The imprinted expression of the IGF2 and H19 genes is controlled by the imprinting control region 1 (ICR1) located at chromosome 11p15.5. This methylation-sensitive chromatin insulator works by binding the zinc-finger protein CTCF in a parent-specific manner. CTCF binds the unmethylated maternal allele and is required for preventing de novo methylation at ICR1. DNA methylation defects involving the ICR1 IGF2/H19 domain result in two growth disorders with opposite phenotypes: an overgrowth disorder, the Beckwith-Wiedemann syndrome (ICR1 gain of methylation in 10% of BWS cases) and a growth retardation disorder, the Silver-Russell syndrome (ICR1 loss of methylation in 60% of SRS cases). Little information is available regarding the mechanism of ICR1 DNA methylation defects. Several deletions removing part of ICR1 (1.4 to 2.2 kb) have been described in a few familial BWS cases with dominant maternal transmission. In order to evaluate precisely the incidence of ICR1 mutations, we investigated, by long range PCR and sequencing, 21 BWS patients (including two brothers) with ICR1 gain of methylation and 16 SRS patients with ICR1 loss of methylation. No mutation of the seven CTCF binding sites was detected in the familial BWS cases. Two additional cases of constitutional genetic lesions were identified in BWS patients with apparently-sporadic forms. One patient was identified with a 8 bp deletion within the B3 repeat, 116 bases 3' of the CTCF binding site 4. Another patient was identified with a 1.8 kb deletion which eliminates CTCF binding sites 2 and 3. A single-nucleotide variation was identified in a SRS patient. Our data showed that ICR1 deletions, including new small deletions, account for apparently sporadic forms of BWS with ICR1 gain of methylation. ICR1 deletions are associated with a high incidence of Wilms' tumour, making their molecular diagnosis particularly important for genetic counseling and tumor surveillance.

ARAUJO, F. M. Ocorrência Familial e Associação de Polimorfismos dos Genes H19 e IGF2 com as Síndromes Hipertensivas Gestacionais. 2007. 118f. Disertação (Mestrado) Faculdade de Medicina, Universidade de São Paulo, Ribeirão Preto, 2007. As síndromes hipertensivas gestacionais [Pré-eclâmpsia/eclâmpsia (PE/E), hipertensão gestacional (HG) e hipertensão arterial crônica (HAC)] estão entre as maiores causas de morte materna e fetal. A PE é a mais prevalente dessas síndromes e o papel dos fatores genéticos na sua etiologia é bem aceito, embora o padrão de herança seja ainda assunto para debate. Os genes H19 e IGF2 sofrem imprinting (marcação) genômico e estão envolvidos na formação placentária e no desenvolvimento fetal. O objetivo do presente trabalho foi a pesquisa de ocorrência familial e da associação com os polimorfismos H19/RsaI e do IGF2/ApaI das síndromes hipertensivas gestacionais e do peso do recém-nascido. Todas as pacientes do estudo foram atendidas no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo e o projeto foi aprovado pelo Comitê de Ética deste hospital e pela Comissão Nacional de Ética em Pesquisa. Para a condução do estudo familial foram selecionadas 226 mulheres (75 apresentavam PE, 49 com HG e 102 do grupo controle). Os dados foram analisados pelos Testes Exato de Fisher e do Qui-quadrado, resultando em uma maior freqüência estatisticamente significativa (p <0,05) de parentes de primeiro-grau com PE/E entre o grupo de PE/E comparado aos outros grupos. Não foi observada influência da cor da pele na distribuição entre os grupos de pacientes. Para a pesquisa de polimorfismos de comprimento de fragmento de restrição H19/RsaI (alelos A e B) e IGF2/ApaI (alelos A e G) através da reação em cadeia da polimerase , foi extraído DNA de sangue periférico de 236 pacientes (55 apresentavam PE, 40 com HG, 34 com HAC e 107 do grupo controle). Os resultados, analisados através dos Testes do Qui-quadrado e G, não mostraram associação estatisticamente significativa entre os polimorfismos e as síndromes hipertensivas gestacionais ou HAC. Houve uma maior freqüência do alelo G na população estudada. Foi observado que em torno de 80% das pacientes dos quatro grupos estudados apresentou pelo menos uma cópia do alelo B e uma do alelo G, concomitantemente. A associação do peso do recém-nascido com os polimorfismos foi analisada utilizando-se os Testes Kolmogorov-Smirnov (a P<0,05) e os Não-paramétricos de Kruskal-Wallis (a P<0,05), não tendo sido evidenciadas diferenças estatisticamente significativas. No grupo da PE houve uma diminuição estatisticamente significativa do peso dos recém-nascidos quando não havia correção para a idade gestacional. Embora não tenha sido evidenciada correlação entre os polimorfismos e os fenótipos estudados, trabalhos futuros com um número amostral maior serão importantes para auxiliar no entendimento do envolvimento de fatores epigenéticos nas síndromes hipertensivas gestacionais e fornecer indícios para a prevenção, o tratamento e o aconselhamento genético. / ARAUJO, F. M. Familial Occurrence and H19 and IGF2 Polymorphism Association with Gestational Hypertensive Disorders. 2007. 118p. Dissertation (Master\'s degree) - University of Medicine, University of São Paulo, Ribeirão Preto, 2007. Gestational hypertensive disorders [preeclampsia/eclampsia (PE/E), gestational hypertension (GH) and chronic hypertension (CH)] are among the largest causes of maternal and fetal death. PE is the more prevalent of those syndromes and the role of the genetic factors in its etiology is well accepted, although the pattern of inheritance is still subject for debate. The imprinted genes H19 and IGF2 are involved in the placental formation and in the fetal development. The objective of the present study was to verify the familial occurrence of these disorders and the H19/RsaI and IGF2/ApaI polymorphism association with gestational hypertensive disorders and the weight of the newborn. All patients of the study were referred to the Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, University of São Paulo, and the project was approved by the Hospital Ethic Committee and the National Commission of Ethics in Research. For the familial study, 226 women were selected (75 presented PE/E, 49 with GH and 102 from the control group). The data were analyzed by Exact of Fisher and Qui-square tests, and the frequency of families with at least one female first-degree relative (mothers and/or sisters) with PE/E was higher among the PE/E group compared to the other groups, and it was statistically significant (P<0.05). There was no statistically significant influence of the \"skin color\". Blood samples of 236 pregnant women (55 with PE/E, 40 with GH, 34 with CH and 107 from the control group) were obtained for DNA extraction, and PCR. Genotyping was carried out by enzymatic digestion with ApaI (IGF2) and RsaI (H19). The statistical analyses were performed by Qui-square and G tests. The genotypes were not significantly associated with the different groups. A higher frequency of the G allele (IGF2) was observed. Around 80% of the patients presented at least one copy of the allele B (H19) and G (IGF2), concomitantly. The association of the weight of the newborn with the polymorphisms was analyzed using the Kolmogorov-Smirnov (P <0.05) and the No-parametric Test of Kruskal-Wallis (P <0.05) tests, and statistically significant differences were not evidenced. In the group of the PE/E there was a statistically significant decrease of the weight of the newborn when the correction for the gestational age was not carried out. Although correlation has not been evidenced between the polymorphisms and the phenotypes, future studies with a higher number of patients and other imprinted genes will be important to elucidate the involvement of epigenetic factors for the prevention, treatment and genetic counseling of the gestational hypertensive disorders

ARAUJO, F. M. Ocorrência Familial e Associação de Polimorfismos dos Genes H19 e IGF2 com as Síndromes Hipertensivas Gestacionais. 2007. 118f. Disertação (Mestrado) Faculdade de Medicina, Universidade de São Paulo, Ribeirão Preto, 2007. As síndromes hipertensivas gestacionais [Pré-eclâmpsia/eclâmpsia (PE/E), hipertensão gestacional (HG) e hipertensão arterial crônica (HAC)] estão entre as maiores causas de morte materna e fetal. A PE é a mais prevalente dessas síndromes e o papel dos fatores genéticos na sua etiologia é bem aceito, embora o padrão de herança seja ainda assunto para debate. Os genes H19 e IGF2 sofrem imprinting (marcação) genômico e estão envolvidos na formação placentária e no desenvolvimento fetal. O objetivo do presente trabalho foi a pesquisa de ocorrência familial e da associação com os polimorfismos H19/RsaI e do IGF2/ApaI das síndromes hipertensivas gestacionais e do peso do recém-nascido. Todas as pacientes do estudo foram atendidas no Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto da Universidade de São Paulo e o projeto foi aprovado pelo Comitê de Ética deste hospital e pela Comissão Nacional de Ética em Pesquisa. Para a condução do estudo familial foram selecionadas 226 mulheres (75 apresentavam PE, 49 com HG e 102 do grupo controle). Os dados foram analisados pelos Testes Exato de Fisher e do Qui-quadrado, resultando em uma maior freqüência estatisticamente significativa (p <0,05) de parentes de primeiro-grau com PE/E entre o grupo de PE/E comparado aos outros grupos. Não foi observada influência da cor da pele na distribuição entre os grupos de pacientes. Para a pesquisa de polimorfismos de comprimento de fragmento de restrição H19/RsaI (alelos A e B) e IGF2/ApaI (alelos A e G) através da reação em cadeia da polimerase , foi extraído DNA de sangue periférico de 236 pacientes (55 apresentavam PE, 40 com HG, 34 com HAC e 107 do grupo controle). Os resultados, analisados através dos Testes do Qui-quadrado e G, não mostraram associação estatisticamente significativa entre os polimorfismos e as síndromes hipertensivas gestacionais ou HAC. Houve uma maior freqüência do alelo G na população estudada. Foi observado que em torno de 80% das pacientes dos quatro grupos estudados apresentou pelo menos uma cópia do alelo B e uma do alelo G, concomitantemente. A associação do peso do recém-nascido com os polimorfismos foi analisada utilizando-se os Testes Kolmogorov-Smirnov (a P<0,05) e os Não-paramétricos de Kruskal-Wallis (a P<0,05), não tendo sido evidenciadas diferenças estatisticamente significativas. No grupo da PE houve uma diminuição estatisticamente significativa do peso dos recém-nascidos quando não havia correção para a idade gestacional. Embora não tenha sido evidenciada correlação entre os polimorfismos e os fenótipos estudados, trabalhos futuros com um número amostral maior serão importantes para auxiliar no entendimento do envolvimento de fatores epigenéticos nas síndromes hipertensivas gestacionais e fornecer indícios para a prevenção, o tratamento e o aconselhamento genético. / ARAUJO, F. M. Familial Occurrence and H19 and IGF2 Polymorphism Association with Gestational Hypertensive Disorders. 2007. 118p. Dissertation (Master\'s degree) - University of Medicine, University of São Paulo, Ribeirão Preto, 2007. Gestational hypertensive disorders [preeclampsia/eclampsia (PE/E), gestational hypertension (GH) and chronic hypertension (CH)] are among the largest causes of maternal and fetal death. PE is the more prevalent of those syndromes and the role of the genetic factors in its etiology is well accepted, although the pattern of inheritance is still subject for debate. The imprinted genes H19 and IGF2 are involved in the placental formation and in the fetal development. The objective of the present study was to verify the familial occurrence of these disorders and the H19/RsaI and IGF2/ApaI polymorphism association with gestational hypertensive disorders and the weight of the newborn. All patients of the study were referred to the Hospital das Clínicas da Faculdade de Medicina de Ribeirão Preto, University of São Paulo, and the project was approved by the Hospital Ethic Committee and the National Commission of Ethics in Research. For the familial study, 226 women were selected (75 presented PE/E, 49 with GH and 102 from the control group). The data were analyzed by Exact of Fisher and Qui-square tests, and the frequency of families with at least one female first-degree relative (mothers and/or sisters) with PE/E was higher among the PE/E group compared to the other groups, and it was statistically significant (P<0.05). There was no statistically significant influence of the \"skin color\". Blood samples of 236 pregnant women (55 with PE/E, 40 with GH, 34 with CH and 107 from the control group) were obtained for DNA extraction, and PCR. Genotyping was carried out by enzymatic digestion with ApaI (IGF2) and RsaI (H19). The statistical analyses were performed by Qui-square and G tests. The genotypes were not significantly associated with the different groups. A higher frequency of the G allele (IGF2) was observed. Around 80% of the patients presented at least one copy of the allele B (H19) and G (IGF2), concomitantly. The association of the weight of the newborn with the polymorphisms was analyzed using the Kolmogorov-Smirnov (P <0.05) and the No-parametric Test of Kruskal-Wallis (P <0.05) tests, and statistically significant differences were not evidenced. In the group of the PE/E there was a statistically significant decrease of the weight of the newborn when the correction for the gestational age was not carried out. Although correlation has not been evidenced between the polymorphisms and the phenotypes, future studies with a higher number of patients and other imprinted genes will be important to elucidate the involvement of epigenetic factors for the prevention, treatment and genetic counseling of the gestational hypertensive disorders

L'expression du gène Igf2, qui est soumis à l'empreinte génomique parentale chez les mammifères, est hautement régulée au cours du développement embryonnaire et de la période périnatale grâce à divers mécanismes transcriptionnels et post-transcriptionnels. Ces mécanismes mettent à contribution de longs ARN non codants produits au sein même du locus, dont le plus connu est l'ARN H19. En utilisant une approche de complémentation génétique par un transgène H19 dans myoblastes H19 KO de souris, nous démontrons l'existence de plusieurs nouveaux promoteurs d'Igf2. L'un de ces promoteurs, qui est conservé chez l'homme, peut être activé par un ARN ectopique antisens d'H19 (lncARN 91H) en dépit d'une méthylation complète de la région de contrôle empreinte située en cis sur le même allèle. Nous montrons également que les lncARN 91H présentent une certaine spécificité tissulaire et que leur transcription peut être initiée à partir des séquences conservées CS4, CS5 et CS9 situées en aval du gène H19. Quant à l'ARN H19, qui est l'ARN non codant majeur du locus, il semble pouvoir réguler ses transcrits antisens dans les myoblastes H19 KO complémentés par le transgène H19, mais surtout il participe activement à la régulation post-transcriptionnelle du gène Igf2 chez la souris. Nous observons en effet qu'il favorise la coupure endoribonucléolytique de l'ARN Igf2 par un mécanisme qui reste à découvrir. Enfin, nous mettons en évidence l'existence d'un l'arrêt de l'élongation de la transcription du gène d'Igf2, pour lequel nous proposons un modèle de régulation faisant intervenir un autre long ARN non codant du locus: le lncARN PIHit. Au-delà des mécanismes qui restent à explorer, nos résultats renforcent l'idée que la structure tridimensionnelle de la chromatine participe à la régulation de l'expression des gènes chez les mammifères. / In mammals, the expression of the Igf2 gene, which is subject to parental genomic imprinting, is tightly regulated during embryonic development and the perinatal period through several transcriptional and post-transcriptional mechanisms. These mechanisms are involving long non-coding RNAs (lncRNAs) produced within the locus; among them the best known is probably the H19 RNA. Using a genetic complementation assay consisting in transfections of an H19 transgene into H19 KO myoblasts, we discovered several novel Igf2 promoters in the mouse. One of these promoters, that is conserved in the human, can be activated by ectopic H19 antisens RNAs (91H lncRNAs) despite a complete methylation of the Imprinting-Control Region located in cis on the same allele. We also show that the 91H lncRNAs possess some tissue-specific features and that their transcription can be initiated from the CS4, CS5 and CS9 conserved sequences located downstream of the H19 gene. On the other hand, the H19 RNA, that is the major lncRNA of the locus, appears to regulate its antisense transcripts in H19 KO myoblasts complemented with the H19 transgene, but its major function seems to be in regulating post-transcriptionally the Igf2 gene expression. Indeed, we have observed that it favours the endoribonucleolytic cleavage of the Igf2 messenger RNAs through a mechanism that remains to be elucidated. Finally, we reveal the existence of a premature transcriptional elongation stop of the Igf2 gene, for which we propose a regulation model involving another lncRNA of the locus: the PIHit lncRNA. Beyond the mechanisms that remain to be explored, our results strengthen the idea that, in mammals, the three-dimensional organization of the chromatin is involved in regulating gene expression.