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Wiśniowiecka-Kowalnik B, Nowakowska BA. Genetics and epigenetics of autism spectrum disorder-current evidence in the field. J Appl Genet 2019; 60:37-47. [PMID: 30627967 PMCID: PMC6373410 DOI: 10.1007/s13353-018-00480-w] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 12/14/2018] [Accepted: 12/18/2018] [Indexed: 12/26/2022]
Abstract
Autism spectrum disorders (ASD) is a heterogenous group of neurodevelopmental disorders characterized by problems in social interaction and communication as well as the presence of repetitive and stereotyped behavior. It is estimated that the prevalence of ASD is 1–2% in the general population with the average male to female ratio 4–5:1. Although the causes of ASD remain largely unknown, the studies have shown that both genetic and environmental factors play an important role in the etiology of these disorders. Array comparative genomic hybridization and whole exome/genome sequencing studies identified common and rare copy number or single nucleotide variants in genes encoding proteins involved in brain development, which play an important role in neuron and synapse formation and function. The genetic etiology is recognized in ~ 25–35% of patients with ASD. In this article, we review the current state of knowledge about the genetic etiology of ASD and also propose a diagnostic algorithm for patients.
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Yeh E, Weiss LA. If genetic variation could talk: What genomic data may teach us about the importance of gene expression regulation in the genetics of autism. Mol Cell Probes 2016; 30:346-356. [PMID: 27751841 DOI: 10.1016/j.mcp.2016.10.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2016] [Revised: 10/09/2016] [Accepted: 10/13/2016] [Indexed: 11/25/2022]
Abstract
Autism spectrum disorder (ASD) has been long known to have substantial genetic etiology. Much research has attempted to identify specific genes contributing to ASD risk with the goal of tying gene function to a molecular pathological explanation for ASD. A unifying molecular pathology would potentially increase understanding of what is going wrong during development, and could lead to diagnostic biomarkers or targeted preventative or therapeutic directions. We review past and current genetic mapping approaches and discuss major results, leading to the hypothesis that global dysregulation of gene or protein expression may be implicated in ASD rather than disturbance of brain-specific functions. If substantiated, this hypothesis might indicate the need for novel experimental and analytical approaches in order to understand this neurodevelopmental disorder, develop biomarkers, or consider treatment approaches.
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Affiliation(s)
- Erika Yeh
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA, 94143, USA
| | - Lauren A Weiss
- Department of Psychiatry, University of California, San Francisco, San Francisco, CA, 94143, USA; Institute for Human Genetics, University of California, San Francisco, San Francisco, CA, 94143, USA.
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Ren CM, Liang Y, Wei F, Zhang YN, Zhong SQ, Gu H, Dong XS, Huang YY, Ke H, Son XM, Tang D, Chen Z. Balanced translocation t(3;18)(p13;q22.3) and points mutation in the ZNF407 gene detected in patients with both moderate non-syndromic intellectual disability and autism. Biochim Biophys Acta Mol Basis Dis 2012. [PMID: 23195952 DOI: 10.1016/j.bbadis.2012.11.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Intellectual disability (ID) is a common disease. While the etiology remains incompletely understood, genetic defects are a major contributor, which include mutations in genes encoding zinc finger proteins. These proteins modulate gene expression via binding to DNA. Consistent with this knowledge, we report here the identification of mutations in the ZNF407 gene in ID/autistic patients. In our study of an ID patient with autism, a reciprocal translocation 46,XY,t(3;18)(p13;q22.3) was detected. By using FISH and long-range PCR approaches, we have precisely mapped the breakpoints associated with this translocation in a gene-free region in chromosome 3 and in the third intron of the ZNF407 gene in chromosome18. The latter reduces ZNF407 expression. Consistent with this observation, in our subsequent investigation of 105 ID/autism patients with similar clinical presentations, two missense mutations Y460C and P1195A were identified. These mutations cause non-conservative amino acid substitutions in the linker regions between individual finger structures. In line with the linker regions being critical for the integrity of zinc finger motifs, both mutations may result in loss of ZNF407 function. Taken together, we demonstrate that mutations in the ZNF407 gene contribute to the pathogenesis of a group of ID patients with autism.
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Affiliation(s)
- Cong-mian Ren
- Department of Medical Genetics, Sun Yat-sen University, Guangzhou, People's Republic of China
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Iourov IY, Vorsanova SG, Yurov YB. Molecular cytogenetics and cytogenomics of brain diseases. Curr Genomics 2011; 9:452-65. [PMID: 19506734 PMCID: PMC2691674 DOI: 10.2174/138920208786241216] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2008] [Revised: 07/06/2008] [Accepted: 07/09/2008] [Indexed: 01/08/2023] Open
Abstract
Molecular cytogenetics is a promising field of biomedical research that has recently revolutionized our thinking on genome structure and behavior. This is in part due to discoveries of human genomic variations and their contribution to biodiversity and disease. Since these studies were primarily targeted at variation of the genome structure, it appears apposite to cover them by molecular cytogenomics. Human brain diseases, which encompass pathogenic conditions from severe neurodegenerative diseases and major psychiatric disorders to brain tumors, are a heavy burden for the patients and their relatives. It has been suggested that most of them, if not all, are of genetic nature and several recent studies have supported the hypothesis assuming them to be associated with genomic instabilities (i.e. single-gene mutations, gross and subtle chromosome imbalances, aneuploidy). The present review is focused on the intriguing relationship between genomic instability and human brain diseases. Looking through the data, we were able to conclude that both interindividual and intercellular genomic variations could be pathogenic representing, therefore, a possible mechanism for human brain malfunctioning. Nevertheless, there are still numerous gaps in our knowledge concerning the link between genomic variations and brain diseases, which, hopefully, will be filled by forthcoming studies. In this light, the present review considers perspectives of this dynamically developing field of neurogenetics and genomics.
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Affiliation(s)
- I Y Iourov
- National Research Center of Mental Health, Russian Academy of Medical Sciences
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Devillard F, Guinchat V, Moreno-De-Luca D, Tabet AC, Gruchy N, Guillem P, Nguyen Morel MA, Leporrier N, Leboyer M, Jouk PS, Lespinasse J, Betancur C. Paracentric inversion of chromosome 2 associated with cryptic duplication of 2q14 and deletion of 2q37 in a patient with autism. Am J Med Genet A 2010; 152A:2346-54. [PMID: 20684015 DOI: 10.1002/ajmg.a.33601] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
We describe a patient with autism and a paracentric inversion of chromosome 2q14.2q37.3, with a concurrent duplication of the proximal breakpoint at 2q14.1q14.2 and a deletion of the distal breakpoint at 2q37.3. The abnormality was derived from his mother with a balanced paracentric inversion. The inversion in the child appeared to be cytogenetically balanced but subtelomere FISH revealed a cryptic deletion at the 2q37.3 breakpoint. High-resolution single nucleotide polymorphism array confirmed the presence of a 3.5 Mb deletion that extended to the telomere, and showed a 4.2 Mb duplication at 2q14.1q14.2. FISH studies using a 2q14.2 probe showed that the duplicated segment was located at the telomeric end of chromosome 2q. This recombinant probably resulted from breakage of a dicentric chromosome. The child had autism, mental retardation, speech and language delay, hyperactivity, growth retardation with growth hormone deficiency, insulin-dependent diabetes, and mild facial dysmorphism. Most of these features have been previously described in individuals with simple terminal deletion of 2q37. Pure duplications of the proximal chromosome 2q are rare and no specific syndrome has been defined yet, so the contribution of the 2q14.1q14.2 duplication to the phenotype of the patient is unknown. These findings underscore the need to explore apparently balanced chromosomal rearrangements inherited from a phenotypically normal parent in subjects with autism and/or developmental delay. In addition, they provide further evidence indicating that chromosome 2q terminal deletions are among the most frequently reported cytogenetic abnormalities in individuals with autism.
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Vorsanova SG, Voinova VY, Yurov IY, Kurinnaya OS, Demidova IA, Yurov YB. Cytogenetic, Molecular-Cytogenetic, and Clinical-Genealogical Studies of the Mothers of Children with Autism: A Search for Familial Genetic Markers for Autistic Disorders. ACTA ACUST UNITED AC 2010; 40:745-56. [DOI: 10.1007/s11055-010-9321-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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SCAMP5, NBEA and AMISYN: three candidate genes for autism involved in secretion of large dense-core vesicles. Hum Mol Genet 2010; 19:1368-78. [DOI: 10.1093/hmg/ddq013] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Cai G, Edelmann L, Goldsmith JE, Cohen N, Nakamine A, Reichert JG, Hoffman EJ, Zurawiecki DM, Silverman JM, Hollander E, Soorya L, Anagnostou E, Betancur C, Buxbaum JD. Multiplex ligation-dependent probe amplification for genetic screening in autism spectrum disorders: efficient identification of known microduplications and identification of a novel microduplication in ASMT. BMC Med Genomics 2008; 1:50. [PMID: 18925931 PMCID: PMC2588447 DOI: 10.1186/1755-8794-1-50] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 10/16/2008] [Indexed: 11/10/2022] Open
Abstract
Background It has previously been shown that specific microdeletions and microduplications, many of which also associated with cognitive impairment (CI), can present with autism spectrum disorders (ASDs). Multiplex ligation-dependent probe amplification (MLPA) represents an efficient method to screen for such recurrent microdeletions and microduplications. Methods In the current study, a total of 279 unrelated subjects ascertained for ASDs were screened for genomic disorders associated with CI using MLPA. Fluorescence in situ hybridization (FISH), quantitative polymerase chain reaction (Q-PCR) and/or direct DNA sequencing were used to validate potential microdeletions and microduplications. Methylation-sensitive MLPA was used to characterize individuals with duplications in the Prader-Willi/Angelman (PWA) region. Results MLPA showed two subjects with typical ASD-associated interstitial duplications of the 15q11-q13 PWA region of maternal origin. Two additional subjects showed smaller, de novo duplications of the PWA region that had not been previously characterized. Genes in these two novel duplications include GABRB3 and ATP10A in one case, and MKRN3, MAGEL2 and NDN in the other. In addition, two subjects showed duplications of the 22q11/DiGeorge syndrome region. One individual was found to carry a 12 kb deletion in one copy of the ASPA gene on 17p13, which when mutated in both alleles leads to Canavan disease. Two subjects showed partial duplication of the TM4SF2 gene on Xp11.4, previously implicated in X-linked non-specific mental retardation, but in our subsequent analyses such variants were also found in controls. A partial duplication in the ASMT gene, located in the pseudoautosomal region 1 (PAR1) of the sex chromosomes and previously suggested to be involved in ASD susceptibility, was observed in 6–7% of the cases but in only 2% of controls (P = 0.003). Conclusion MLPA proves to be an efficient method to screen for chromosomal abnormalities. We identified duplications in 15q11-q13 and in 22q11, including new de novo small duplications, as likely contributing to ASD in the current sample by increasing liability and/or exacerbating symptoms. Our data indicate that duplications in TM4SF2 are not associated with the phenotype given their presence in controls. The results in PAR1/PAR2 are the first large-scale studies of gene dosage in these regions, and the findings at the ASMT locus indicate that further studies of the duplication of the ASMT gene are needed in order to gain insight into its potential involvement in ASD. Our studies also identify some limitations of MLPA, where single base changes in probe binding sequences alter results. In summary, our studies indicate that MLPA, with a focus on accepted medical genetic conditions, may be an inexpensive method for detection of microdeletions and microduplications in ASD patients for purposes of genetic counselling if MLPA-identified deletions are validated by additional methods.
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Affiliation(s)
- Guiqing Cai
- Laboratory of Molecular Neuropsychiatry, Mount Sinai School of Medicine, New York, NY 10029, USA.
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Abstract
This review on autism spectrum disorder (ASD) focusses on recent insights in the clinical picture, such as continuity of the phenotype and the concept of broader phenotype, on epidemiology and on clinical issues relevant to physicians, including new methods for early screening and diagnosis, psychiatric and somatic co-morbidity, and the expansion of so-called complementary and alternative treatments. ASD is a disorder with mainly genetic causes and recent insights show that a variety of genetic mechanisms may be involved, i.e. single gene disorders, copy number variations and polygenic mechanisms. Technological advances in genetics have lead to a number of promising findings, which, together with other lines of fundamental research, suggest that ASD may be a disorder of connectivity in the brain, at least in a subgroup of patients. It is possible that part of the genetic load in autism actually reflects gene-environment interaction, but there is no evidence for purely environmental causes in a substantial number of cases. Clinical research suggests that ASD may be a multi-system disorder in at least a subgroup of subjects, affecting the gastro-intestinal (GI) tract, the immune system and perhaps other systems. Behavioural treatments remain the cornerstone of management, and are mainly aimed at stimulation of the domains of impaired development and reducing secondary behaviours. These treatments are constantly being refined, but the main progress in this area may be the increase of research on effectiveness.
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Affiliation(s)
- Jean G Steyaert
- Department of Child and Adolescent Psychiatry, Katholieke Universiteit Leuven (UZ Leuven), Herestraat 49, 3000, Leuven, Belgium.
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De novo balanced translocation t (7;16) (p22.1; p11.2) associated with autistic disorder. J Biomed Biotechnol 2008; 2008:231904. [PMID: 18475318 PMCID: PMC2373955 DOI: 10.1155/2008/231904] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 01/24/2008] [Indexed: 11/18/2022] Open
Abstract
The high incidence of de novo chromosomal aberrations in a population of persons with autism suggests a causal relationship between certain chromosomal aberrations and the occurrence of isolated idiopathic autism. We report on the clinical and cytogenetic findings in a male patient with autism, no physical abnormalities and a de novo balanced (7;16)(p22.1;p16.2) translocation. G-banded chromosomes and fluorescent in situ hybridization (FISH) were used to examine the patient's karyotype as well as his parents'. FISH with specific RP11-BAC clones mapping near 7p22.1 and 16p11.2 was used to refine the location of the breakpoints. This is, in the best of our knowledge, the first report of an individual with autism and this specific chromosomal aberration.
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Abstract
The autism spectrum disorders represent a collective of neurogenetic conditions that have in common altered socialization and communication. Much attention has been given lately to the marked increased in the reported incidence of these conditions. Significant debate also exists as to the basis of the reported increase. Regardless, clinical geneticists and pediatric neurologists alike are seeing a tremendous increase in the number of referrals for autism and related conditions. Continuing advances in genetic testing provide a moving target for the clinician in determining an appropriate diagnostic plan. In this article, we review the most recent advances in genetic testing technology and their potential application to the etiologic evaluation of patients with autism spectrum disorders.
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Two patients with balanced translocations and autistic disorder: CSMD3 as a candidate gene for autism found in their common 8q23 breakpoint area. Eur J Hum Genet 2008; 16:696-704. [PMID: 18270536 DOI: 10.1038/ejhg.2008.7] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Recent studies estimated a rate of 3-5% of cytogenetic abnormalities involving many different chromosomes in autistic spectrum disorders (ASDs). Here, we report on two unrelated male patients with de novo translocations, autistic behaviour and psychomotor delay. These two patients carry a balanced chromosome translocation t(5;8)(q14.3;q23.3) and t(6;8)(q13;q23.2), respectively. A detailed physical map covering the regions involved in the translocations was constructed using BAC clones mapping on chromosomes 5q14.3, 6q13 and 8q23. Fluorescence in situ hybridisation (FISH) analyses were carried out using these genomic clones. We fine mapped the two translocation breakpoints on chromosomes 8 identifying their position within a short 5 Mb genomic region. Breakpoints on chromosomes 8 in both patients do not interrupt any known gene but both map in a region containing the CSMD3 gene, which thereby can be considered as a candidate for ASDs.
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Vorsanova SG, Yurov IY, Demidova IA, Voinova-Ulas VY, Kravets VS, Solov'ev IV, Gorbachevskaya NL, Yurov YB. Variability in the heterochromatin regions of the chromosomes and chromosomal anomalies in children with autism: identification of genetic markers of autistic spectrum disorders. ACTA ACUST UNITED AC 2007; 37:553-8. [PMID: 17657425 DOI: 10.1007/s11055-007-0052-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2005] [Indexed: 10/23/2022]
Abstract
Cytogenetic and molecular cytogenetic analysis of children with autism (90 subjects) and their mothers (18 subjects) is presented. Anomalies and fragility were found in chromosome X in four cases of autism: mos 47,XXX[98]/46, XX[2]; 46,XY,r(22)(p11q13); 46,XY,inv(2)(p11.2q13),16qh-; and 46,Y,fra(X)(q27.3),16qh-. C staining and quantitative fluorescent in situ hybridization (FISH) were used to demonstrate a significant increase in the frequency of variations in the heterochromatin regions of chromosomes in children with autism as compared with a control group (48% and 16% respectively). Pericentric chromosome inversion 9phqh was not characteristic of patients with autism, while variation in heterochromatin regions 1phqh, 9qh+, and 16qh-were found significantly more frequently in children with autism. These data provide the basis for discussing the possible role of the gene position effect in the pathogenesis of autism and the possible search for biological markers of autistic disorders.
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Affiliation(s)
- S G Vorsanova
- Moscow Research Institute of Pediatrics and Child Surgery, Federal Agency for Health and Social Development (Roszdrav)
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Yurov YB, Vorsanova SG, Iourov IY, Demidova IA, Beresheva AK, Kravetz VS, Monakhov VV, Kolotii AD, Voinova-Ulas VY, Gorbachevskaya NL. Unexplained autism is frequently associated with low-level mosaic aneuploidy. J Med Genet 2007; 44:521-5. [PMID: 17483303 PMCID: PMC2597925 DOI: 10.1136/jmg.2007.049312] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
BACKGROUND Autism is a common childhood neurodevelopmental disorder with a possible genetic background. About 5-10% of autism cases are associated with chromosomal abnormalities or monogenic disorders. However, the role of subtle genomic imbalances in autism has not been delineated. This study aimed to investigate a hypothesis suggesting autism to be associated with subtle genomic imbalances presenting as low-level chromosomal mosaicism. METHODS We surveyed stochastic (background) aneuploidy in children with/without autism by interphase three-colour fluorescence in situ hybridisation. The rate of chromosome loss and gain involving six arbitrarily selected autosomes and the sex chromosomes was assessed in the peripheral blood cells of 60 unaffected children and 120 children with autism. RESULTS Of 120 analysed boys with autism, 4 (3.3%) with rare structural chromosomal abnormalities (46,XY,t(1;6)(q42.1;q27); 46,XY,inv(2)(p11q13); 46,XY,der(6),ins(6;1)(q21;p13.3p22,1)pat; and 46,XY,r(22)(p11q13)) were excluded from further molecular cytogenetic analysis. Studying <420 000 cells in 60 controls and 116 children with idiopathic autism, we determined the mean frequency of stochastic aneuploidy in control and autism: (1) autosome loss 0.58% (95% CI 0.42 to 0.75%) and 0.60% (95% CI 0.37 to 0.83%), respectively, p = 0.83; (2) autosome gain 0.15% (95% CI 0.09 to 0.21%) and 0.22% (95% CI 0.14 to 0.30%), respectively, p = 0.39; and (3) chromosome X gain 1.11% (95% CI 0.90 to 1.31%) and 1.01% (95% CI 0.85 to 1.17%), respectively, p = 0.30. A frequency of mosaic aneuploidy greater the background level was found in 19 (16%) of 116 children with idiopathic autism, whereas outlier values were not found in controls (p = 0.0019). CONCLUSIONS Our findings identify low-level aneuploidy as a new genetic risk factor for autism. Therefore, molecular cytogenetic analysis of somatic mosaicism is warranted in children with unexplained autism.
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Abstract
Autism is a neurodevelopmental disorder characterized by impairments in social interactions, communication, and behavior. Multiple lines of evidence support the notion that most cases of autism likely have an underlying genetic cause or predisposition. Like mental retardation, autism is likely to be caused by many different genetic mechanisms and genes rather than a single, or few, major genes or environmental effects. In this review, we will focus on the cytogenetic contribution to uncovering regions of the genome involved in autism. Some common cytogenetic imbalances already known to cause autism will be highlighted. Routine genetic testing in clinical (CLIA-certified) diagnostic laboratories can identify the specific etiology and recurrence risk in 10% to 15% of autism cases and is clinically indicated for any child with autism. Powerful new methods for identifying novel regions of the genome causing or contributing to autism also will be discussed and will start to explain the etiology for some percentage of the remaining 85% to 90% of autism cases.
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MESH Headings
- Adolescent
- Adult
- Allelic Imbalance/genetics
- Asperger Syndrome/diagnosis
- Asperger Syndrome/genetics
- Asperger Syndrome/psychology
- Autistic Disorder/diagnosis
- Autistic Disorder/genetics
- Autistic Disorder/psychology
- Child
- Child Development Disorders, Pervasive/diagnosis
- Child Development Disorders, Pervasive/genetics
- Child Development Disorders, Pervasive/psychology
- Child, Preschool
- Chromosome Deletion
- Chromosomes, Human, Pair 15/genetics
- Chromosomes, Human, Pair 2/genetics
- Chromosomes, Human, Pair 22/genetics
- Fragile X Syndrome/diagnosis
- Fragile X Syndrome/genetics
- Fragile X Syndrome/psychology
- Gene Duplication
- Genetic Testing
- Genotype
- Humans
- Oligonucleotide Array Sequence Analysis
- Phenotype
- Social Environment
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Affiliation(s)
- Christa Lese Martin
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA 30322, USA.
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Castermans D, Vermeesch JR, Fryns JP, Steyaert JG, Van de Ven WJM, Creemers JWM, Devriendt K. Identification and characterization of the TRIP8 and REEP3 genes on chromosome 10q21.3 as novel candidate genes for autism. Eur J Hum Genet 2007; 15:422-31. [PMID: 17290275 DOI: 10.1038/sj.ejhg.5201785] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Autism is a genetic neurodevelopmental disorder of unknown cause and pathogenesis. The identification of genes involved in autism is expected to increase our understanding of its pathogenesis. Infrequently, neurodevelopmental disorders like autism are associated with chromosomal anomalies. To identify candidate genes for autism, we initiated a positional cloning strategy starting from individuals with idiopathic autism carrying a de novo chromosomal anomaly. We report on the clinical, cytogenetic and molecular findings in a male person with autism, no physical abnormalities and normal IQ, carrying a de novo balanced paracentric inversion 46,XY,inv(10)(q11.1;q21.3). The distal breakpoint disrupts the TRIP8 gene, which codes for a protein predicted to be a transcriptional regulator associated with nuclear thyroid hormone receptors. However, no link between thyroid gland and autism has been reported so far. In addition, the same breakpoint abolishes expression of a nearby gene, REEP3, through a position effect. Receptor Expression-Enhancing Proteins (REEP) 3 is one of the six human homologs of yeast Yop1p, a probable regulator of cellular vesicle trafficking between the endoplasmatic reticulum and the Golgi network. These observations suggest that TRIP8 and REEP3 are both positional candidate genes for autism. In addition, our data indicate that in the selection of positional candidate genes when studying chromosomal aberrations, position effects should be taken into account.
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Affiliation(s)
- Dries Castermans
- Laboratory for Biochemical Neuroendocrinology, Department of Human Genetics, Flanders Interuniversity Institute for Biotechnology, Catholic University of Leuven, Leuven, Belgium
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Havlovicova M, Novotna D, Kocarek E, Novotna K, Bendova S, Petrak B, Hrdlicka M, Sedlacek Z. A girl with neurofibromatosis type 1, atypical autism and mosaic ring chromosome 17. Am J Med Genet A 2007; 143A:76-81. [PMID: 17163520 DOI: 10.1002/ajmg.a.31569] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We describe a girl with neurofibromatosis type 1 (NF1), mild dysmorphic features, growth and mental retardation, autism, and mosaicism of ring chromosome 17 and chromosome 17 monosomy. The extent of genetic material deleted from the ring chromosome was determined using a combination of classical cytogenetics, fluorescence in situ hybridization (FISH) and multiplex ligation-dependent probe amplification (MLPA) to be 0.6-2.5 Mb on 17p, and up to about 10 Mb on 17q. Based on our observations and on a review of the literature we argue that in addition to a universal "ring syndrome" which is based on ring instability and is less specific for the chromosome involved, various ring chromosomes underlie their own characteristic phenotypes. We propose that the symptoms leading to the diagnosis of NF1 in our patient could be attributed to mosaic hemizygosity for the NF1 gene in some of her somatic cells. A similar mechanism or a direct involvement of respective disease genes in the aberration could possibly influence also the development of autism and other symptoms. We raise a question if the loss of one copy of chromosome 17 from a substantial fraction of somatic cells can have specific consequences also for future risks of the patient, for example, due to the mosaic hemizygosity for the BRCA1 and TP53 genes.
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Affiliation(s)
- Marketa Havlovicova
- Institute of Biology and Medical Genetics, Charles University Second Medical School and University Hospital Motol, Prague, Czech Republic.
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Zou YS, Van Dyke DL, Ellison JW. Microarray comparative genomic hybridization and FISH studies of an unbalanced cryptic telomeric 2p deletion/16q duplication in a patient with mental retardation and behavioral problems. Am J Med Genet A 2007; 143A:746-51. [PMID: 17345620 DOI: 10.1002/ajmg.a.31645] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We describe a 7-year-old patient with pervasive developmental disorder and behavioral problems who has a de novo cryptic unbalanced der(2)t(2;16)(p25.3;q24.3) chromosome resulting in deletion of distal 2p and duplication of distal 16q. These segmental aneusomies were detected by microarray comparative genomic hybridization analysis, as was a distal 17p13.3 duplication that was inherited from her father. FISH analysis using bacterial artificial chromosomes confirmed a deletion of approximately 1,700 kbp of DNA from 2pter (containing at least six complete genes or transcription units) and a duplication of approximately 500 kbp from 16qter (including up to ten genes or transcription units). Several genes in these regions are plausible candidates for contributing to the patient's phenotype.
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Affiliation(s)
- Ying S Zou
- Cytogenetics Laboratory, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA
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Abstract
PURPOSE Clinical geneticists are often asked to evaluate patients with autism spectrum disorders (ASDs) in reference to questions about cause and recurrence risk. Recent advances in diagnostic testing technology have greatly increased the options available to them. It is not currently clear what the overall diagnostic yield of a battery of tests, either collectively or individually, might be. The purpose of this study was to evaluate the diagnostic yield of a stepwise approach we have implemented in our clinics. METHODS We used a three-tiered neurogenetic evaluation scheme designed to determine the cause of ASDs in patients referred for clinical genetic consultation. We reviewed the results of our diagnostic evaluations on all patients referred with a confirmed diagnosis of autism over a 3-year period. RESULTS By using this approach, we found an overall diagnostic yield for ASDs of more than 40%. This represents a significant increase in the diagnostic yield reported just a few years ago. CONCLUSIONS Given the implications of these diagnoses on recurrence risk and associated medical conditions, a targeted neurogenetic evaluation of all persons with ASDs seems warranted. We discuss the issues in the future implementation of a fourth tier to the evaluation with the potential for an even higher diagnostic yield.
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Affiliation(s)
- G Bradley Schaefer
- Munroe-Meyer Institute for Genetics and Rehabilitation, 985430 University of Nebraska Medical Center, Omaha, NE 68198, USA
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21
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Abstract
Autism is a highly heritable complex neurodevelopmental disorder characterized by distinct impairments of cognitive function in the field of social interaction and speech development. Different approaches have been undertaken worldwide to identify susceptibility loci or genes for autism spectrum disorders. No clear conclusions can be made today about genetic loci involved in these disorders. The review will focus on relevant results from the last decade of research with emphasis on whole genome screens and association studies.
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Affiliation(s)
- Sabine M Klauck
- Division of Molecular Genome Analysis, Deutsches Krebsforschungszentrum, Heidelberg, Germany.
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22
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Identification of novel autism candidate regions through analysis of reported cytogenetic abnormalities associated with autism. Mol Psychiatry 2006. [PMID: 16205736 DOI: 10.1038/sj.mp.4001757] [Citation(s) in RCA: 211] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The identification of the candidate genes for autism through linkage and association studies has proven to be a difficult enterprise. An alternative approach is the analysis of cytogenetic abnormalities associated with autism. We present a review of all studies to date that relate patients with cytogenetic abnormalities to the autism phenotype. A literature survey of the Medline and Pubmed databases was performed, using multiple keyword searches. Additional searches through cited references and abstracts from the major genetic conferences from 2000 onwards completed the search. The quality of the phenotype (i.e. of the autism spectrum diagnosis) was rated for each included case. Available specific probe and marker information was used to define optimally the boundaries of the cytogenetic abnormalities. In case of recurrent deletions or duplications on chromosome 15 and 22, the positions of the low copy repeats that are thought to mediate these rearrangements were used to define the most likely boundaries of the implicated 'Cytogenetic Regions Of Interest' (CROIs). If no molecular data were available, the sequence position of the relevant chromosome bands was used to obtain the approximate molecular boundaries of the CROI. The findings of the current review indicate: (1) several regions of overlap between CROIs and known loci of significant linkage and/or association findings, and (2) additional regions of overlap among multiple CROIs at the same locus. Whereas the first finding confirms previous linkage/association findings, the latter may represent novel, not previously identified regions containing genes that contribute to autism. This analysis not only has confirmed the presence of several known autism risk regions but has also revealed additional previously unidentified loci, including 2q37, 5p15, 11q25, 16q22.3, 17p11.2, 18q21.1, 18q23, 22q11.2, 22q13.3 and Xp22.2-p22.3.
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23
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Bacchelli E, Maestrini E. Autism spectrum disorders: Molecular genetic advances. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2006; 142C:13-23. [PMID: 16419096 DOI: 10.1002/ajmg.c.30078] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Despite the strong genetic basis of autism spectrum disorders (ASD), research efforts in the last decade have not been successful in the identification of confirmed susceptibility genes. We review the present status of genetic linkage, candidate gene, and association studies, pointing out the limitations of these approaches and the challenge of dealing with the clinical and genetic complexity of autism. Finally, we outline how recent technological and bioinformatic advances, together with an increasing understanding of the structure of the human genome, have set the stage to perform more comprehensive and well powered studies, possibly leading to a turning point in the understanding of the genetic basis of this devastating disorder.
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Affiliation(s)
- Elena Bacchelli
- Dipartimento di Biologia Evoluzionistica Sperimentale, Bologna University, via Selmi 3, 40126 Bologna, Italy
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24
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Iourov IY, Vorsanova SG, Yurov YB. Chromosomal variation in mammalian neuronal cells: known facts and attractive hypotheses. INTERNATIONAL REVIEW OF CYTOLOGY 2006; 249:143-91. [PMID: 16697283 DOI: 10.1016/s0074-7696(06)49003-3] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Chromosomal mosaicism is still a genetic enigma. Although the mechanisms and consequences of this phenomenon have been studied for over 50 years, there are a number of gaps in our knowledge concerning causes, genetic mechanisms, and phenotypic manifestations of chromosomal mosaicism. Neuronal cell-specific chromosomal mosaicism is not an exception. Originally, neuronal cells of the mammalian brain were assumed to possess identical genomes. However, recent studies have shown chromosomal variations, manifested as chromosome abnormalities in cells of the developing and adult mammalian nervous system. Here, we review data obtained on the variation in chromosome complement in mammalian neuronal cells and hypothesize about the possible relevance of large-scale genomic (i.e., chromosomal) variations to brain development and functions as well as neurodevelopmental and neurodegenerative disorders. We propose to cover the term "molecular neurocytogenetics to cover all studies the aim of which is to reveal chromosome variations and organization in the mammalian brain.
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Affiliation(s)
- Ivan Y Iourov
- National Research Center of Mental Health, Russian Academy of Sciences, Moscow, Russia 119152
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25
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Ethell IM, Pasquale EB. Molecular mechanisms of dendritic spine development and remodeling. Prog Neurobiol 2005; 75:161-205. [PMID: 15882774 DOI: 10.1016/j.pneurobio.2005.02.003] [Citation(s) in RCA: 264] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2004] [Revised: 01/28/2005] [Accepted: 02/22/2005] [Indexed: 12/19/2022]
Abstract
Dendritic spines are small protrusions that cover the surface of dendrites and bear the postsynaptic component of excitatory synapses. Having an enlarged head connected to the dendrite by a narrow neck, dendritic spines provide a postsynaptic biochemical compartment that separates the synaptic space from the dendritic shaft and allows each spine to function as a partially independent unit. Spines develop around the time of synaptogenesis and are dynamic structures that continue to undergo remodeling over time. Changes in spine morphology and density influence the properties of neural circuits. Our knowledge of the structure and function of dendritic spines has progressed significantly since their discovery over a century ago, but many uncertainties still remain. For example, several different models have been put forth outlining the sequence of events that lead to the genesis of a spine. Although spines are small and apparently simple organelles with a cytoskeleton mainly composed of actin filaments, regulation of their morphology and physiology appears to be quite sophisticated. A multitude of molecules have been implicated in dendritic spine development and remodeling, suggesting that intricate networks of interconnected signaling pathways converge to regulate actin dynamics in spines. This complexity is not surprising, given the likely importance of dendritic spines in higher brain functions. In this review, we discuss the molecules that are currently known to mediate the exquisite sensitivity of spines to perturbations in their environment and we outline how these molecules interface with each other to mediate cascades of signals flowing from the spine surface to the actin cytoskeleton.
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Affiliation(s)
- Iryna M Ethell
- Division of Biomedical Sciences, University of California Riverside, Riverside, CA 92521, USA
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