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Anticipation (genetics)

About: Anticipation (genetics) is a research topic. Over the lifetime, 669 publications have been published within this topic receiving 21784 citations. The topic is also known as: Genetic Anticipation & Anticipation, Genetic.


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Journal ArticleDOI
TL;DR: It is confirmed that anticipation is present even when the parent is heterozygous for a small CTG expansion, and the parental sex has an impact on the size of the repeat in the next generation, larger increases being transmitted by males with a small expansion.
Abstract: Myotonic dystrophy type 1 is the most common form of adult muscular dystrophy and has the world's highest prevalence in the Saguenay-Lac-St-Jean region, due to a founder effect. This autosomal dominant disorder results from an unstable CTG repeat expansion in DMPK. This region of Canada has had a family screening and predictive testing program for this disorder since 1988. Heterozygotes for small expansions (50-100 CTG repeats) can be asymptomatic or minimally affected. The aim of this study was to assess anticipation for these individuals. At the time of this study, the molecular data of 40 individuals and their 76 affected children were available. We compared 76 parent-child pairs. Most offspring (92.1%) had a larger number of repeats than their parent and the median number of repeats in the offspring was 325 (range, 57-2000). The number of CTG repeats was significantly greater when the mutation was transmitted by a father (median, 425 repeats; range, 70-2000), than when it was transmitted by a mother (median, 200 repeats; range, 57-1400). The majority (65.8%) of children also had a more severe phenotype than their parent but the sex of the parent had no significant influence on the severity of the child's phenotype. No congenital phenotype was observed. These results confirm that anticipation is present even when the parent is heterozygous for a small CTG expansion. The parental sex has an impact on the size of the repeat in the next generation, larger increases being transmitted by males with a small expansion.

23 citations

Journal ArticleDOI
TL;DR: Indirect molecular data indicate the familial character of the disease, with strong anticipation of transmission, in a boy with juvenile Huntington disease with a very early age at disease onset (3 years).
Abstract: Huntington disease is a dominantly inherited, neurodegenerative disorder, usually with onset in the fourth to fifth decade of life but in a small proportion of patients before the age of 20 years. The early-onset form, juvenile Huntington disease, is clinically different from that of more common adult-onset forms and includes cognitive decline, parkinsonism, myoclonus, and seizures. We report a case of a boy with juvenile Huntington disease with a very early age at disease onset (3 years). The suspected clinical diagnosis was confirmed by DNA analysis, which revealed (CAG)(n) expansion into the range characteristic of juvenile Huntington disease (95 repeats). The clinical course of the disease was typical for the juvenile form of Huntington disease, but the diagnosis was not so obvious because there was no history of any neurodegenerative disorder in the family. The child died at the age of 11 years. The detailed neuropathologic investigations performed postmortem showed the characteristic features of Huntington disease. As the patient's de novo mutation was very unlikely to occur, genetic counseling and the possibility of predictive testing were proposed to the family. Indirect molecular data indicate the familial character of the disease, with strong anticipation of transmission.

22 citations

Journal ArticleDOI
TL;DR: Clinical study revealed that great variation occurred in the age of onset, initial symptoms, and associated signs of spinocerebellar ataxia, and intergenerational instability of the array was associated with the clinical phenomenon of anticipation.
Abstract: Objective: To investigate the clinical and molecular characteristics of spinocerebellar ataxia type 7 (SCA7) in Chinese kindreds. Background: Spinocerebellar ataxia type 7 is caused by the expansion of an unstable CAG repeat in the first exon of the SCA7 gene. Methods: Clinical and related examinations were performed in all affected or at-risk individuals from 4 Chinese families presenting with autosomal dominant cerebellar ataxia and decreased visual acuity. The size of the (CAG)n array of the SCA7 gene was detected by polymerase chain reaction, polyacrylamide gel electrophoresis, and related techniques in the 4 families and 67 healthy controls. The relationship between expanded repeat number and age of onset was statistically analyzed. Results: The SCA7 mutation was identified in 2 families. Clinical study revealed that great variation occurred in the age of onset, initial symptoms, and associated signs. Meanwhile, the analysis of 11 parent-child couples demonstrated the existence of marked anticipation. Some distinct retinal changes were noted in 2 affected patients. All SCA7 patients in our series exhibited expanded CAG repeats, ranging from 44 to 85 repeats, with a strong negative correlation between repeat size and age of onset. Repeat lengths of expanded alleles showed somatic mosaicism in leukocyte DNA. There were some subtle clinical differences between the SCA7-positive and -negative cases. Conclusions: Clinical variation occurred not only among the SCA7 families but also within the same kindred. Meiotic and mitotic instability of the CAG repeat in the SCA7 gene were demonstrated, and intergenerational instability of the array was associated with the clinical phenomenon of anticipation. Arch Neurol. 2000;57:1513-1518

22 citations

Journal ArticleDOI
TL;DR: The results of these meta‐analyses demonstrate that the risks for both schizophrenia and bipolar disorder are largely, if not entirely, independent of CAG‐repeat length in exon 1 of KCNN3.
Abstract: Schizophrenia and bipolar disorder both show some evidence for genetic anticipation. In addition, significant expansion of anonymous CAG repeats throughout the genome has been detected in both of these disorders. The gene KCNN3, which codes for a small/intermediate conductance, calcium-regulated potassium channel, contains a highly polymorphic CAG-repeat array in exon 1. Initial evidence for association of both schizophrenia and bipolar disorder with increased CAG-repeat length of KCNN3 has not been consistently replicated. In the present study, we performed several meta-analyses to evaluate the pooled evidence for association with CAG-repeat length of KCNN3 derived from case-control and family-based studies of both disorders. Each group of studies was analyzed under two models, including a test for direct association with repeat length, and a test for association with dichotomized repeat-length groups. No evidence for a linear relationship between disease risk and repeat length was observed, as all pooled odds ratios approximated 1.0. Results of dichotomized allele-group analyses were more variable, especially for schizophrenia, where case-control studies found a significant association with longer repeats but family-based studies implicated shorter alleles. The results of these meta-analyses demonstrate that the risks for both schizophrenia and bipolar disorder are largely, if not entirely, independent of CAG-repeat length in exon 1 of KCNN3. This study cannot exclude the possibility that some aspect of this polymorphism, such as repeat-length disparity in heterozygotes, influences risk for these disorders. Further, it remains unknown if this polymorphism, or one in linkage disequilibrium with it, contributes to some distinct feature of the disorder, such as symptom severity or anticipation. © 2003 Wiley-Liss, Inc.

22 citations

Journal ArticleDOI
Shoji Tsuji1
TL;DR: Recent studies suggest that gene products with expanded polyglutamine tracts may be toxic to neuronal cells, and the mechanisms of neurotoxicity should be thoroughly investigated.
Abstract: Expansion of trinucleotide repeats has been identified as a common mechanism of hereditary neurodegenerative diseases including spinal and bulbar muscular atrophy (SBMA), Huntington's disease, dentatorubral-pallidoluysian atrophy (DRPLA), Machado-Joseph disease (MJD), fragile X syndrome, myotonic dystrophy and Friedreich's ataxia. These diseases share unique features, which are difficult to explain based on Mendelian inheritance. These unique clinical genetic features include genetic anticipation and a broad spectrum of clinical presentations, which have been shown to be associated with the instability of the trinucleotide repeats. Recent studies suggest that gene products with expanded polyglutamine tracts may be toxic to neuronal cells, and the mechanisms of neurotoxicity should be thoroughly investigated. To develop therapeutic measures, creation of animal models or cell culture systems for the investigation of neurotoxicity will be indispensable.

22 citations


Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202116
202013
201911
201818
201716
201615