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Typescript (Photocopy) / Includes published papers co-authored by the author at the end of volume 2 / Bibliography: leaves 195-237 of vol. 1 / 2 v. : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Paediatrics, Faculty of Medicine, University of Adelaide, 1991

A form of familial sex-linked mental retardation has been associated with the expression of a fragile site near the terminal end of the long arm of the X chromosome. Previous reports on the fragile X chromosome showed expression of the fragile site to be limited to chromosome preparations from peripheral blood lymphocytes of mentally retarded males and their female relatives in families in which the disorder was segregating. Fragile site expression has also been shown to be a function of the medium employed in cell culture. The fragile X chromosome could only be demonstrated in lymphocytes cultured in medium 199 or media deprived of folic acid. This study was undertaken to develop a method for demonstrating the fragile X chromosome in cultured skin fibroblasts. Fibroblast cell lines from five patients (two mentally retarded males, two obligate carrier females, and a potential carrier female) from a family in which familial sex-linked mental retardation was known to be segregating were established and routinely maintained in a complete culture medium. Forty-three hours prior to chromosome harvest, cells from each patient were transferred to media deficient in folic acid. Under conditions of folic acid deprivation, it was possible to elicit expression of the fragile X chromosome in skin fibroblasts from all five patients studied. No fragile X chromosomes were detected in fibroblasts from three normal control subjects. In a preliminary assessment of the reliability of the fibroblast method, three patients (two mentally retarded males and a potential carrier female) from a second unrelated family in which the disorder is known to be segregating were studied with this method. The fragile X chromosome could be demonstrated in fibroblasts from both of the retarded male patients but could not be. demonstrated in fibroblast chromosome preparations from the potential carrier female. Lymphocytes for all patients studied were grown under similar folate deprived conditions for the purpose of comparing the effectiveness of fibroblast culture with lymphocyte culture in demonstrating the expression of the fragile X chromosome. Neither tissue was shown to consistently provide a higher frequency of expression of the fragile X chromosome. In addition to folate deprivation, it was shown that two other features of the fibroblast method influenced the frequency of expression of the fragile X chromosome. The fragile site was expressed at a significantly higher frequency in chromosome preparations in which the chromosomes were not severely contracted. The frequency of expression in fibroblasts was also shown to be significantly higher with a hypotonic treatment at chromosome harvest using 1% NaCitrate rather than 0.075M KC1. Because fragile site expression was shown to be a function of the degree of chromosome condensation, two agents, 5-BrdU and actinomycin-D, were studied to examine their decondensation effects on the frequency of expression. Neither BrdU nor actinomycin D proved effective in accentuating the frequency of expression. Since fibroblasts behave much like amniocytes in terms of cell culture and chromosome harvest, the development of a method for demonstrating the fragile X chromosome in cultured skin fibroblasts is a step toward the prospect of reliable antenatal diagnosis of familial sex-linked mental retardation associated with a fragile X chromosome. / Medicine, Faculty of / Medical Genetics, Department of / Graduate

No description available.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / O retardo mental (RM) é caracterizado por um funcionamento intelectual significantemente abaixo da média (QI<70). A prevalência de RM varia entre estudos epidemiológicos, sendo estimada em 2-3% da população mundial, constituindo assim, um dos mais importantes problemas de saúde pública. Há um consenso geral de que o RM é mais comum no sexo masculino, um achado atribuído às numerosas mutações nos genes encontrados no cromossomo X, levando ao retardo mental ligado ao X (RMLX). Dentre os genes presentes no cromossomo X, o Jumonji AT-rich interactive domain IC (JARID1C) foi recentemente identificado como um potencial candidato etiológico do RM, quando mutado. O JARID1C codifica uma proteína que atua como uma desmetilase da lisina 4 da histona H3 (H3K4), imprescindível para a regulação epigenética. Tão recente como a identificação do gene JARID1C, é a descoberta de que mudanças no número de cópias de sequências de DNA, caracterizadas por microdeleções e microduplicações, poderiam ser consideradas como razões funcionalmente importantes de RMLX. Atualmente, cerca de 5-10% dos casos de RM em homens são reconhecidos por ocorrerem devido a estas variações do número de cópias no cromossomo X. Neste estudo, investigamos mutações no gene JARID1C, através do rastreamento dos éxons 9, 11, 12, 13, 15 e 16, em 121 homens de famílias com RM provavelmente ligado ao X. Paralelamente, realizamos a análise da variação do número de cópias em 16 genes localizados no cromossomo X através da técnica de MLPA no mesmo grupo de pacientes. Esta metodologia consiste em uma amplificação múltipla que detecta variações no número de cópias de até 50 sequências diferentes de DNA genômico, sendo capaz de distinguir sequências que diferem em apenas um nucleotídeo. O DNA genômico foi extraído a partir de sangue periférico e as amostras foram amplificadas pela técnica de PCR, seguida da análise por sequenciamento direto. Foram identificadas três variantes na sequência do gene JARID1C entre os pacientes analisados: a variante intrônica 2243+11 G>T, que esteve presente em 67% dos pacientes, a variante silenciosa c.1794C>G e a mutação inédita nonsense c.2172C>A, ambas presentes em 0,82% dos indivíduos investigados. A análise através do MLPA revelou uma duplicação em um dos pacientes envolvendo as sondas referentes ao gene GDI1 e ao gene HUWE1. Este trabalho expande o estudo de mutações no gene JARID1C para a população brasileira ereforça a importância da triagem de mutações neste gene em homens portadores de RM familiar de origem idiopática, assim como, é primeiro relato científico relativo à investigação de variações no número de cópias de genes localizados no cromossomo X em homens brasileiros com RM, através da técnica de MLPA. / Mental retardation (MR) is defined as a disability characterized by significant below average intellectual functioning (IQ>70). The prevalence of MR varies between epidemiological studies, estimated at 2-3% of the population, thus constituting a major public health problem. There is a general consensus that MR is more common in males, a finding attributed, in part, to mutations in the genes located on the X chromosome, leading to an X-linked mental retardation (XLMR). Among all the genes present on X chromosome, Jumonji AT-rich interactive domain IC (JARID1C) was recently identified as aetiologic potential candidate of MR, when mutated. The JARID1C gene encodes a protein that acts as a histone demethylase specific for histone 3 lysine 4 (H3K4) and it is indispensable for the epigenetic regulation. As recently as the identification of the JARID1C gene, it is the discovery that changes in the number of copies of DNA sequences, characterized by microdeletions and microduplications, could be regarded as functionally important reasons to XLMR. Currently, about 5-10% of men MR cases are known to occur due to these variations in the number of copies of chromosome X. In this study we investigated mutations in the JARID1C gene by screening of exons 9, 11, 12, 13, 15 and 16 in 121 patients from families with X-linked MR. At the same time we analyzed the variation in the number of copies in 16 genes located in X chromosome through the MLPA technique. This metodology consists of a multiplex amplification that detects variations in the number of copies up to 50 different genomic DNA sequences, being able to distinguish sequences that differ by only one nucleotide. Genomic DNA was extracted from peripheral blood and the samples were amplified by PCR followed by direct sequencing analysis. We identified three sequence variants among 121 patients. The intronic variant c.2243 +11 G> T, which was present in 67% of patients analyzed, the silent variant c.1794C> G and the novel nonsense mutation c.2172C> A, which was present in 0,82% of patients analyzed. The MLPA analysis revealed that the patient 58 exhibited a duplication involving probes for the GDI1 gene and the HUWE1 gene, resulting in an increase in the number of copies of this gene. This work expands the study of mutations in the JARID1C gene for the Brazilian population and reinforces the importance of screening for mutations in this gene in men with idiopathic mental retardation, and it is the first scientific report on the investigation of variations in the number of copies in genes located on chromosome X in Brazilian men with MR using the MLPA technique.

Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de Janeiro / O retardo mental (RM) é caracterizado por um funcionamento intelectual significantemente abaixo da média (QI<70). A prevalência de RM varia entre estudos epidemiológicos, sendo estimada em 2-3% da população mundial, constituindo assim, um dos mais importantes problemas de saúde pública. Há um consenso geral de que o RM é mais comum no sexo masculino, um achado atribuído às numerosas mutações nos genes encontrados no cromossomo X, levando ao retardo mental ligado ao X (RMLX). Dentre os genes presentes no cromossomo X, o Jumonji AT-rich interactive domain IC (JARID1C) foi recentemente identificado como um potencial candidato etiológico do RM, quando mutado. O JARID1C codifica uma proteína que atua como uma desmetilase da lisina 4 da histona H3 (H3K4), imprescindível para a regulação epigenética. Tão recente como a identificação do gene JARID1C, é a descoberta de que mudanças no número de cópias de sequências de DNA, caracterizadas por microdeleções e microduplicações, poderiam ser consideradas como razões funcionalmente importantes de RMLX. Atualmente, cerca de 5-10% dos casos de RM em homens são reconhecidos por ocorrerem devido a estas variações do número de cópias no cromossomo X. Neste estudo, investigamos mutações no gene JARID1C, através do rastreamento dos éxons 9, 11, 12, 13, 15 e 16, em 121 homens de famílias com RM provavelmente ligado ao X. Paralelamente, realizamos a análise da variação do número de cópias em 16 genes localizados no cromossomo X através da técnica de MLPA no mesmo grupo de pacientes. Esta metodologia consiste em uma amplificação múltipla que detecta variações no número de cópias de até 50 sequências diferentes de DNA genômico, sendo capaz de distinguir sequências que diferem em apenas um nucleotídeo. O DNA genômico foi extraído a partir de sangue periférico e as amostras foram amplificadas pela técnica de PCR, seguida da análise por sequenciamento direto. Foram identificadas três variantes na sequência do gene JARID1C entre os pacientes analisados: a variante intrônica 2243+11 G>T, que esteve presente em 67% dos pacientes, a variante silenciosa c.1794C>G e a mutação inédita nonsense c.2172C>A, ambas presentes em 0,82% dos indivíduos investigados. A análise através do MLPA revelou uma duplicação em um dos pacientes envolvendo as sondas referentes ao gene GDI1 e ao gene HUWE1. Este trabalho expande o estudo de mutações no gene JARID1C para a população brasileira ereforça a importância da triagem de mutações neste gene em homens portadores de RM familiar de origem idiopática, assim como, é primeiro relato científico relativo à investigação de variações no número de cópias de genes localizados no cromossomo X em homens brasileiros com RM, através da técnica de MLPA. / Mental retardation (MR) is defined as a disability characterized by significant below average intellectual functioning (IQ>70). The prevalence of MR varies between epidemiological studies, estimated at 2-3% of the population, thus constituting a major public health problem. There is a general consensus that MR is more common in males, a finding attributed, in part, to mutations in the genes located on the X chromosome, leading to an X-linked mental retardation (XLMR). Among all the genes present on X chromosome, Jumonji AT-rich interactive domain IC (JARID1C) was recently identified as aetiologic potential candidate of MR, when mutated. The JARID1C gene encodes a protein that acts as a histone demethylase specific for histone 3 lysine 4 (H3K4) and it is indispensable for the epigenetic regulation. As recently as the identification of the JARID1C gene, it is the discovery that changes in the number of copies of DNA sequences, characterized by microdeletions and microduplications, could be regarded as functionally important reasons to XLMR. Currently, about 5-10% of men MR cases are known to occur due to these variations in the number of copies of chromosome X. In this study we investigated mutations in the JARID1C gene by screening of exons 9, 11, 12, 13, 15 and 16 in 121 patients from families with X-linked MR. At the same time we analyzed the variation in the number of copies in 16 genes located in X chromosome through the MLPA technique. This metodology consists of a multiplex amplification that detects variations in the number of copies up to 50 different genomic DNA sequences, being able to distinguish sequences that differ by only one nucleotide. Genomic DNA was extracted from peripheral blood and the samples were amplified by PCR followed by direct sequencing analysis. We identified three sequence variants among 121 patients. The intronic variant c.2243 +11 G> T, which was present in 67% of patients analyzed, the silent variant c.1794C> G and the novel nonsense mutation c.2172C> A, which was present in 0,82% of patients analyzed. The MLPA analysis revealed that the patient 58 exhibited a duplication involving probes for the GDI1 gene and the HUWE1 gene, resulting in an increase in the number of copies of this gene. This work expands the study of mutations in the JARID1C gene for the Brazilian population and reinforces the importance of screening for mutations in this gene in men with idiopathic mental retardation, and it is the first scientific report on the investigation of variations in the number of copies in genes located on chromosome X in Brazilian men with MR using the MLPA technique.