A Gradient of JAK Pathway Activity Patterns the Anterior-Posterior Axis of the Follicular Epithelium

Xi, Rongwen; McGregor, Jennifer R.; Harrison, Douglas A.

doi:10.1016/s1534-5807(02)00412-4

Cited by 182 publications

(276 citation statements)

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“…Two reliable dpp enhancer trap lines, dpp-lacZ and dpp-GAL4, failed to show any signal in cap cells (Takaesu et al, 2002;Xi et al, 2003). Expression of the niche marker Hh is easily detected in cap cells using an hh-lacZ enhancer trap.…”

Section: Increasing Dpp Expression In the Niche Delays Gsc Agingmentioning

confidence: 98%

Age‐related changes of germline stem cell activity, niche signaling activity and egg production in Drosophila

et al. 2008

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SummaryAdult stem cells are important in replenishing aged cells to maintain tissue homeostasis. Aging in turn may exert profound effects on stem cell's regenerative potential, but to date the mechanisms of such stem cell aging are poorly understood, and it is not clear to what extent stem cell aging contributes to tissue or organ aging. Here we show in female Drosophila that germline stem cell (GSC) division rate progressively declines with age, which is accompanied by reduced decapentaplegic ( dpp ) niche signaling pathway activation within GSCs. Egg production also rapidly declines with age, which is accompanied by both decreased stem cell division and increased incidence of cell death of developing eggs, especially in the oldest females. Genetically increasing dpp expression delays GSC activity decline and transiently increases egg production. We conclude that age-related decline of reproduction is caused by both decreased GSC activity and increased incidence of cell death during oogenesis, while decreased GSC activity is attributed to declined signaling from the regulatory niche. We suggest that niche functional decay may be an important mechanism for stem cell aging and system failure.

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Section: Increasing Dpp Expression In the Niche Delays Gsc Agingmentioning

confidence: 98%

Age‐related changes of germline stem cell activity, niche signaling activity and egg production in Drosophila

et al. 2008

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“…Therefore, the mislocalization of Kin:␤Gal suggests that the microtubule reorganization initiated by EGFR signaling has not occurred properly in egg chambers bearing the CAM phenotype. The CAM phenotype has been reported in similarly positioned PFC clones of the phosphatase Dlar (13) and the JAK-STAT component hopskotch (6), but the mechanism underlying these two cases has not yet been identified.…”

Section: Egfr Signalingmentioning

confidence: 99%

Dystroglycan down-regulation links EGF receptor signaling and anterior–posterior polarity formation in the Drosophila oocyte

Poulton

Deng²

2006

Proc. Natl. Acad. Sci. U.S.A.

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Anterior-posterior axis formation in the Drosophila oocyte requires activation of the EGF receptor (EGFR) pathway in the posterior follicle cells (PFC), where it also redirects them from the default anterior to the posterior cell fate. The relationship between EGFR activity in the PFC and oocyte polarity is unclear, because no EGFR-induced changes in the PFC have been observed that subsequently affect oocyte polarity. Here, we show that an extracellular matrix receptor, Dystroglycan, is down-regulated in the PFC by EGFR signaling, and this down-regulation is necessary for proper localization of posterior polarity determinants in the oocyte. Failure to down-regulate Dystroglycan disrupts apicobasal polarity in the PFC, which includes mislocalization of the extracellular matrix component Laminin. Our data indicate that Dystroglycan links EGFR-induced repression of the anterior follicle cell fate and anterior-posterior polarity formation in the oocyte.axis specification ͉ gurken ͉ intercellular communication ͉ microtubules ͉ oogenesis F ormation of the main body axes is a critical stage in the development of most multicellular organisms. In Drosophila melanogaster, the main body axes are determined by the polarization of the developing oocyte. Each oocyte develops in the posterior region of an individual egg chamber, which is comprised of the oocyte, 15 germ-line nurse cells, and a surrounding monolayer of somatic follicle cells. The anterior-posterior (AP) body axis is established during stages 9-10 of oogenesis by the microtubuledependent localization of bicoid (bcd) and oskar (osk) RNAs to the anterior and posterior ends of the developing oocyte, respectively (1-4). Formation of the correct microtubule arrangement and AP polarity requires activation of the EGF receptor (EGFR) signaling pathway in the follicle cells directly contacting the oocyte at the posterior of the egg chamber, causing these cells to differentiate as posterior follicle cells (PFCs). EGFR [Torpedo (Top) in Drosophila] is activated in the PFC in early oogenesis by secretion of Gurken (Grk; a TGF-␣ homologue) from the adjacent oocyte. Previous studies have demonstrated that EGFR activation in the PFC cues a complete reorganization of the oocyte microtubule cytoskeleton, such that by stage 9, there is a distinct accumulation of microtubule plus ends in a well defined compartment at the posterior cortex of the oocyte, and the minus ends appear to be concentrated predominately at the anterior region of the oocyte, with some extending along the lateral cortex (3-5). It is this microtubule polarity within the oocyte that serves as the basis for the localization of the RNAs and associated proteins that define the AP axis. Mutations inhibiting EGFR activation in the PFCs preclude this microtubule reorganization and, thus, axis formation. In these cases, osk RNA is mislocalized to the center of the oocyte, and bcd RNA accumulates at both poles of the oocyte (1, 2).Mutations disrupting EGFR activation also inhibit differentiation of the follicle cells c...

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“…By activating this signaling pathway in adjacent follicle cells during mid-oogenesis, anterior PCs induce their differentiation into border cells and, subsequently, PCs and border cells migrate together through the egg chamber to attain the oocyte and subsequently form the micropyle, the sperm entry point into the oocyte (Figure 1a). 11,12 During early stages of oogenesis, PCs undergo a highly regulated cell death program, whereby a small excess of PCs that is produced (1-4 supernumerary cells) is eliminated by apoptosis such that by mid-oogenesis 100% of the follicles contain exactly two PCs at each anterior and posterior extremity. 13 This restriction fulfills a physiological role as inducing prolonged survival of supernumerary PCs by blocking apoptosis leads to follicular cell patterning defects including recruitment of excess border cells and perturbed migration of these cells.…”

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confidence: 99%

Physiological apoptosis of polar cells during Drosophila oogenesis is mediated by Hid-dependent regulation of Diap1

et al. 2010

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Although much has been learned in recent years about the apoptotic machinery, the mechanisms underlying survival and death choices during development of metazoans remain less clearly understood. During early oogenesis in Drosophila, a small excess in the number of specialized somatic cells, called polar cells (PCs), produced at follicle extremities is reduced to exactly two cells through apoptosis by mid-oogenesis. We have found that PCs destined to die first lose their apical contacts and then round up and shrink progressively until they disappear. Caspases are activated only once the cells have begun to shrink, suggesting that they are implicated in this part of the process, but not in the initial loss of cell polarity. Loss-of-function analyses based on mutant, clonal and RNAi approaches show that among the RHG family of pro-apoptotic factors, Hid is specifically necessary for PC apoptosis, as well as the initiator caspase Dronc and its adaptor Dark/Apaf-1, and likely several effector caspases, in particular Drice. In addition, we show that Hid protein and transcripts accumulate specifically in PCs destined to die, while the anti-apoptotic factor Diap1 is downregulated in these cells in a hid-dependent manner. Therefore, our results implicate the Hid-Diap1 module as an important regulatory point in a developmental case of apoptosis.

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A Gradient of JAK Pathway Activity Patterns the Anterior-Posterior Axis of the Follicular Epithelium

Cited by 182 publications

References 38 publications

Age‐related changes of germline stem cell activity, niche signaling activity and egg production in Drosophila

Age‐related changes of germline stem cell activity, niche signaling activity and egg production in Drosophila

Dystroglycan down-regulation links EGF receptor signaling and anterior–posterior polarity formation in the Drosophila oocyte

Physiological apoptosis of polar cells during Drosophila oogenesis is mediated by Hid-dependent regulation of Diap1

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