| 1. |
- Adhikari, Deepak, et al.
(författare)
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Disruption of Tsc2 in oocytes leads to overactivation of the entire pool of primordial follicles
- 2009
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Ingår i: Molecular human reproduction. - : Oxford University Press. - 1360-9947 .- 1460-2407. ; 15:12, s. 765-770
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Tidskriftsartikel (refereegranskat)abstract
- To maintain the length of reproductive life in a woman, it is essential that most of her ovarian primordial follicles are maintained in a quiescent state to provide a continuous supply of oocytes. However, our understanding of the molecular mechanisms that control the quiescence and activation of primordial follicles is still in its infancy. In this study, we provide some genetic evidence to show that the tumor suppressor tuberous sclerosis complex 2 (Tsc2), which negatively regulates mammalian target of rapamycin complex 1 (mTORC1), functions in oocytes to maintain the dormancy of primordial follicles. In mutant mice lacking the Tsc2 gene in oocytes, the pool of primordial follicles is activated prematurely due to elevated mTORC1 activity in oocytes. This results in depletion of follicles in early adulthood, causing premature ovarian failure (POF). Our results suggest that the Tsc1-Tsc2 complex mediated suppression of mTORC1 activity is indispensable for maintenance of the dormancy of primordial follicles, thus preserving the follicular pool, and that mTORC1 activity in oocytes promotes follicular activation. Our results also indicate that deregulation of Tsc/mTOR signaling in oocytes may cause pathological conditions of the ovary such as infertility and POF.
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| 2. |
- Liu, Yan, et al.
(författare)
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Dynamic niche-specific adaptations in Neisseria meningitidis during infection
- 2016
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Ingår i: Microbes and infection. - : Elsevier BV. - 1286-4579 .- 1769-714X. ; 18:2, s. 109-117
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Tidskriftsartikel (refereegranskat)abstract
- Neisseria meningitidis is an opportunistic human pathogen that usually colonizes the nasopharyngeal mucosa asymptomatically. Upon invasion into the blood and central nervous system, this bacterium triggers a fulminant inflammatory reaction with the manifestations of septicemia and meningitis, causing high morbidity and mortality. To reveal the bacterial adaptations to specific and dynamic host environments, we performed a comprehensive proteomic survey of N. meningitidis isolated from the nasal mucosa, CSF and blood of a mouse disease model. We could identify 51 proteins whose expression pattern has been changed during infection, many of which have not yet been characterized. The abundance of proteins was markedly lower in the bacteria isolated from the nasal mucosa compared to the bacteria from the blood and CSF, indicating that initiating adhesion is the harshest challenge for meningococci. The high abundance of the glutamate dehydrogenase (GdhA) and Opa1800 proteins in all bacterial isolates suggests their essential role in bacterial survival in vivo. To evaluate the biological relevance of our proteomic findings, four candidate proteins from representative functional groups, such as the bacterial chaperone GroEL, IMP dehydrogenase GuaB, and membrane proteins PilQ and NMC0101, were selected and their impact on bacterial fitness was investigated by mutagenesis assays. This study provides an integrated picture of bacterial niche-specific adaptations during consecutive infection processes.
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| 3. |
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| 4. |
- Schmid, Martin R., et al.
(författare)
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Genetic Screen in Drosophila Larvae Links ird1 Function to Toll Signaling in the Fat Body and Hemocyte Motility
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:7
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Tidskriftsartikel (refereegranskat)abstract
- To understand how Toll signaling controls the activation of a cellular immune response in Drosophila blood cells (hemocytes), we carried out a genetic modifier screen, looking for deletions that suppress or enhance the mobilization of sessile hemocytes by the gain-of-function mutation Toll(10b) (Tl-10b). Here we describe the results from chromosome arm 3R, where five regions strongly suppressed this phenotype. We identified the specific genes immune response deficient 1 (ird1), headcase (hdc) and possibly Rab23 as suppressors, and we studied the role of ird1 in more detail. An ird1 null mutant and a mutant that truncates the N-terminal kinase domain of the encoded Ird1 protein affected the Tl-10b phenotype, unlike mutations that affect the C-terminal part of the protein. The ird1 null mutant suppressed mobilization of sessile hemocytes, but enhanced other Tl-10b hemocyte phenotypes, like the formation of melanotic nodules and the increased number of circulating hemocytes. ird1 mutants also had blood cell phenotypes on their own. They lacked crystal cells and showed aberrant formation of lamellocytes. ird1 mutant plasmatocytes had a reduced ability to spread on an artificial substrate by forming protrusions, which may explain why they did not go into circulation in response to Toll signaling. The effect of the ird1 mutation depended mainly on ird1 expression in hemocytes, but ird1-dependent effects in other tissues may contribute. Specifically, the Toll receptor was translocated from the cell membrane to intracellular vesicles in the fat body of the ird1 mutant, and Toll signaling was activated in that tissue, partially explaining the Tl-10b-like phenotype. As ird1 is otherwise known to control vesicular transport, we conclude that the vesicular transport system may be of particular importance during an immune response.
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| 5. |
- Yang, Hairu, et al.
(författare)
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Drosophila muscles regulate the immune response against wasp infection via carbohydrate metabolism
- 2017
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Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- We recently found that JAK/STAT signaling in skeletal muscles is important for the immune response of Drosophila larvae against wasp infection, but it was not clear how muscles could affect the immune response. Here we show that insulin signaling is required in muscles, but not in fat body or hemocytes, during larval development for an efficient encapsulation response and for the formation of lamellocytes. This effect requires TOR signaling. We show that muscle tissue affects the immune response by acting as a master regulator of carbohydrate metabolism in the infected animal, via JAK/STAT and insulin signaling in the muscles, and that there is indirect positive feedback between JAK/STAT and insulin signaling in the muscles. Specifically, stimulation of JAK/STAT signaling in the muscles can rescue the deficient immune response when insulin signaling is suppressed. Our results shed new light on the interaction between metabolism, immunity, and tissue communication.
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| 6. |
- Yang, Hairu, 1983-
(författare)
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Drosophila skeletal muscles regulate the cellular immune response against wasp infection
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drosophila melanogaster is widely used as a model organism to study the innate immune system because it lacks an adaptive immune response that could mask its innate immune response. The innate immune response of Drosophila primarily consists of humoral and cellular immune responses. The humoral immune response ismediated by antimicrobial peptides, and is induced by bacterial and fungal infections. The cellular immune response is mediated by blood cells (hemocytes), and is induced by bacterial and wasp infection. While the humoral immune response of Drosophila has been studied extensively, the cellular immune response is less well understood.In this work, I investigated the communication between different signaling pathways and tissues in Drosophila during infection by the parasitic wasp Leptopilina boulardi. I find that JAK/STAT signaling is strongly activated by wasp infection, in both hemocytes and (unexpectedly) larval skeletal muscles. This activation is mediated by the cytokines Upd2 and Upd3, which are secreted from circulating hemocytes. Deletion of upd2 or/and upd3 weakens the wasp-induced activation of JAK/STAT signaling in skeletal muscles and the cellular immune response to wasp infection, leading to reduced encapsulation of wasp eggs and a decrease in the number of circulating lamelloyctes. The suppression of JAK/STAT signaling also significantly weakens the cellular immune response in skeletal muscles, but not in fat bodies and hemocytes. However, the activation of this signaling in skeletal muscles has no obvious effect on the cellular immune response. Together, these results suggest that rather than being uninvolved bystanders, Drosophila skeletal musclesactively participate in cellular immune responses against wasp infection.To answer how Drosophila larval muscles participate cellular immune response, I min-screened the effects of several immune related signaling pathways in the muscles and the fat body on the cellular immune response. Interestingly, the cellular immune response was only significantly compromised by the suppression ofinsulin signaling in skeletal muscles, in a way that was veryreminiscent of the phenotypes induced by suppressing JAK/STAT signaling in muscles. While wasp infection activates JAK/STAT signaling in muscles, it has the opposite effect on insulin signaling. In addition, I find that insulin signaling in skeletal muscles can positively regulate JAK/STAT signaling. On the other hand, suppression of JAK/STAT signaling in muscles reduces insulin signaling locally in muscles and systemically in the fat body. Suppression of either insulin or JAK/STAT signaling in muscles leads to reductions in glycogen storage in muscles, the trehalose concentration in the hemolymph, and the frequency of feeding behavior. All these results indicate that JAK/STAT and insulin signaling in Drosophila skeletal muscles regulate cellular immune responses via their effects on carbohydrate metabolism. Our findings shed new light on the interactions between diabetes, metabolism, the immune system, and tissue communication.
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| 7. |
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| 8. |
- Yang, Hairu, et al.
(författare)
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JAK/STAT signaling in Drosophila muscles controls the cellular immune response against parasitoid infection
- 2015
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Ingår i: EMBO Reports. - : EMBO. - 1469-221X .- 1469-3178. ; 16:12, s. 1664-1672
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Tidskriftsartikel (refereegranskat)abstract
- The role of JAK/STAT signaling in the cellular immune response of Drosophila is not well understood. Here, we show that parasitoid wasp infection activates JAK/STAT signaling in somatic muscles of the Drosophila larva, triggered by secretion of the cytokines Upd2 and Upd3 from circulating hemocytes. Deletion of upd2 or upd3, but not the related os (upd1) gene, reduced the cellular immune response, and suppression of the JAK/STAT pathway in muscle cells reduced the encapsulation of wasp eggs and the number of circulating lamellocyte effector cells. These results suggest that JAK/STAT signaling in muscles participates in a systemic immune defense against wasp infection.
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| 9. |
- Yang, Hairu, et al.
(författare)
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Tissue communication in a systemic immune response of Drosophila.
- 2016
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Ingår i: Fly. - Philadelphia : Taylor & Francis. - 1933-6942 .- 1933-6934. ; 10:3, s. 115-122
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Tidskriftsartikel (refereegranskat)abstract
- Several signaling pathways, including the JAK/STAT and Toll pathways, are known to activate blood cells (hemocytes) in Drosophila melanogaster larvae. They are believed to regulate the immune response against infections by parasitoid wasps, such as Leptopilina boulardi, but how these pathways control the hemocytes is not well understood. Here, we discuss the recent discovery that both muscles and fat body take an active part in this response. Parasitoid wasp infection induces Upd2 and Upd3 secretion from hemocytes, leading to JAK/STAT activation mainly in hemocytes and in skeletal muscles. JAK/STAT activation in muscles, but not in hemocytes, is required for an efficient encapsulation of wasp eggs. This suggests that Upd2 and Upd3 are important cytokines, coordinating different tissues for the cellular immune response in Drosophila. In the fat body, Toll signaling initiates a systemic response in which hemocytes are mobilized and activated hemocytes (lamellocytes) are generated. However, the contribution of Toll signaling to the defense against wasps is limited, probably because the wasps inject inhibitors that prevent the activation of the Toll pathway. In conclusion, parasite infection induces a systemic response in Drosophila larvae involving major organ systems and probably the physiology of the entire organism.
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