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Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disorder of the tyrosine degradation pathway. The defective fumarylacetoacetate hydrolase enzyme causes the accumulation of upstream metabolites such as fumarylacetoacetate (FAA), maleylacetoacetate (MAA), succinylacetone (SA) and p-hydroxyphenylpyruvic acid (pHPPA). In vitro and in vivo studies showed that the accumulation of these metabolites are detrimental to cell homeostasis, by inducing cell cycle arrest, apoptosis, and endoplasmic reticulum stress, depleting GSH, inhibiting DNA ligase, causing chromosomal instability, etc. For in vivo studies different models of HT1 were developed. Most notably was the fah deficient mouse, whose neonatally lethal phenotype is rescued by the administration of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC). Although, this model most closely resembles the human phenotype with elevated tyrosine levels and the development of hepatocellular carcinoma (HCC), the model is not human genome based. Both the in vitro and in vivo studies suggested that DNA repair is affected in HT1. However, it is not yet clear which DNA repair mechanisms are affected and if only protein functionality is affected, or if expression of DNA repair proteins are also affected. Characteristic of HT1 is the high prevalence of HCC and the presence of liver mosaicism. The liver mosaicism observed in HT1 patients are the result of reversion of the inherited mutation to wild-type. The general consensus is that the reversion is the result of a true back mutation. However, the mechanism underlying the back mutation is still unresolved. It was suggested that cancer develops either through a chromosomal instability mutator phenotype, a microsatellite instability mutator phenotype, or a point mutation instability mutator phenotype. In HT1 only chromosomal instability was reported. The aims of this study were to contribute to the understanding of the molecular basis of the genetic mosaicism in hereditary tyrosinemia type 1. More specifically, determine whether baseand nucleotide DNA repair mechanisms are affected and to what extent, and to determine if microsatellite instability is found in HT1. To achieve these aims, a parallel approach was followed: i.e. to develop a HT1 hepatic cell model and to use HT1 related models and HT1 patient material. To assess the molecular basis of the genetic mosaicism in HT1, the comet assay, gene expression assays, microsatellite instability assays, high resolution melting and dideoxy sequencing techniques were employed. Results from the comet assay showed that the HT1 accumulating metabolites, SA and pHPPA, decreased the capacity of cells for base- and nucleotide excision repair. Gene expression assays showed that short term exposure to SA and/or pHPPA do not affect expression of hOGG1 or ERCC1. The expression of these genes were, however, low in HT1 patient samples. Microsatellite instability assays showed allelic imbalance on chromosome 7 of the mouse genome, and microsatellite instability in the lymphocytes of HT1 patients. Although high resolution melt and sequencing results did not reveal any de novo mutations in fah or hprt1, the appearance of de novo mutations on other parts of the genome can not be ruled out. To conclude, results presented in this thesis, for the first time show that in HT1 the initiating proteins of the base- and nucleotide repair mechanisms are affected, the gene expression of DNA repair proteins are low, and microsatellite instability is found in HT1. By contributing to the elucidation of the mechanism underlying the development of HT1-associated HCC, and providing evidence for the development of a mutator phenotype, the results presented in this thesis contributes to the understanding of the molecular mechanisms underlying the genetic mosaicism in HT1. In addition to these contributions, a hypothesis is posited, which suggests that a point mutation instability (PIN) mutator phenotype is the mechanism underlying the mutation reversions seen in HT1. / Thesis (Ph.D. (Biochemistry))--North-West University, Potchefstroom Campus, 2012

Mosaicism is represented by two or more chromosomally different cell lines in an individual. Mosaics are most often caused by chromosome malsegregation during mitosis, resulting in the gain or loss of chromosomes, known as aneuploidy, but structural aberrations can also occur in mosaic form. The problem is the limitation of detection with standart cytogenetic methods. The present study was carried out to compare the efficiency of FISH, array CGH and cytogenetic techniques in detection of mosaicism. In the practical part the results of 45 patients with mosaicisms of aneuplody of gonosomes (26 patients) and mosaicisms of autosomes (19 patients) were compared. The data show that we have different peripheral blood karyotype and FISH results in 23 of 37 patients (62%). There was a case of failure of detection of the mosaicism on the karyotype and the FISH method revealed a abnormal cell lines with a percentage of less than 5%. The array CGH method confirmed the karyotype and FISH results in 10 out of 12 patients (83%) in peripheral blood tests. The work also dealt with artificially made mosaics. From the results, it is obvious that the FISH method has a more accurate percentage of mosaic capture compared to the karyotype. The results indicate that using the techniques in parallel allow in clinical...

O imprinting genômico, processo regulado epigeneticamente segundo o qual os genes se expressam de acordo com sua origem parental, está envolvido no crescimento e desenvolvimento placentário. Na região 11p15.5 encontram-se vários genes regulados por duas regiões controladoras de imprinting (ICR1 e ICR2), onde se encontram as regiões diferencialmente metiladas H19DMR e KvDMR1. Acredita-se que o padrão de imprinting seja dinamicamente regulado durante o desenvolvimento da placenta. Em humanos, há poucas informações sobre imprinting genômico e desenvolvimento placentário, principalmente para estágios precoces do desenvolvimento devido às dificuldades técnicas de obtenção dessas placentas. A descrição de mosaicismo do padrão de metilação restrito a placenta ou entre a placenta e o feto evidencia um perfil epigenético único deste órgão. A 5-hidroximetilação, a qual não tem um papel de silenciamento gênico, pode ser confundida com a metilação do DNA nas análises moleculares. O objetivo principal do presente estudo foi o de verificar a influência da idade gestacional (IG) no perfil de metilação do DNA das ICRs 1 e 2 em vilosidade coriônica, bem como a existência de mosaicismo do perfil de metilação intra-placentário. Neste trabalho também foi investigada a presença de hidroximetilação na KvDMR1. Foram coletadas amostras de tecido placentário, sendo 25 de vilosidades coriônicas (VC) (15 de 3° trimestre gestacional e 10 do 1° trimestre) e nove de cordão umbilical (UC) de 1° trimestre (pareadas com a VC). Quatro placentas de 3° trimestre foram analisadas em separado para o estudo de mosaicismo. O perfil de metilação do DNA das regiões foi verificado por PCR Específica para a Metilação (MS-PCR), Análise Combinada de Bissulfito e Restrição Enzimática (COBRA) e Método de Digestão Enzimática Sensível à Metilação Associada à PCR em Tempo Real (DESM-RT), além do ensaio para hidroximetilação na KvDMR1. Com os ensaios qualitativos (MS-PCR e COBRA) foi observado um perfil de metilação monoalélico, sendo que na H19DMR foi identificada a presença de CpGs diferentemente metilados. Para a H19DMR foram observadas médias de 0,43 de metilação em VC e 0,31 em UC de 1° trimestre, e de 0,41 em VC de 3° trimestre. Para a KvDMR1, foram encontradas médias de 0,47 em VC e 0,57 em UC de 1° trimestre, e de 0,41 em VC de 3° trimestre. A presença de hidroximetilação na KvDMR1 foi excluída. Não foram observadas diferenças significativas entre as médias das diferentes IGs ou entre tecidos pelos testes t e F para ambas as regiões. Não foi observada correlação positiva no perfil de metilação para H19DMR e KvDMR1 entre os tecidos. Em relação ao mosaicismo, não houve diferenças significativas no perfil de metilação entre os diferentes cotilédones amostrados numa mesma placenta. Os resultados demonstram uma discordância entre tecido embrionário (UC) e extraembrionário (VC). Apesar de não serem observadas alterações significantes nos perfis de metilação da H19DMR e KvDMR1 em diferentes IGs, as informações apresentadas são importantes para as pesquisas sobre a dinâmica do fenômeno de imprinting genômico ao longo da gestação, para os estudos de mosaicismo intraplacentário bem como o perfil epigenético da placenta em relação a outros tecidos. / Genomic imprinting, an epigenetically regulated process by which genes are expressed accordingly to their parental origin, is involved in placental growth and development. In 11p15.5 region, there are many genes regulated by two Imprinting Control Regions (ICR1 and ICR2), in which are found two Differentially Methylated Regions, H19DMR and KvDMR1, respectively. Imprinting patterns seem to be adjusted during placenta development. In humans, there is little information on genomic imprinting and placental development, especially for early stages of development due to technical difficulties in obtaining these placentas. The description of mosaicism in methylation pattern restricted to placenta or between placenta and fetus shows a unique epigenetic profile of this organ. The 5-hidroxymethylation, which has no role in gene silencing, can be confused with DNA methylation in molecular analysis. The main aim of our study was to verify the influence of gestational age (GA) in DNA methylation profile of ICRs 1 and 2 in chorionic villi, as well as the existence of intra-placental methylation profile mosaicism. The presence of hydroximethylation in the KvDMR1 was also investigated. Samples were collected from placentas, 25 from chorionic villi (CV) (15 of the 3rd gestational trimester and 10 of the 1st trimester) and nine from umbilical cord (UC) in 1st trimester (paired with the CV samples). Four 3rd trimester placentas were separately analyzed for mosaicism. DNA methylation profile was verified by Methylation Specific PCR (MS-PCR), and Combined Bisulfite Restriction Analysis (COBRA) and Methylation-Sensitive Enzyme Digestion Method associated with Real-Time PCR (DESM-RT), in addition to hydroximethylation test in the KvDMR1 region. With qualitative assays (MS-PCR and COBRA), it was observed a monoallelic methylation pattern, and, only for the H19DMR, differently methylated CpGs were observed. For the H19DMR, we observed methylation means of 0.43 in CV and 0.31 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. For KvDMR1, we observed means of 0.47 in CV and 0.57 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. No hydroximethylation in the KvDMR1 was observed. There were no significant differences between the means of different GAs or between tissues by F and t tests for both regions. No positive correlation was found on methylation profile for H19DMR and KvDMR1 between tissues. In relation to mosaicism, there were no significant differences in methylation profile between different cotyledons sampled in the same placenta. The results showed a discrepancy between embryonic (UC) and extra-embryonic (CV) tissues. Although it was not observed significant changes in methylation profiles of H19DMR and KvDMR1 in different GAs, the presented results are important to research on dynamics of genomic imprinting phenomenon during pregnancy, studies of intra-placental mosaicism and placenta epigenetic profile in relation to other tissues.

Hereditary tyrosinemia type 1 (HT1) is an autosomal recessive disorder of the tyrosine degradation pathway. The defective fumarylacetoacetate hydrolase enzyme causes the accumulation of upstream metabolites such as fumarylacetoacetate (FAA), maleylacetoacetate (MAA), succinylacetone (SA) and p-hydroxyphenylpyruvic acid (pHPPA). In vitro and in vivo studies showed that the accumulation of these metabolites are detrimental to cell homeostasis, by inducing cell cycle arrest, apoptosis, and endoplasmic reticulum stress, depleting GSH, inhibiting DNA ligase, causing chromosomal instability, etc. For in vivo studies different models of HT1 were developed. Most notably was the fah deficient mouse, whose neonatally lethal phenotype is rescued by the administration of 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC). Although, this model most closely resembles the human phenotype with elevated tyrosine levels and the development of hepatocellular carcinoma (HCC), the model is not human genome based. Both the in vitro and in vivo studies suggested that DNA repair is affected in HT1. However, it is not yet clear which DNA repair mechanisms are affected and if only protein functionality is affected, or if expression of DNA repair proteins are also affected. Characteristic of HT1 is the high prevalence of HCC and the presence of liver mosaicism. The liver mosaicism observed in HT1 patients are the result of reversion of the inherited mutation to wild-type. The general consensus is that the reversion is the result of a true back mutation. However, the mechanism underlying the back mutation is still unresolved. It was suggested that cancer develops either through a chromosomal instability mutator phenotype, a microsatellite instability mutator phenotype, or a point mutation instability mutator phenotype. In HT1 only chromosomal instability was reported. The aims of this study were to contribute to the understanding of the molecular basis of the genetic mosaicism in hereditary tyrosinemia type 1. More specifically, determine whether baseand nucleotide DNA repair mechanisms are affected and to what extent, and to determine if microsatellite instability is found in HT1. To achieve these aims, a parallel approach was followed: i.e. to develop a HT1 hepatic cell model and to use HT1 related models and HT1 patient material. To assess the molecular basis of the genetic mosaicism in HT1, the comet assay, gene expression assays, microsatellite instability assays, high resolution melting and dideoxy sequencing techniques were employed. Results from the comet assay showed that the HT1 accumulating metabolites, SA and pHPPA, decreased the capacity of cells for base- and nucleotide excision repair. Gene expression assays showed that short term exposure to SA and/or pHPPA do not affect expression of hOGG1 or ERCC1. The expression of these genes were, however, low in HT1 patient samples. Microsatellite instability assays showed allelic imbalance on chromosome 7 of the mouse genome, and microsatellite instability in the lymphocytes of HT1 patients. Although high resolution melt and sequencing results did not reveal any de novo mutations in fah or hprt1, the appearance of de novo mutations on other parts of the genome can not be ruled out. To conclude, results presented in this thesis, for the first time show that in HT1 the initiating proteins of the base- and nucleotide repair mechanisms are affected, the gene expression of DNA repair proteins are low, and microsatellite instability is found in HT1. By contributing to the elucidation of the mechanism underlying the development of HT1-associated HCC, and providing evidence for the development of a mutator phenotype, the results presented in this thesis contributes to the understanding of the molecular mechanisms underlying the genetic mosaicism in HT1. In addition to these contributions, a hypothesis is posited, which suggests that a point mutation instability (PIN) mutator phenotype is the mechanism underlying the mutation reversions seen in HT1. / Thesis (Ph.D. (Biochemistry))--North-West University, Potchefstroom Campus, 2012

Orientador: Carlos Eduardo Steiner / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-17T00:08:21Z (GMT). No. of bitstreams: 1 Cunha_KarinaSoares_M.pdf: 3290868 bytes, checksum: 62ac845d38c989b1515d635bf2bfa79b (MD5) Previous issue date: 2010 / Resumo: O Mosaico pigmentar tipo Ito é uma alteração cutânea frequente, caracterizada por hipopigmentação da pele que, na maioria dos casos, segue o padrão linhas de Blaschko, geralmente associada a anomalias extracutâneas, sobretudo anomalias do Sistema Nervoso Central (SNC). Sugere-se que esse padrão decorre da presença e migração de duas linhagens celulares no período embrionário, com diferente expressão de genes associados à pigmentação, que darão origem à epiderme e ao SNC no feto. Diversos tipos de mosaicismo foram associados ao quadro e acredita-se que os casos em que não houve tal detecção se devam à limitação das células analisadas. Devido à função, origem embrionária e migração celular, possivelmente o mosaicismo seria melhor identificado em melanócitos e queratinócitos, principalmente na presença de alterações no SNC, as alterações poderiam ter envolvimento com o prognóstico neurológico. Neste estudo foi realizada análise citogenética de linfócitos e fibroblastos de 15 indivíduos com mosaico pigmentar do tipo Ito. Os objetivos incluíram padronizar a cultura de células de melanócitos e queratinócitos, visando analisar o cariótipo desses indivíduos nesses tipos celulares. O estudo citogenético nesses tipos celulares, porém, não pode ser realizado devido à dificuldade de se obter metáfases adequadas para análise. Assim, foi desenvolvido protocolo de cultura e análise citogenética em queratinócitos, o qual funcionou adequadamente em indivíduos testes, porém sem resultado semelhante nos sujeitos de pesquisa. A preparação cromossômica a partir de melanócitos, por outro lado, não se mostrou adequada. Na análise de linfócitos e fibroblastos, foram encontradas alterações cromossômicas diferentes em quatro indivíduos (26% da casuística), presentes em ambos os tipos celulares. Não foram observadas divergências nas amostras a partir de pele hipo e normopigmentadas. Essas alterações incluíram um caso de t(X;21) regular, para o qual foram realizados estudos complementares de forma a aprimorar a investigação laboratorial, sendo análise por array-CGH, FISH e estudo de inativação de X. Um caso se tratou de trissomia 18 em mosaico, nesse indivíduo não foi possível a coleta de biópsia, porém foi realizado FISH interfásico em células da mucosa oral. Houve também um caso de r(22) em mosaico, o único que apresentou diferença na proporção de células alteradas em fibroblastos e linfócitos, possivelmente por maior instabilidade in vitro de cromossomos em anel em culturas de longa duração. O último caso alterado se refere a um cromossomo marcador, também em mosaico. Os resultados obtidos foram comparados com dados da literatura prévia. Assim, apenas um caso apresentou alteração cromossômica não em mosaico, representada por uma translocação X/autossomo regular, para a qual as técnicas de estudo utilizadas não detectaram justificativa para o padrão de mosaicismo observado clinicamente / Abstract: Pigmentary mosaicism of Ito type is a skin abnormality often characterized by hypopigmentation of the skin following, in most cases, the Blaschko lines, usually associated with extracutaneous abnormalities, especially abnormalities of the central nervous system (CNS). It is suggested that this pattern arises from the presence and migration of two cell lineages in the embryonic period, with different expression of genes associated with pigmentation, which will give rise to the epidermis and the CNS in the fetus. Several types of mosaicism have been associated with this disorder. In cases in which no mosaicismo was detected, it is believed that this may be secondary to the limitation of the cells analyzed. Due to the function and embryonic cell migration, in individuals with pigmentary mosaicism, a cytogenetic mosaicism possibly would be better identified in melanocytes and keratinocytes, especially in the presence of changes in the CNS. Besides, these changes could prognose the neurological outcome. This study comprehended cytogenetic analysis of lymphocytes and fibroblasts from 15 individuals with pigmentary mosaicism of Ito type. The targets included standardize the cell culture of melanocytes and keratinocytes in order to analyze the karyotype of these individuals in these cell types. The cytogenetic study in these cell types, however, was not possible due to difficulties in obtaining adequate metaphases for analysis. Given this difficulty, another cell type (fibroblasts) was studied. In the end, chromosomal abnormalities in lymphocytes and fibroblasts were identified in four individuals. These included one case of a balanced traslocation X/21, one case of trisomy 18 mosaicism, one case of a ring 22 mosaic and one marker chromosome, also in mosaic. Considering the results of cytogenetic lymphocytes and fibroblasts, additional studies were undertaken to enhance the laboratory investigation of these cases, including array-CGH, FISH and study of X inactivation. The results were compared with previous literature data. In conclusion, we developed protocol for culture and cytogenetic analysis in keratinocytes, which worked well on test subjects, but without similar results in study subjects. The chromosome preparation from melanocytes, however, was not adequate. There were no differences in samples from different area of skin. Only one case showed different proportion of cells altered in fibroblasts and lymphocytes, possibly due to instability of ring chromosomes in long duration cultures. Finally, only one case showed no chromosomal abnormality in mosaic, represented by a regular translocation X/autosome, for which the techniques used to study detected no explanation for the pattern of mosaicism observed clinically / Mestrado / Ciencias Biomedicas / Mestre em Ciências Médicas

O imprinting genômico, processo regulado epigeneticamente segundo o qual os genes se expressam de acordo com sua origem parental, está envolvido no crescimento e desenvolvimento placentário. Na região 11p15.5 encontram-se vários genes regulados por duas regiões controladoras de imprinting (ICR1 e ICR2), onde se encontram as regiões diferencialmente metiladas H19DMR e KvDMR1. Acredita-se que o padrão de imprinting seja dinamicamente regulado durante o desenvolvimento da placenta. Em humanos, há poucas informações sobre imprinting genômico e desenvolvimento placentário, principalmente para estágios precoces do desenvolvimento devido às dificuldades técnicas de obtenção dessas placentas. A descrição de mosaicismo do padrão de metilação restrito a placenta ou entre a placenta e o feto evidencia um perfil epigenético único deste órgão. A 5-hidroximetilação, a qual não tem um papel de silenciamento gênico, pode ser confundida com a metilação do DNA nas análises moleculares. O objetivo principal do presente estudo foi o de verificar a influência da idade gestacional (IG) no perfil de metilação do DNA das ICRs 1 e 2 em vilosidade coriônica, bem como a existência de mosaicismo do perfil de metilação intra-placentário. Neste trabalho também foi investigada a presença de hidroximetilação na KvDMR1. Foram coletadas amostras de tecido placentário, sendo 25 de vilosidades coriônicas (VC) (15 de 3° trimestre gestacional e 10 do 1° trimestre) e nove de cordão umbilical (UC) de 1° trimestre (pareadas com a VC). Quatro placentas de 3° trimestre foram analisadas em separado para o estudo de mosaicismo. O perfil de metilação do DNA das regiões foi verificado por PCR Específica para a Metilação (MS-PCR), Análise Combinada de Bissulfito e Restrição Enzimática (COBRA) e Método de Digestão Enzimática Sensível à Metilação Associada à PCR em Tempo Real (DESM-RT), além do ensaio para hidroximetilação na KvDMR1. Com os ensaios qualitativos (MS-PCR e COBRA) foi observado um perfil de metilação monoalélico, sendo que na H19DMR foi identificada a presença de CpGs diferentemente metilados. Para a H19DMR foram observadas médias de 0,43 de metilação em VC e 0,31 em UC de 1° trimestre, e de 0,41 em VC de 3° trimestre. Para a KvDMR1, foram encontradas médias de 0,47 em VC e 0,57 em UC de 1° trimestre, e de 0,41 em VC de 3° trimestre. A presença de hidroximetilação na KvDMR1 foi excluída. Não foram observadas diferenças significativas entre as médias das diferentes IGs ou entre tecidos pelos testes t e F para ambas as regiões. Não foi observada correlação positiva no perfil de metilação para H19DMR e KvDMR1 entre os tecidos. Em relação ao mosaicismo, não houve diferenças significativas no perfil de metilação entre os diferentes cotilédones amostrados numa mesma placenta. Os resultados demonstram uma discordância entre tecido embrionário (UC) e extraembrionário (VC). Apesar de não serem observadas alterações significantes nos perfis de metilação da H19DMR e KvDMR1 em diferentes IGs, as informações apresentadas são importantes para as pesquisas sobre a dinâmica do fenômeno de imprinting genômico ao longo da gestação, para os estudos de mosaicismo intraplacentário bem como o perfil epigenético da placenta em relação a outros tecidos. / Genomic imprinting, an epigenetically regulated process by which genes are expressed accordingly to their parental origin, is involved in placental growth and development. In 11p15.5 region, there are many genes regulated by two Imprinting Control Regions (ICR1 and ICR2), in which are found two Differentially Methylated Regions, H19DMR and KvDMR1, respectively. Imprinting patterns seem to be adjusted during placenta development. In humans, there is little information on genomic imprinting and placental development, especially for early stages of development due to technical difficulties in obtaining these placentas. The description of mosaicism in methylation pattern restricted to placenta or between placenta and fetus shows a unique epigenetic profile of this organ. The 5-hidroxymethylation, which has no role in gene silencing, can be confused with DNA methylation in molecular analysis. The main aim of our study was to verify the influence of gestational age (GA) in DNA methylation profile of ICRs 1 and 2 in chorionic villi, as well as the existence of intra-placental methylation profile mosaicism. The presence of hydroximethylation in the KvDMR1 was also investigated. Samples were collected from placentas, 25 from chorionic villi (CV) (15 of the 3rd gestational trimester and 10 of the 1st trimester) and nine from umbilical cord (UC) in 1st trimester (paired with the CV samples). Four 3rd trimester placentas were separately analyzed for mosaicism. DNA methylation profile was verified by Methylation Specific PCR (MS-PCR), and Combined Bisulfite Restriction Analysis (COBRA) and Methylation-Sensitive Enzyme Digestion Method associated with Real-Time PCR (DESM-RT), in addition to hydroximethylation test in the KvDMR1 region. With qualitative assays (MS-PCR and COBRA), it was observed a monoallelic methylation pattern, and, only for the H19DMR, differently methylated CpGs were observed. For the H19DMR, we observed methylation means of 0.43 in CV and 0.31 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. For KvDMR1, we observed means of 0.47 in CV and 0.57 in UC of 1st trimester, and 0.41 in CV of 3rd trimester. No hydroximethylation in the KvDMR1 was observed. There were no significant differences between the means of different GAs or between tissues by F and t tests for both regions. No positive correlation was found on methylation profile for H19DMR and KvDMR1 between tissues. In relation to mosaicism, there were no significant differences in methylation profile between different cotyledons sampled in the same placenta. The results showed a discrepancy between embryonic (UC) and extra-embryonic (CV) tissues. Although it was not observed significant changes in methylation profiles of H19DMR and KvDMR1 in different GAs, the presented results are important to research on dynamics of genomic imprinting phenomenon during pregnancy, studies of intra-placental mosaicism and placenta epigenetic profile in relation to other tissues.

Orientadores: Andréa Trevas Maciel Guerra, Maricilda Palandi de Mello / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-23T00:38:47Z (GMT). No. of bitstreams: 1 Santos_AnaPaulados_M.pdf: 2717833 bytes, checksum: 8a3a2ff5cccd42ca60c0bc51ba3b0067 (MD5) Previous issue date: 2013 / Resumo: As disgenesias gonadais parcial (DGP) e mista (DGM) caracterizam-se por ambiguidade genital e presença de gônada disgenética associada a testículo disgenético ou dois testículos disgenéticos. Na DGP o cariótipo é 46,XY; na DGM, há mosaico 45,X/46,XY ou suas variantes (mais de duas linhagens e (ou) anomalias estruturais do cromossomo Y). Esses mosaicos podem determinar, ainda, fenótipo feminino com síndrome de Turner (ST), distúrbio da diferenciação do sexo ovotesticular (DDS OT) e esterilidade em homens com genitais normais. Independentemente do fenótipo gonadal e genital, esses indivíduos apresentam outros sinais clínicos decorrentes da linhagem 45,X, como baixa estatura, dismorfismos, anomalias cardíacas e renais e diversas afecções adquiridas. Nos últimos anos surgiram evidências de ligação entre microdeleções do Y e o mosaicismo com linhagem 45,X. Há, ainda, indicações de que a instabilidade cromossômica trazida por essas deleções possa ser mais pronunciada nas gônadas. O objetivo deste trabalho foi investigar a presença de microdeleções do Y em indivíduos com DGP e naqueles com mosaico 45,X/46,XY ou suas variantes e diferentes fenótipos. A casuística constou de 15 indivíduos com DGP e 15 com mosaicismo, dos quais a maioria apresentava DGM (11 casos). Foram analisados 38 sequence tagged sites (STS) cobrindo a região específica masculina (MSY, male specific region) em Yp, centrômero e Yq por meio da técnica de reação em cadeia da polimerase (PCR) multiplex e individual. Todos os STS investigados nos indivíduos com DGP tiveram amplificação positiva, porém havia STS de Yq ausentes em seis indivíduos com mosaicismo e DGM, dos quais dois sem alterações estruturais de Y evidentes ao cariótipo. Essas deleções se localizavam em regiões contendo genes relacionados à espermatogênese (AZFb e AZFc - azoospermia factor). A ausência de deleções nos indivíduos com DGP não confirma a hipótese de que a instabilidade desse cromossomo nas gônadas seja uma das causas dessa afecção. Por outro lado, as deleções encontradas no segundo grupo indicam, em alguns casos, associação entre alterações estruturais do Y detectáveis somente a nível molecular e o surgimento de mosaicismo. Caso sejam criados no sexo masculino e busquem procedimentos de fertilização in vitro, há risco de que esses indivíduos transmitam cromossomos Y instáveis na divisão celular / Abstract: Partial and mixed gonadal dysgenesis (PGD and MGD) are characterized by genital ambiguity and the finding of either a streak gonad and a dysgenetic testis or two dysgenetic testes. In PGD there is a 46,XY karyotype, whereas in MGD there is a 45,X/46,XY mosaic or its variants (more than two lineages and/or structural abnormalities of the Y chromosome). These mosaics are also compatible with a female phenotype and Turner syndrome, ovotesticular disorder of sex development, and infertility in men with normal external genitalia. Regardless of the gonadal and genital phenotypes, these individuals present other clinical features associated with the 45,X cell line, including short stature, dysmorphisms, cardiovascular and renal anomalies and various acquired diseases. During the last few years, evidences of a link between Y microdeletions and 45,X mosaicism have been reported. There are also indications that the instability caused by such deletions might be more significant in germ cells. The aim of this work was to investigate the presence of Y chromosome microdeletions in individuals with PGD and in those with 45,X/46,XY mosaicism or its variants and variable phenotypes. Our sample comprised 15 individuals with PGD and 15 with mosaicism, most of them with a MGD phenotype (n=11). Thirty-eight sequence tagged sites (STS) spanning the male specific region (MSY) on the Y chromosome (Yp, centromere and Yq) where analyzed by multiplex PCR and some individual reactions. All STS showed positive amplifications in the PGD group. Conversely, in the group with mosaicism, six individuals with MGD had been identified with Yq microdeletions, two of them did not have structural abnormalities of the Y chromosome recognized by routine cytogenetic analysis. The deleted STSs were located within AZFb and AZFc (Azoospermia Factor) regions, which harbor several genes responsible for spermatogenesis. Absence of deletions in individuals with PGD does not confirm the hypothesis that instability of the Y chromosome in the gonads could be one of the causes of such condition. However, deletions identified in the second group indicate that mosaicism may be associated with Y chromosome abnormalities detectable only at the molecular level. If patients with mosaicism and Y microdeletions reared as males decide to undergo in vitro fertilization, Y chromosomes which tend to be unstable during cell division may be transmitted to offspring / Mestrado / Ciencias Biomedicas / Mestra em Ciências Médicas

Please read the abstract in the section 00front of this document / Dissertation (MSc (Microbiology))--University of Pretoria, 2005. / Microbiology and Plant Pathology / unrestricted

Mosaicism occurs due to postzygotic genetic alterations during early embryonic development. The phenomenon is common, present in all humans, animals, and plants, and is associated with phenotypic variability and heterogeneity. Mosaic pathogenic gene variants result in a mosaic disease state, in which the individual can present with mild, generalized disease, a localized disease phenotype in specific organs and tissue regions, or full-blown clinical features which are indistinguishable from the heterozygous disease state. Multiple studies have described the prevalence and clinical correlations associated with low-level mosaicism for various genetic disorders, including several tumor suppressor gene (TSG) syndromes, which are well-known to display mosaicism. However, the extent of mosaicism research varies widely between TSG syndromes. Currently there is no comprehensive, up to date review covering multiple TSGs and focusing on mosaicism prevalence, diagnostic strategies and transmission risk. Here, in this literature review, I focus on 8 common tumor suppressor genes NF1, NF2, TSC1, TSC2, RB1, PTEN, VHL, and TP53; reporting the following disease aspects: • Role and function of each tumor suppressor gene, disease prevalence, inheritance pattern, penetrance/expressivity pattern, age of onset clinical features, organs affected, and benign or malignant tumors seen • Different types of mosaicism, including critical review of recent, representative publications for each tumor suppressor gene syndrome • Established criteria for clinical diagnosis of inherited versus mosaic disease, molecular diagnosis, and current methods of genetic analysis Then more extensively, this thesis discusses the most informative, representative original studies for each TSG and provides a summary which covers: • The number of mosaic patients analyzed and the spectrum of clinical features of the cohort they were sampled from • The spectrum of variant allele frequency (VAF), tissue types analyzed, and different analysis methods performed • Whether or not the mosaic patients met clinical criteria for diagnosis of inherited disease • The number of patients who were persistently classified as no mutation identified (NMI) after genetic analysis • Spectrum and type of mosaic mutational event(s) identified • Age of onset and age range of mosaic patients • Patient ascertainment and family history (sporadic or familial cases) and • Type of mosaicism seen Furthermore, it compares and discusses disease severity, possibility of malignancy, and genotype-phenotype correlations for each TSG. Ultimately, by juxtaposing these TSGs, this review aims to centralize existing knowledge about mosaicism and provide insight into how molecular techniques can be broadly applied for better diagnosis of mosaic disease. / 2022-11-10T00:00:00Z