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Elhawary NA, AlJahdali IA, Abumansour IS, Azher ZA, Falemban AH, Madani WM, Alosaimi W, Alghamdi G, Sindi IA. Phenotypic variability to medication management: an update on fragile X syndrome. Hum Genomics 2023; 17:60. [PMID: 37420260 DOI: 10.1186/s40246-023-00507-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 07/03/2023] [Indexed: 07/09/2023] Open
Abstract
This review discusses the discovery, epidemiology, pathophysiology, genetic etiology, molecular diagnosis, and medication-based management of fragile X syndrome (FXS). It also highlights the syndrome's variable expressivity and common comorbid and overlapping conditions. FXS is an X-linked dominant disorder associated with a wide spectrum of clinical features, including but not limited to intellectual disability, autism spectrum disorder, language deficits, macroorchidism, seizures, and anxiety. Its prevalence in the general population is approximately 1 in 5000-7000 men and 1 in 4000-6000 women worldwide. FXS is associated with the fragile X messenger ribonucleoprotein 1 (FMR1) gene located at locus Xq27.3 and encodes the fragile X messenger ribonucleoprotein (FMRP). Most individuals with FXS have an FMR1 allele with > 200 CGG repeats (full mutation) and hypermethylation of the CpG island proximal to the repeats, which silences the gene's promoter. Some individuals have mosaicism in the size of the CGG repeats or in hypermethylation of the CpG island, both produce some FMRP and give rise to milder cognitive and behavioral deficits than in non-mosaic individuals with FXS. As in several monogenic disorders, modifier genes influence the penetrance of FMR1 mutations and FXS's variable expressivity by regulating the pathophysiological mechanisms related to the syndrome's behavioral features. Although there is no cure for FXS, prenatal molecular diagnostic testing is recommended to facilitate early diagnosis. Pharmacologic agents can reduce some behavioral features of FXS, and researchers are investigating whether gene editing can be used to demethylate the FMR1 promoter region to improve patient outcomes. Moreover, clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 and developed nuclease defective Cas9 (dCas9) strategies have promised options of genome editing in gain-of-function mutations to rewrite new genetic information into a specified DNA site, are also being studied.
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Affiliation(s)
- Nasser A Elhawary
- Department of Medical Genetics, College of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia.
| | - Imad A AlJahdali
- Department of Community Medicine, College of Medicine, Umm Al-Qura University, Mecca, Saudi Arabia
| | - Iman S Abumansour
- Department of Medical Genetics, College of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Zohor A Azher
- Department of Medical Genetics, College of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Alaa H Falemban
- Department of Pharmacology and Toxicology, College of Medicine, Umm Al-Qura University, Mecca, 24382, Saudi Arabia
| | - Wefaq M Madani
- Department of Hematology and Immunology, Faculty of Medicine, Umm Al-Qura University, Mecca, Saudi Arabia
| | - Wafaa Alosaimi
- Department of Hematology, Maternity and Children Hospital, Mecca, Saudi Arabia
| | - Ghydda Alghamdi
- Department of Medical Genetics, College of Medicine, Umm Al-Qura University, Mecca, 21955, Saudi Arabia
| | - Ikhlas A Sindi
- Department of Biology, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia
- Preparatory Year Program, Batterjee Medical College, Jeddah, 21442, Saudi Arabia
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2
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Constantin L. The Role of MicroRNAs in Cerebellar Development and Autism Spectrum Disorder During Embryogenesis. Mol Neurobiol 2016; 54:6944-6959. [PMID: 27774573 DOI: 10.1007/s12035-016-0220-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/12/2016] [Indexed: 02/03/2023]
Abstract
MicroRNAs (miRNAs) are a class of small non-coding RNA molecules with wide-ranging and subtle effects on protein production. Their activity during the development of the cerebellum provides a valuable exemplar of how non-coding molecules may assist the development and function of the central nervous system and drive neurodevelopmental disorders. Three distinct aspects of miRNA contribution to early cerebellar development will here be reviewed. Aspects are the establishment of the cerebellar anlage, the generation and maturation of at least two principal cell types of the developing cerebellar microcircuit, and the etiology and early progression of autism spectrum disorder. It will be argued here that the autism spectrum is an adept model to explore miRNA impact on the cognitive and affective processes that descend from the developing cerebellum.
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Affiliation(s)
- Lena Constantin
- School of Biomedical Sciences, The University of Queensland, St Lucia, QLD, 4072, Australia. .,Institute for Molecular Bioscience, The University of Queensland, St Lucia, QLD, 4072, Australia.
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Multiple recurrent de novo CNVs, including duplications of the 7q11.23 Williams syndrome region, are strongly associated with autism. Neuron 2011; 70:863-85. [PMID: 21658581 DOI: 10.1016/j.neuron.2011.05.002] [Citation(s) in RCA: 887] [Impact Index Per Article: 68.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/18/2011] [Indexed: 11/22/2022]
Abstract
We have undertaken a genome-wide analysis of rare copy-number variation (CNV) in 1124 autism spectrum disorder (ASD) families, each comprised of a single proband, unaffected parents, and, in most kindreds, an unaffected sibling. We find significant association of ASD with de novo duplications of 7q11.23, where the reciprocal deletion causes Williams-Beuren syndrome, characterized by a highly social personality. We identify rare recurrent de novo CNVs at five additional regions, including 16p13.2 (encompassing genes USP7 and C16orf72) and Cadherin 13, and implement a rigorous approach to evaluating the statistical significance of these observations. Overall, large de novo CNVs, particularly those encompassing multiple genes, confer substantial risks (OR = 5.6; CI = 2.6-12.0, p = 2.4 × 10(-7)). We estimate there are 130-234 ASD-related CNV regions in the human genome and present compelling evidence, based on cumulative data, for association of rare de novo events at 7q11.23, 15q11.2-13.1, 16p11.2, and Neurexin 1.
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Guruju MR, Lavanya K, Thelma B, Sujatha M, OmSai V, Nagarathna V, Amarjyothi P, Jyothi A, Anandaraj M. Assessment of a clinical checklist in the diagnosis of fragile X syndrome in India. J Clin Neurosci 2009; 16:1305-10. [DOI: 10.1016/j.jocn.2008.12.018] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 12/21/2008] [Accepted: 12/21/2008] [Indexed: 11/28/2022]
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Abu-Elneel K, Liu T, Gazzaniga FS, Nishimura Y, Wall DP, Geschwind DH, Lao K, Kosik KS. Heterogeneous dysregulation of microRNAs across the autism spectrum. Neurogenetics 2008; 9:153-61. [PMID: 18563458 DOI: 10.1007/s10048-008-0133-5] [Citation(s) in RCA: 195] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2008] [Accepted: 04/24/2008] [Indexed: 11/24/2022]
Abstract
microRNAs (miRNAs) are approximately 21 nt transcripts capable of regulating the expression of many mRNAs and are abundant in the brain. miRNAs have a role in several complex diseases including cancer as well as some neurological diseases such as Tourette's syndrome and Fragile x syndrome. As a genetically complex disease, dysregulation of miRNA expression might be a feature of autism spectrum disorders (ASDs). Using multiplex quantitative polymerase chain reaction (PCR), we compared the expression of 466 human miRNAs from postmortem cerebellar cortex tissue of individuals with ASD (n = 13) and a control set of non-autistic cerebellar samples (n = 13). While most miRNAs levels showed little variation across all samples suggesting that autism does not induce global dysfunction of miRNA expression, some miRNAs among the autistic samples were expressed at significantly different levels compared to the mean control value. Twenty-eight miRNAs were expressed at significantly different levels compared to the non-autism control set in at least one of the autism samples. To validate the finding, we reversed the analysis and compared each non-autism control to a single mean value for each miRNA across all autism cases. In this analysis, the number of dysregulated miRNAs fell from 28 to 9 miRNAs. Among the predicted targets of dysregulated miRNAs are genes that are known genetic causes of autism such Neurexin and SHANK3. This study finds that altered miRNA expression levels are observed in postmortem cerebellar cortex from autism patients, a finding which suggests that dysregulation of miRNAs may contribute to autism spectrum phenotype.
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Affiliation(s)
- Kawther Abu-Elneel
- Neuroscience Research Institute, Department of Molecular Cellular and Developmental Biology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
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Degirmenci B, Miral S, Kaya GC, Iyilikçi L, Arslan G, Baykara A, Evren I, Durak H. Technetium-99m HMPAO brain SPECT in autistic children and their families. Psychiatry Res 2008; 162:236-43. [PMID: 18302983 DOI: 10.1016/j.pscychresns.2004.12.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2004] [Revised: 11/24/2004] [Accepted: 12/20/2004] [Indexed: 11/17/2022]
Abstract
The purpose of the study was to investigate perfusion patterns in autistic children (AC) and their families. Ten AC (9 boys, 1 girl; mean age: 6.9+/-1.7 years) with autistic disorder defined by DSM-III-R criteria, five age-matched children (3 boys, 2 girls) as a control group, and the immediate family members of eight AC (8 mothers, 8 fathers, 7 siblings; mean ages: 39+/-4 years, 36+/-5 years and 13+/-5 years, respectively) were included in the study. Age- and sex-matched control groups for both the parents and the siblings were also included in the study. Brain perfusion images were obtained 1 h after the intravenous injection of an adjusted dose of Tc-99m HMPAO to children and the adults. Visual and semiquantitative evaluations were performed. Hypoperfusion was seen in the right posterior parietal cortex in three AC, in bilateral parietal cortex in one AC, bilateral frontal cortex in two AC, left parietal and temporal cortex in one AC, and right parietal and temporal cortex in one AC. Asymmetric perfusion was observed in the caudate nucleus in four AC. In semiquantitative analyses, statistically significant hypoperfusion was found in the right inferior and superior frontal, left superior frontal, right parietal, right mesial temporal and right caudate nucleus. In parents of AC, significant hypoperfusion was noted in the right parietal and bilateral inferior frontal cortex. In siblings of AC, perfusion in the right frontal cortex, right nucleus caudate and left parietal cortex was significantly decreased. This preliminary study suggests the existence of regional brain perfusion alterations in frontal, temporal, and parietal cortex and in caudate nucleus in AC and in their first-degree family members.
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Affiliation(s)
- Berna Degirmenci
- Department of Nuclear Medicine, Dokuz Eylul University Medical School, 35340, Inciralti, Izmir, Turkey.
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Zafeiriou DI, Ververi A, Vargiami E. Childhood autism and associated comorbidities. Brain Dev 2007; 29:257-72. [PMID: 17084999 DOI: 10.1016/j.braindev.2006.09.003] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2006] [Revised: 08/25/2006] [Accepted: 09/06/2006] [Indexed: 12/11/2022]
Abstract
Autism is a heterogeneous neurodevelopmental disorder with a variety of different etiologies, but with a heritability estimate of more than 90%. Although the strong correlation between autism and genetic factors has been long established, the exact genetic background of autism is still unclear. This review refers to all the genetic syndromes that have been described in children with pervasive developmental disorders (tuberous sclerosis, fragile X, Down, neurofibromatosis, Angelman, Prader-Willi, Gilles de la Tourette, Williams, etc.). Issues covered include prevalence and main characteristics of each syndrome, as well as the possible base of its association with autism in terms of contribution to the current knowledge on the etiology and genetic base of pervasive developmental disorders.
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Affiliation(s)
- Dimitrios I Zafeiriou
- 1st Department of Pediatrics, Aristotle University of Thessaloniki, Egnatia St. 106, 54622 Thessaloniki, Greece.
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Abstract
Twin and family studies in autistic disorders (AD) have elucidated a high heritability of the narrow and broad phenotype of AD. In this review on the genetics of AD, we will initially delineate the phenotype of AD and discuss aspects of differential diagnosis, which are particularly relevant with regard to the genetics of autism. Cytogenetic and molecular genetic studies will be presented in detail, and the possibly involved aetiopathological pathways will be described. Implications of the different genetic findings for genetic counselling will be mentioned.
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Affiliation(s)
- C M Freitag
- Department of Child and Adolescent Psychiatry, Saarland University Hospital, Homburg, Germany.
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Yang MS, Gill M. A review of gene linkage, association and expression studies in autism and an assessment of convergent evidence. Int J Dev Neurosci 2006; 25:69-85. [PMID: 17236739 DOI: 10.1016/j.ijdevneu.2006.12.002] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2006] [Revised: 12/05/2006] [Accepted: 12/06/2006] [Indexed: 01/01/2023] Open
Abstract
Autism is a neurodevelopmental disorder with high heritability and a likely complex genetic architecture. Much genetic evidence has accumulated in the last 20 years but no gene has been unequivocally identified as containing risk variants for autism. In this article we review the past and present literature on neuro-pathological, genetic linkage, genetic association, and gene expression studies in this disorder. We sought convergent evidence to support particular genes or chromosomal regions that might be likely to contain risk DNA variants. The convergent evidence from these studies supports the current hypotheses that there are multiple genetic loci predisposing to autism, and that genes involved in neurodevelopment are especially important for future genetic studies. Convergent evidence suggests the chromosome regions 7q21.2-q36.2, 16p12.1-p13.3, 6q14.3-q23.2, 2q24.1-q33.1, 17q11.1-q21.2, 1q21-q44 and 3q21.3-q29, are likely to contain risk genes for autism. Taken together with results from neuro-pathological studies, genes involved in brain development located at the above regions should be prioritized for future genetic research.
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Affiliation(s)
- Mao Sheng Yang
- Department of Psychiatry, Institute of Molecular Medicine, Trinity Centre for Health Sciences, Trinity College Dublin, St. James's Hospital, Dublin 8, Ireland.
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Steiner CE, Guerreiro MM, Marques-de-Faria AP, Lopes-Cendes I. Laboratorial diagnosis of fragile-X syndrome: experience in a sample of individuals with pervasive developmental disorders. ARQUIVOS DE NEURO-PSIQUIATRIA 2005; 63:564-70. [PMID: 16172701 DOI: 10.1590/s0004-282x2005000400002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Fragile X syndrome is a frequent genetic disease associated to developmental disorders, including learning disability, mental retardation, behavioral problems and pervasive developmental disorders (autism and related conditions). We studied a sample of 82 individuals (69 males and 13 females) presenting with pervasive developmental disorders using three techniques for the diagnosis of fragile X syndrome (FXS). Cytogenetic analysis detected the fragile site in four males, but only one showed a consistent positive rate. Molecular study based on the PCR technique was inconclusive for most females (92.3%), which where latter submitted to Southern blotting analysis, and for one male (1.4%), excluding the FRAXA mutation in the remaining male individuals (98.6%). Molecular tests using the Southern blotting technique confirmed only one positive case (1.2%) in a male subject. These results showed that Southern blotting analysis of the FRAXA mutation has the best sensitivity and specificity for the diagnosis of FXS but also validated the PCR technique as a confinable screening test.
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Affiliation(s)
- Carlos Eduardo Steiner
- Departamento de Genética Médica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brazil
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11
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Abstract
Early diagnosis of language disorders and autism is important, and early intervention for autism and some language disorders makes a difference. Developmental surveillance of children to detect these disorders should be a routine part of medical practice. The persistence and pervasiveness of communication and socialising deficits differentiate children with autism from those with specific developmental language disorders. Hearing and vision assessment is essential in any communication disorder. Interventions, targeted to identified areas of need, should encompass communication enhancement, behavioural therapy, educational modification, parent education and family support. Pharmacological interventions have an important but discrete role in autism, but there are no magic bullets. It is important to remember that the normal childhood illnesses occur in children with developmental disorders. Parents should be directed to reliable websites on the Internet, and given information and books to read as well as phone numbers of relevant services (eg, autism associations). There is a need for increased government financial support for early intervention programs.
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Affiliation(s)
- John Wray
- c/o State Child Development Centre, Women's and Children's Health Service, West Perth, WA, Australia.
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12
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Reddy KS. Cytogenetic abnormalities and fragile-X syndrome in Autism Spectrum Disorder. BMC MEDICAL GENETICS 2005; 6:3. [PMID: 15655077 PMCID: PMC548305 DOI: 10.1186/1471-2350-6-3] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/08/2004] [Accepted: 01/18/2005] [Indexed: 11/15/2022]
Abstract
BACKGROUND Autism is a behavioral disorder with impaired social interaction, communication, and repetitive and stereotypic behaviors. About 5-10 % of individuals with autism have 'secondary' autism in which an environmental agent, chromosome abnormality, or single gene disorder can be identified. Ninety percent have idiopathic autism and a major gene has not yet been identified. We have assessed the incidence of chromosome abnormalities and Fragile X syndrome in a population of autistic patients referred to our laboratory. METHODS Data was analyzed from 433 patients with autistic traits tested using chromosome analysis and/or fluorescence in situ hybridization (FISH) and/or molecular testing for fragile X syndrome by Southern and PCR methods. RESULTS The median age was 4 years. Sex ratio was 4.5 males to 1 female [354:79]. A chromosome (cs) abnormality was found in 14/421 [3.33 %] cases. The aberrations were: 4/14 [28%] supernumerary markers; 4/14 [28%] deletions; 1/14 [7%] duplication; 3/14 [21%] inversions; 2/14 [14%] translocations. FISH was performed on 23 cases for reasons other than to characterize a previously identified cytogenetic abnormality. All 23 cases were negative. Fragile-X testing by Southern blots and PCR analysis found 7/316 [2.2 %] with an abnormal result. The mutations detected were: a full mutation (fM) and abnormal methylation in 3 [43 %], mosaic mutations with partial methylation of variable clinical significance in 3 [43%] and a permutation carrier [14%]. The frequency of chromosome and fragile-X abnormalities appears to be within the range in reported surveys (cs 4.8-1.7%, FRAX 2-4%). Limitations of our retrospective study include paucity of behavioral diagnostic information, and a specific clinical criterion for testing. CONCLUSIONS Twenty-eight percent of chromosome abnormalities detected in our study were subtle; therefore a high resolution cytogenetic study with a scrutiny of 15q11.2q13, 2q37 and Xp23.3 region should be standard practice when the indication is autism. The higher incidence of mosaic fragile-X mutations with partial methylation compared to FRAXA positive population [50% vs 15-40%] suggests that faint bands and variations in the Southern band pattern may occur in autistic patients.
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Spence SJ, Sharifi P, Wiznitzer M. Autism spectrum disorder: screening, diagnosis, and medical evaluation. Semin Pediatr Neurol 2004; 11:186-95. [PMID: 15575413 DOI: 10.1016/j.spen.2004.07.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Autism spectrum disorder (ASD) are a group of behaviorally defined neurodevelopmental disabilities with core deficits in socialization, communication, and behavior, although the presentation can be extremely variable. This article describes the core deficits in ASD, as well as the differential diagnosis and the more commonly associated comorbid disorders. The importance of early diagnosis is emphasized, and screening and assessment tools are reviewed. Finally, the role of the pediatric neurologist is discussed with regard to specific components of the evaluation, including history, physical examination, and ancillary testing.
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Affiliation(s)
- Sarah J Spence
- Department of Psychiatry, UCLA Center for Autism Research and Treatment, CA, USA
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Yonan AL, Palmer AA, Smith KC, Feldman I, Lee HK, Yonan JM, Fischer SG, Pavlidis P, Gilliam TC. Bioinformatic analysis of autism positional candidate genes using biological databases and computational gene network prediction. GENES BRAIN AND BEHAVIOR 2003; 2:303-20. [PMID: 14606695 DOI: 10.1034/j.1601-183x.2003.00041.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Common genetic disorders are believed to arise from the combined effects of multiple inherited genetic variants acting in concert with environmental factors, such that any given DNA sequence variant may have only a marginal effect on disease outcome. As a consequence, the correlation between disease status and any given DNA marker allele in a genomewide linkage study tends to be relatively weak and the implicated regions typically encompass hundreds of positional candidate genes. Therefore, new strategies are needed to parse relatively large sets of 'positional' candidate genes in search of actual disease-related gene variants. Here we use biological databases to identify 383 positional candidate genes predicted by genomewide genetic linkage analysis of a large set of families, each with two or more members diagnosed with autism, or autism spectrum disorder (ASD). Next, we seek to identify a subset of biologically meaningful, high priority candidates. The strategy is to select autism candidate genes based on prior genetic evidence from the allelic association literature to query the known transcripts within the 1-LOD (logarithm of the odds) support interval for each region. We use recently developed bioinformatic programs that automatically search the biological literature to predict pathways of interacting genes (PATHWAYASSIST and GENEWAYS). To identify gene regulatory networks, we search for coexpression between candidate genes and positional candidates. The studies are intended both to inform studies of autism, and to illustrate and explore the increasing potential of bioinformatic approaches as a compliment to linkage analysis.
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Affiliation(s)
- A L Yonan
- Columbia Genome Center, Columbia University, New York, NY 10032, USA
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Bonora E, Beyer KS, Lamb JA, Parr JR, Klauck SM, Benner A, Paolucci M, Abbott A, Ragoussis I, Poustka A, Bailey AJ, Monaco AP. Analysis of reelin as a candidate gene for autism. Mol Psychiatry 2003; 8:885-92. [PMID: 14515139 DOI: 10.1038/sj.mp.4001310] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetic studies indicate that chromosome 7q is likely to contain an autism susceptibility locus (AUTS1). We have followed a positional candidate gene approach to identify relevant gene(s) and report here the analysis of reelin (RELN), a gene located under our peak of linkage. Screening RELN for DNA changes identified novel missense variants absent in a large control group; however, the low frequency of these mutations does not explain the relatively strong linkage results on 7q. Furthermore, analysis of a previously reported triplet repeat polymorphism and intragenic single nucleotide polymorphisms, using the transmission disequilibrium test, provided no evidence for association with autism in IMGSAC and German singleton families. The analysis of RELN suggests that it probably does not play a major role in autism aetiology, although further analysis of several missense mutations is warranted in additional affected individuals.
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Affiliation(s)
- E Bonora
- The Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, UK
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Korvatska E, Van de Water J, Anders TF, Gershwin ME. Genetic and immunologic considerations in autism. Neurobiol Dis 2002; 9:107-25. [PMID: 11895365 DOI: 10.1006/nbdi.2002.0479] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
According to recent epidemiological surveys, autistic spectrum disorders have become recognized as common childhood psychopathologies. These life-lasting conditions demonstrate a strong genetic determinant consistent with a polygenic mode of inheritance for which several autism susceptibility regions have been identified. Parallel evidence of immune abnormalities in autistic patients argues for an implication of the immune system in pathogenesis. This review summarizes advances in the molecular genetics of autism, as well as recently emerging concerns addressing the disease incidence and triggering factors. The neurochemical and immunologic findings are analyzed in the context of a neuroimmune hypothesis for autism. Studies of disorders with established neuroimmune nature indicate multiple pathways of the pathogenesis; herein, we discuss evidence of similar phenomena in autism.
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Affiliation(s)
- Elena Korvatska
- Division of Rheumatology, Allergy, and Clinical Immunology, University of California at Davis, Davis, California 95616, USA
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Weidenheim KM, Goodman L, Dickson DW, Gillberg C, Råstam M, Rapin I. Etiology and pathophysiology of autistic behavior: clues from two cases with an unusual variant of neuroaxonal dystrophy. J Child Neurol 2001; 16:809-19. [PMID: 11732766 DOI: 10.1177/08830738010160110601] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Two unrelated individuals with autistic behavior had numerous swollen axon terminals (spheroids) located in specific brain regions relevant to their behavioral symptoms. Spheroids are characteristic of neuroaxonal dystrophy, but the clinical profile and anatomic distribution of the lesions in these two patients differed from those of previously described patients with neuroaxonal dystrophy. Spheroids were numerous in the sensory nuclei of the spinal cord and medulla, specific nuclei and the reticular formation of the brainstem tegmentum, hypothalamus, anterior and dorsomedial thalamus, hippocampus, and cingulate and orbitofrontal cortices. Spheroids were sparse in the primary and association cortices and basal ganglia and absent in the hemispheric white matter. Cerebellar atrophy was present in both cases but associated with spheroids in only one case. These cases represent a new variant of neuroaxonal dystrophy in which behavioral symptoms characteristic of autism dominated the clinical picture. Neuroaxonal dystrophy should be included in the list of diseases that may be found in persons with autism.
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Affiliation(s)
- K M Weidenheim
- Department of Pathology (Neuropathology), Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, New York 10467, USA.
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Abstract
OBJECTIVE To review systematically the empirical evidence for the involvement of genetic risk factors in infantile autism. METHOD We aimed at including all relevant papers written in English. We conducted a Medline search in September 2000. In addition we searched the reference lists of related papers. RESULTS A relatively small number of reports including family and twin studies, comorbidity, cytogenetic and molecular genetic studies were reviewed. CONCLUSION As well family, twin, cytogenetic and molecular genetic studies supported the importance of genetic risk factors in infantile autism. In most individual cases probably at least a few gene variants simultaneously determine the genetic risk. Presently the most interesting chromosome regions concerning the aetiology of autism are chromosomes 7q31-35, 15q11-13 and 16p13.3 which have been suggested by different lines of genetic research.
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Affiliation(s)
- M Lauritsen
- Department of Psychiatric Demography, Institute for Basic Psychiatric Research, Psychiatric Hospital in Aarhus, Aarhus University Hospital, DK-8240 Risskov, Denmark
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Yirmiya N, Pilowsky T, Nemanov L, Arbelle S, Feinsilver T, Fried I, Ebstein RP. Evidence for an association with the serotonin transporter promoter region polymorphism and autism. AMERICAN JOURNAL OF MEDICAL GENETICS 2001; 105:381-6. [PMID: 11378854 DOI: 10.1002/ajmg.1365] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
We have examined three functional polymorphisms, serotonin transporter promoter region polymorphism (5-HTTLPR), dopamine D4 exon III repeat region (DRD4), and catechol-O-methyltransferase (COMT), in a small family-based design toward identifying candidate genes that confer risk for autism. A significant excess of the long/long 5-HTTLPR genotype was observed (likelihood ratio = 7.18; P = 0.027; 2 df; n = 33 families) as well as preferential transmission of the long allele of the 5-HTTLPR (TDT chi-square = 5.44; P<0.025; 1 df). No association was observed between the COMT and DRD4 polymorphisms and autism in this sample. Some previous studies have observed linkage between autism and the 5-HTTLPR polymorphism and the current results are similar to those first reported by Klauck et al. [1997: Hum Genet 100:224-229; 1997: Hum Mol Genet 6:2233-2238]. Additionally, elevated serotonin levels have been consistently found in 30%-50% of autistic patients and may represent a marker for familial autism. Hyperserotonemia in autism appears to be due to enhanced 5-HT uptake, as free 5-HT levels are normal and the current report of an excess of the long/long 5-HTTLPR genotype in autism could provide a partial molecular explanation for high platelet serotonin content in autism.
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Affiliation(s)
- N Yirmiya
- Hebrew University of Jerusalem, Jerusalem, Israel
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Steele MM, Al-Adeimi M, Siu VM, Fan YS. Brief report: A case of autism with interstitial deletion of chromosome 13. J Autism Dev Disord 2001; 31:231-4. [PMID: 11450821 DOI: 10.1023/a:1010759401344] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
A case of an 18-year-old male who meets the DSM-IV criteria for autistic disorder and borderline intelligence is described. Cytogenetic evaluation revealed a karyotype of 46, XY, del(13)(q14q22). The relevance of this case to the etiology of autism is discussed.
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Affiliation(s)
- M M Steele
- Department of Psychiatry, University of Western Ontario, London Health Sciences Centre, Canada.
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Bennett CN, Horrobin DF. Gene targets related to phospholipid and fatty acid metabolism in schizophrenia and other psychiatric disorders: an update. Prostaglandins Leukot Essent Fatty Acids 2000; 63:47-59. [PMID: 10970713 DOI: 10.1054/plef.2000.0191] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Phospholipids make up about 60% of the brain's dry weight and play key roles in many brain signal tranduction mechanisms. A recent review(1)identified the increasing evidence that abnormal phospholipid and related fatty acid metabolism may contribute to illnesses such as schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder. This current paper reviews the main pathways of phospholipid metabolism, emphasizing the role of phospholipases of the A2 in signal tranduction processes. It also updates the chromosomal locations of regions likely to be involved in these disorders, and relates these to the known locations of genes directly or indirectly involved in phospholipid and fatty acid metabolism.
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Iqbal MA, Sakati N, Nester M, Ozand P. Cytogenetic diagnosis of fragile X syndrome: study of 305 suspected cases in Saudi Arabia. Ann Saudi Med 2000; 20:214-7. [PMID: 17322660 DOI: 10.5144/0256-4947.2000.214] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Fragile X syndrome is the most common cause of inherited mental retardation. Patients with fragile X syndrome show variable mental disability, typical long and narrow facial appearance with large ears and prominent fontanelle and frequent macro-orchidism. It is generally associated with a fragile site at Xq 27.3, which can be observed in the metaphase chromosome following selective culture conditions. At the molecular level, the fragile X syndrome is associated with an amplification of CGG repeat sequence of the FMR1 gene. The prevalence estimates are reported as one per 1500 males and one per 2500 females. Estimated prevalence rates of fragile X syndrome in different ethnic groups range from 0.4-0.8 per 1000 in males and 0.2-0.6 per 1000 in females. In this study, we have determined the frequency of fragile X-positive cases in 305 preselected patients. MATERIALS AND METHODS Three hundred and five Saudi patients with mental retardation/developmental delay/clinical suspicion of fragile X syndrome were screened for fragile X chromosome by cytogenetic methods. The majority of patients (95.59%) screened were under the age of 20 years. RESULTS Two hundred and ninety-nine patients (98.03%) were in the category of mild to moderate mental retardation. Twenty-four males (7.86%) and two females (0.65%) were found to express fragile X site at q27.3. The frequency of fragile X-positive cells in males ranged between 7% and 58% (mean 26+/-13.11), while in the females it was between 14% and 21% (mean 12.5+/-35), respectively. CONCLUSION The frequency of fragile X positive cases found in this study is similar to other reports of fragile X syndrome in preselected patients.
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Affiliation(s)
- M A Iqbal
- Department of Pathology, Section of Cytogenetics/Molecular Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
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Stodgell CJ, Ingram JL, Hyman SL. The role of candidate genes in unraveling the genetics of autism. AUTISM : THE INTERNATIONAL JOURNAL OF RESEARCH AND PRACTICE 2000. [DOI: 10.1016/s0074-7750(00)80006-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Filipek PA, Accardo PJ, Baranek GT, Cook EH, Dawson G, Gordon B, Gravel JS, Johnson CP, Kallen RJ, Levy SE, Minshew NJ, Ozonoff S, Prizant BM, Rapin I, Rogers SJ, Stone WL, Teplin S, Tuchman RF, Volkmar FR. The screening and diagnosis of autistic spectrum disorders. J Autism Dev Disord 1999; 29:439-84. [PMID: 10638459 DOI: 10.1023/a:1021943802493] [Citation(s) in RCA: 462] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Child Neurology Society and American Academy of Neurology recently proposed to formulate Practice Parameters for the Diagnosis and Evaluation of Autism for their memberships. This endeavor was expanded to include representatives from nine professional organizations and four parent organizations, with liaisons from the National Institutes of Health. This document was written by this multidisciplinary Consensus Panel after systematic analysis of over 2,500 relevant scientific articles in the literature. The Panel concluded that appropriate diagnosis of autism requires a dual-level approach: (a) routine developmental surveillance, and (b) diagnosis and evaluation of autism. Specific detailed recommendations for each level have been established in this document, which are intended to improve the rate of early suspicion and diagnosis of, and therefore early intervention for, autism.
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Horrobin DF, Bennett CN. New gene targets related to schizophrenia and other psychiatric disorders: enzymes, binding proteins and transport proteins involved in phospholipid and fatty acid metabolism. Prostaglandins Leukot Essent Fatty Acids 1999; 60:141-67. [PMID: 10359017 DOI: 10.1054/plef.1999.0027] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Phospholipids make up about 60% of the brain's dry weight. In spite of this, phospholipid metabolism has received relatively little attention from those seeking genetic factors involved in psychiatric and neurological disorders. However, there is now increasing evidence from many quarters that abnormal phospholipid and related fatty acid metabolism may contribute to illnesses such as schizophrenia, bipolar disorder, depression and attention deficit hyperactivity disorder. To date the possible specific proteins and genes involved have been relatively ill-defined. This paper reviews the main pathways of phospholipid metabolism, emphasizing the roles of phospholipases of the A2 and C series in signal transduction processes. It identifies some likely protein candidates for involvement in psychiatric and neurological disorders. It also reviews the chromosomal locations of regions likely to be involved in these disorders, and relates these to the known locations of genes directly or indirectly involved in phospholipid and fatty acid metabolism.
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Affiliation(s)
- D F Horrobin
- Laxdale Research, Kings Park House, Laurelhill Business Park, Stirling, UK
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