Thèse d'exercice : Médecine : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

Noonan spectrum disorders belong to the RASopathies, a group of clinically related developmental disorders caused by dysregulation of the RAS-MAPK pathway. This thesis describes genetic and clinical investigations of six families with Noonan spectrum disorders. In the first family, the index patient presented with severe Noonan syndrome (NS) and multiple café-au-lait (CAL) spots, while four additional family members displayed multiple CAL spots only. Genetic analysis of four RAS-MAPK genes revealed a de novo PTPN11 mutation and a paternally inherited NF1 mutation, which could explain the atypically severe NS, but not the CAL spots trait in the family. The co-occurrence of two mutations was also present in another patient with a severe/complex NS-like phenotype. Genetic analysis of nine RASopathy-associated genes identified a de novo SHOC2 mutation and a maternally inherited PTPN11 mutation. The latter was also identified in her brother. Both the mother and the brother displayed mild phenotypes of NS. The results from these studies suggest that an additive effect of co-occurring mutations contributes to severe/complex NS phenotypes. The inherent difficulty in diagnosing Noonan spectrum disorders is evident in families with neurofibromatosis-Noonan syndrome (NFNS). An analysis of nine RASopathy-associated genes in a five-generation family with NFNS revealed a novel NF1 mutation in all affected family members. Notably, this family was initially diagnosed with NS and CAL spots. The clinical overlap between NS and NFNS was further demonstrated in three additional NFNS families. An analysis of twelve RASopathy-associated genes revealed three different NF1 mutations, all segregating with the disorder in each family. These mutations have been reported in patients with NF1, but have, to our knowledge, not been associated with NFNS previously. Together, these findings support the notion that NFNS is a variant of NF1. Due to the clinical overlap between NS and NFNS, we propose screening for NF1 mutations in NS patients negative for mutations in NS-associated genes, preferentially when CAL spots are present. In conclusion, this thesis suggests that co-occurrence of mutations or modifying loci in the RAS-MAPK pathway contributes to the clinical variability observed within Noonan spectrum disorders and further demonstrates the importance of accurate genetic diagnosis.

Noonan syndrome (NS) is one of several autosomal dominant “RASopathies” caused by mutations in components of the RAS-RAF-MEK-ERK MAPK pathway. Germ line mutations in RAF1 (encoding the serine-threonine kinase for MEK1/2) account for ~3-5% of NS, and unlike other NS alleles, RAF1 mutations that confer increased kinase activity are highly associated with hypertrophic cardiomyopathy (HCM). Notably, some NS-associated RAF1 mutations show normal or decreased kinase activity. To explore the pathogenesis of such mutations, I generated “knock-in” mice that express kinase-activating (L613V) or -impaired (D486N) Raf1 mutants, respectively. Knock-in mice expressing the kinase-activated allele Raf1L613V developed typical NS features (short stature, facial dysmorphia, haematological abnormalities), as well as HCM. As expected, agonist-evoked Mek/Erk activation was enhanced in multiple cell types expressing Raf1L613V. Moreover, postnatal Mek inhibition normalized the growth, facial, and cardiac defects in L613V/+ mice, showing that enhanced Mek/Erk activation by Raf1 mutant is critical for evoking NS phenotypes. D486N/+ female mice exhibited a mild growth defect. Male and female D486N/D486N mice developed concentric cardiac hypertrophy and incompletely penetrant, but severe, growth defects. Remarkably, Mek/Erk activation was enhanced in Raf1D486N-expressing cells compared with controls. In both mouse and human cells, RAF1D486N, as well as other kinase-impaired RAF1 mutants, show increased heterodimerization with BRAF, which is necessary and sufficient to promote increased MEK/ERK activation. Furthermore, kinase-activating RAF1 mutants also require heterodimerization to enhance MEK/ERK activation. Our results suggest that increased heterodimerization ability is the common pathogenic mechanism for NS-associated RAF1 mutations.

INTRODUÇÃO: a síndrome de Noonan apresenta herança autossômica dominante e é considerada uma doença relativamente frequente na população, com uma incidência estimada entre 1/1000 e 1/2500 nascidos vivos. Dentre os seus acometimentos destacam-se: dismorfismos faciais, baixa estatura, alterações cardíacas e criptorquia. A síndrome de Noonan é muito confundida com as síndromes Noonan-like devido à sobreposição dos achados clínicos. Estas, mais raras que a síndrome de Noonan, incluem as síndromes de LEOPARD, neurofibromatose-Noonan, cardiofaciocutânea e Costello. Atualmente sabe-se que tanto a síndrome de Noonan como as síndromes Noonan-like envolvem mutações em genes pertencentes à via de sinalização RAS-MAPK. Na síndrome de Noonan, pelo menos quatro genes desta via são responsáveis pelo fenótipo: PTPN11, SOS1, RAF1 e KRAS. Mutações no gene PTPN11, o primeiro gene descrito em associação com a síndrome, são encontradas em aproximadamente 40% dos casos. O segundo gene descrito, o gene KRAS, é responsável por cerca de 2% dos casos que não apresentam mutações no gene PTPN11. Mutações no gene KRAS estão presentes em pacientes com síndrome de Noonan com retardo mental e/ou atraso no desenvolvimento mais acentuados e em pacientes com a síndrome cardiofaciocutânea cujo envolvimento ectodérmico é mais sutil. OBJETIVO: devido à recente associação do gene KRAS com a síndrome de Noonan e outras síndromes Noonan-like é importante: (1) testar a frequência de mutação neste gene em pacientes que apresentam ou não mutações no gene PTPN11 e (2) tentar estabelecer uma correlação genótipo-fenótipo mais precisa, o que permitirá a realização de um aconselhamento genético mais adequado. MÉTODOS: foram avaliados 95 probandos com síndrome de Noonan e 30 com síndromes Noonan-like. O estudo molecular foi realizado através da reação em cadeia de polimerase, seguida das reações de purificação e sequenciamento bidirecional. RESULTADOS: foram encontradas mutações no gene PTPN11 em 20/46 (43%) pacientes com síndrome de Noonan, duas delas não descritas anteriormente. Relacionando o quadro clínico dos pacientes com síndrome de Noonan deste estudo, com e sem mutação no gene PTPN11, nota-se que os pacientes com mutação apresentam incidência significativamente maior de baixa estatura, de estenose pulmonar valvar e menor frequência de miocardiopatia hipertrófica. Uma mutação no gene KRAS foi encontrada em um paciente com síndrome de Costello, mutação esta ainda não relatada. Alterações gênicas em mais de um gene da via RAS-MAPK foram observadas em dois pacientes, sendo que uma delas em cada paciente não predizia um efeito fenotípico importante. Foram também encontrados três polimorfismos no gene KRAS, porém com mesma frequência no grupo controle. A fim de verificar a influência destes polimorfismos, as principais características da síndrome de Noonan foram relacionadas entre os pacientes com esta síndrome que apresentavam mutação no gene PTPN11 e comparadas quanto à presença ou ausência desses polimorfismos. Nenhuma diferença estatisticamente significante foi encontrada. CONCLUSÃO: Pacientes com síndrome de Noonan e mutações no gene PTPN11 apresentaram uma maior incidência de baixa estatura e de estenose pulmonar valvar e uma menor incidência de miocardiopatia hipertrófica. O gene KRAS, até então relacionado às síndromes de Noonan e cardiofaciocutânea, mostrou-se também responsável pela síndrome de Costello. Tanto as alterações gênicas consideradas não patogênicas como os polimorfismos encontrados no gene KRAS parecem não ter uma grande influência sobre a variabilidade fenotípica na síndrome de Noonan. Contudo, não é possível afastar totalmente que estas alterações apresentem um efeito sutil e que, em conjunto com outras variações genéticas e/ou ambientais, tenham um efeito modulador / INTRODUCTION: Noonan syndrome shows autosomal dominant inheritance, and is a relatively frequent disease in the population, with an estimated incidence between 1/1000 and 1/2500 live births. The main clinical features are: facial dysmorphisms, short stature, cryptorchidism and cardiac abnormalities. The differential diagnosis between Noonan syndrome and Noonan-like syndromes is not always easy, due to the overlap of the their clinicla findings. The Noonan-like syndromes, more rare that the Noonan syndrome, include the LEOPARD syndrome, neurofibromatosis-Noonan, cardiofaciocutaneous and Costello. Currently it is known that Noonan syndrome and Noonan-like syndromes involve mutations in genes belonging to the RAS-MAPK signaling pathway. In Noonan syndrome, at least four genes of this pathway are responsible for the phenotype: PTPN11, SOS1, RAF1 and KRAS. Mutations in PTPN11, the first gene described in association with this syndrome, are found in approximately 40% of cases. The second gene described, the KRAS gene, is responsible for about 2% of the cases that dont have mutations in the PTPN11 gene. Mutations in the KRAS gene are present in patients with Noonan syndrome with mental retardation and/or developmental delay more pronounced and in patients with cardiofaciocutaneous syndrome whose ectodermal involvement is more subtle. OBJECTIVE: Due to the recent association of the KRAS gene with Noonan and Noonan-like syndromes is important: (1) to test the frequency of mutation in this gene in patients with or without mutations in PTPN11 and (2) to estabilish a more precise genotype-phenotype correlation, allowing the realization of a more appropriate genetic counseling. METHODS: 95 probands with Noonan syndrome and 30 with Noonan-like syndromes were evaluated. The molecular analysis was performed by the polymerase chain reaction, followed by purification and bidirectional sequencing. RESULTS: PTPN11 gene mutation was found in 20/46 (43%) patients with Noonan syndrome, two of them not previously described. By correlating the clinical features of patients with Noonan syndrome in this study, with or without mutations in the PTPN11 gene, it was noted that patients with mutations have significantly higher incidence of short stature, pulmonary stenosis and lower incidence of hypertrophic cardiomyopathy. Mutations in KRAS gene were found in two patients a patient with Noonan syndrome ant the other with Costello syndrome. Gene alterations in more than one gene at the RASMAPK patway were observed in two patients, but one of the mutations in each patient didnt predict a significant phenotypic effect. Were also foud three polymorphisms in the KRAS gene, but with the same frequency in the control group. To check the influence of these polymorphisms, the main features of Noonan syndrome were related among patients with this syndrome who had mutations in the PTPN11 gene and compared of the presence or absence of these polymorphisms. No statistically significant difference was found. CONCLUSION: Patients with Noonan syndrome and PTPN11 gene mutation had a higher incidence of short stature and pulmonary valve stenosis and a lower incidence of hypertrophic cardiomyopathy. The KRAS gene, previously related to Noonan and cardiofaciocutaneous syndrome, was also responsible for Costello syndrome. Gene alterations considered as nonpathogenic and polymorphisms found in the KRAS gene seem to have a not great influence on the phenotypic variability in Noonan syndrome. However, it is not possible to completely rule out that these changes have a subtle effect and that, together with other genetic variations and/or environmental factors, may have a modulating effect

Noonan syndrome (NS) is one of several autosomal dominant “RASopathies” caused by mutations in components of the RAS-RAF-MEK-ERK MAPK pathway. Germ line mutations in RAF1 (encoding the serine-threonine kinase for MEK1/2) account for ~3-5% of NS, and unlike other NS alleles, RAF1 mutations that confer increased kinase activity are highly associated with hypertrophic cardiomyopathy (HCM). Notably, some NS-associated RAF1 mutations show normal or decreased kinase activity. To explore the pathogenesis of such mutations, I generated “knock-in” mice that express kinase-activating (L613V) or -impaired (D486N) Raf1 mutants, respectively. Knock-in mice expressing the kinase-activated allele Raf1L613V developed typical NS features (short stature, facial dysmorphia, haematological abnormalities), as well as HCM. As expected, agonist-evoked Mek/Erk activation was enhanced in multiple cell types expressing Raf1L613V. Moreover, postnatal Mek inhibition normalized the growth, facial, and cardiac defects in L613V/+ mice, showing that enhanced Mek/Erk activation by Raf1 mutant is critical for evoking NS phenotypes. D486N/+ female mice exhibited a mild growth defect. Male and female D486N/D486N mice developed concentric cardiac hypertrophy and incompletely penetrant, but severe, growth defects. Remarkably, Mek/Erk activation was enhanced in Raf1D486N-expressing cells compared with controls. In both mouse and human cells, RAF1D486N, as well as other kinase-impaired RAF1 mutants, show increased heterodimerization with BRAF, which is necessary and sufficient to promote increased MEK/ERK activation. Furthermore, kinase-activating RAF1 mutants also require heterodimerization to enhance MEK/ERK activation. Our results suggest that increased heterodimerization ability is the common pathogenic mechanism for NS-associated RAF1 mutations.

INTRODUÇÃO: a síndrome de Noonan apresenta herança autossômica dominante e é considerada uma doença relativamente frequente na população, com uma incidência estimada entre 1/1000 e 1/2500 nascidos vivos. Dentre os seus acometimentos destacam-se: dismorfismos faciais, baixa estatura, alterações cardíacas e criptorquia. A síndrome de Noonan é muito confundida com as síndromes Noonan-like devido à sobreposição dos achados clínicos. Estas, mais raras que a síndrome de Noonan, incluem as síndromes de LEOPARD, neurofibromatose-Noonan, cardiofaciocutânea e Costello. Atualmente sabe-se que tanto a síndrome de Noonan como as síndromes Noonan-like envolvem mutações em genes pertencentes à via de sinalização RAS-MAPK. Na síndrome de Noonan, pelo menos quatro genes desta via são responsáveis pelo fenótipo: PTPN11, SOS1, RAF1 e KRAS. Mutações no gene PTPN11, o primeiro gene descrito em associação com a síndrome, são encontradas em aproximadamente 40% dos casos. O segundo gene descrito, o gene KRAS, é responsável por cerca de 2% dos casos que não apresentam mutações no gene PTPN11. Mutações no gene KRAS estão presentes em pacientes com síndrome de Noonan com retardo mental e/ou atraso no desenvolvimento mais acentuados e em pacientes com a síndrome cardiofaciocutânea cujo envolvimento ectodérmico é mais sutil. OBJETIVO: devido à recente associação do gene KRAS com a síndrome de Noonan e outras síndromes Noonan-like é importante: (1) testar a frequência de mutação neste gene em pacientes que apresentam ou não mutações no gene PTPN11 e (2) tentar estabelecer uma correlação genótipo-fenótipo mais precisa, o que permitirá a realização de um aconselhamento genético mais adequado. MÉTODOS: foram avaliados 95 probandos com síndrome de Noonan e 30 com síndromes Noonan-like. O estudo molecular foi realizado através da reação em cadeia de polimerase, seguida das reações de purificação e sequenciamento bidirecional. RESULTADOS: foram encontradas mutações no gene PTPN11 em 20/46 (43%) pacientes com síndrome de Noonan, duas delas não descritas anteriormente. Relacionando o quadro clínico dos pacientes com síndrome de Noonan deste estudo, com e sem mutação no gene PTPN11, nota-se que os pacientes com mutação apresentam incidência significativamente maior de baixa estatura, de estenose pulmonar valvar e menor frequência de miocardiopatia hipertrófica. Uma mutação no gene KRAS foi encontrada em um paciente com síndrome de Costello, mutação esta ainda não relatada. Alterações gênicas em mais de um gene da via RAS-MAPK foram observadas em dois pacientes, sendo que uma delas em cada paciente não predizia um efeito fenotípico importante. Foram também encontrados três polimorfismos no gene KRAS, porém com mesma frequência no grupo controle. A fim de verificar a influência destes polimorfismos, as principais características da síndrome de Noonan foram relacionadas entre os pacientes com esta síndrome que apresentavam mutação no gene PTPN11 e comparadas quanto à presença ou ausência desses polimorfismos. Nenhuma diferença estatisticamente significante foi encontrada. CONCLUSÃO: Pacientes com síndrome de Noonan e mutações no gene PTPN11 apresentaram uma maior incidência de baixa estatura e de estenose pulmonar valvar e uma menor incidência de miocardiopatia hipertrófica. O gene KRAS, até então relacionado às síndromes de Noonan e cardiofaciocutânea, mostrou-se também responsável pela síndrome de Costello. Tanto as alterações gênicas consideradas não patogênicas como os polimorfismos encontrados no gene KRAS parecem não ter uma grande influência sobre a variabilidade fenotípica na síndrome de Noonan. Contudo, não é possível afastar totalmente que estas alterações apresentem um efeito sutil e que, em conjunto com outras variações genéticas e/ou ambientais, tenham um efeito modulador / INTRODUCTION: Noonan syndrome shows autosomal dominant inheritance, and is a relatively frequent disease in the population, with an estimated incidence between 1/1000 and 1/2500 live births. The main clinical features are: facial dysmorphisms, short stature, cryptorchidism and cardiac abnormalities. The differential diagnosis between Noonan syndrome and Noonan-like syndromes is not always easy, due to the overlap of the their clinicla findings. The Noonan-like syndromes, more rare that the Noonan syndrome, include the LEOPARD syndrome, neurofibromatosis-Noonan, cardiofaciocutaneous and Costello. Currently it is known that Noonan syndrome and Noonan-like syndromes involve mutations in genes belonging to the RAS-MAPK signaling pathway. In Noonan syndrome, at least four genes of this pathway are responsible for the phenotype: PTPN11, SOS1, RAF1 and KRAS. Mutations in PTPN11, the first gene described in association with this syndrome, are found in approximately 40% of cases. The second gene described, the KRAS gene, is responsible for about 2% of the cases that dont have mutations in the PTPN11 gene. Mutations in the KRAS gene are present in patients with Noonan syndrome with mental retardation and/or developmental delay more pronounced and in patients with cardiofaciocutaneous syndrome whose ectodermal involvement is more subtle. OBJECTIVE: Due to the recent association of the KRAS gene with Noonan and Noonan-like syndromes is important: (1) to test the frequency of mutation in this gene in patients with or without mutations in PTPN11 and (2) to estabilish a more precise genotype-phenotype correlation, allowing the realization of a more appropriate genetic counseling. METHODS: 95 probands with Noonan syndrome and 30 with Noonan-like syndromes were evaluated. The molecular analysis was performed by the polymerase chain reaction, followed by purification and bidirectional sequencing. RESULTS: PTPN11 gene mutation was found in 20/46 (43%) patients with Noonan syndrome, two of them not previously described. By correlating the clinical features of patients with Noonan syndrome in this study, with or without mutations in the PTPN11 gene, it was noted that patients with mutations have significantly higher incidence of short stature, pulmonary stenosis and lower incidence of hypertrophic cardiomyopathy. Mutations in KRAS gene were found in two patients a patient with Noonan syndrome ant the other with Costello syndrome. Gene alterations in more than one gene at the RASMAPK patway were observed in two patients, but one of the mutations in each patient didnt predict a significant phenotypic effect. Were also foud three polymorphisms in the KRAS gene, but with the same frequency in the control group. To check the influence of these polymorphisms, the main features of Noonan syndrome were related among patients with this syndrome who had mutations in the PTPN11 gene and compared of the presence or absence of these polymorphisms. No statistically significant difference was found. CONCLUSION: Patients with Noonan syndrome and PTPN11 gene mutation had a higher incidence of short stature and pulmonary valve stenosis and a lower incidence of hypertrophic cardiomyopathy. The KRAS gene, previously related to Noonan and cardiofaciocutaneous syndrome, was also responsible for Costello syndrome. Gene alterations considered as nonpathogenic and polymorphisms found in the KRAS gene seem to have a not great influence on the phenotypic variability in Noonan syndrome. However, it is not possible to completely rule out that these changes have a subtle effect and that, together with other genetic variations and/or environmental factors, may have a modulating effect

No description available.

A síndrome de Noonan (SN) é uma doença de herança autossômica, relativamente frequente na população e que apresenta heterogeneidade genética. Caracteriza-se por dismorfismos faciais, baixa estatura, pescoço curto/alado, alterações cardíacas, deformidades esternais e criptorquia. A SN apresenta sobreposição dos achados clínicos com outras síndromes mais raras, denominadas síndromes Noonan-like (SNL): síndrome cardio-facio-cutânea (CFC), síndrome de Costello (SC), neurofibromatose-síndrome de Noonan (NFSN), síndrome de Noonan com manchas lentiginosas/síndrome de LEOPARD (SL), síndrome de Noonan-like com perda de cabelos anágenos (SNL-PCA) e síndrome de Noonan-like com leucemia mielomonocítica juvenil (SNL-LMMJ). As SN e SNL decorrem de mutações em genes pertencentes à via de sinalização RAS/MAPK alguns dos quais são protooncogenes, o que tem despertado o interesse na caracterização do risco de desenvolvimento de neoplasias nessas síndromes. Os objetivos deste estudo visam o sequencimento conjunto dos genes PTPN11, SOS1, RAF1, KRAS, SHOC2, BRAF e HRAS em pacientes com diagnóstico clínico das SN e SNL a fim de: determinar a frequência de mutação; estabelecer uma correlação genótipo-fenótipo; estabelecer um fluxograma para o estudo molecular a partir dos hotspots; e avaliar se a variabilidade fenotípica apresentada nos pacientes com SN pode ser explicada pela presença de mutações em mais de um gene da via RAS/MAPK. Foram avaliados 194 probandos - 152 com SN e 42 com SNL (19 CFC, 15 NFNS, 4 CS e 4 LS). Mutações foram identificadas em 99 pacientes 80 com SN (53%); 19 com SNL. Apenas um paciente com SN apresentou mutação em dois genes da via RAS/MAPK (PTPN11 e SOS1). O estudo molecular na SN mostrou, assim como na literatura, um maior envolvimento do gene PTPN11 (34%), seguido dos genes SOS1 (12%) e RAF1 (7%). A comparação dos achados clínicos, levando em consideração as alterações gênicas, também confirma as correlações já descritas na literatura; entre elas observamos que pacientes com SN e mutação no gene: PTPN11, apresentaram maior frequência de estenose pulmonar valvar (EPV) e baixa estatura; SOS1, apresentaram maior frequência de EPV; RAF1, apresentaram maior frequência de miocardiopatia hipertrófica, e menor frequência de EPV e déficit intelectual; SHOC2, apresentaram anormalidades de cabelo. Na nossa casuística também foram observados alguns achados raros: craniosinostose, tumor expansivo em fossa posterior e a primeira descrição de um tumor sólido (schwanomatose) em um paciente com mutação no gene KRAS. A partir deste estudo foi possível estabelecer um fluxograma para investigação molecular devido à correlação genótipo-fenótipo, que embora não seja totalmente precisa, explica parte da grande variabilidade clínica observada em especial quanto ao tipo de cardiopatia. A presença de mutações em diferentes genes da via RAS/MAPK não é frequente, além de não agravar o fenótipo e não explicar a variabilidade fenotípica observada. Embora um grande avanço no conhecimento sobre SN e SNL tenha sido alcançado, vários aspectos precisam ser melhor elucidados, como: caracterização precisa da propensão ao desenvolvimento de neoplasias, estudos que permitam avaliar as consequências biológicas das mutações, identificação de outros genes responsáveis, assim como outros fatores genéticos e/ou ambientais que possam explicar a variabilidade clínica inter e intrafamilial / Noonan syndrome (NS) is a relatively common, autosomal dominant disease that presents a marked genetic heterogeneity. It is characterized by facial dysmorphisms, short stature, webbed/short neck, cardiac abnormalities, esternal anomalies and cryptorchidism. NS shows clinical overlap of some of its findings with other rarer syndromes, known as Noonan-like syndromes (NLS): cardio-facio-cutaneous syndrome (CFC), Costello syndrome (CS), neurofibromatosis-Noonan syndrome (NFNS), Noonan syndrome with lentiginous stains/LEOPARD syndrome (LS), Noonan-like syndrome with loose anagen hair (NLS-LAH) and Noonan-like syndrome with juvenile myelomonocytic leukemia (NLS-JMML). NS and NLS are related to mutations in genes belonging of RAS-MAPK signaling pathway. Some of these genes are classified as proto-oncogenes. This fact also arouses the interest in the characterization of the risk for cancer development in this group of patients. The objectives of this study are to sequence the genes associated with NS and NLS (PTPN11, SOS1, RAF1, KRAS, SHOC2, HRAS and BRAF) in patients that fulfilled clinical diagnostic criteria for NS or NLS to: determine the frequency of the mutations; establish a genotype-phenotype correlation; estabilish a flowchart for molecular study from the hotspots; and evaluate when the phenotypic variability presented in NS patients can be explained by the presence of mutations in more than one gene of the RAS/MAPK pathway. This study evaluated 194 probands 152 with NS e 42 with NLS (19 CFC, 15 NFSN, 4 SC e 4 SL). Mutations were identified in 99 patients 80 with NS (53%), 19 with NLS. Only one patient presented mutation in two different genes of the RAS/MAPK pathway (PTPN11 and SOS1). The molecular analysis showed a predominance of mutations in the PTPN11 gene (34%), followed by the SOS1 (12%) and RAF1 (7%) genes in patients with NS, in accordance with the literature. Patients with NS and mutation in the: PTPN11 gene, presented a higher frequency of valvular pulmonary stenosis (VPS) and short stature; SOS1 gene, showed a higher frequency of VPS; RAF1 gene, showed a higher frequency of hypertrophic cardiomyopathy and lower frequency of VPS and intellectual deficit; and SHOC2 gene, showed more hair abnormalities. This genotype-phenotype correlations is also concordant with the literature. In our study, we also observed some rare finds in some patients: craniosynostosis, expansive tumor in the posterior fossa and the first description of a solid tumor (schwanomatose) in a patient with NS and KRAS gene mutation. Based on this genotype-phenotype correlation, we have proposed a flowchart for molecular investigation. The presence of mutation in more them one gene of the RAS/MAPK pathway was not frequent; additionally, it did not aggravate the phenotype and could not explain the phenotypic variability observed. Although a great advance in the knowledge about SN and SNL has been achieved, several aspects remain to be clarified, as the exact risk for cancer development, functional studies to assess the biological consequences of the mutations and the identification of other genes, as well as other genetic and/or environmental factors that influence the interand intrafamilial clinical variability

A síndrome de Noonan (SN) é uma doença de herança autossômica, relativamente frequente na população e que apresenta heterogeneidade genética. Caracteriza-se por dismorfismos faciais, baixa estatura, pescoço curto/alado, alterações cardíacas, deformidades esternais e criptorquia. A SN apresenta sobreposição dos achados clínicos com outras síndromes mais raras, denominadas síndromes Noonan-like (SNL): síndrome cardio-facio-cutânea (CFC), síndrome de Costello (SC), neurofibromatose-síndrome de Noonan (NFSN), síndrome de Noonan com manchas lentiginosas/síndrome de LEOPARD (SL), síndrome de Noonan-like com perda de cabelos anágenos (SNL-PCA) e síndrome de Noonan-like com leucemia mielomonocítica juvenil (SNL-LMMJ). As SN e SNL decorrem de mutações em genes pertencentes à via de sinalização RAS/MAPK alguns dos quais são protooncogenes, o que tem despertado o interesse na caracterização do risco de desenvolvimento de neoplasias nessas síndromes. Os objetivos deste estudo visam o sequencimento conjunto dos genes PTPN11, SOS1, RAF1, KRAS, SHOC2, BRAF e HRAS em pacientes com diagnóstico clínico das SN e SNL a fim de: determinar a frequência de mutação; estabelecer uma correlação genótipo-fenótipo; estabelecer um fluxograma para o estudo molecular a partir dos hotspots; e avaliar se a variabilidade fenotípica apresentada nos pacientes com SN pode ser explicada pela presença de mutações em mais de um gene da via RAS/MAPK. Foram avaliados 194 probandos - 152 com SN e 42 com SNL (19 CFC, 15 NFNS, 4 CS e 4 LS). Mutações foram identificadas em 99 pacientes 80 com SN (53%); 19 com SNL. Apenas um paciente com SN apresentou mutação em dois genes da via RAS/MAPK (PTPN11 e SOS1). O estudo molecular na SN mostrou, assim como na literatura, um maior envolvimento do gene PTPN11 (34%), seguido dos genes SOS1 (12%) e RAF1 (7%). A comparação dos achados clínicos, levando em consideração as alterações gênicas, também confirma as correlações já descritas na literatura; entre elas observamos que pacientes com SN e mutação no gene: PTPN11, apresentaram maior frequência de estenose pulmonar valvar (EPV) e baixa estatura; SOS1, apresentaram maior frequência de EPV; RAF1, apresentaram maior frequência de miocardiopatia hipertrófica, e menor frequência de EPV e déficit intelectual; SHOC2, apresentaram anormalidades de cabelo. Na nossa casuística também foram observados alguns achados raros: craniosinostose, tumor expansivo em fossa posterior e a primeira descrição de um tumor sólido (schwanomatose) em um paciente com mutação no gene KRAS. A partir deste estudo foi possível estabelecer um fluxograma para investigação molecular devido à correlação genótipo-fenótipo, que embora não seja totalmente precisa, explica parte da grande variabilidade clínica observada em especial quanto ao tipo de cardiopatia. A presença de mutações em diferentes genes da via RAS/MAPK não é frequente, além de não agravar o fenótipo e não explicar a variabilidade fenotípica observada. Embora um grande avanço no conhecimento sobre SN e SNL tenha sido alcançado, vários aspectos precisam ser melhor elucidados, como: caracterização precisa da propensão ao desenvolvimento de neoplasias, estudos que permitam avaliar as consequências biológicas das mutações, identificação de outros genes responsáveis, assim como outros fatores genéticos e/ou ambientais que possam explicar a variabilidade clínica inter e intrafamilial / Noonan syndrome (NS) is a relatively common, autosomal dominant disease that presents a marked genetic heterogeneity. It is characterized by facial dysmorphisms, short stature, webbed/short neck, cardiac abnormalities, esternal anomalies and cryptorchidism. NS shows clinical overlap of some of its findings with other rarer syndromes, known as Noonan-like syndromes (NLS): cardio-facio-cutaneous syndrome (CFC), Costello syndrome (CS), neurofibromatosis-Noonan syndrome (NFNS), Noonan syndrome with lentiginous stains/LEOPARD syndrome (LS), Noonan-like syndrome with loose anagen hair (NLS-LAH) and Noonan-like syndrome with juvenile myelomonocytic leukemia (NLS-JMML). NS and NLS are related to mutations in genes belonging of RAS-MAPK signaling pathway. Some of these genes are classified as proto-oncogenes. This fact also arouses the interest in the characterization of the risk for cancer development in this group of patients. The objectives of this study are to sequence the genes associated with NS and NLS (PTPN11, SOS1, RAF1, KRAS, SHOC2, HRAS and BRAF) in patients that fulfilled clinical diagnostic criteria for NS or NLS to: determine the frequency of the mutations; establish a genotype-phenotype correlation; estabilish a flowchart for molecular study from the hotspots; and evaluate when the phenotypic variability presented in NS patients can be explained by the presence of mutations in more than one gene of the RAS/MAPK pathway. This study evaluated 194 probands 152 with NS e 42 with NLS (19 CFC, 15 NFSN, 4 SC e 4 SL). Mutations were identified in 99 patients 80 with NS (53%), 19 with NLS. Only one patient presented mutation in two different genes of the RAS/MAPK pathway (PTPN11 and SOS1). The molecular analysis showed a predominance of mutations in the PTPN11 gene (34%), followed by the SOS1 (12%) and RAF1 (7%) genes in patients with NS, in accordance with the literature. Patients with NS and mutation in the: PTPN11 gene, presented a higher frequency of valvular pulmonary stenosis (VPS) and short stature; SOS1 gene, showed a higher frequency of VPS; RAF1 gene, showed a higher frequency of hypertrophic cardiomyopathy and lower frequency of VPS and intellectual deficit; and SHOC2 gene, showed more hair abnormalities. This genotype-phenotype correlations is also concordant with the literature. In our study, we also observed some rare finds in some patients: craniosynostosis, expansive tumor in the posterior fossa and the first description of a solid tumor (schwanomatose) in a patient with NS and KRAS gene mutation. Based on this genotype-phenotype correlation, we have proposed a flowchart for molecular investigation. The presence of mutation in more them one gene of the RAS/MAPK pathway was not frequent; additionally, it did not aggravate the phenotype and could not explain the phenotypic variability observed. Although a great advance in the knowledge about SN and SNL has been achieved, several aspects remain to be clarified, as the exact risk for cancer development, functional studies to assess the biological consequences of the mutations and the identification of other genes, as well as other genetic and/or environmental factors that influence the interand intrafamilial clinical variability

In addition to their role in hemostasis, platelets appear to contribute to vascular inflammatory diseases. Platelets achieve this through the secretion of various prothrombotic and pro-inflammatory molecules. Platelet secretion is mediated by integral membrane proteins called Soluble NSF Attachment protein REceptors (SNAREs). SNAREs come from both granule/vesicle membranes (v-SNAREs) and target membranes (t-SNAREs) to form a trans-bilayer complex that promotes membrane fusion and subsequent granule cargo release. The work described in this dissertation dissects various, yet related aspects of platelet secretion in both physiological relevant and pathological circumstances. Atherosclerosis is a leading cause of death in the westernized countries and a major contributor to heart attacks and strokes. Given the potential involvement of platelets in atherosclerosis and previous work from our laboratory showing that VAMP-8 is the primary v-SNARE for platelet secretion, one part of this dissertation focuses on the role of VAMP-8- mediated secretion in atherosclerosis. The data showed that the deletion of VAMP-8 in the ApoE-/- null model of chronic atherosclerosis attenuated plaque development compared to the wild type littermates. Aged (50 week) VAMP-8-/-/ApoE-/- mice showed a reduction in lesion size compared to ApoE-/- controls, as measured by Oil Red-O staining of the plaques in the aortic sinus and by en face analysis of plaques in the aortic arch. These data show that the loss of VAMP-8 attenuates the development of atherosclerotic plaques and suggest that platelet secretion contributes to atherosclerosis. Considering the vital role of platelet secretion in both physiological and pathological conditions, it is essential to understand how it is regulated. SNARE proteins are controlled by a range of regulatory molecules that affect where, when, and with whom they form trans-bilayer complexes for membrane fusion. One family of such regulators is the Munc18 family: platelets contain three (Munc18a-c). The second part of this dissertation focuses on the role of Munc18b/STXBP2. Mutations in the Munc18b/STXBP2 gene underlie Familial Hemophagocytic Lymphohistocytosis type 5 (FHL5), which is a life- threatening disease caused by dysregulation of the immune system. Platelets from two biallelic FHL5 patients had almost undetectable levels of Munc18b/STXBP2 levels; the levels of Munc18a increased slightly and Munc18c levels were unaffected. Syntaxin 11 levels were affected but the levels of other secretory machinery proteins were normal. Platelet secretion from dense and alpha granule in two biallelic patients and the one heterozygous patient was decreased. The release of serotonin from dense granules, and platelet factor 4 (PF4) from alpha granules was profoundly affected in the biallelic patients and partially affected in the heterozygote heterozygous patient. Lysosome release was affected only from the platelets of the biallelic patients. These data indicate that Munc18b plays a key role in platelet secretion. Ras is the prototypical member of a family of low molecular weight, GTP-binding proteins. It affects various cellular functions by cycling between an active, guanine triphosphate (GTP) and an inactive guanine diphosphate (GDP) -bound state. Little is known about the role of Ras activation in platelets. The third part of this dissertation focuses on what could be learned about Ras’ role by analyzing platelets from patients with Noonan Syndrome. Specific mutations in the genes encoding elements of Ras signaling pathways are associated with Noonan Syndrome. Platelets from Noonan Syndrome patients with a mutation in kRas (F156V) were analyzed and shown to have a defect in aggregation in response to low levels of agonist. These data suggest that Ras may play a functionally relevant role in platelet activation. In summary, the experiments presented in investigations of this dissertation support a role for platelet secretion in several pathological conditions and suggest that platelet secretion assays may serve as useful as diagnostic tools for some genetic diseases. In addition, these studies elucidate the importance of understanding the regulation of platelet exocytosis, to drive the development of new antithrombotic therapeutics.