• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 54
  • 31
  • 6
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 122
  • 122
  • 35
  • 31
  • 26
  • 20
  • 18
  • 17
  • 16
  • 12
  • 11
  • 11
  • 11
  • 10
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

Investigação genômica de pacientes inférteis com oligozoospermia / Genomic investigation of infertile patients with oligozoospermia

Juliana Dourado Grzesiuk 13 December 2016 (has links)
A infertilidade afeta aproximadamente 15% dos casais, sendo atualmente reconhecido o envolvimento de fatores masculinos em metade dos casos. Alterações nas análises seminais são detectadas na maioria dos homens inférteis e a mais frequente é a baixa concentração de espermatozoides no ejaculado, conhecida como oligozoospermia. Vários estudos mostram uma forte relação entre fatores genéticos e a infertilidade, incluindo alterações cromossômicas e microdeleções do cromossomo Y, porém as causas da oligozoospermia ainda permanecem obscuras. O desenvolvimento de novas tecnologias de investigação vem possibilitando a detecção de alterações a nível genômico, como mutações e variações no número de cópias (CNVs). O presente trabalho teve por objetivo a caracterização genômica de homens com oligozoospermia sem causa definida, visando estabelecer correlação entre alterações no número de cópias e perdas de heterozigosidade (LOHs) e o fenótipo de infertilidade. Foram selecionados 18 pacientes após rigorosa avaliação clínica e investigação do histórico reprodutivo, sendo excluídos pacientes portadores de alterações cromossômicas e portadores de microdeleções do cromossomo Y. Seis homens comprovadamente férteis foram selecionados para o grupo controle. A investigação genômica de ambos os grupos, amostral e controle, foi realizada pela técnica de hibridação genômica comparativa em microarranjos (aCGH) utilizando a plataforma de resolução 180K (Agilent®,US), analisada pelo software Nexus 8.0. Foram detectadas alterações possivelmente patogênicas no cromossomo Y, no cromossomo X e em autossomos. Um ganho na região de AZFc envolvendo apenas os genes DAZ1 e DAZ4 foi detectado em nove pacientes e em quatro controles, sendo classificado como alteração benigna. Porém, alterações na região de AZFc possivelmente relacionadas ao fenótipo de oligozoospermia foram detectadas em três pacientes e incluíram extensas duplicações e deleções envolvendo, entre outros genes, as quatro cópias do gene DAZ. Após comparação de regiões selecionadas com a literatura e com diferentes bancos de dados genéticos, sugerimos que os genes PLEC, SPATC1, COL1A1, MOV10L1, SYCE3 e ODF3B possam estar associados a alterações na produção espermática. Adicionalmente, entre os doze miRNAs presentes em regiões de LOH possivelmente relacionadas ao fenótipo de infertilidade, dez têm como alvo genes com funções relacionadas à espermatogênese e reprodução humana. Estudos adicionais a nível de expressão e sequenciamento gênico são necessários para confirmar a correlação entre o genótipo e o fenótipo de oligozoospermia. / Infertility affects about 15% of the couples, and it is currently recognized, that male factors are involved in about 50% of cases. Changes in seminal parameters are detected in most infertile men and the most common alteration, known as oligozoospermia, is a low concentration of sperm in the ejaculate. Several studies show a strong relationship between genetic factors and infertility, including chromosomal abnormalities and microdeletions of Y chromosome, however, the causes of oligozoospermia remain unclear. The development of new research technologies has allowed the detection of changes at genomic levels, such as mutations and copy number variations (CNVs). This study aimed to perform a genomic characterization of patients with idiopathic oligozoospermia to determine whether there is a correlation between changes of copy number and losses of heterozygosity (LOHs) in relation to the phenotype of infertility. Eighteen patients were selected for the cases after rigorous clinical examination and investigation of their reproductive history. Patients with chromosomal abnormalities or microdeletions of the Y chromosome were excluded. Six proven fertile men comprised the control group. Genomic investigation of both groups was performed by microarray comparative genomic hybridization (aCGH) using 4X180K platform (Agilent, US) analysed by Nexus 8.0 software. Potential pathogenic changes were detected on Y chromosome, as well as on the X and autosome chromosomes. A gain in AZFc region involving only DAZ1 and DAZ4 genes was detected in nine patients and four controls, and was considered as benign. However, changes in AZFc region, that could be related to the oligozoospermia phenotype were detected in three patients. These changes included extensive duplications and deletions involving the four copies of the DAZ gene together with copy number changes affecting other genes. After comparing the selected regions with the literature and with different databases, we suggest that changes such as LOH affecting PLEC, SPATC1, COL1A1, MOV10L1, SYCE3 and ODF3B genes may influence sperm production. Our analysis indicates that, ten out of the twelve miRNAs present in LOH regions could be involved in the infertility phenotype and could have target genes with functions related to spermatogenesis and human reproduction. Additional studies involving gene sequencing and expression analysis are needed to confirm the the correlation between the genotype and oligozoospermia phenotype.
112

Forensic identification of six of Tanzanian populations using the extended haplotype markers

Mwema, Hadija Saidi January 2011 (has links)
Magister Scientiae - MSc / The aim of the present study was to evaluate the power of discrimination and genetic (diversity) parameters in the Y chromosome extended haploytpe markers in populations of Tanzania for forensic and populations studies. Eleven Y chromosome extended haplotype markers were selected for this study, these includes Minimal haplotypes markers i.e. DYS19, DYS390, DYS391, DYS392, DYS393, DYS385a/b, DYS389I/II and two additional markers DYS438 and DYS439. Six populations of Tanzania were investigated under this study. These populations were selected based on the language family categories; Niger Congo (Kuria and Sukuma), Nilo Saharan (Luo and Maasai) and Afro Asiatic (Iraqw and Alagwa). / South Africa
113

A genetic investigation into a Lebanese population: from STR’s to SNP’s

Ghemrawi, Mirna 26 June 2018 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / In the past, the present and the future, Lebanon has been an important link between the East and the West. It was always known as the ‘Switzerland of the East’. Over the years, it was a hotspot for different civilizations that uniquely shaped the genomic backbone of the current Lebanese. It is also a good representation of genetically admixed individuals with diverse phenotype characteristics and unique features. Lebanon, quite like other Middle Eastern populations, lacks sufficient genetic studies that helps to better comprehend the complex genomic composition of different traits and diseases. The lack of good representation of the Middle East and North Africa (MENA) region in global studies has led to ambiguity in discovering special ancestry markers and patterns in the Lebanese genome. Yet, in this study, a thorough investigation into a Lebanese collection shows new patterns that potentially would be helpful in forensic and genealogical applications. The investigation into the autosomal and Y-STRs revealed unique alleles that would be valuable in future forensic investigation analysis. In addition, the assessment of phenotype prediction models to predict eye, hair and skin color showed promising results in terms of prediction performance. Those results encourage the future use of intelligence tools in the regions that in return would aid in serving justice and furthering science research. In fact, ancestry and genetic distance studies confirms the presence of admixture within Lebanon between Europe and North Africa. / 2029-06-01
114

Detecção de microdeleções do cromossomo Y em pacientes inférteis, comparando os resultados obtidos pelas técnicas de PCR e MLPA / Detection of Y chromosome microdeletions in infertile patients, comparing the results obtained by PCR and MLPA techniques

Camila Sommerauer Franchim 25 September 2018 (has links)
INTRODUÇÃO: O cromossomo Y contém genes primordiais para o desenvolvimento testicular e a espermatogênese. Sua conformação repetitiva predispõe à ocorrência de deleções e duplicações, que tem impacto clínico. As microdeleções nas regiões AZF afetam loci responsáveis pela espermatogênese e são uma das causas mais frequentes de azoospermia e oligozoospermia. Seu diagnóstico tem valor preditivo para o sucesso na recuperação cirúrgica de espermatozoides testiculares em homens azoospérmicos. A técnica utilizada para detectá-las é a reação de polimerização em cadeia (PCR), porém os protocolos divergem entre si, havendo muita variabilidade na incidência destas deleções. À vista disso, sugerimos utilizar a técnica de Amplificação de Múltiplas Sondas dependente de Ligação (MLPA). OBJETIVO: Comparar os resultados obtidos com as técnicas de PCR e MLPA na detecção de microdeleções do cromossomo Y em homens inférteis. RESULTADOS: Analisamos 43 pacientes inférteis (azoospérmicos e oligozoospérmicos) e 40 homens férteis (controle) pelas técnicas de PCR e MLPA. Encontramos 7 deleções por PCR (16,2%) e 9 por MLPA (21%), além de 5 duplicações e um mosaico. DISCUSSÂO: Além das deleções, as duplicações também podem gerar instabilidades nos genes do cromossomo, podendo levar a infertilidade. CONCLUSÕES: Os resultados obtidos por ambas as técnicas revela que a MLPA é uma técnica mais sensível que a técnica de PCR para detectar microdeleções do cromossomo Y / INTRODUCTION: The Y chromosome contains several genes responsible for testicular development and spermatogenesis. Its repetitive conformation predisposes this chromosome to deletions and duplications that have clinical impact. Microdeletions in the AZF regions affect loci responsible for spermatogenesis and are one of the most frequent causes of azoospermia and oligozoospermia. This diagnosis may have a predictive value for success in the surgical recovery of testicular spermatozoa in azoospermic men. The gold standard method for this detection is polymerase chain reaction (PCR), but protocols diverge among them, generating a great variability in the incidence of these deletions. PURPOSE: We evaluated another molecular diagnostic method, Multiplex Ligand Probe Dependent Amplification (MLPA), which generates more genomic data (such as duplications and rearrangements) in a single reaction, leading to a better understanding of these patients phenotype. OBJECTIVE: To compare the results obtained with PCR and MLPA techniques in the detection of Y chromosome microdeletions in infertile men. RESULTS: We analyzed 43 infertile patients (azoospermic and oligozoospermic) and 40 fertile men (control) by PCR and MLPA techniques. We found 7 deletions by PCR (16.2%) and 9 by MLPA (21%), in addition to 5 duplications and one mosaic. DISCUSSION: Besides deletions, duplications can also generate instability in the chromosome genes, which may lead to infertility, and it is important being capable to diagnose these alterations with a faster and more effectively method. CONCLUSIONS: The results obtained by both techniques reveal that MLPA is more sensitive than PCR to detect microdeletions of the Y chromosome
115

Detecção de microdeleções do cromossomo Y em pacientes inférteis, comparando os resultados obtidos pelas técnicas de PCR e MLPA / Detection of Y chromosome microdeletions in infertile patients, comparing the results obtained by PCR and MLPA techniques

Franchim, Camila Sommerauer 25 September 2018 (has links)
INTRODUÇÃO: O cromossomo Y contém genes primordiais para o desenvolvimento testicular e a espermatogênese. Sua conformação repetitiva predispõe à ocorrência de deleções e duplicações, que tem impacto clínico. As microdeleções nas regiões AZF afetam loci responsáveis pela espermatogênese e são uma das causas mais frequentes de azoospermia e oligozoospermia. Seu diagnóstico tem valor preditivo para o sucesso na recuperação cirúrgica de espermatozoides testiculares em homens azoospérmicos. A técnica utilizada para detectá-las é a reação de polimerização em cadeia (PCR), porém os protocolos divergem entre si, havendo muita variabilidade na incidência destas deleções. À vista disso, sugerimos utilizar a técnica de Amplificação de Múltiplas Sondas dependente de Ligação (MLPA). OBJETIVO: Comparar os resultados obtidos com as técnicas de PCR e MLPA na detecção de microdeleções do cromossomo Y em homens inférteis. RESULTADOS: Analisamos 43 pacientes inférteis (azoospérmicos e oligozoospérmicos) e 40 homens férteis (controle) pelas técnicas de PCR e MLPA. Encontramos 7 deleções por PCR (16,2%) e 9 por MLPA (21%), além de 5 duplicações e um mosaico. DISCUSSÂO: Além das deleções, as duplicações também podem gerar instabilidades nos genes do cromossomo, podendo levar a infertilidade. CONCLUSÕES: Os resultados obtidos por ambas as técnicas revela que a MLPA é uma técnica mais sensível que a técnica de PCR para detectar microdeleções do cromossomo Y / INTRODUCTION: The Y chromosome contains several genes responsible for testicular development and spermatogenesis. Its repetitive conformation predisposes this chromosome to deletions and duplications that have clinical impact. Microdeletions in the AZF regions affect loci responsible for spermatogenesis and are one of the most frequent causes of azoospermia and oligozoospermia. This diagnosis may have a predictive value for success in the surgical recovery of testicular spermatozoa in azoospermic men. The gold standard method for this detection is polymerase chain reaction (PCR), but protocols diverge among them, generating a great variability in the incidence of these deletions. PURPOSE: We evaluated another molecular diagnostic method, Multiplex Ligand Probe Dependent Amplification (MLPA), which generates more genomic data (such as duplications and rearrangements) in a single reaction, leading to a better understanding of these patients phenotype. OBJECTIVE: To compare the results obtained with PCR and MLPA techniques in the detection of Y chromosome microdeletions in infertile men. RESULTS: We analyzed 43 infertile patients (azoospermic and oligozoospermic) and 40 fertile men (control) by PCR and MLPA techniques. We found 7 deletions by PCR (16.2%) and 9 by MLPA (21%), in addition to 5 duplications and one mosaic. DISCUSSION: Besides deletions, duplications can also generate instability in the chromosome genes, which may lead to infertility, and it is important being capable to diagnose these alterations with a faster and more effectively method. CONCLUSIONS: The results obtained by both techniques reveal that MLPA is more sensitive than PCR to detect microdeletions of the Y chromosome
116

Diversitat genòmica a les poblacions del Nord d'Àfrica

Bosch Fusté, Elena 18 February 2000 (has links)
S'ha estudiat la variabilitat genètica de les poblacions del nord d'Àfrica a partir de l'anàlisi de diverses regions genòmiques per tal d'entendre les poblacions analitzades d'una banda, i comprendre la dinàmica del genoma per l'altra. Els resultats obtinguts ens han permès verificar diferents hipòtesis sobre la història de les poblacions d'aquesta regió com són l'efecte paral·lel i independent de l'onada de difusió del neolític des de l'Orient Mitjà al llarg d'ambdues ribes de la Mediterrànea; i l'efecte de l'arabització. S'ha pogut estimar també la contribució genètica masculina nord africana a la península ibèrica i detectat certa contribució genètica del pobles sub-saharians a les poblacions nordafricanes. Per altra banda, el tipatge de marcadors genètics que evolucionen a velocitats diferents al cromosoma Y ha permès mostrar que el background genètic predomina sobre el background poblacional en l'estructura de la variació genètica dels microsatèl·lits en la regió no recombinant del cromosoma Y humà. / The genetic variability of the North African populations has been studied through the analysis of different genomic regions in order to understand both the analysed populations and the dynamics of the genome. The obtained results allow us to verify different hypotheses about the population history of this region including the parallel and independent effect of the Neolithic wave of advance from the Middle East and along both Mediterranean coasts; and the effect of Arabization phenomena. We also tried to estimate the North African male genetic contribution to the Iberian peninsula and detected Sub-Saharian genetic influences to the North African peoples. Moreover, the typing of genetic markers with different evolutionary rates on the Y chromosome allowed us to demonstrate that variation in microsatellites is deeply structured by genetic background on the non-recombining region of the human Y chromosome.
117

Populační struktura, migrace a dynamika Afriky a Arábie / Population structure, migration and dynamics in Africa and Arabia

Čížková, Martina January 2020 (has links)
In addition to the interaction of evolutionary forces, the population history of the African Sahel and Arabia has been influenced by the spread of Neolithic cultural innovations. The reflection of these processes today is a very complex structured diversity of the current populations, which is presented here through the analysis of several genetic markers. The aim is to provide a comprehensive view of the history of demographic processes in the Sahel and Arabia, by combining genetic, linguistic, subsistence and geographical data obtained from local populations. A study of a large dataset of mtDNA sequences showed that Arabia was a major crossroads in gene flow, and although it was colonized by anatomically modern humans from East Africa, today's differentiation from Africa is greater than the differentiation between local populations in these regions. Even the Sahel was an important biocorridor in the past. Today, we encounter populations of various subsistence strategies (nomadic pastoralists and settled farmers), between which gene flow has been severely restricted. A comparison of uniparently inherited loci in both groups points to different migratory activity in the eastern and western parts of the Sahel. Analyzes of Alu elements, which indicated the inclination of West African herders (Fulbs)...
118

Régions de susceptibilité dans les remaniements du chromosome Y et mosaïcisme : facteurs de risque du développement sexuel anormal

Beaulieu Bergeron, Mélanie 01 1900 (has links)
Le développement sexuel est un processus complexe qui dépend de nombreux gènes, une mutation pouvant entraîner un développement sexuel anormal. Par ailleurs, des anomalies chromosomiques peuvent avoir des répercussions importantes sur la détermination gonadique, surtout lorsqu'il s'agit du chromosome Y puisqu'il porte le gène clé du développement sexuel masculin. Premièrement, nous avons identifié par cytogénétique moléculaire le point de cassure chez 5 patients avec une translocation X;Y et 10 patients avec un chromosome Y isodicentrique. Nous avons ainsi démontré que certaines régions sont plus à risque d'être remaniées, notamment lorsqu'elles contiennent des palindromes ou d'autres séquences répétées. Nous avons également établi une relation entre la distance séparant le centromère et le point de cassure et l'instabilité des chromosomes Y isodicentriques lors des divisions cellulaires. Deuxièmement, nous avons étudié en cytogénétique les gonades de 22 patients avec un chromosome Y normal ou remanié et présentant un développement sexuel anormal. Nous avons mis en évidence la perte du chromosome Y remanié dans une majorité de cellules gonadiques des 10 patients étudiés, expliquant leur phénotype sexuel anormal. Cependant, chez 11 des 12 patients avec un chromosome Y normal, aucun mosaïcisme expliquant clairement leur détermination gonadique anormale n'a été retrouvé. Finalement, nous avons analysé par immunohistochimie les gonades dysgénésiques de 30 patients avec une anomalie du développement sexuel et un chromosome Y normal ou remanié. Nos travaux ont montré la présence de cellules germinales immatures au sein de cordons sexuels primitifs sous forme de tissu gonadique indifférencié dans 15 gonades, dont 9 ont évolué en tumeur gonadique. Dans 13 autres gonades, ces cellules germinales immatures avaient disparues par apoptose. Dans l'ensemble, notre recherche met en évidence la susceptibilité du chromosome Y à subir des remaniements et à être instable lors des divisions cellulaires, et indique que le mosaïcisme peut avoir des répercussions sur la détermination gonadique. Nos travaux montrent également que le tissu gonadique indifférencié peut évoluer vers deux entités, une tumeur gonadique ou une bandelette suite à l'apoptose des cellules germinales, mettant en lumière la nécessité d'analyser le tissu gonadique des patients XY avec dysgénésie gonadique dont les gonades sont laissées en place. / Sexual development is a complex process which depends on numerous genes, mutations possibly resulting in an abnormal sexual development. Furthermore, chromosome abnormalities can have important repercussions on gonadal determination, especially when it comes to the Y chromosome since it carries the master gene of male sexual development. First, we identified by molecular cytogenetics the breakpoint in 5 patients with an X;Y translocation and 10 patients with an isodicentric Y chromosome. We were thus able to show that some regions are more at risk of being rearranged, especially when they contain palindromes or other repeated sequences. We were also able to establish a relationship between the distance separating the centromere from the breakpoint and instability of isodicentric Y chromosomes during cell divisions. Second, we studied by cytogenetics the gonads of patients with a normal or rearranged Y chromosome and presenting an abnormal sexual development. We demonstrated loss of the rearranged Y chromosome in a majority of gonadal cells of the 10 analyzed patients, explaining their abnormal sexual phenotype. On the other hand, in 11 of the 12 patients with a normal Y chromosome, no mosaicism clearly explaining their abnormal gonadal determination was found. Finally, we also analyzed by immunohistochemistry the dysgenetic gonads of 30 patients with an abnormal sexual developement and a normal or rearranged Y chromosome. We showed the presence of immature germ cells in primitive sex cords as undifferentiated gonadal tissue in 15 gonads, including 9 that evolved in a gonadal tumor. In 13 other gonads, these immature germ cells had disappeared through apoptosis. Altogether, our research demonstrates that the Y chromosome is susceptible to rearrangements and can be unstable through cell divisions, and that mosaicism may have repercussions on gonadal determination. Our work also shows that undifferentiated gonadal tissue can evolve in two entities, a gonadal tumor or a streak following apoptosis of germ cells, thus emphasizing the necessity of studying the gonads of XY patients with gonadal dysgenesis when gonads are left in place.
119

Evolução cromossômica: estudo da variabilidade cariotípica em Platyrrhini e das homeologias e sintenias com cromossomos humanos / Chromosome evolution: Karyotype variability in Platyrrhini and studies of sinteny and homologies between human chromosomes

Iughetti, Cristiani Gifalli 29 September 2008 (has links)
Estudamos os cariótipos de espécimes de macacos brasileiros (Platyrrhini, Primates) com técnicas citogenéticas tradicionais e de FISH com as sondas totais dos cromossomos 14, 15 e X humanos e do cromossomo Y de Brachyteles arachnoides obtida por microdissecção cromossômica. Vinte e quatro espécimes de Alouatta guariba clamitans, doze machos e doze fêmeas foram estudados. Para os machos, encontramos um número diplóide de 2n = 49, devido à ausência aparente do cromossomo Y provavelmente decorrente de uma translocação Y-autossomo, e 2n = 46 cromossomos, com variação nas fórmulas cromossômicas com 17, 19, 20, 21 ou 24 cromossomos metacêntricos ou submetacêntricos e 22, 28, 29, 30 ou 32 acrocêntricos. Para as fêmeas, uma variabilidade maior no número diplóide foi observada com 46, 48 e 50 cromossomos e as fórmulas cromossômicas encontradas mostraram 18, 19, 20, 21, 27 ou 28 cromossomos metacêntricos ou submetacêntricos e 18, 19, 27, 30, 31 e 32 acrocêntricos. Os cromossomos X eram submetacêntricos. Pares heteromórficos foram observados. Uma fêmea com 48 cromossomos foi descrita pela primeira vez, este número diplóide só havia sido descrito em um único exemplar macho. A confirmação da subespécie dos indivíduos analisados se deu pela presença do par cromossômico característico de Alouatta guariba clamitans, o par 1, e pela região geográfica de procedência dos exemplares. O sexo dos espécimes também foi confirmado ou mesmo determinado pela análise dos cariótipos. Para Alouatta guariba clamitans, corroboramos a tendência à redução do número diplóide orientada no sentido norte-sul. As grandes diferenças cromossômicas entre as populações do sul e sudeste sugerem que Alouatta guariba clamitans seja representante de duas subespécies ou mesmo de duas espécies separadas, evidenciando a necessidade de uma revisão de sua taxonomia. Analisamos um macho de A. sara em coloração convencional, bandamentos GTG e CGB. O cariótipo era formado por 50 cromossomos, com 16 metacêntricos ou submetacêntricos, 31 acrocêntricos e 3 microcromossomos, dois submetacêntricos e um acrocêntrico. O cromossomo X era submetacêntrico e o cromossomo Y estava aparentemente ausente, provavelmente devido a uma translocação Y-autossomo. Um heteromorfismo foi observado. A heterocromatina estava presente na região pericentromérica dos cromossomos, incluindo os três microcromossomos. Duas fêmeas de Ateles paniscus paniscus foram estudadas em coloração convencional. Os espécimes apresentaram 32 cromossomos, com 30 cromossomos metacêntricos ou submetacêntricos e 2 acrocêntricos. A classificação foi baseada no número diplóide e presença do cromossomo 2 metacêntrico característico desta subespécie. Também analisamos dois machos de Ateles sp. em coloração convencional que apresentaram um número diplóide de 34 cromossomos, agrupados em 32 metacêntricos ou submetacêntricos e 2 acrocêntricos. O cromossomo Y era o menor metacêntrico do complemento. Os cromossomos X dos quatro Ateles analisados eram submetacêntricos. A descrição de pares cromossômicos heteromórficos neste gênero é freqüente. Sugerimos que os indivíduos de Ateles sp. sejam classificados como Ateles paniscus chamek. A diferença no número cromossômico entre os exemplares analisados é devido à presença do par metacêntrico em A. p. paniscus que é resultante da fusão in tandem de dois cromossomos de A. p. chamek. A variabilidade intra e interespecífica observada neste gênero podem ser explicadas por inversões pericêntricas. Estudamos uma fêmea e um macho de Callimico goeldii em coloração convencional. Ambos apresentaram 48 cromossomos agrupados em 28 cromossomos metacêntricos ou submetacêntricos e 18 cromossomos acrocêntricos, além do cromossomo X submetacêntrico e do Y acrocêntrico. Heteromorfismos foram observados. Não encontramos variabilidade no número diplóide e a diferença nas fórmulas cromossômicas é devido à morfologia dos cromossomos sexuais. Três machos e quatro fêmeas de Callithrix sp. foram analisados em coloração convencional e bandamentos GTG e CBG. O número cromossômico encontrado foi de 2n = 46, com 30 autossomos metacêntricos ou submetacêntricos, 14 autossomos acrocêntricos, o cromossomo X submetacêntrico e o cromossomo Y acrocêntrico. Duas fêmea e um macho apresentaram linhagens quiméricas 46,XX/46,XY. Heteromorfismos foram encontrados. A heterocromatina estava presente na região pericentromérica dos cromossomos e em blocos extracentroméricos. Não conseguimos determinar com exatidão a espécie de Callithrix, porém pela fórmula cromossômica e morfologia do cromossomo Y sugerimos que possam ser das espécies C. jacchus, C. penicillata ou C. aurita. O macho de Cebus nigritus estudado em coloração convencional apresentou 54 cromossomos divididos em 20 autossomos metacêntricos ou submetacêntricos e 32 acrocêntricos, além do cromossomo X que é um submetacêntrico e do Y que é um acrocêntrico. Não foram observados heteromorfismos. Levando em consideração as características fenotípicas, semelhanças entre os cromossomos com os cariótipos mostrando a mesma fórmula cromossômica e distribuição geográfica, sugerimos que C. nigritus seja sinônimo de C. vellerosus. Estudamos uma fêmea de Callicebus caligatus em coloração convencional que apresentou 48 cromossomos, com 16 metacêntricos ou submetacêntricos e 32 acrocêntricos. Heteromorfismos foram observados. Também analisamos uma fêmea de Callicebus nigrifrons com a mesma coloração e a classificação foi confirmada pela análise citogenética. Esta fêmea mostrou um número diplóide de 2n = 42, compreendendo 30 autossomos metacêntricos ou submetacêntricos e 12 acrocêntricos. Nenhum heteromorfismo foi observado. Os cromossomos X das duas fêmeas eram submetacêntricos. As duas espécies de Callicebus apresentaram números diplóides e fórmulas cromossômicas diferentes, com um predomínio de cromossomos acrocêntricos em C. caligatus e um predomínio de cromossomos não-acrocêntricos em C. nigrifrons, indicando que a redução do número diplóide foi direcionada por eventos de fusão cromossômica. Estudamos a conservação da associação sintênica HSA 14/15 em praticamente todos os gêneros de macacos do Novo Mundo. O homeólogo ao HSA 14 conservou a sintenia para o cromossomo inteiro enquanto o homeólogo ao HSA 15 está fragmentado. Esta associação favorece a origem monofilética da família Atelidae e da subfamília Callitrichinae. Um padrão 14/15/14 foi observado em Alouatta sara e 15/14/15/14 em Aotus nigriceps, mostrando um alto grau de instabilidade citogenética nesta região em alguns gêneros, estando mais susceptível a quebra e inversão. Relatamos a presença desta associação também em Cacajao melanocephalus, que não havia sido estudado com a técnica de FISH. A presença da associação sintênica HSA 14/15 em todas as espécies e subespécies de macacos do Novo Mundo estudadas indica que esta sintenia é um caractere ancestral, concordando com o provável cariótipo ancestral de Platyrrhini. A pintura com a sonda total do cromossomo X humano em praticamente todos os gêneros de Platyrrhini confirmou a Lei de Ohno, que dita a conservação evolutiva do cromossomo X em mamíferos placentários. A sonda total do cromossomo Y de Brachyteles arachnoides produzida por microdissecção cromossômica mostrou uma homeologia entre o cromossomo Y de todos os gêneros pertencentes à subfamília Atelinae (Ateles belzebuth marginatus, Lagothrix lagothricha e Brachyteles arachnoides). Lagothrix e Brachyteles apresentaram um cromossomo Y acrocêntrico diminuto e Ateles mostrou um cromossomo Y acrocêntrico pequeno, mas não diminuto. Não conseguimos hibridar esta sonda em metáfases de espécimes da subfamília Alouattinae, que junto com a subfamília Atelinae compõem a família Atelidae. O uso de caracteres citogenéticos-moleculares pode proporcionar informações valiosas para a elucidação das relações filogenéticas na subfamília Atelinae. Os nossos dados mostram que o cromossomo Y nesta subfamília compartilha uma história comum, devendo mostrar o mesmo padrão filogenético, corroborando a separação da família Atelidae nas subfamílias Atelinae e Alouattinae. Os diferentes números diplóides e fórmulas cromossômicas observados nesse trabalho indicam a grande variabilidade intra e interespecífica e intrapopulacional existente em Platyrrhini, com uma marcante reorganização no seu genoma, decorrente de processos de inversões pericêntricas, fusões cromossômicas, translocações entre cromossomos e outros rearranjos mais complexos. A análise citogenética em Platyrrhini é importante para a identificação das espécies para uma posterior soltura em região geográfica adequada, para os programas de reprodução em cativeiro aumentando as possibilidades de reprodução ex situ e para a deposição em museus. Também é uma ferramenta importante para a identificação das origens dos espécimes com procedência incerta. Uma maior integração e direcionamento dos dados citogenéticos, morfológicos e moleculares é necessária para o entendimento da variação e definição das taxa de forma mais objetiva. A destruição e fragmentação das florestas, as práticas agrícolas, a caça e a subtração de indivíduos como animais de estimação têm afetado negativamente a sobrevivência dos macacos brasileiros. / We studied the karyotypes of Brazilian monkeys (Platyrrhini, Primates) using both traditional cytogenetic techniques as well as FISH. FISH analysis employed human probes for chromosome 14, 15 and the X chromosome and a probe of the Y chromosome of Brachyteles arachnoides obtained by chromosome microdissection. Twenty-four individuals of Alouatta guariba clamitans were studied, twelve males and twelve females. For males, we found a diploid number of 2n = 49 due to the presumed absence of the Y chromosome probably due to a Y-autosome translocation, and 2n = 46 chromosomes, with 17, 19, 20, 21 or 24 biarmed chromosomes and 22, 28, 29, 30 or 32 acrocentrics. For females, a greater variability in the diploid number was observed with 46, 48 and 50 chromosomes and 18, 19, 20, 21, 27 or 28 biarmed chromosomes and 18, 19, 27, 30, 31 and 32 acrocentrics. The X chromosomes were submetacentric. Heteromorphisms were observed. A female with 48 chromosomes was described for the first time; this diploid number had only been described before for a single male. The subspecies has been confirmed by the presence of a characteristic chromosome pair of Alouatta guariba clamitans, pair 1, and by the geographic origin of the samples. The sex was also confirmed or determined by karyotype analysis. The major chromosomal differences between populations of the south and southeast of Brazil suggest that Alouatta guariba clamitans may be representative of two subspecies or even two separate species, highlighting the need for a taxonomic review. A male of A. sara was studied and we observed a diploid number of 2n = 50 chromosomes, with 16 biarmed, 31 acrocentrics and 3 microchromosomes, two submetacentrics and one acrocentric. The X chromosome was submetacentric and the Y chromosome was presumably missing, probably due to a Y-autosome translocation. A heteromorphism was observed. The heterochromatin was present in the pericentromeric region of chromosomes, including the three microchromosomes. Two females of Ateles paniscus paniscus were studied. The specimens had 32 chromosomes, with 30 biarmed and 2 acrocentrics. A heteromorphism was observed. The classification was based on the diploid number and presence of a metacentric chromosome, pair 2, characteristic of this subspecies. We also analyzed two males of Ateles sp. that showed a diploid number of 34 chromosomes, grouped in 32 biarmed and 2 acrocentrics. The Y chromosome was the smallest metacentric. The X chromosomes were submetacentrics. The description of heteromorphisms in this genus is frequent. We suggest that these two individuals of Ateles sp. are classified as Ateles paniscus chamek. The difference in the diploid number of the specimens is due to the presence of a metacentric in A. p. paniscus that is the result of the in tandem fusion of two chromosomes of A. p. chamek. The variability in this genus can be explained by pericentric inversions. We studied a female and a male of Callimico goeldii. Both had 48 chromosomes grouped in 28 biarmed chromosomes and 18 acrocentrics, plus an X submetacentric chromosome and a Y acrocentric. Heteromorphisms were observed. We observed no variations in the diploid number and all differences are due to the morphology of the sex chromosomes. Three males and four females of Callithrix sp. were studied. The chromosome number was 2n = 46, with 30 biarmed, 14 acrocentrics, a submetacentric X chromosome and an acrocentric Y chromosome. Two females and one male showed 46,XX/46,XY chimerisms. Heteromorphisms were found. The heterochromatin was present in the pericentromeric region and in extracentromeric blocks. We observed no variations in the diploid number and the only differences are due to the morphology of the sex chromosomes. We could not determine the Callithrix species, but the karyotypes suggest C. jacchus, C. penicillata or C. aurita. The Cebus nigritus male studied showed 54 chromosomes grouped in 20 biarmed and 32 acrocentrics, and a submetacentric X chromosome and an acrocentric Y. There were no heteromorphisms. Taking into account the phenotypic characteristics, similarities between chromosomes and geographical distribution, we suggest that C. nigritus is synonymous with C. vellerosus. We studied a female Callicebus caligatus that showed 48 chromosomes, with 16 biarmed and 32 acrocentrics. Heteromorphisms were observed. We also analyzed a female Callicebus nigrifrons, whose taxonomic placement was confirmed by cytogenetic analysis. Its diploid number was 2n = 42, including 30 biarmed and 12 acrocentrics. No heteromorphisms were observed. The X chromosomes were submetacentrics. The two Callicebus species showed different diploid numbers, with a predominance of acrocentric chromosomes in C. caligatus and a predominance of biarmed chromosomes in C. nigrifrons, indicating that the reduction in the diploid number was due to events of chromosomal fusion. We studied the syntenic association HSA 14/15 conservation in almost all genera of Platyrrhini. The HSA 14 homolog retained synteny for the entire chromosome however the HSA 15 homolog was fragmented. The association suggests a monophyletic origin of the Atelidae family and Callitrichinae subfamily. A 14/15/14 pattern was observed in Alouatta sara and a 15/14/15/14 pattern in Aotus nigriceps, showing a high degree of instability in this region in some genera. We report the presence of this association also in Cacajao melanocephalus, who had not been previously studied with FISH technique. The presence of the HSA 14/15 syntenic association in all species and subspecies of Platyrrhini that we studied indicates that this is an ancestral trait, agreeing with Platyrrhini ancestor karyotype. The painting with human X chromosome in almost all genera of Platyrrhini consistent with Ohnos Law, indicating evolutionary conservation of the X chromosome in placental mammals. The signals were found exclusively in the X chromosome homologs. The Y chromosome probe of Brachyteles arachnoides produced by chromosome microdissection showed homology between the Y chromosomes of all genera belonging to the Atelinae subfamily (Ateles belzebuth marginatus, Lagothrix lagothricha and Brachyteles arachnoides). Lagothrix and Brachyteles Y chromosomes are extremely small acrocentrics and the Ateles Y chromosome is small. We could not hybridize this probe in metaphases form Alouatta, which along with the Atelinae genera comprise family Atelidae. The use of molecular-cytogenetic traits can provide valuable information for the elucidation of phylogenetic relationships in tne Atelinae subfamily. Our data show that the Y chromosome in the subfamily Atelinae shares a common history and is consistent with the separation of family Atelidae into the subfamilies Atelinae and Alouattinae. In conclusion our study indicates a great degree of chromosomal varaibility within Platyrrhini and suggests a marked reorganization of the genome within this primate group, due to such processes as pericentric inversions, chromosome fusions, translocations between chromosomes and other complex rearrangements. Cytogenetic analyse in Platyrrhini are important for species identification. Such information can in turn be useful for a variety of conservation and systematic purposes including repatriation of animals in an appropriate geographical region, for captive breeding programs, increasing the chances of ex-situ breeding, and for the deposition of specimens in museums. It is also an important tool for identifying the geographical origins of specimens with uncertain origin. Integration of cytogenetic, morphological and molecular data is necessary for the understanding of variation and definition of the taxa and understanding evolutionary processes at these different levels. Forests destruction and fragmentation, agricultural practices, hunting and subtraction of individuals as pets have negatively affected the survival of Brazilian monkeys.
120

Régions de susceptibilité dans les remaniements du chromosome Y et mosaïcisme : facteurs de risque du développement sexuel anormal

Beaulieu Bergeron, Mélanie 01 1900 (has links)
Le développement sexuel est un processus complexe qui dépend de nombreux gènes, une mutation pouvant entraîner un développement sexuel anormal. Par ailleurs, des anomalies chromosomiques peuvent avoir des répercussions importantes sur la détermination gonadique, surtout lorsqu'il s'agit du chromosome Y puisqu'il porte le gène clé du développement sexuel masculin. Premièrement, nous avons identifié par cytogénétique moléculaire le point de cassure chez 5 patients avec une translocation X;Y et 10 patients avec un chromosome Y isodicentrique. Nous avons ainsi démontré que certaines régions sont plus à risque d'être remaniées, notamment lorsqu'elles contiennent des palindromes ou d'autres séquences répétées. Nous avons également établi une relation entre la distance séparant le centromère et le point de cassure et l'instabilité des chromosomes Y isodicentriques lors des divisions cellulaires. Deuxièmement, nous avons étudié en cytogénétique les gonades de 22 patients avec un chromosome Y normal ou remanié et présentant un développement sexuel anormal. Nous avons mis en évidence la perte du chromosome Y remanié dans une majorité de cellules gonadiques des 10 patients étudiés, expliquant leur phénotype sexuel anormal. Cependant, chez 11 des 12 patients avec un chromosome Y normal, aucun mosaïcisme expliquant clairement leur détermination gonadique anormale n'a été retrouvé. Finalement, nous avons analysé par immunohistochimie les gonades dysgénésiques de 30 patients avec une anomalie du développement sexuel et un chromosome Y normal ou remanié. Nos travaux ont montré la présence de cellules germinales immatures au sein de cordons sexuels primitifs sous forme de tissu gonadique indifférencié dans 15 gonades, dont 9 ont évolué en tumeur gonadique. Dans 13 autres gonades, ces cellules germinales immatures avaient disparues par apoptose. Dans l'ensemble, notre recherche met en évidence la susceptibilité du chromosome Y à subir des remaniements et à être instable lors des divisions cellulaires, et indique que le mosaïcisme peut avoir des répercussions sur la détermination gonadique. Nos travaux montrent également que le tissu gonadique indifférencié peut évoluer vers deux entités, une tumeur gonadique ou une bandelette suite à l'apoptose des cellules germinales, mettant en lumière la nécessité d'analyser le tissu gonadique des patients XY avec dysgénésie gonadique dont les gonades sont laissées en place. / Sexual development is a complex process which depends on numerous genes, mutations possibly resulting in an abnormal sexual development. Furthermore, chromosome abnormalities can have important repercussions on gonadal determination, especially when it comes to the Y chromosome since it carries the master gene of male sexual development. First, we identified by molecular cytogenetics the breakpoint in 5 patients with an X;Y translocation and 10 patients with an isodicentric Y chromosome. We were thus able to show that some regions are more at risk of being rearranged, especially when they contain palindromes or other repeated sequences. We were also able to establish a relationship between the distance separating the centromere from the breakpoint and instability of isodicentric Y chromosomes during cell divisions. Second, we studied by cytogenetics the gonads of patients with a normal or rearranged Y chromosome and presenting an abnormal sexual development. We demonstrated loss of the rearranged Y chromosome in a majority of gonadal cells of the 10 analyzed patients, explaining their abnormal sexual phenotype. On the other hand, in 11 of the 12 patients with a normal Y chromosome, no mosaicism clearly explaining their abnormal gonadal determination was found. Finally, we also analyzed by immunohistochemistry the dysgenetic gonads of 30 patients with an abnormal sexual developement and a normal or rearranged Y chromosome. We showed the presence of immature germ cells in primitive sex cords as undifferentiated gonadal tissue in 15 gonads, including 9 that evolved in a gonadal tumor. In 13 other gonads, these immature germ cells had disappeared through apoptosis. Altogether, our research demonstrates that the Y chromosome is susceptible to rearrangements and can be unstable through cell divisions, and that mosaicism may have repercussions on gonadal determination. Our work also shows that undifferentiated gonadal tissue can evolve in two entities, a gonadal tumor or a streak following apoptosis of germ cells, thus emphasizing the necessity of studying the gonads of XY patients with gonadal dysgenesis when gonads are left in place.

Page generated in 0.058 seconds