Master of Science / Department of Animal Sciences and Industry / Timothy G. Rozell / Several alternatively-spliced mRNA transcripts of the follicle stimulating hormone receptor (FSHR) have been identified in sheep, including FSHR-1 (G protein-coupled form), FSHR-2 (dominant negative form), and FSHR-3 (growth factor type-1 form). Coupling of the FSHR to signaling pathways which activate different downstream effectors leads to speculation that specific splice variants may be transcribed under differing physiological conditions. This is the first study to correlate expression patterns of FSHR-1, FSHR-2, and FSHR-3 and development of follicles in the mature sheep ovary. In Experiment 1, 8 Suffolk-cross ewes were allowed to come into estrus naturally and were euthanized 24 (n=3), 36 (n=3), and 48 (n=2) hours after the onset of estrus. In Experiment 2, 7 Suffolk-cross ewes received CIDRs for 14 days. At CIDR removal, PMSG (500IU) was administered to treatment ewes (n=3), while controls (n=4) received no PMSG. Ewes were euthanized 24 (n=4; 2 CIDR only, 2 PMSG) or 36 (n=3; 2 CIDR only, 1 PMSG) hours later. All visible follicles were aspirated and pooled according to follicular diameter: small (≤ 2.0 mm), medium (2.1-4.0 mm), large (4.1-6.0 mm), and preovulatory (≥ 6.1 mm). Granulosa cells were separated from follicular fluid by centrifugation. Total RNA was extracted from granulosa cells (GC) and reversed transcribed. The resulting cDNA was subjected to qPCR, using primer sets designed to amplify each variant specifically. For Experiment 1, regardless of time after onset of estrus, relative expression of FSHR-3 exceeded that of both FSHR-1 and FSHR-2 in medium follicles (p < 0.01), and tended to be higher in small follicles (p=0.09). For Experiment 2, treatment with PMSG did not significantly alter expression patterns of FSHR variants (p=0.18). The FSHR-3 was expressed higher than FSHR-2 in all follicle sizes (p < 0.01) and was numerically more highly expressed than FSHR-1, although this difference was not significant (p > 0.11). These experiments show that in addition to the well characterized G protein-coupled form of the FSHR, alternatively spliced variants of the FSHR may participate in follicular dynamics during the first follicular wave of the sheep estrous cycle. Furthermore, these results would indicate that an “alternatively” spliced form of the FSHR (FSHR-3) is the predominant form of the FSHR in the sheep.

L’interleukine-4, cytokine clef du système immunitaire, est l’une des composantesprincipales de la réponse humorale. Un variant d’épissage de l’IL-4 humaine, nommé IL-4δ2est caractérisé par une délétion de l’exon 2. L’expression d’isoformes de cytokines peut êtrespécifique d’un tissu, d’un stimulus ou d’un état pathologique. Un intérêt particulier leur estaccordé car leur présence ou leur niveau d’expression peut en faire des biomarqueurspotentiels de certains stades pathologiques. Ainsi, ce projet a été consacré à l’étude del’expression et de la fonctionnalité de l’IL-4δ2 dans le but de mieux caractériser son rôle ausein de la réponse immunitaire.Une étude cinétique des niveaux d’expression de l’interleukine-4 et de son variant,réalisée chez des donneurs sains, montre une expression de ces deux variants dépendante dudonneur. L’étude a été poursuivie pour déterminer le type cellulaire capable de produire l’IL-4δ2. Ainsi, l’IL-4δ2 ne semble pas être exprimée par les cellules CD4+ et CD8+ à l’inversedes granulocytes.La fonction agoniste ou antagoniste à l’IL-4, de l’isoforme δ2, sujette à controverse, ajustifié une exploration de sa fonctionnalité. Nous avons ainsi évalué la capacité de l’IL-4δ2 àactiver les voies de signalisation de l’IL-4. Une absence d’activation de mécanismescellulaires similaires à l’IL-4 nous suggère un potentiel rôle inhibiteur de ce variant.Au cours du travail sur l’IL-4δ2, un nouveau variant d’épissage de l’IL-4 a étédécouvert chez l’homme. Par épissage alternatif, un nouvel exon est retenu dans l’ARNm dece variant. L’étude de celui-ci nous a permis de proposer, pour cet ARNm, une dégradationpar le mécanisme de Nonsens-Mediated Decay (NMD). Cette découverte apporte un niveausupplémentaire dans la compréhension du système de régulation de l’IL-4.Ce sujet d’étude apporte de nouveaux éléments quant à l’expression et la fonction del’IL-4δ2. De plus, l’identification d’un nouveau variant d’épissage enrichit la connaissancesur la régulation de l’expression du gène de l’Il4. D’une façon générale, la prise en comptedes variants d’épissage des cytokines devrait permettre de mieux caractériser la réponseimmunitaire, essentielle dans un contexte de vaccinologie. / Interleukin-4 (IL-4) is a key cytokine driving the humoral component of the immunesystem. An alternative splice variant of human IL-4, deleted of the second exon and so calledIL-4δ2 has been described. The expression of alternative splice variants is known to be tissuespecific,dependent of a particular stimulus or a pathological state. Their potential asbiomarkers is of increasing interest. Thus, this project was dedicated to the functionality ofIL-4δ2, improving characterization of the immune response.A kinetic study on the expression levels of IL-4 and its spliced variant, conducted onhealthy donors has shown to be donor-specific. The determination of the cell type able toproduce IL-4δ2 indicated that, CD4+ and CD8+ cells were not expressing the isoform, incontrast to granulocytes.The controversial agonist or antagonist function of IL-4δ2 was discussed throughfunctionality. The ability of IL-4δ2 to induce the signaling pathways of IL-4 was evaluated.An absence of similar profile of activation to IL-4 suggests a potential inhibitory role of IL-4δ2.During the study on IL-4δ2, a new alternatively spliced variant of IL-4 was discoveredin humans. Upon splicing, a new exon is retained in this variant. Its functional outcome as asubstrate for Nonsens-Mediated Decay (NMD) allowed bringing a new insight in thecomprehension of IL-4 regulatory system.Our work brought novel elements in the expression and functionality of IL-4δ2.Moreover, the discovery of a new alternatively spliced variant enriched the knowledge on theregulation pathways of Il4 gene expression. A focus on alternatively spliced variants ofcytokines is likely to clarify the complex regulation of the immune system.