help delineate the basic neurological pathways that are involved. This information, in turn, can help define disorders and their perceptual and processing deficits. Initial molecular genetic studies of dyslexia, for example, appear to converge on defects in neuronal and axonal migration. Further study of individuals with abnormalities of these genes may lead to the recognition of characteristic cognitive deficits attributable to the neurological dysfunction. Such abnormalities may affect other disorders as well, and studies of co-morbidity of dyslexia with attention deficit disorder and speech sound disorder are helping to define the scope of these genes and show the etiological and cognitive commonalities between these conditions. The genetic contributions to specific language impairment (SLI) are not as well defined at this time, but similar molecular approaches are being applied to identify genes that influence SLI and comorbid disorders. While there is co-morbidity of SLI with dyslexia, it appears that most of the common genetic effects may be with the language characteristics of autism spectrum disorders rather than with dyslexia and related disorders. Identification of these genes and their neurological and cognitive effects should lay out a functional network of interacting genes and pathways that subserve language development. Understanding these processes can form the basis for refined procedures for diagnosis and treatment.
Collapse
Affiliation(s)
- Shelley D Smith
- Department of Pediatrics, University of Nebraska Medical Center, Omaha, Nebraska 68198-5456, USA.
| |
Collapse
|
28
|
Lewis BA, Shriberg LD, Freebairn LA, Hansen AJ, Stein CM, Taylor HG, Iyengar SK. The genetic bases of speech sound disorders: evidence from spoken and written language. JOURNAL OF SPEECH, LANGUAGE, AND HEARING RESEARCH : JSLHR 2006; 49:1294-312. [PMID: 17197497 DOI: 10.1044/1092-4388(2006/093)] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
The purpose of this article is to review recent findings suggesting a genetic susceptibility for speech sound disorders (SSD), the most prevalent communication disorder in early childhood. The importance of genetic studies of SSD and the hypothetical underpinnings of these genetic findings are reviewed, as well as genetic associations of SSD with other language and reading disabilities. The authors propose that many genes contribute to SSD. They further hypothesize that some genes contribute to SSD disorders alone, whereas other genes influence both SSD and other written and spoken language disorders. The authors postulate that underlying common cognitive traits, or endophenotypes, are responsible for shared genetic influences of spoken and written language. They review findings from their genetic linkage study and from the literature to illustrate recent developments in this area. Finally, they discuss challenges for identifying genetic influence on SSD and propose a conceptual framework for study of the genetic basis of SSD.
Collapse
Affiliation(s)
- Barbara A Lewis
- Behavioral Pediatrics and Psychology 6038, Rainbow Babies and Children's Hospital, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH 44106-6038, USA.
| | | | | | | | | | | | | |
Collapse
|
29
|
Bates TC, Luciano M, Castles A, Coltheart M, Wright MJ, Martin NG. Replication of reported linkages for dyslexia and spelling and suggestive evidence for novel regions on chromosomes 4 and 17. Eur J Hum Genet 2006; 15:194-203. [PMID: 17119535 DOI: 10.1038/sj.ejhg.5201739] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We report the first genome-wide linkage analysis for reading and spelling in a sample of 403 families of twins, aged between 12 and 25 years taken from the normal population and unselected for reading ability. These traits showed heritabilities of 0.52-0.73, and support for linkage exceeded replication levels (lod > 1.44) of seven of the 11 linkages reported in dyslexic samples, namely: 2q22.3, 3p12-q13, 6q11.2, 7q32, 15q21.1, 18p21, and Xq27.3. For five of these (2q22.3, 6q11.2, 7q32, 18p21, and Xq27), this study provides the first independent replication. 1p34-36 and 2p15-16 received some support, with lods of 1.2 and 0.83, respectively, whereas two regions received little support (6p23-21.3 and 11p15.5). This study also identified two novel linkages at 4p15.33-16.1 and 17p13.3, which received suggestive support (max. lod 2.08 and 1.99, respectively).
Collapse
Affiliation(s)
- Timothy C Bates
- Department of Psychology, University of Edinburgh, Edinburgh, UK.
| | | | | | | | | | | |
Collapse
|
30
|
Abstract
Dyslexia is the most common and carefully studied of the learning disabilities in school-age children. It is characterized by a marked impairment in the development of reading skills, and affects a large number of people (5-10%). Reading difficulties may also arise from poor vision, emotional problems, decreased hearing ability, and behavioral disorders, such as attention-deficit hyperactivity (ADHD). Although many areas of the brain are involved in reading, analysis of postmortem brain specimens by a variety of imaging techniques most consistently suggests that deficiency within a specific component of the language system - the phonologic module - in the temporo-parietal-occipital brain region underlies dyslexia. It is a highly familial and heritable disorder with susceptibility loci on chromosomes 1, 2, 3, 6, 11, 13, 15 and 18. Recently, four candidate genes (KIAA 0319, DYX1C1, DCDC2 and ROBO1) are shown to be associated with dyslexia. Although some of these results are controversial because of the genetic heterogeneity of the disorder, the available evidence suggests that dyslexia could be due to the abnormal migration and maturation of neurons during early development. Interestingly, in spite of genetic heterogeneity, the pathology appears to involve common phonological coding deficits. The condition can be managed by a highly structured educational training exercise.
Collapse
Affiliation(s)
- Barkur S Shastry
- Department of Biological Sciences, Oakland University, Rochester, MI, 48309, USA.
| |
Collapse
|
31
|
Richards TL, Aylward EH, Field KM, Grimme AC, Raskind W, Richards AL, Nagy W, Eckert M, Leonard C, Abbott RD, Berninger VW. Converging evidence for triple word form theory in children with dyslexia. Dev Neuropsychol 2006; 30:547-89. [PMID: 16925475 DOI: 10.1207/s15326942dn3001_3] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
This article has 3 parts. The 1st part provides an overview of the family genetics, brain imaging, and treatment research in the University of Washington Multidisciplinary Learning Disabilities Center (UWLDC) over the past decade that points to a probable genetic basis for the unusual difficulty that individuals with dyslexia encounter in learning to read and spell. Phenotyping studies have found evidence that phonological, orthographic, and morphological word forms and their parts may contribute uniquely to this difficulty. At the same time, reviews of treatment studies in the UWLDC (which focused on children in Grades 4 to 6) and other research centers provide evidence for the plasticity of the brain in individuals with dyslexia. The 2nd part reports 4 sets of results that extend previously published findings based on group analyses to those based on analyses of individual brains and that support triple word form awareness and mapping theory: (a) distinct brain signatures for the phonological, morphological, and orthographic word forms; (b) crossover effects between phonological and morphological treatments and functional magentic resonance imaging (fMRI) tasks in response to instruction, suggestive of cross-word form computational and mapping processes; (c) crossover effects between behavioral measures of phonology or morphology and changes in fMRI activation following treatment; and (d) change in the relationship between structural MRI and functional magnetic resonance spectroscopy (fMRS) lactate activation in right and left inferior frontal gyri following treatment emphasizing the phonological, morphological, and orthographic word forms. In the 3rd part we discuss the next steps in this programmatic research to move beyond word form alone.
Collapse
Affiliation(s)
- Todd L Richards
- Department of Radiology, University of Washington, Seattle, WA 98195, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Abstract
Reading reflects the complex integration of several cognitive processes and proves more difficult to achieve for a significant proportion of the population. Developmental dyslexia (DD), or specific reading disability, is influenced by genes, a fact that has led several research groups to attempt to identify susceptibility genes through the sequential analysis of genetic linkage and association. Strong evidence has now emerged for the presence of genes influencing DD at several chromosomal loci and for at least one of these, there is evidence implicating specific genes. In this review, we present the evidence for a genetic contribution to DD and its component processes and review the current status of molecular genetic research aimed at identifying susceptibility genes for this common, complex disorder.
Collapse
Affiliation(s)
- Julie Williams
- Department of Psychological Medicine, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff CF14 4XN, UK.
| | | |
Collapse
|
33
|
Stein CM, Millard C, Kluge A, Miscimarra LE, Cartier KC, Freebairn LA, Hansen AJ, Shriberg LD, Taylor HG, Lewis BA, Iyengar SK. Speech sound disorder influenced by a locus in 15q14 region. Behav Genet 2006; 36:858-68. [PMID: 16786424 DOI: 10.1007/s10519-006-9090-7] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2005] [Accepted: 05/23/2006] [Indexed: 10/24/2022]
Abstract
Despite a growing body of evidence indicating that speech sound disorder (SSD) has an underlying genetic etiology, researchers have not yet identified specific genes predisposing to this condition. The speech and language deficits associated with SSD are shared with several other disorders, including dyslexia, autism, Prader-Willi Syndrome (PWS), and Angelman's Syndrome (AS), raising the possibility of gene sharing. Furthermore, we previously demonstrated that dyslexia and SSD share genetic susceptibility loci. The present study assesses the hypothesis that SSD also shares susceptibility loci with autism and PWS. To test this hypothesis, we examined linkage between SSD phenotypes and microsatellite markers on the chromosome 15q14-21 region, which has been associated with autism, PWS/AS, and dyslexia. Using SSD as the phenotype, we replicated linkage to the 15q14 region (P=0.004). Further modeling revealed that this locus influenced oral-motor function, articulation and phonological memory, and that linkage at D15S118 was potentially influenced by a parent-of-origin effect (LOD score increase from 0.97 to 2.17, P=0.0633). These results suggest shared genetic determinants in this chromosomal region for SSD, autism, and PWS/AS.
Collapse
Affiliation(s)
- Catherine M Stein
- Department of Epidemiology and Biostatistics, Case Western Reserve University, and Department of Pediatrics, Rainbow Babies & Childrens Hospital, Cleveland, OH 44106, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
Igo RP, Chapman NH, Berninger VW, Matsushita M, Brkanac Z, Rothstein JH, Holzman T, Nielsen K, Raskind WH, Wijsman EM. Genomewide scan for real-word reading subphenotypes of dyslexia: novel chromosome 13 locus and genetic complexity. Am J Med Genet B Neuropsychiatr Genet 2006; 141B:15-27. [PMID: 16331673 PMCID: PMC2556979 DOI: 10.1002/ajmg.b.30245] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Dyslexia is a common learning disability exhibited as a delay in acquiring reading skills despite adequate intelligence and instruction. Reading single real words (real-word reading, RWR) is especially impaired in many dyslexics. We performed a genome scan, using variance components (VC) linkage analysis and Bayesian Markov chain Monte Carlo (MCMC) joint segregation and linkage analysis, for three quantitative measures of RWR in 108 multigenerational families, with follow up of the strongest signals with parametric LOD score analyses. We used single-word reading efficiency (SWE) to assess speed and accuracy of RWR, and word identification (WID) to assess accuracy alone. Adjusting SWE for WID provided a third measure of RWR efficiency. All three methods of analysis identified a strong linkage signal for SWE on chromosome 13q. Based on multipoint analysis with 13 markers we obtained a MCMC intensity ratio (IR) of 53.2 (chromosome-wide P < 0.004), a VC LOD score of 2.29, and a parametric LOD score of 2.94, based on a quantitative-trait model from MCMC segregation analysis (SA). A weaker signal for SWE on chromosome 2q occurred in the same location as a significant linkage peak seen previously in a scan for phonological decoding. MCMC oligogenic SA identified three models of transmission for WID, which could be assigned to two distinct linkage peaks on chromosomes 12 and 15. Taken together, these results indicate a locus for efficiency and accuracy of RWR on chromosome 13, and a complex model for inheritance of RWR accuracy with loci on chromosomes 12 and 15.
Collapse
Affiliation(s)
- Robert P. Igo
- Department of Medicine, University of Washington, Seattle, WA
- Department of Biostatistics, University of Washington, Seattle, WA
| | | | | | - Mark Matsushita
- Department of Medicine, University of Washington, Seattle, WA
| | - Zoran Brkanac
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA
| | | | | | - Kathleen Nielsen
- Department of Educational Psychology, University of Washington, Seattle, WA
| | - Wendy H. Raskind
- Department of Medicine, University of Washington, Seattle, WA
- Department of Psychiatry and Behavioral Sciences, University of Washington, Seattle, WA
| | - Ellen M. Wijsman
- Department of Medicine, University of Washington, Seattle, WA
- Department of Biostatistics, University of Washington, Seattle, WA
| |
Collapse
|
35
|
Meng H, Hager K, Held M, Page GP, Olson RK, Pennington BF, DeFries JC, Smith SD, Gruen JR. TDT-association analysis of EKN1 and dyslexia in a Colorado twin cohort. Hum Genet 2005; 118:87-90. [PMID: 16133186 DOI: 10.1007/s00439-005-0017-9] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2004] [Accepted: 06/18/2005] [Indexed: 11/26/2022]
Abstract
A candidate gene, EKN1, was recently described in a cohort from Finland for the dyslexia locus on chromosome 15q, DYX1. This report described a (2;15) (q11;21) translocation disrupting EKN1 that cosegregated with dyslexia in a two-generation family. It also characterized a sequence polymorphism in the 5' untranslated region and a missense mutation that showed significant association in 109 dyslexics compared to 195 controls (p=0.002 and p=0.006, respectively). To confirm these results we interrogated the same polymorphisms in a cohort of 150 nuclear families with dyslexia ascertained through the Colorado Learning Disabilities Research Center. Using QTDT analysis with nine individual quantitative tasks and two composite measures of reading performance, we could not replicate the reported association. We conclude that the polymorphisms identified in the Finland sample are unlikely to be functional DNA changes contributing to dyslexia, and that if variation in EKN1 is causal such changes are more likely to be in regulatory regions that were not sequenced in this study. Alternatively, the published findings of association with markers in EKN1 may reflect linkage disequilibrium with variation in another gene(s) in the region.
Collapse
Affiliation(s)
- Haiying Meng
- Department of Pediatrics, Yale Child Health Research Center, Yale University School of Medicine, 464 Congress Avenue, New Haven, CT 06520-8081, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Gayán J, Willcutt EG, Fisher SE, Francks C, Cardon LR, Olson RK, Pennington BF, Smith SD, Monaco AP, DeFries JC. Bivariate linkage scan for reading disability and attention-deficit/hyperactivity disorder localizes pleiotropic loci. J Child Psychol Psychiatry 2005; 46:1045-56. [PMID: 16178928 DOI: 10.1111/j.1469-7610.2005.01447.x] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
BACKGROUND There is a growing interest in the study of the genetic origins of comorbidity, a direct consequence of the recent findings of genetic loci that are seemingly linked to more than one disorder. There are several potential causes for these shared regions of linkage, but one possibility is that these loci may harbor genes with manifold effects. The established genetic correlation between reading disability (RD) and attention-deficit/hyperactivity disorder (ADHD) suggests that their comorbidity is due at least in part to genes that have an impact on several phenotypes, a phenomenon known as pleiotropy. METHODS We employ a bivariate linkage test for selected samples that could help identify these pleiotropic loci. This linkage method was employed to carry out the first bivariate genome-wide analysis for RD and ADHD, in a selected sample of 182 sibling pairs. RESULTS We found evidence for a novel locus at chromosome 14q32 (multipoint LOD=2.5; singlepoint LOD=3.9) with a pleiotropic effect on RD and ADHD. Another locus at 13q32, which had been implicated in previous univariate scans of RD and ADHD, seems to have a pleiotropic effect on both disorders. 20q11 is also suggested as a pleiotropic locus. Other loci previously implicated in RD or ADHD did not exhibit bivariate linkage. CONCLUSIONS Some loci are suggested as having pleiotropic effects on RD and ADHD, while others might have unique effects. These results highlight the utility of this bivariate linkage method to study pleiotropy.
Collapse
Affiliation(s)
- J Gayán
- Wellcome Trust Centre for Human Genetics, University of Oxford, UK.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
37
|
Schumacher J, König IR, Plume E, Propping P, Warnke A, Manthey M, Duell M, Kleensang A, Repsilber D, Preis M, Remschmidt H, Ziegler A, Nöthen MM, Schulte-Körne G. Linkage analyses of chromosomal region 18p11-q12 in dyslexia. J Neural Transm (Vienna) 2005; 113:417-23. [PMID: 16075186 DOI: 10.1007/s00702-005-0336-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2005] [Accepted: 05/14/2005] [Indexed: 11/28/2022]
Abstract
Dyslexia is characterized as a significant impairment in reading and spelling ability that cannot be explained by low intelligence, low school attendance or deficits in sensory acuity. It is known to be a hereditary disorder that affects about 5% of school aged children, making it the most common of childhood learning disorders. Several susceptibility loci have been reported on chromosomes 1, 2, 3, 6, 15, and 18. The locus on chromosome 18 has been described as having the strongest influence on single word reading, phoneme awareness, and orthographic coding in the largest genome wide linkage study published to date (Fisher et al., 2002). Here we present data from 82 German families in order to investigate linkage of various dyslexia-related traits to the previously described region on chromosome 18p11-q12. Using two- and multipoint analyses, we did not find support for linkage of spelling, single word reading, phoneme awareness, orthographic coding and rapid naming to any of the 14 genotyped STR markers. Possible explanations for our non-replication include differences in study design, limited power of our study and overestimation of the effect of the chromosome 18 locus in the original study.
Collapse
|
38
|
Raskind WH, Igo RP, Chapman NH, Berninger VW, Thomson JB, Matsushita M, Brkanac Z, Holzman T, Brown M, Wijsman EM. A genome scan in multigenerational families with dyslexia: Identification of a novel locus on chromosome 2q that contributes to phonological decoding efficiency. Mol Psychiatry 2005; 10:699-711. [PMID: 15753956 DOI: 10.1038/sj.mp.4001657] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Dyslexia is a common and complex developmental disorder manifested by unexpected difficulty in learning to read. Multiple different measures are used for diagnosis, and may reflect different biological pathways related to the disorder. Impaired phonological decoding (translation of written words without meaning cues into spoken words) is thought to be a core deficit. We present a genome scan of two continuous measures of phonological decoding ability: phonemic decoding efficiency (PDE) and word attack (WA). PDE measures both accuracy and speed of phonological decoding, whereas WA measures accuracy alone. Multipoint variance component linkage analyses (VC) and Markov chain Monte-Carlo (MCMC) multipoint joint linkage and segregation analyses were performed on 108 families. A strong signal was observed on chromosome 2 for PDE using both VC (LOD=2.65) and MCMC methods (intensity ratio (IR)=32.1). The IR is an estimate of the ratio of the posterior to prior probability of linkage in MCMC analysis. The chromosome 2 signal was not seen for WA. More detailed mapping with additional markers provided statistically significant evidence for linkage of PDE to chromosome 2, with VC-LOD=3.0 and IR=59.6 at D2S1399. Parametric analyses of PDE, using a model obtained by complex segregation analysis, provided a multipoint maximum LOD=2.89. The consistency of results from three analytic approaches provides strong evidence for a locus on chromosome 2 that influences speed but not accuracy of phonological decoding.
Collapse
Affiliation(s)
- W H Raskind
- Department of Medicine, University of Washington, Seattle, WA, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
39
|
de Kovel CGF, Hol FA, Heister JGAM, Willemen JJHT, Sandkuijl LA, Franke B, Padberg GW. Genomewide scan identifies susceptibility locus for dyslexia on Xq27 in an extended Dutch family. J Med Genet 2005; 41:652-7. [PMID: 15342694 PMCID: PMC1735895 DOI: 10.1136/jmg.2003.012294] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
CONTEXT Dyslexia is a common disorder with a strong genetic component, but despite significant research effort, the aetiology is still largely unknown. OBJECTIVE To identify loci contributing to dyslexia risk. METHODS This was a genomewide linkage analysis in a single large family. Dutch families with at least two first degree relatives suffering from dyslexia participated in the study. Participants were recruited through an advertisement campaign in papers and magazines. The main outcome measure was linkage between genetic markers and dyslexia phenotype. RESULTS Using parametric linkage analysis, we found strong evidence for a locus influencing dyslexia on Xq27.3 (multipoint lod = 3.68). Recombinations in two family members flanked an 8 cM region, comprising 11 currently confirmed genes. All four males carrying the risk haplotype had very low scores on the reading tests. The presentation in females was more variable, but 8/9 females carrying the risk haplotype were diagnosed dyslexic by our composite score, so we considered the putative risk allele to be dominant with reduced penetrance. Linkage was not found in an additional collection of affected sibling pairs. CONCLUSIONS A locus influencing dyslexia risk is probably located between markers DXS1227 and DXS8091 on the X chromosome, closely situated to a locus indicated by a published genome scan of English sibling pairs. Although the locus may not be a common cause for dyslexia, the relatively small and gene poor region offers hope to identify the responsible gene.
Collapse
Affiliation(s)
- C G F de Kovel
- Department of Theoretical Biology, University of Leiden, NL-2311 GP Leiden, The Netherlands.
| | | | | | | | | | | | | |
Collapse
|
40
|
Cope N, Harold D, Hill G, Moskvina V, Stevenson J, Holmans P, Owen MJ, O'Donovan MC, Williams J. Strong evidence that KIAA0319 on chromosome 6p is a susceptibility gene for developmental dyslexia. Am J Hum Genet 2005; 76:581-91. [PMID: 15717286 PMCID: PMC1199296 DOI: 10.1086/429131] [Citation(s) in RCA: 227] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2004] [Accepted: 01/21/2005] [Indexed: 01/07/2023] Open
Abstract
Linkage between developmental dyslexia (DD) and chromosome 6p has been replicated in a number of independent samples. Recent attempts to identify the gene responsible for the linkage have produced inconsistent evidence for association of DD with a number of genes in a 575-kb region of chromosome 6p22.2, including VMP, DCDC2, KIAA0319, TTRAP, and THEM2. We aimed to identify the specific gene or genes involved by performing a systematic, high-density (approximately 2-3-kb intervals) linkage disequilibrium screen of these genes in an independent sample, incorporating family-based and case-control designs in which dyslexia was defined as an extreme representation of reading disability. Using DNA pooling, we first observed evidence for association with 17 single-nucleotide polymorphisms (SNPs), 13 of which were located in the KIAA0319 gene (P<.01-.003). After redundant SNPs were excluded, 10 SNPs were individually genotyped in 223 subjects with DD and 273 controls. Those SNPs that were significant at P=.05 were next genotyped in a semi-independent sample of 143 trios of probands with DD and their parents, to control for possible population stratification. Six SNPs showed significant evidence of association in both samples (P=.04-.002), including a SNP (rs4504469) in exon 4 of the KIAA0319 gene that changes an amino acid (P=.002; odds ratio 1.5). Logistic regression analysis showed that two SNPs (rs4504469 and rs6935076) in the KIAA0319 gene best explained DD status. The haplotype composed of these two markers was significantly associated with DD (global P=.00001 in the case-control sample; P=.02 in trios). This finding was largely driven by underrepresentation of the most common haplotype in cases (P=.00003 in the case-control sample; P=.006 in trios; 1-degree-of-freedom tests). Our data strongly implicate KIAA0319 as a susceptibility gene for dyslexia. The gene product is expressed in brain, but its specific function is currently unknown.
Collapse
Affiliation(s)
- Natalie Cope
- Department of Psychological Medicine, Wales College of Medicine, Cardiff University, Cardiff, United Kingdom
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Cope NA, Hill G, van den Bree M, Harold D, Moskvina V, Green EK, Owen MJ, Williams J, O'Donovan MC. No support for association between dyslexia susceptibility 1 candidate 1 and developmental dyslexia. Mol Psychiatry 2005; 10:237-8. [PMID: 15477871 DOI: 10.1038/sj.mp.4001596] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
42
|
Marino C, Giorda R, Luisa Lorusso M, Vanzin L, Salandi N, Nobile M, Citterio A, Beri S, Crespi V, Battaglia M, Molteni M. A family-based association study does not support DYX1C1 on 15q21.3 as a candidate gene in developmental dyslexia. Eur J Hum Genet 2005; 13:491-9. [PMID: 15702132 DOI: 10.1038/sj.ejhg.5201356] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
We applied a family-based association approach to investigate the role of the DYX1C1 gene on chromosome 15q as a candidate gene for developmental dyslexia (DD) to 158 families containing at least one dyslexic child. We directly sequenced exons 2 and 10 of the DYX1C1 gene and found eight single nucleotide polymorphism (SNPs), three of which (-3G>A, 1249 G>T, 1259 C>G) were suitable for the genetic analyses. We performed single- and multimarker association analyses with DD as a categorical trait by FBAT version 1.4 and TRANSMIT version 2.5.4 programs. Our sample had a power of at least 80% to detect an association between the selected phenotypes and the informative polymorphisms at a significance level of 5%. The results of the categorical analyses did not support the involvement of the DYX1C1 gene variants in this sample of dyslexics and their relatives. Quantitative and multimarker analyses, which provide greater power to detect loci with a minor effect, consistently yielded nonsignificant results. While D1X1C1 is a good candidate gene for DD, we were unable to replicate the original findings between DYX1C1 gene and DD, perhaps due to genetic heterogeneity.
Collapse
Affiliation(s)
- Cecilia Marino
- Department of Child Psychiatry, Scientific Institute 'Eugenio Medea', via Don L Monza 20, 23842 Bosisio Parini, Italy.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Wigg KG, Couto JM, Feng Y, Anderson B, Cate-Carter TD, Macciardi F, Tannock R, Lovett MW, Humphries TW, Barr CL. Support for EKN1 as the susceptibility locus for dyslexia on 15q21. Mol Psychiatry 2004; 9:1111-21. [PMID: 15249932 DOI: 10.1038/sj.mp.4001543] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Dyslexia has been linked to a number of chromosomal regions including 15q. Recently a gene, EKN1, with unknown function in the linked region, was identified via a translocation breakpoint. This gene was further supported as a susceptibility locus by association studies in a Finnish sample. We investigated the possibility of this locus as a susceptibility gene contributing to dyslexia, analyzed as a categorical trait, and analyzed key reading phenotypes as quantitative traits using six polymorphisms including the two previously reported to be associated with dyslexia. In our sample of 148 families identified through a proband with reading difficulties, we found significant evidence for an association to dyslexia analyzed as a categorical trait and found evidence of association to the reading and related processes of phonological awareness, word identification, decoding, rapid automatized naming, language ability, and verbal short-term memory. However, association was observed with different alleles and haplotypes than those reported to be associated in a Finnish sample. These findings provide support for EKN1 as a risk locus for dyslexia and as contributing to reading component processes and reading-related abilities. Based on these findings, further studies of this gene in independent samples are now required to determine the relationship of this gene to dyslexia.
Collapse
Affiliation(s)
- K G Wigg
- Department of Psychiatry, Cell and Molecular Division, The Toronto Western Hospital, University Health Network, Toronto, Ontario M5T 2S8, Canada
| | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Ylisaukko-Oja T, Peyrard-Janvid M, Lindgren CM, Rehnström K, Vanhala R, Peltonen L, Järvelä I, Kere J. Family-based association study of DYX1C1 variants in autism. Eur J Hum Genet 2004; 13:127-30. [PMID: 15470369 DOI: 10.1038/sj.ejhg.5201272] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
DYX1C1: was recently identified as a candidate gene for developmental dyslexia, which is characterized by an unexpected difficulty in learning to read and write despite adequate intelligence, motivation, and education. It will be important to clarify, whether the phenotype caused by DYX1C1 extends to other language-related or comorbid disorders. Impaired language development is one of the essential features in autism. Therefore, we analyzed the allelic distribution of the DYX1C1 gene by family-based association method in 100 Finnish autism families. No evidence for association was observed with any intragenic marker or with haplotypes constructed from alleles of several adjacent markers. No evidence for deviated allelic diversity was either observed: the frequency of expected dyslexia risk haplotype was comparable to its frequency in Finnish controls. Thus it seems unlikely that DYX1C1 gene would be involved in the genetic etiology of autism in Finnish patients.
Collapse
Affiliation(s)
- Tero Ylisaukko-Oja
- Department of Molecular Medicine, National Public Health Institute, Helsinki, Finland.
| | | | | | | | | | | | | | | |
Collapse
|
45
|
|
46
|
Morris DW, Ivanov D, Robinson L, Williams N, Stevenson J, Owen MJ, Williams J, O'Donovan MC. Association analysis of two candidate phospholipase genes that map to the chromosome 15q15.1-15.3 region associated with reading disability. Am J Med Genet B Neuropsychiatr Genet 2004; 129B:97-103. [PMID: 15274049 DOI: 10.1002/ajmg.b.30033] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Molecular genetic studies have suggested a reading disability (RD, dyslexia) susceptibility locus on chromosome 15q. We have previously mapped this locus by association to the region surrounding D15S994. Very little is known about the neurobiological processes involved in RD, and therefore selecting positional candidate genes for analysis based upon function is difficult. Nevertheless we were able to identify two functional candidates based upon existing hypotheses. Both were phospholipase genes, phospholipase C beta 2 (PLCB2) and phospholipase A2, group IVB (cytosolic; PLA2G4B). D15S944 is located within PLCB2 and is 1.6 Mb from PLA2G4B. We examined each gene for association using a mixed direct and indirect association approach, a case (n = 164)/control (n = 174) sample, and a partially overlapping sample of 178 RD parent-proband trios from South Wales and England. Mutation analysis revealed 14 sequence variants in PLCB2 and 33 variants in PLA2G4B. All non-synonymous SNPs were genotyped as were SNPs across each gene with maximum distance between SNPs of 6 kb. Case-control analyses revealed modest evidence (0.01 < P < 0.05) for association between a single variant in PLCB2 and two variants in PLA2G4B. However, association was not confirmed in the family based sample. As the latter sample has previously generated replicated significant evidence for association between RD and markers/haplotypes surrounding D15S944, it should have sufficient power to detect association to variants in susceptibility gene itself. We conclude that neither gene accounts for the association signal we previously observed. As these are the only clear cut functional candidate genes in the region, identification of the putative susceptibility locus for RD on 15q will require more methodical non-hypothesis driven positional cloning approaches.
Collapse
Affiliation(s)
- D W Morris
- Department of Psychological Medicine, University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom
| | | | | | | | | | | | | | | |
Collapse
|
47
|
Tzenova J, Kaplan BJ, Petryshen TL, Field LL. Confirmation of a dyslexia susceptibility locus on chromosome 1p34-p36 in a set of 100 Canadian families. Am J Med Genet B Neuropsychiatr Genet 2004; 127B:117-24. [PMID: 15108193 DOI: 10.1002/ajmg.b.20139] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Dyslexia is a common and genetically complex trait that manifests primarily as a reading disability independent of general intelligence and educational opportunity. Strong evidence for a dyslexia susceptibility locus on chromosome 1p34-p36 (near marker D1S199) was recently reported, and an earlier study found suggestive evidence for linkage to the same region. We tested for the presence of a dyslexia gene in this region in a sample of 100 Canadian families using both qualitative and quantitative definitions of the phenotype. Using a qualitative definition of dyslexia (affected, unaffected, or uncertain), the largest multipoint Genehunter Maximum LOD-Score (MLS) in 100 core nuclear families was 3.65 at D1S507, distal to D1S199. Quantitative trait locus (QTL) linkage analysis was performed for four measures of dyslexia (phonological awareness, phonological coding, spelling, and rapid automatized naming speed) employing the variance components approach implemented in Genehunter. Using a model with QTL additive and dominance variance and polygenic additive variance, the multipoint LOD scores maximized proximal to D1S199 (between D1S552 and D1S1622), with peaks of 4.01 for spelling and 1.65 for phonological coding (corresponding LOD scores under 1 degree of freedom were 3.30 and 1.13, respectively). In conclusion, our study confirms and strengthens recent findings of a dyslexia susceptibility gene on chromosome 1p34-p36 (now designated DYX8).
Collapse
Affiliation(s)
- Jordana Tzenova
- Department of Medical Genetics, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | | | | | | |
Collapse
|
48
|
Abstract
Developmental dyslexia, or specific reading disability, is a disorder in which children with normal intelligence and sensory abilities show learning deficits for reading. Substantial evidence has established its biological origin and the preponderance of phonological disorders even though important phenotypic variability and comorbidity have been recorded. Diverse theories have been proposed to account for the cognitive and neurological aspects of dyslexia. Findings of genetic studies show that different loci affect specific reading disability although a direct relation has not been established between symptoms and a given genomic locus. In both children and adults with dyslexia, results of neuroimaging studies suggest defective activity and abnormal connectivity between regions crucial for language functions--eg, the left fusiform gyrus for reading--and changes in brain activity associated with performance improvement after various remedial interventions.
Collapse
|
49
|
Loo SK, Fisher SE, Francks C, Ogdie MN, MacPhie IL, Yang M, McCracken JT, McGough JJ, Nelson SF, Monaco AP, Smalley SL. Genome-wide scan of reading ability in affected sibling pairs with attention-deficit/hyperactivity disorder: unique and shared genetic effects. Mol Psychiatry 2004; 9:485-93. [PMID: 14625563 DOI: 10.1038/sj.mp.4001450] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Attention-deficit/hyperactivity disorder (ADHD) and reading disability (RD) are common highly heritable disorders of childhood, which frequently co-occur. Data from twin and family studies suggest that this overlap is, in part, due to shared genetic underpinnings. Here, we report the first genome-wide linkage analysis of measures of reading ability in children with ADHD, using a sample of 233 affected sibling pairs who previously participated in a genome-wide scan for susceptibility loci in ADHD. Quantitative trait locus (QTL) analysis of a composite reading factor defined from three highly correlated reading measures identified suggestive linkage (multipoint maximum lod score, MLS>2.2) in four chromosomal regions. Two regions (16p, 17q) overlap those implicated by our previous genome-wide scan for ADHD in the same sample: one region (2p) provides replication for an RD susceptibility locus, and one region (10q) falls approximately 35 cM from a modestly highlighted region in an independent genome-wide scan of siblings with ADHD. Investigation of an individual reading measure of Reading Recognition supported linkage to putative RD susceptibility regions on chromosome 8p (MLS=2.4) and 15q (MLS=1.38). Thus, the data support the existence of genetic factors that have pleiotropic effects on ADHD and reading ability--as suggested by shared linkages on 16p, 17q and possibly 10q--but also those that appear to be unique to reading--as indicated by linkages on 2p, 8p and 15q that coincide with those previously found in studies of RD. Our study also suggests that reading measures may represent useful phenotypes in ADHD research. The eventual identification of genes underlying these unique and shared linkages may increase our understanding of ADHD, RD and the relationship between the two.
Collapse
Affiliation(s)
- S K Loo
- Center for Neurobehavioral Genetics, University of California, Los Angeles, USA.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
50
|
Abstract
We are rapidly approaching the postgenomic era in which we will know all of the 3 billion DNA bases in the human genome sequence and all of the variations in the genome sequence that are ultimately responsible for genetic influence on behavior. These ongoing advances and new techniques will make it easier to identify genes associated with psychopathology. Progress in identifying such genes has been slower than some experts expected, probably because many genes are involved for each phenotype, which means the effect of any one gene is small. Nonetheless, replicated linkages and associations are being found, for example, for dementia, reading disability, and hyperactivity. The future of genetic research lies in finding out how genes work (functional genomics). It is important for the future of psychology that pathways between genes and behavior be examined at the top-down psychological level of analysis (behavioral genomics), as well as at the bottom-up molecular biological level of cells or the neuroscience level of the brain. DNA will revolutionize psychological research and treatment during the coming decades.
Collapse
Affiliation(s)
- Robert Plomin
- Social, Genetic and Developmental Psychiatry Research Centre, Institute of Psychiatry, King's College London, DeCrespigny Park, London SE5 8AF, UK.
| | | |
Collapse
|