FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / A tese à composta por dois capÃtulos. O primeiro capÃtulo inclui o trabalho cujo objetivo foi investigar o potencial uso de pares de transcritos correlativos baseados em microarranjos como marcadores de fertilidade masculina usando a displasia da bainha fibrosa (DFS) como modelo afetado. Atualmente à bastante reconhecido que a tecnologia de microarranjos pode ser limitada pelos custos e que a qualidade dos transcritos permanece relativamente desconhecida. Para responder essas questÃes, nÃs analizamos pares de transcritos estÃveis por qPCR com um processo sistemÃtico de desenho de primers sistemÃtico. Nesse estudo experimental, nÃs utilizamos amostras de homens com fertilidade comprovada e de homens com diagnÃtico de DFS. Nossa abordagem foi baseada nas sequÃncias de primers dos seis genes de interesse, os quais foram desenhados utilizando os programas Oligo7 e Primer3Plus. A especificidade do primer foi inicialmente analisada in silico atravÃs de pesquisas nos bancos de dados ENSEMBL, University of California Santa Cruz (UCSC), e National Center for Biotechnology Information (NCBI) para uso de sequÃncias especÃficas aos genes alvos. A habilidade dos pares de transcritos em classificar as amostras de homens de fertilidade comprovada das amostras de DFS foi avaliada. Nossos resultados mostraram que em conjunÃÃo com a identificaÃÃo de quatro novos pares estÃveis, a comparaÃÃo dos coeficientes de correlaÃÃo dos valores de C(t) dos DSF revelou a interrupÃÃo de quatro pares estÃveis identificados nas amostras de homens normais. Esta seleÃÃo de pares estÃveis resolve a questÃo sobre a DSF. Em conclusÃo, os resultados mostram efetivamente que o desenho de primers e qPCR podem fornecer um ensaio molecular de baixo custo para avaliar a fertilidade masculina. O segundo capÃtulo divide-se em dois estudos e avalia em carneiros os efeitos de uma dieta suplementada com farelo de castanha de caju. No estudo 1, nosso objetivo foi detectar a presenÃa de transcritos para Heat Shock Protein (HSP70), clusterina (CLU), proteÃna semelhante à subunidade alfa do complexo T (TCP1) e proteÃna do complexo T subunidade 8 (CCT8) no espermatozÃide de ovinos, seguindo a mesma metodologia para qPCR utilizada no capitulo 1. As sequÃncias de primers foram desenhadas utilizando os programas Primer3Plus e Oligo Analyzer. Gene para protamina 2 (PRM2) foi usado como controle interno de reaÃÃo. O sÃmen foi coletado de machos pÃberes Morada Nova utlizando eletroejaculador. As amostras selecionadas para extraÃÃo de RNA espermÃtico seguiram as recomendaÃÃes do ColÃgio Brasileiro de ReproduÃÃo Animal quanto aos parÃmetros de motilidade, vigor e concentraÃÃo. Nossos resultados mostraram a presenÃa de mRNA para a HSP70 nos espermatozÃides de ovinos. Maiores estudos sÃo necessÃrios a fim de confirmar ou refutar a presenÃa das chaperonas TCP1 e CCT8 no espermatozÃide ovino. A presenÃa do transcrito da HSP70 no espermatozÃide de ovinos abre perspectivas para estudos futuros sobre os efeitos do mRNA HSP70 no desenvolvimento embrionÃrio, de modo a avaliar se essa expressÃo ocorre de modo espontÃneo, programado e seqÃencial, e se esses mecanismos se refletem na fertilidade e no desenvolvimento embrionÃrio. O segundo estudo tem como principal objetivo avaliar os efeitos de uma dieta contendo farelo de castanha de caju (FCC) na expressÃo de genes relacionados ao metabolismo dos lipÃdios no mÃsculo Longissimus dorsi de carneiros Morada Nova. Vinte carneiros maduros sexualmente foram divididos em dois grupos baseando-se no peso vivo. Os animais foram mantidos em baias individuais. Durante trÃs meses, o grupo castanha (GCA) foi alimentado com raÃÃo contendo FCC, enquanto o grupo controle (GCO) recebeu raÃÃo à base de milho e soja. As duas dietas eram isocalÃricas e isoprotÃicas, adicionadas de suplemento mineral. Os carneiros tambÃm receberam feno de Tifton e Ãgua à vontade. A quantidade de alimento ofertado (raÃÃo e feno) foi ajustada diariamente para sobra de 10%. Sete genes codificantes de proteÃnas envolvidas direta ou indiretamente foram selecionados como alvos, incluindo: GH, ACACA, CAST, CAPN3, LPL, SCD e FASN. Para normalizaÃÃo, foram selecionados cinco genes candidatos: ACTB, GAPDH, RPL4, RPS18 e TBP. Dentre os sete genes alvos selecionados anteriormente, os alvos GH, ACACA e CAST foram removidos. Os dois primeiros foram removidos devido amplificaÃÃo de alinhamento mÃltiplo (baixa especificidade do primers), enquanto CAST apresentou baixa eficiÃncia de amplificaÃÃo. Da lista de gene alvo final, a expressÃo de somente dois genes foi afetada pela dieta, SCD (p<0.01) e FASN (p<0.05), enquanto LPL (p=0,1022) e CAPN3 (p=0,0939) nÃo apresentaram diferenÃa significativa (p<0.05). Os genes SCD e FASN foram reprimidos no GCA comparada ao GCO. Este à o primeiro relato de que uma raÃÃo contendo FCC afetou a expressÃo gÃnica de proteÃnas envolvidas na deposiÃÃo de lipÃdios no mÃsculo em ovinos. Considerando que uma dieta contendo FCC altera a expressÃo de genes lipogÃnicos sem afetar o ganho de peso nem a eficiÃncia reprodutiva de ovinos, faz da castanha de caju uma importante alternativa para o sistema de produÃÃo de ovinos criados em regiÃes tropicais. / This thesis presents two chapters. In the first chapter, its objective was to investigate the potential use of correlative microarray-based transcript pairs as candidate markers for male fertility using dysplasia of the fibrous sheath (DFS) as an affected model. It is widely recognized that microarray technology may be limited by cost and that the quality of the transcript remains relatively unknown. To address these issues, we analyzed the stable transcript pairs by qPCR with a systematic primer design process. On this experimental study, we used men with proven fertility and men with a diagnosis of DFS. Our approach was based on primer sequences for six genes of interest were designed using Oligo7 and Primer3Plus. Primer specificity was initially assessed in silico by searching the ENSEMBL, University of California Santa Cruz, and National Center for Biotechnology Information databases for nontarget complementary sequences throughout the genome. The ability of transcript pairs to classify samples from males of proven fertility away from DFS was assessed. Our results showed that in conjunction with identifying four new stable transcript pairs, comparison of the DFS qPCR C(t) correlation coefficients revealed the disruption of four stable fertile sample transcript pairs. This suite of transcript pairs resolves DFS. In conclusion, the results show that with effectively designed primers, qPCR may provide an affordable molecular assay to assess male fertility status. Second chapter includes two studies regarding evaluations of ram feeded with supplemented diet with cashew nut. On the frist study, our goal was detect transcripts for Heat Shock Protein (HSP70), Clusterin (CLU), Ovis aries T-complex protein 1 alfa subunit-like protein (TCP1) e Ovis aries chaperonin containing TCP1, subunit 8 (theta) (CCT8) on ram sperm by. For primer designing we used published ESTs from NCBI and manually annotated by us using Primer3Plus and OligoAnalizer. PRM2 was used as internal qPCR control. Semen samples from mature Morada Nova ram were collected by eletroejaculator, washed in PBS and prepared for further RNA extraction. Selected samples followed quality recommendatios from ColÃgio Brasileiro de ReproduÃÃo Animal regarding motility, vigor and concentration. Our results showed presence of mRNA HSP70 on ram sperm and they can possible be envolved in early embryo development, oocyte activation and post fertilization events. Further analyses will be necessary to confirm presence of TCP1 and CCT8 on ram sperm. Our findings indicate new perpectives about the effects of these chaperones during embryo development mesuring if its expression reflects male fertility on the early embryo development. On the second study the the main goal is to evaluate the effects of a lipid-enriched diet containing cashew nut brain on the expression of genes related to lipid metabolism in the longissimus dorsi muscle of Morada Nova rams. Twenty sexually mature and reproductively sound rams were divided in two groups based on ram live weight, and each ram was kept on individual pens. During three months, group 1 (G1) rams were fed with a lipid-rich diet, containing cashew nut bran (CNB), while group 2 (G2) was fed with a meal based on corn and soy. Both diets were isocaloric and isoproteic, and had a mineral mix added-in. The rams also were offered Tifton grass hay and had free access to water. The amount of diet offered (ration plus hay) was adjusted everyday to a maximum waste of 10%. Seven genes coding for proteins directly or indirectly involved in lipid metabolism were initially selected as targets, incluiding GH, ACACA, CAST, CAPN3, LPL, SCD, and FASN. Also, five genes were selected as reference genes, ACTB, GAPDH, RPL4, RPS18 and TBP. From the seven genes originally selected as targets, GH, ACACA and CAST were removed, leaving the final list with four targets. The first two genes were removed due to alternative pairing of the primers (low specificity), while CAST showed low amplification efficiency during PCR reaction. From the final target list, the expression of only two genes was affected by diet, SCD (p<0.01) and FASN (p<0.05), while LPL (p=0,1022) and CAPN3 (p=0,0939) were not different at the p<0.05 level. Both SCD and FASN genes were down-regulated in G1 (lipid-rich diet containing CNB) compared to G2. These genes are involved in lipogenic pathways, related to tissue lipid deposition; therefore, these results were expected. This is the first time that a fat-rich diet based on CNB was shown to affect gene expression of proteins involved in fat deposition in carcass muscles of rams. Longissimus dorsi is one of the finest meat cuts. Considering that human diets rich in poli-unsaturated fatty acids (PUFA) can decrease the risk of heart and other chronic diseases, a change in the fatty acid profile of this muscle could contribute to a healthier diet, aggregating value to the end-product of the lamb meat market. The effects of CNB-based diet on the gene expression of SCD and FASN support the notion that such diet, as previously shown for other sources of lipid in ruminants, can potentially change the fatty acid composition of L. dorsi, but this hypothesis needs to be experimentally verified by profiling fatty acids in animals fed CNB versus carbohydrate-based diets. CNB use as an ingredient in animal feeding is environmentally-friendly, since it contributes to by-product recycling from the agroindustrial plants in Northeast Brazil. Also, considering that CNB-based diet changes lipogenic gene expression without affecting weight gain or reproductive status of the rams, as shown in another work from our team, makes CNB a very important alternative food in ram production systems in tropical regions.

Made available in DSpace on 2014-07-29T15:16:33Z (GMT). No. of bitstreams: 1 dissertacao wyara biologia.pdf: 1287742 bytes, checksum: 4b2f592f2b219248664d4916820cd874 (MD5) Previous issue date: 2009-03-31 / Male idiopathic infertility is related to defects in normal spermatogenesis, due to genetic causes. The spermatogenesis is a dependent process on high levels of male sex hormones, the androgens. The androgen, in turn, perform its function when associated with the androgen receptor (AR), protein encoded by AR gene. Mutation in AR gene lead to a synthesis of non functional AR, which results in the failure of the process of spermatogenesis and, consequently, causes male infertility. This work has as its main objective the verification of the occurrence of mutation in the AR gene in patients with male idiopathic infertility who come from the HC-UFG Human Reproduction Center. Samples were analyzed from 206 patients. The result was that 95 patients were found to be normal while 111 with an altered result for the spermogram. The samples were amplified for exons 1, 4, 6, 7 and 8 of the AR gene and the results subjected to statistical analysis, Mann Whitney, logistic regression, and chi tests. The existence of the relationship between defects of sperm and AR gene mutation was verified. The analysis of the relationship between the spermogram and the AR gene mutation in five evaluated exons was significant only for exons 1 and 7. Patients with numerical unsettled spermogram had a higher frequency of mutations in exon 7, teratozoospermics in exon 1 and exon 7 in astenozoospermics patients. Exons 4, 6 and 8 showed no meaningful statistical relationship in reference to the alteration of the spermogram. Among results related to social custom, alcohol proved to be significant for mutation in the AR gene. This study has reaffirmed the relationship between the presence of mutation in AR genes as probable causes of defects in spermatogenesis. Consequently, male idiopathic infertility depends not only on the genetic factor, but also on the association between this factor and the environment where man inhabits / A infertilidade masculina idiopática está relacionada a defeitos na espermatogênese normal, devido a causas genéticas. A espermatogênese é um processo dependente de altos níveis de hormônios sexuais masculinos, os andrógenos. E os andrógenos, por sua vez, exercem sua função quando associados ao receptor androgênico (RA), proteína codificada pelo gene RA. Mutações no gene RA levam a síntese do RA não funcional, o que acarreta em falhas no processo de espermatogênese e consequentemente causam infertilidade masculina. O trabalho teve como principal objetivo verificar a ocorrência ou não de mutação no gene RA em pacientes com infertilidade masculina idiopática do Centro de Reprodução Humana do HCUFG. Foram analisadas 206 amostras de pacientes, sendo 95 normais e 111 alterados para o espermograma. As amostras foram amplificadas para os exons 1, 4, 6, 7 e 8 do gene RA e os resultados submetidos às análises estatísticas, teste U, quiquadrado e regressão logística. Foi verificada a existência de relação entre alteração no espermograma e mutação no gene RA. A análise da relação entre espermograma e mutação no gene RA dos cinco exons avaliados foi significativa somente para os exons 1 e 7. Os pacientes com alteração numérica para o espermograma apresentaram uma freqüência maior de mutações no exon 7, os pacientes teratozoospérmicos no exon 1 e os astenozoospérmicos no exon 7. Os exons 4, 6 e 8 não apresentaram relação estatística significativa para alterações no espermograma. Dentre os resultados referentes aos hábitos sociais, o etilismo mostrou-se significativo para mutações no gene RA. A realização desse estudo vem reafirmar a relação entre presença de mutações no gene RA como prováveis causas de defeitos na espermatogênese e, consequentemente, infertilidade masculina idiopática, não dependendo exclusivamente do fator gênico, mas da associação entre este fator e o meio ambiente onde o homem está inserido

L’infertilité représente un problème majeur de santé publique en concernant 10 à 15% des couples en âge de procréer. Un facteur masculin est responsable de l’infertilité du couple dans près de la moitié des cas. Pour environ 30% d'entre eux, l'étiologie reste inexpliquée. Le premier axe du travail a concerné l’étude moléculaire d’une cohorte de patients infertiles (azoospermie non-obstructive/cryptozoospermie ou désordre du développement sexuel ou DSD) pour lesquels les analyses du caryotype standard et/ou des microdélétions des régions AZF par PCR n’ont pas permis d’expliquer le phénotype. L'impact des variations de nombre de copies de l'ADN (CNV) détectées par l'hybridation génomique comparative sur puce à ADN est peu documenté. Un design personnalisé de puce à ADN de format 400K, pangénomique et enrichi sur un large panel de 445 gènes liés à l'infertilité et à un DSD a été développé. Cette puce a permis l’identification de 171 CNV d’intérêt. Ces résultats soulignent l’intérêt de ce design comme outil diagnostic dans le cadre du bilan de l’infertilité masculine. Le second axe du travail a été de modéliser l’infertilité masculine in vitro dans un contexte d’anomalie génétique. Des cellules souches pluripotentes induites humaines (hiPS) ont été générées à partir d’érythroblastes de deux patients infertiles porteurs d’un remaniement chromosomique complexe ou d’un caryotype 46,XX-SRY négatif avec mutation du gène de l’AMH. Dans un deuxième temps, la fonctionnalité des lignées de cellules hiPS générées a été testée par différenciation in vitro en cellules germinales primordiales (CGP). Elles expriment les marqueurs clés du stade CGP dont SOX17, le déterminant germinal le plus précoce des CGP. Les perspectives de ce travail seront de poursuivre la différenciation germinale vers des stades plus matures et ainsi de pouvoir étudier le processus méiotique dans un contexte d’anomalie génétique. / Infertility represents a major public health problem and concerns 10 to 15% of couples in the general population. A male factor is responsible for the infertility of the couple in about half of all cases. In approximately 30% of them, the etiology remains unexplained.The first working axis concerned the molecular study of a cohort of infertile patients (nonobstructiveazoospermia/ cryptozoospermia and disorder of the sex development or DSD) for whom analyses of standard karyotype and/or microdeletions of AZF regions were not able to explain the phenotype. The impact of copy number variations of DNA (CNVs) detected by comparative genomic hybridization (CGH-array) is poorly documented. A custom design 400K micoarray, genome-wide and enriched on a wide panel of 445 genes linked with infertility and DSD has been achieved. This array allowed the identification of 171 CNVs of interest.These results underline the potential of this design for diagnosis of male infertility. The second objective of this work was the in vitro modelisation of male infertility in a context of genetic abnormality. For that purpose, human induced pluripotent stem cells (hiPSCs) were generated from erythroblasts by means of not integrative Sendaï virus, in two patients carrying genetic abnormalities (complex chromosomal rearrangement and 46,XX-SRY negative karyotype associated with AMH gene mutation). Secondly, functionality of hiPSCs generated was tested by germ cells in vitro differentiation. Primordial germ cell (PGC) stage was successfully obtained. Cells expressed key PGC markers such as SOX17. The perspectives of this work will be to continuethe germinal differentiation towards more mature stages and so to be able studying the meiotic process in a context of genetic abnormality.

Les protéines Binder of Sperm (BSP) appartiennent à une superfamille de protéines exprimées dans le système reproducteur masculin, plus particulièrement dans les vésicules séminales chez les ongulés, et dans l’épididyme chez l’humain et la souris. Jusqu'à présent, des rôles variés chez différentes espèces ont été démontrés pour les protéines BSP, tels que dans la motilité et la capacitation chez le bovin. Cependant, leur rôle demeure élusif chez d’autres mammifères comme la souris et l’humain. Des études in vivo récentes ont démontré que la délétion des gènes Bsph1 et Bsph2 chez la souris n’a aucune conséquence sur la fertilité, et n’induit aucune anomalie au niveau de l'appareil reproducteur masculin. Afin d'élucider le rôle spécifique de la protéine BSP chez l'humain (BSPH1), nous avons d’abord développé une méthode de purification efficace permettant d’obtenir la protéine BSPH1 fonctionnelle car ces protéines ne sont présentes qu'en quantité infime dans l’épididyme humain. Suite, a la purification de BSPH1, j’ai réalisé des expériences in vitro et cherché à identifier son réseau d'interaction protéique. Il a été démontré que les protéines BSP interagissent avec des groupes pseudo-choline tels que le diéthylaminométhyle par affinité plutôt que par des interactions ioniques. Le diéthylaminoéthyle est chargé positivement et par conséquence, est un échangeur d'anions faible, mais les BSP interagissent avec affinité à la résine. Cette étude présente également une nouvelle méthode de purification rapide et peu coûteuse, qui fournit des protéines BSP recombinantes de grande pureté qui peuvent être utilisées pour étudier leurs rôles dans la fécondation chez les mammifères. Nous avons montré que la pré-incubation des ovocytes avec la protéine BSPH1 recombinante peut diminuer le taux de fécondation de manière dose-dépendante. Les spermatozoïdes ont également été pré-incubés avec un anticorps anti-BSPH1 et ont montré une diminution du taux de fécondation. Pour identifier le réseau d’interaction protéique de BSPH1, j'ai utilisé la méthode « Proximity-dependent biotin identification » (BioID) couplée à la spectrométrie de masse. Les résultats de la spectrométrie de masse ont démontré une interaction entre BSPH1 et toutes les sous-unités du complexe CCT / TRIC (Chaperonin containing tailless complex polypeptide 1 (CCT) ou tailless complex polypeptide 1 ring complex (TRiC)). Ce complexe interagit avec un autre complexe appelé BBSome (Bardet–Bied syndrome complex), qui joue un rôle important dans le transport de protéines à travers les cils primaires. BSPH1 a également interagi avec un grand nombre de protéines de la famille CEP (centrosome-associated proteins), importantes dans la formation des cils primaires par les microtubules et de la maturation du centrosome, qui soutiennent le rôle de BSPH1 dans les cils primaires. Dans l’ensemble, cette étude démontre que BSPH1 pourrait avoir un nouveau rôle en tant que chaperonne, à travers les cils primaires dans les cellules qui l’expriment dans l’appareil reproducteur masculin. / Binder of SPerm (BSP) proteins belong to a superfamily of proteins expressed in the male reproductive tract, particularly in seminal vesicles of ungulates (e.g., bovine, ram) and in the epididymis of humans and mice. So far, BSP proteins have been shown to play different roles in different species such as in motility and capacitation in bovine; however, their role remains unclear in other mammals. For instance, depletion of Bsph1/Bsph2 in mice had no effect on fertility. In order to elucidate the specific role of BSP protein in humans (BSPH1), I sought to investigate a purification method to produce functional human BSP protein, as these proteins are only present in minute amounts in the human epididymis. Following purification of BSPH1, I carried out in vitro experiments and sought to identify its protein interaction network. BSP proteins have been shown to interact with pseudo-choline groups such as diethylaminomethyl through affinity rather than ionic interactions. Diethylaminoethyl is positively charged and therefore is a weak anion exchanger, but BSPs interact through affinity to this resin. This study presents a new, rapid and cost-effective purification method that provides recombinant BSP proteins of a high purity level, which can be used to study their roles in mammalian fertilization. We showed that pre-incubation of oocytes with recombinant BSPH1 can decrease fertilization rate in a dose-dependant manner. Sperm were also preincubated with anti-BSPH1 antibody and showed a decrease in fertilization rate. Secondly, I used BioID (proximity-dependent biotin identification), coupled with mass spectrometry to identify the protein-protein interaction network of BSPH1 by proximity labeling. Mass spectrometry results showed an interaction between BSPH1 and all subunits of the CCT/TRIC complex (Chaperonin containing tailless complex polypeptide 1 (CCT) or tailless complex polypeptide 1 ring complex (TRiC). This complex interacts with another complex called BBSome (Bardet–Biedl syndrome complex), which plays a role in protein trafficking through primary cilium. I also identified BBS proteins, as well as other proteins, that interact with the BBSome complex and regulate protein trafficking in the cilia. BSPH1 also interacted with a large number of CEP (centrosome-associated proteins) family proteins, important in the formation of primary cilium through microtubules and centrosome maturation, which further support the potential implication of BSPH1 with the primary cilia. Overall, this study demonstrates that BSPH1 may have a new role as a chaperone involved in protein trafficking through the primary cilia in cells that express it in the male reproductive system

Infertility affects 15% of reproductive-aged couples. The milieu surrounding the growing embryo is of outmost importance, and should be optimised during in vitro fertilisation (IVF). Many biological processes, such as angiogenesis, coagulation, and immune processes need to be well regulated for a pregnancy to occur and progress normally. Histidine-rich glycoprotein (HRG) is a plasma protein that regulates components of these systems by building complexes with various ligands. A single nucleotide polymorphism (SNP) in HRG, denoted HRG C633T, seem to be of importance for IVF treatment outcomes. The aim of this thesis was to further investigate the proposed human fertility effects of the HRG C633T SNP. According to the findings of this thesis, the HRG C633T genotype is associated with primary recurrent miscarriage. Male HRG C633T genotype is associated with semen characteristics in infertile men, and pregnancy rates following IVF. However, the distribution of the HRG C633T SNP does not differ between infertile and fertile couples. We further examined the role of the region surrounding the HRG C633T SNP for regulation of endometrial angiogenesis and human embryo development. The region affects primary endometrial endothelial cell migration, proliferation and tube-formation in vitro but does not appear to affect human embryo development. No effect of the HRG peptide was noted on the secretome of human embryos. However, early embryos secrete proteins into the surrounding culture media and the level of secretion of VEGF-A, IL-6, EMMPRIN and PlGF is greater in embryos of higher developmental stages. In conclusion, the HRG C633T genotype appears to play a role only if infertility is established. The region surrounding HRG C633T SNP is of relevance in vitro for regulation of human endometrial endothelial cell angiogenesis. To predict which embryos to transfer in IVF, we have highlighted a number of proteins of interest for further investigation.

Les récepteurs couplés aux protéines G (RCPG) sont impliqués dans la majeure partie des communications intercellulaires. Un grand nombre de RCPG ont été découverts en comparant la séquence des récepteurs connus avec les données fournies par le séquençage du génome humain. Pour plus d'une centaine de ces récepteurs, le ligand activateur ou agoniste est inconnu. Ces récepteurs sont dès lors qualifiés d'orphelins.<p>Les LGR forment une sous-famille de RCPG structurellement proches de la rhodopsine qui comprend les récepteurs aux hormones glycoprotéiques (TSH, LH, hCG, FSH) et à la relaxine. LGR4 est un membre de cette famille dont ni la fonction précise, ni l'agoniste ne sont connus.<p>Dans un premier temps, une cartographie détaillée de l'expression de Lgr4 chez la souris a été obtenue. Nous avons tiré parti de l'existence d'une lignée de souris transgéniques dont le gène Lgr4 a été interrompu par l'introduction d'une cassette comportant deux marqueurs histologiques. L'activité beta-galactosidase d'un de ces marqueurs a été analysée chez les souris hétérozygotes. Ces dernières ne présentent pas de phénotype particulier, ce qui permet d'estimer que l'expression des marqueurs rend effectivement compte de l'expression normale du gène Lgr4. Lgr4 est exprimé dans un grand nombre de structures, notamment dans le cartilage, le rein, les appareils reproducteurs mâle et femelle et certaines cellules du système nerveux.<p>Ensuite, le phénotype des souris homozygotes pour l'inactivation de Lgr4 (LGR4KO) a été exploré. Ces souris présentent à la naissance un poids inférieur à leurs congénères des autres phénotypes. Les mâles sont stériles à cause d'une malformation des tubules efférents et de l'épididyme. Un blocage au niveau des tubules efférents reliant le testicule à l'épididyme contraint les spermatozoïdes à s'accumuler à la sortie du testicule, dans la région du rete testis. De plus, les tubes de l'épididyme, pourtant normaux à la naissance, ne s'allongent pas pour former la structure convolutée habituelle. L'épithélium de ces tubes est aplati et est entouré d'une quantité anormalement élevée de mésenchyme.<p>Dans un troisième temps, des outils nécessaires aux futures tentatives d'identification de l'agoniste naturel de LGR4 ont été réalisés. Il s'agit :(1) d'anticorps monoclonaux dirigés contre la partie extracellulaire du récepteur humain. (2) d'un appât moléculaire pour la ‘pêche au ligand’. Cet appât est constitué du domaine extracellulaire du récepteur humain couplé à un marqueur histologique. (3) d'une construction peptidique constituée du domaine extracellulaire du récepteur humain couplé à une queue poly-histidine. Cette construction est destinée à servir de greffon lors de chromatographies d'affinités devant permettre de purifier le ligand. (4) de lignées cellulaires exprimant le récepteur LGR4 humain ainsi que le système æquorine devant permettre de détecter l'activation de ce récepteur.<p>Les données apportées par ce travail montrent un rôle important du récepteur LGR4 au cours du développement et permettent de circonscrire le champ des recherches futures. Ceci, ainsi que les outils moléculaires développés, constitue une base pour l'identification future de l'agoniste et la détermination précise de la fonction de LGR4. / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

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