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      The First Case of X-linked Alpha-thalassemia/Mental Retardation (ATR-X) Syndrome in Korea

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          Abstract

          Mutation of the ATRX gene leads to X-linked alpha-thalassemia/mental retardation (ATR-X) syndrome and several other X-linked mental retardation syndromes. We report the first case of ATR-X syndrome documented here in Korea. A 32-month-old boy came in with irritability and fever. He showed dysmorphic features, mental retardation and epilepsy, so ATR-X syndrome was considered. Hemoglobin H inclusions in red blood cells supported the diagnosis and genetic studies confirmed it. Mutation analysis for our patient showed a point mutation of thymine to cytosine on the 9th exon in the ATRX gene, indicating that Trp(C), the 220th amino acid, was replaced by Ser(R). Furthermore, we investigated the same mutation in family members, and his mother and two sisters were found to be carriers.

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          Most cited references14

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          Mutations in ATRX, encoding a SWI/SNF-like protein, cause diverse changes in the pattern of DNA methylation.

          A goal of molecular genetics is to understand the relationship between basic nuclear processes, epigenetic changes and the numerous proteins that orchestrate these effects. One such protein, ATRX, contains a highly conserved plant homeodomain (PHD)-like domain, present in many chromatin-associated proteins, and a carboxy-terminal domain which identifies it as a member of the SNF2 family of helicase/ATPases. Mutations in ATRX give rise to characteristic developmental abnormalities including severe mental retardation, facial dysmorphism, urogenital abnormalities and alpha-thalassaemia. This circumstantial evidence suggests that ATRX may act as a transcriptional regulator through an effect on chromatin. We have recently shown that ATRX is localized to pericentromeric heterochromatin during interphase and mitosis, suggesting that ATRX might exert other chromatin-mediated effects in the nucleus. Moreover, at metaphase, some ATRX is localized at or close to the ribosomal DNA (rDNA) arrays on the short arms of human acrocentric chromosomes. Here we show that mutations in ATRX give rise to changes in the pattern of methylation of several highly repeated sequences including the rDNA arrays, a Y-specific satellite and subtelomeric repeats. Our findings provide a potential link between the processes of chromatin remodelling, DNA methylation and gene expression in mammalian development.
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            Mutations in the chromatin-associated protein ATRX.

            ATRX belongs to the SNF2 family of proteins, many of which have been demonstrated to have chromatin remodeling activity. Constitution mutations in the X-encoded gene give rise to alpha thalassemia mental retardation (ATR-X) syndrome and a variety of related conditions that are often associated with profound developmental delay, facial dysmorphism, genital abnormalities, and alpha thalassemia. Acquired mutations in ATRX are observed in the preleukemic condition alpha thalassemia myelodysplastic syndrome (ATMDS). Mutations in ATRX have been shown to perturb gene expression and DNA methylation. This is a comprehensive report of 127 mutations including 32 reported here for the first time. Missense mutations are shown to cluster in the two main functional domains. The truncating mutations appear to be "rescued" to some degree and so it appears likely that most if not all constitutional ATRX mutations are hypomorphs. (c) 2008 Wiley-Liss, Inc.
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              Alpha thalassaemia-mental retardation, X linked

              X-linked alpha thalassaemia mental retardation (ATR-X) syndrome in males is associated with profound developmental delay, facial dysmorphism, genital abnormalities and alpha thalassaemia. Female carriers are usually physically and intellectually normal. So far, 168 patients have been reported. Language is usually very limited. Seizures occur in about one third of the cases. While many patients are affectionate with their caregivers, some exhibit autistic-like behaviour. Patients present with facial hypotonia and a characteristic mouth. Genital abnormalities are observed in 80% of children and range from undescended testes to ambiguous genitalia. Alpha-thalassaemia is not always present. This syndrome is X-linked recessive and results from mutations in the ATRX gene. This gene encodes the widely expressed ATRX protein. ATRX mutations cause diverse changes in the pattern of DNA methylation at heterochromatic loci but it is not yet known whether this is responsible for the clinical phenotype. The diagnosis can be established by detection of alpha thalassaemia, identification of ATRX gene mutations, ATRX protein studies and X-inactivation studies. Genetic counselling can be offered to families. Management is multidisciplinary: young children must be carefully monitored for gastro-oesophageal reflux as it may cause death. A number of individuals with ATR-X are fit and well in their 30s and 40s.
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                Author and article information

                Journal
                J Korean Med Sci
                JKMS
                Journal of Korean Medical Science
                The Korean Academy of Medical Sciences
                1011-8934
                1598-6357
                January 2011
                22 December 2010
                : 26
                : 1
                : 146-149
                Affiliations
                [1 ]Department of Pediatrics, Chung-Ang University College of Medicine, Seoul, Korea.
                [2 ]Department of Laboratory Medicine, Chung-Ang University College of Medicine, Seoul, Korea.
                Author notes
                Address for Correspondence: Soo Ahn Chae, MD. Department of Pediatrics, Chung-Ang University Medical Center, 29 Heukseok-ro, Dongjak-gu, Seoul 156-070, Korea. Tel: +82.2-6299-1479, Fax: +82.2-814-4920, kidbrain@ 123456korea.com
                Article
                10.3346/jkms.2011.26.1.146
                3012841
                21218045
                eb68ffe0-0781-4bf8-92a1-50ac43639c35
                © 2011 The Korean Academy of Medical Sciences.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License ( http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 09 January 2010
                : 30 April 2010
                Categories
                Case Report
                Pediatrics

                Medicine
                atrx,mental retardation, x-linked,alpha-thalassemia,hemoglobin h
                Medicine
                atrx, mental retardation, x-linked, alpha-thalassemia, hemoglobin h

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