A perda auditiva é o defeito mais comum ao nascimento e cerca de 70 milhões de pessoas no mundo apresentam algum grau de perda auditiva. Além da alta incidência, as implicações da perda auditiva na linguagem, na cognição e no desenvolvimento emocional e social reforçam sua importância. No entanto, em grande parte dos pacientes, a causa da deficiência auditiva não é esclarecida. Nós usamos hibridação comparativa do genoma baseada em arrays (Array Comparative Genomic Hybridization aCGH) para investigar alterações no número de cópias de segmentos de DNA (Copy Number Variation CNV) em 31 indivíduos que apresentavam deficiência auditiva e sinais clínicos adicionais, mas que não puderam ser classificados em síndrome conhecida. A escolha de indivíduos sindrômicos se baseou no pressuposto de que, em média, apresentam alterações genômicas maiores e, portanto, mais provavelmente detectáveis com o uso de aCGH de 1 Mb, que era a plataforma disponível no início do projeto. CNVs não descrita em bancos de dados de indivíduos normais foram identificadas em oito pacientes, quatro delas ocorreram de novo enquanto as outras quatro foram herdadas de um genitor fenotipicamente normal. As alterações de novo definem segmentos cromossômicos que provavelmente contém genes relacionados à deficiência auditiva e sensíveis a dose, especificamente: 1q23.3-q25.2, 2q22q23, 6p25.3 e 11q13.2-q13.4. As alterações raras identificadas tanto nos pacientes quanto em um genitor normal poderiam ser um evento ao acaso, sem papel na deficiência auditiva; no entanto, a possibilidade de que essas alterações possam funcionar como fatores de predisposição não podem ser descartadas. Se considerarmos apenas as CNVs de novo como causativas dos fenótipos investigados, detectamos quatro pacientes portadores entre os 31 investigados (13%). Se considerarmos também as CNVs herdadas como possivelmente causativas, a taxa de desequilíbrios cromossômicos associados à surdez será de 26%. Esses resultados são provavelmente uma substimativa e esses números seriam possivelmente maiores com o uso de uma das plataformas de alta resolução disponíveis atualmente. Esses resultados, embora limitados, indicam que investigação por aCGH em pacientes com surdez sindrômica idiopática está entre os testes mais eficientes para detectar etiologia dos fenótipos, devendo ser incorporado à rotina no diagnóstico e aconselhamento genético. / Hearing loss is the most common congenital deficiency and about 70 million people worldwide present some degree of hearing impairment. In addition to its high incidence, hearing loss impacts language, cognition and social and emotional development. However, in a large proportion of patients, the cause of the hearing deficiency cannot be elucidated. We screened copy number changes by 1 Mb-array Comparative Genomic Hybridization (aCGH) in 31 individuals with syndromic hearing impairment whose clinical features were untypical for known disorders. The choice of evaluating syndromic rather than non-syndromic individuals was based on the assumption that they are more likely to carry larger genomic alterations which could be more easily detected by the comparatively low resolution 1 Mb aCCG, which was the available platform when this project started. Copy number changes (CNV) not documented in the database of normal individuals were detected in eight patients, four de novo imbalances and four inherited from a normal parent. The de novo alterations define candidate chromosome segments likely to harbor dosage sensitive genes related to hearing impairment, namely 1q23.3-q25.2, 2q22q23, 6p25.3 and 11q13.2- q13.4. The rare imbalances also present in normal parents might be casually associated with hearing impairment, but also have a possible role as a predisposition factor. When only the de novo CNVs were considered causative for the disease phenotypes, our study revealed relevant copy number changes in 4 patients (13%). If we also count the rare CNVs that had been inherited as possibly causative, the frequency of chromosome imbalances associated with syndromic deafness in our sample becomes 26%. These figures are probably underestimates and will probably become larger when high resolution oligoarray platforms are applied. These results indicate that aCGH is an efficient tool for defining the etiology of syndromic deafness and its use in routine diagnosis of hearing impairment and for genetic counseling is highly recommended.

A perda auditiva é o defeito mais comum ao nascimento e cerca de 70 milhões de pessoas no mundo apresentam algum grau de perda auditiva. Além da alta incidência, as implicações da perda auditiva na linguagem, na cognição e no desenvolvimento emocional e social reforçam sua importância. No entanto, em grande parte dos pacientes, a causa da deficiência auditiva não é esclarecida. Nós usamos hibridação comparativa do genoma baseada em arrays (Array Comparative Genomic Hybridization aCGH) para investigar alterações no número de cópias de segmentos de DNA (Copy Number Variation CNV) em 31 indivíduos que apresentavam deficiência auditiva e sinais clínicos adicionais, mas que não puderam ser classificados em síndrome conhecida. A escolha de indivíduos sindrômicos se baseou no pressuposto de que, em média, apresentam alterações genômicas maiores e, portanto, mais provavelmente detectáveis com o uso de aCGH de 1 Mb, que era a plataforma disponível no início do projeto. CNVs não descrita em bancos de dados de indivíduos normais foram identificadas em oito pacientes, quatro delas ocorreram de novo enquanto as outras quatro foram herdadas de um genitor fenotipicamente normal. As alterações de novo definem segmentos cromossômicos que provavelmente contém genes relacionados à deficiência auditiva e sensíveis a dose, especificamente: 1q23.3-q25.2, 2q22q23, 6p25.3 e 11q13.2-q13.4. As alterações raras identificadas tanto nos pacientes quanto em um genitor normal poderiam ser um evento ao acaso, sem papel na deficiência auditiva; no entanto, a possibilidade de que essas alterações possam funcionar como fatores de predisposição não podem ser descartadas. Se considerarmos apenas as CNVs de novo como causativas dos fenótipos investigados, detectamos quatro pacientes portadores entre os 31 investigados (13%). Se considerarmos também as CNVs herdadas como possivelmente causativas, a taxa de desequilíbrios cromossômicos associados à surdez será de 26%. Esses resultados são provavelmente uma substimativa e esses números seriam possivelmente maiores com o uso de uma das plataformas de alta resolução disponíveis atualmente. Esses resultados, embora limitados, indicam que investigação por aCGH em pacientes com surdez sindrômica idiopática está entre os testes mais eficientes para detectar etiologia dos fenótipos, devendo ser incorporado à rotina no diagnóstico e aconselhamento genético. / Hearing loss is the most common congenital deficiency and about 70 million people worldwide present some degree of hearing impairment. In addition to its high incidence, hearing loss impacts language, cognition and social and emotional development. However, in a large proportion of patients, the cause of the hearing deficiency cannot be elucidated. We screened copy number changes by 1 Mb-array Comparative Genomic Hybridization (aCGH) in 31 individuals with syndromic hearing impairment whose clinical features were untypical for known disorders. The choice of evaluating syndromic rather than non-syndromic individuals was based on the assumption that they are more likely to carry larger genomic alterations which could be more easily detected by the comparatively low resolution 1 Mb aCCG, which was the available platform when this project started. Copy number changes (CNV) not documented in the database of normal individuals were detected in eight patients, four de novo imbalances and four inherited from a normal parent. The de novo alterations define candidate chromosome segments likely to harbor dosage sensitive genes related to hearing impairment, namely 1q23.3-q25.2, 2q22q23, 6p25.3 and 11q13.2- q13.4. The rare imbalances also present in normal parents might be casually associated with hearing impairment, but also have a possible role as a predisposition factor. When only the de novo CNVs were considered causative for the disease phenotypes, our study revealed relevant copy number changes in 4 patients (13%). If we also count the rare CNVs that had been inherited as possibly causative, the frequency of chromosome imbalances associated with syndromic deafness in our sample becomes 26%. These figures are probably underestimates and will probably become larger when high resolution oligoarray platforms are applied. These results indicate that aCGH is an efficient tool for defining the etiology of syndromic deafness and its use in routine diagnosis of hearing impairment and for genetic counseling is highly recommended.

Les variations du nombre de copies (i.e., VNC, perte ou gain de matériel génétique de plus de 1 kilobase) figurent parmi les facteurs biologiques les plus associés aux troubles neurodéveloppementaux (TNDs), tels que les troubles du spectre autistique (TSAs) ou la psychose précoce. Les variants génétiques classés comme pathogéniques sont identifiés chez environ 20% des enfants avec des symptômes de TSA référés en génétique clinique. Actuellement, seules les VNCs les plus récurrentes (i.e., plusieurs individus non apparentés ont le même variant) ont été associées avec les TSAs et leurs tailles d’effets ont pu être décrites avec précision grâce à des études d'associations (i.e., cas-contrôles). Cependant, la plupart des VNCs identifiées dans les cliniques neurodéveloppementales et génétiques sont ultra-rares. À ma connaissance, aucune méthode n’a été développée afin d’estimer et de prédire de façon précise la contribution de tels variants aux phénotypes cliniques. De ce fait, l’impact de ces variants ultra-rares sur les risques d'avoir des TNDs, comme les TSAs ou la psychose précoce, reste incertain. Une étude récente de mon groupe de recherche a démontré que les tailles d'effet des délétions et duplications à travers le génome sur les capacités cognitives pouvaient être prédites statistiquement avec 78% de précision en utilisant des mesures d'intolérance à la perte de fonction. Le but de cette thèse est de développer des modèles similaires pour définir les tailles d'effet des VNCs à travers le génome sur les risques de TSA et de psychose précoce, ainsi que sur quelques traits cognitifs et comportementaux affectés dans ces troubles. J’ai analysé tous les VNCs ≥ 50 kilobases identifiées via les données de puces de génotypage et de séquençage sur génome entier chez 137 enfants et adolescents avec une psychose précoce (Boston Children’s hospital), 5,540 probands avec des TSAs (Simons Simplex Collection et MSSNG), et 17,471 personnes de la population générale (Lothian birth cohort, Generation Scotland, IMAGEN et Saguenay Youth Study). Les gènes codants totalement compris dans les VNCs ont été annotés avec neufs variables quantitatives, incluant le score d’intolérance à la perte de fonction et d’autres scores fonctionnels et génétiques. Des modèles statistiques incluant ces scores ont été testés afin de sélectionner celui qui explique le mieux l’effet des VNCs à travers le génome sur le risque de TSA et le quotient intellectuel (QI). Le meilleur modèle a été utilisé par la suite pour investiguer les tailles d’effets des VNCs sur d’autres traits cognitifs et comportementaux liés aux TSAs, ainsi que sur le risque de psychose précoce. Le score d’intolérance à la perte de fonction expliquait le mieux les effets des VNCs sur le risque de TSA et la cognition générale. Les modèles incluant ces scores ont démontré que les délétions et les duplications augmentaient les risques de psychose précoce et de TSA, même après ajustement pour le QI. Il n’y avait aucune différence de tailles d’effets des VNCs entre la psychose précoce et le TSA. La fréquence de loci associé précédemment avec des TNDs et des troubles neuropsychiatriques était également similaire entre dans les TSA et la psychose précoce, et le modèle estimait précisément la taille d'effet de la plupart de ces loci sur le risque de TSA en comparaison aux observation empiriques publiées précédemment. Les CNVs à travers le génome mesurés par le score d’intolérance à la perte de fonction diminuaient de façon similaire le QI dans les populations TSA et générale. Les effets des duplications étaient systématiquement plus faibles que les effets des délétions pour chacun de ces phénotypes, ce qui suggère un effet plus pathogénique des délétions. Les délétions et les duplications affectaient différentiellement la communication sociale, les comportements, et la mémoire phonologique, tandis qu'elles affectaient similairement les capacités motrices dans les populations TSA. L'enrichissement similaire des VNCs à travers le génome dans la psychose précoce et le TSA suggère un effet pléiotropique des VNCs dans ces différentes symptomatologies. Le dépistage routinier pour les VNCs doit être accessible dans les soins cliniques standards des jeunes avec une psychose précoce, comme il est recommandé pour les TSAs. Une telle pratique contribue à établir une médecine personnalisée et peut apporter des bénéfices médicaux comme la détection de comorbidités, la prédiction de la progression de la maladie, et faciliter la communication avec les parents à propos de la nature biologique du trouble. Les modèles appliqués dans ce projet, entraînés sur des VNCs incluant plus de 4,500 gènes, suggèrent des propriétés hautement polygéniques du dosage génique dans les TNDs. J’ai estimé que chaque VNC de 1 mégabase, incluant au moins un gène scorant pour l’intolérance à la perte de fonction, augmente le risque de TSA. La combinaison de ces résultats ouvre de nouvelles perspectives dans la compréhension des effets des VNCs à travers le génome sur les TNDs et les traits associés (e.g., QI ou symptômes comportementaux). Ces modèles ont été implémentés dans un outil en ligne qui a pour but d'aider les cliniciens à estimer les tailles d’effet des VNCs identifiés en clinique et à interpréter leur contribution au phénotype du patient. / Copy number variants (CNVs; i.e., loss or gain of genetic material of over 1 kilobase) are robustly associated with neurodevelopmental disorders (NDDs), such as autism spectrum disorder (ASD) and early-onset psychosis (EOP). Genetic variants classified as pathogenic are identified in approximately 20% of children with ASD symptoms referred to genetic clinics. To date, only the most recurrent CNVs (i.e., similar variants across multiple unrelated individuals) were associated with ASD and their effect-sizes were characterized through association studies (i.e., case-controls). However, most of the CNVs routinely identified in neurodevelopmental and genetic clinics are ultra-rare. To my knowledge, no method was developed to accurately estimate and predict the contribution of such variants to clinical phenotypes. Therefore, the impact of these ultra-rare variants on risk for NDDs, such as ASD and EOP, remains undocumented. A recent study from my research group has shown that the effect-size of genome-wide deletions and duplications on cognitive ability can be statistically predicted with an 78% accuracy using measures of loss-of-function (LoF) intolerance. The aim of this thesis was to develop similar models to define the effect-size of genome-wide CNVs on ASD and EOP risk, as well as on several cognitive and behavioral traits altered in these disorders. I analyzed all CNVs ≥ 50 kilobases called from genotyping arrays and whole genome sequencing data from 137 children and adolescents with EOP (Boston Children’s hospital), 5,540 probands with ASD (Simons Simplex Collection and MSSNG), and 17,471 individuals from unselected populations (Lothian birth cohort, Generation Scotland, IMAGEN and Saguenay Youth Study). Coding genes fully encompassed by CNVs were annotated with nine quantitative variables, including the LoF intolerance score and other functional and genetic scores. Statistical models including these scores were tested to select the one that best explained the effects of genome-wide CNVs on ASD risk and IQ. The best model was subsequently used to investigate the effect-size of genome-wide CNVs on cognitive and behavioral domains related to ASD, as well as on EOP risk. The LoF intolerance score best explained the effect-sizes of genome-wide CNVs on ASD-risk and general cognition. Models including such scores demonstrated that deletions or duplications increased risks for EOP and for ASD, even after adjusting for IQ. There was no difference in effect-sizes between EOP and ASD. The frequency of loci previously associated with NDDs or neuropsychiatric disorders was also similar between EOP and ASD, and the model accurately estimated the effect-size of most of these loci on the risk for ASD comparing to previously published empirical observations. Genome-wide CNVs measured by LoF intolerance score also similarly decreased IQ in both ASD and unselected populations. The effect of duplications was smaller than the effect of deletion for all phenotypes investigated, suggesting a higher pathogenicity of deletions. Deletions and duplications were found to differentially affect social communication, behavior, and phonological memory, whereas both equally affected motor skills in the ASD population. The identical enrichment of genome-wide CNVs in EOP and ASD suggests a pleiotropic effect of CNVs in these different symptomatology. Routine screening for CNVs should be made available in the standard clinical care for EOP youth, as is recommended in ASD. Such practice contributes to the establishment of personalized medicine and may bring medical benefits as detecting medical comorbidities, prediction of the disease progression, and facilitating the communication with parents about the biological nature of the disorder. The models applied in this project, trained on CNVs encompassing more than 4,500 genes, suggest highly polygenic properties of gene dosage in NDDs. I estimated that any 1 megabase CNV, encompassing at least one gene scoring for intolerance to LoF, would increase ASD risk. Overall, these results open new avenues for understanding the effect of genome-wide CNVs on NDD risk and related traits (e.g., IQ or behavioral symptoms). These models were implemented in an online tool which aims to help clinicians estimate the effect-size of CNVs identified in the clinic and interpret their contribution to the patient’s phenotype.

No description available.

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

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

Les délétions et les duplications délétères (Variations de nombre de copies, CNV) sont identifiés dans environ 11% des individus référés dans des cliniques du neurodéveloppement pédiatrique. Certains CNVs récurrents ont été formellement associés avec des troubles du neurodéveloppement, mais la majorité des CNVs sont non-récurrents et donc trop rares pour être évalués par des études d’association. Dans cette optique, nous avons récemment développé une nouvelle approche pour estimer l’effet des CNVs non-documentés sur le quotient intellectuel non-verbal (QINV) et nous visons étendre cette approche pour l’appliquer sur une mesure de traits autistiques. Nous avons identifié les CNVs dans deux cohortes d’autisme du Simons Simplex Collection (SSC) et du MSSNG, dans leurs apparentés de premier-degré, dans une cohorte du neurodéveloppement et dans une population générale. Des modèles statistiques intégrant les scores des gènes inclus dans les CNVs ont été utilisés pour expliquer leur effet sur l’intelligence générale et sur la réciprocité sociale. Les délétions et les duplications diminuent le QINV et l’effet des duplications est 3 fois inférieur à celui des délétions. L’effet différentiel est aussi observé pour la réciprocité sociale avec un ratio d’altération de 2:1 pour les délétions et les duplications et cet effet est principalement expliqué par le QINV. Les estimés de notre modèle pour l’intelligence générale et la réciprocité sociale concordent bien avec des observations déjà publiés. Nos modèles entraînés sur des CNVs couvrant >4,500 gènes suggèrent que l’effet des CNVs sur la cognition et la réciprocité sociale est dû à leurs propriétés polygéniques. Ces modèles pourront aider dans l’interprétation des CNVs en clinique. / Deleterious deletions and duplications (copy number variations, CNVs) are identified in up to 11% of individuals referred to neurodevelopmental pediatric clinics. However, only few recurrent CNVs have been formally associated with neurodevelopmental disorders because the majority are too rare to perform individual association studies. We recently developed a new framework to estimate the effect size of undocumented CNVs on non-verbal intelligence quotient (NVIQ) and sought to extend this approach to another score measuring autistic traits. We identified CNVs in an autism sample from the Simons Simplex Collection (SSC) and MSSNG, in their first-degree relatives, in a neurodevelopmental cohort and in individuals from an unselected population. Statistical models integrating scores of the genes encompassed in the CNVs were used to explain their effect on general intelligence and on social responsiveness. Deletions and duplications decreased NVIQ and the effect of duplications was three-fold smaller than deletions. There was also a differential effect on social responsiveness: the ratio of the impairment conferred by deletions and duplications was 2:1 and this effect was mainly driven by NVIQ. Models estimates for general intelligence and social responsiveness were consistent with previously published observations. Our models, trained on CNVs encompassing >4,500 genes, suggest highly polygenic properties of CNVs with respect to cognition and social responsiveness. These models will help interpreting CNVs identified in the clinic.

Les variants du nombre de copies (CNV) offre un cadre riche pour étudier les mécanismes neurobiologiques qui sous tendent la vulnérabilité aux troubles neuropsychiatriques. Notamment, les délétions du 16p11.2 et 22q11.2 sont parmi les facteurs génétiques les plus fréquents associés au trouble du spectre de l’autisme (TSA) et à la schizophrénie (SCZ). À l’heure actuelle, les perturbations fonctionnelles cérébrales qui sous-tendent cette vulnérabilité cognitive restent mécomprises. Récemment, l’analyse par gradient du connectome humain a révélé une réorganisation le long de l’axe dominant sensorimoteur à transmodal dans le TSA et la SCZ. Dans cette étude, nous avons cherché à étendre cette approche analytique aux porteurs d’une délétion du 16p11.2 et du 22q11.2 conférant un risque élevé pour de mêmes conditions. À cette fin, nous avons utilisé les données d’imagerie par résonance magnétique au repos combinant les données de deux cohortes génétiques, pour un total de 180 sujets incluant 61 porteurs. Par le biais d’un paradigme cas-contrôle, nous rapportons la première évidence d’une compression du gradient fonctionnel sensorimoteur à transmodal chez les porteurs de telles délétions. En dernier lieu, nous présentons une étude exploratoire d’association endophénotype-phénome dans la population générale du UK Biobank. Nous démontrons que la ressemblance aux profils de compression corticale des délétions est reliée à plusieurs traits humains complexes, en concordance avec les dimensions cliniques impactées par ces mêmes CNV. / Copy number variants (CNVs) present a unique opportunity to study the neural mechanisms underlying vulnerability to neuropsychiatric disorders. Notably, deletions of the 16p11.2 and 22q11.2 region are among the most common genetic variations associated with autism spectrum disorder (ASD) and schizophrenia (SCZ). However, brain functional disruptions underlying this cognitive vulnerability remains unclear. Recent gradient analysis framework developed to study parsimonious connectome dimensions at the system-level have reported disruptions along the overarching sensorimotor-to-transmodal gradient in ASD and SCZ. In this study, we sought to extend this gradient approach to carriers of a deletion at the 16p11.2 and 22q11.2 region. To achieve this, we pooled resting-state functional magnetic resonance imaging data from a total of 180 subjects, including 61 carriers, distributed among two genetic cohorts. By the means of a case-control study design, we provide the first evidence of a compressed cortical functional gradient in CNV carriers compared to healthy controls. Finally, we provide an exploratory endophenotype-phenome association study in the general UK Biobank population. We demonstrate that resemblance to 16p11.2 and 22q11.2 deletion profiles of cortical compression is related to several complex human traits, in concordance with clinical dimensions known to be impacted by the same CNV.

L’hypothyroïdie congénitale par dysgénésie thyroïdienne (HCDT) est la condition endocrinienne néonatale la plus fréquemment rencontrée, avec une incidence d’un cas sur 4000 naissances vivantes. L’HCDT comprend toutes les anomalies du développement de la thyroïde. Parmi ces anomalies, le diagnostic le plus fréquent est l’ectopie thyroïdienne (~ 50% des cas). L’HCDT est fréquemment associée à un déficit sévère en hormones thyroïdiennes (hypothyroïdisme) pouvant conduire à un retard mental sévère si non traitée. Le programme de dépistage néonatal assure un diagnostic et un traitement précoce par hormones thyroïdiennes. Cependant, même avec un traitement précoce (en moyenne à 9 jours de vie), un retard de développement est toujours observé, surtout dans les cas les plus sévères (c.-à-d., perte de 10 points de QI). Bien que des cas familiaux soient rapportés (2% des cas), l’HCTD est essentiellement considérée comme une entité sporadique. De plus, plus de 92% des jumeaux monozygotiques sont discordants pour les dysgénésies thyroïdiennes et une prédominance féminine est rapportée (spécialement dans le cas d’ectopies thyroïdiennes), ces deux observations étant clairement incompatible avec un mode de transmission héréditaire mendélien. Il est donc cohérent de constater que des mutations germinales dans les facteurs de transcription thyroïdiens connus (NKX2.1, PAX8, FOXE1, and NKX2.5) ont été identifiées dans seulement 3% des cas sporadiques testés et furent, de plus, exclues lors d’analyse d’association dans certaines familles multiplex. Collectivement, ces données suggèrent que des mécanismes non mendéliens sont à l’origine de la majorité des cas de dysgénésie thyroïdienne. Parmi ces mécanismes, nous devons considérer des modifications épigénétiques, des mutations somatiques précoces (au stade du bourgeon thyroïdien lors des premiers stades de l’embryogenèse) ou des défauts développementaux stochastiques (c.-à-d., accumulation aléatoire de mutations germinales ou somatiques). Voilà pourquoi nous proposons un modèle «2 hits » combinant des mutations (épi)génétiques germinales et somatiques; ce modèle étant compatible avec le manque de transmission familial observé dans la majorité des cas d’HCDT. Dans cette thèse, nous avons déterminé si des variations somatiques (épi)génétiques sont associées à l’HCTD via une approche génomique et une approche gène candidat. Notre approche génomique a révélé que les thyroïdes ectopiques ont un profil d’expression différent des thyroïdes eutopiques (contrôles) et que ce profil d’expression est enrichi en gènes de la voie de signalisation Wnt. La voie des Wnt est cruciale pour la migration cellulaire et pour le développement de plusieurs organes dérivés de l’endoderme (p.ex. le pancréas). De plus, le rôle de la voie des Wnt dans la morphogénèse thyroïdienne est supporté par de récentes études sur le poisson-zèbre qui montrent des anomalies du développement thyroïdien lors de la perturbation de la voie des Wnt durant différentes étapes de l’organogénèse. Par conséquent, l’implication de la voie des Wnt dans l’étiologie de la dysgénésie thyroïdienne est biologiquement plausible. Une trouvaille inattendue de notre approche génomique fut de constater que la calcitonine était exprimée autant dans les thyroïdes ectopiques que dans les thyroïdes eutopiques (contrôles). Cette trouvaille remet en doute un dogme de l’embryologie de la thyroïde voulant que les cellules sécrétant la calcitonine (cellules C) proviennent exclusivement d’une structure extrathyroïdienne (les corps ultimobranchiaux) fusionnant seulement avec la thyroïde en fin de développement, lorsque la thyroïde a atteint son emplacement anatomique définitif. Notre approche gène candidat ne démontra aucune différence épigénétique (c.-à-d. de profil de méthylation) entre thyroïdes ectopiques et eutopiques, mais elle révéla la présence d’une région différentiellement méthylée (RDM) entre thyroïdes et leucocytes dans le promoteur de FOXE1. Le rôle crucial de FOXE1 dans la migration thyroïdienne lors du développement est connu et démontré dans le modèle murin. Nous avons démontré in vivo et in vitro que le statut de méthylation de cette RDM est corrélé avec l’expression de FOXE1 dans les tissus non tumoraux (c.-à-d., thyroïdes et leucocytes). Fort de ces résultats et sachant que les RDMs sont de potentiels points chauds de variations (épi)génétiques, nous avons lancé une étude cas-contrôles afin de déterminer si des variants génétiques rares localisés dans cette RDM sont associés à la dysgénésie thyroïdienne. Tous ces résultats générés lors de mes études doctorales ont dévoilé de nouveaux mécanismes pouvant expliquer la pathogenèse de la dysgénésie thyroïdienne, condition dont l’étiologie reste toujours une énigme. Ces résultats ouvrent aussi plusieurs champs de recherche prometteurs et vont aider à mieux comprendre tant les causes des dysgénésies thyroïdiennes que le développement embryonnaire normal de la thyroïde chez l’homme. / Congenital hypothyroidism from thyroid dysgenesis (CHTD) is the most common congenital endocrine disorder with an incidence of 1 in 4,000 live births. CHTD includes multiple abnormalities in thyroid gland development. Among them, the most common diagnostic category is thyroid ectopy (~ 50 % of cases). CHTD is frequently associated with a severe deficiency in thyroid hormones (hypothyroidism), which can lead to severe mental retardation if left untreated. The newborn biochemical screening program insures the rapid institution of thyroid hormone replacement therapy. Even with early treatment (on average at 9 d), subtle developmental delay is still be observed in severe cases (i.e., IQ loss of 10 points). Although there have been some reports of familial occurrence (in 2% of the cases), CHTD is mainly considered as a sporadic entity. Furthermore, monozygotic (MZ) twins show a high discordance rate (92%) for thyroid dysgenesis and female predominance is observed in thyroid dysgenesis (especially thyroid ectopy), these two observations being incompatible with simple Mendelian inheritance. In addition, germline mutations in the thyroid related transcription factors NKX2.1, PAX8, FOXE1, and NKX2.5 have been identified in only 3% of sporadic cases and linkage analysis has excluded these genes in some multiplex families with CHTD. Collectively, these data point to the involvement of non-Mendelian mechanisms in the etiology of the majority of cases of thyroid dysgenesis. Among the plausible mechanisms are epigenetic modifications, somatic mutations occurring in the thyroid bud early during embryogenesis, or stochastic developmental events. Hence, we proposed a two-hit model combining germline and somatic (epi)genetic variations that can explain the lack of clear familial transmission of CTHD. In this present thesis, we assessed the role of somatic (epi)genetic variations in the pathogenesis of thyroid dysgenesis via a genome-wide as well as a candidate gene approach. Our genome wide approach revealed that ectopic thyroids show a differential gene expression compared to that of normal thyroids, with enrichment for the Wnt signalling pathway. The Wnt signalling pathway is crucial for cell migration and for the development of several endoderm-derived organs (e.g., pancreas). Moreover, a role of Wnt signalling in thyroid organogenesis was further supported by recent zebrafish studies which showed thyroid abnormalities resulting from the disruption of the Wnt pathway during different steps of organogenesis. Thus, Wnt pathway involvement in the etiology of thyroid ectopy is biologically plausible. An unexpected finding of our genome-wide gene expression analysis of ectopic thyroids was that they express calcitonin similar to normally located (orthotopic) thyroids. Such a finding, although in contradiction with our current knowledge of the embryological development of the thyroid attributes C cell origins to extrathyroidal structures (ultimobrachial bodies) upon fusion with a fully-formed, normally situated gland. Using a candidate gene approach, we were unable to demonstrate any differences in the methylation profile between ectopic and eutopic thyroids, but nevertheless we documented the presence of a differentially methylated region (DMR) between thyroids and leukocytes in the promoter of FOXE1, a gene encoding the only thyroid related transcription factor known to play a crucial role in regulating the migration of the thyroid precursors during development as shown by animal studies. We demonstrated by in vivo and in vitro studies that the methylation status of this DMR is correlated with differential expression of FOXE1 in non-tumoral tissues (thyroids and leukocytes). Knowing that DMRs are hotspots for epi(genetic) variations, its screening among CTHD patients is justifiable in our search for a molecular basis of thyroid dysgenesis, currently underway in a case-control study. The results generated during my graduate studies represent unique and novel mechanisms underlying the pathogenesis of CHTD, the etiology of which is still an enigma. They also paved the way for many future studies that will aid in better understanding both the normal and pathogenic development of the thyroid gland.