Molecular dissection of smooth septate junctions: understanding their roles in arthropod physiology

Furuse, Mikio; Izumi, Yasushi

doi:10.1111/nyas.13366

Cited by 30 publications

(32 citation statements)

References 31 publications

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“…1B). However, our analysis led us to rediscover an interesting property of the epithelium: the smooth septate junctions (SJ), which form the occluding barrier to paracellular diffusion, form at the apical side of the lateral domain, above lateral adherens junctions (AJ) (10,11) ( Fig. 1D, E).…”

Section: Main Textmentioning

confidence: 99%

“…The intestinal stem cells lie beneath the epithelium and differentiating enterocytes must therefore integrate into the epithelium from the basal side, inserting between the septate junctions of the flanking enterocytes, while maintaining an intact barrier. We therefore examined the effects of mutants in the core septate junction components, Tsp2a and Mesh (11). More than 90% of mutant cells fail to integrate through the septate junctions of the neighbouring wild-type cells, and the clones form cysts on the basal side of the epithelium ( Fig.…”

Section: Main Textmentioning

confidence: 99%

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An alternative mode of epithelial polarity in the Drosophila midgut

Chen

Sayadian

Lowe

et al. 2018

Preprint

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Abstract:Apical-basal polarity is essential for the formation and function of epithelial tissues, whereas loss of polarity is a hallmark of tumours. Studies in Drosophila have identified conserved polarity factors that define the apical (Crumbs, Stardust, Par-6, aPKC), junctional (Baz/Par-3) and basolateral (Scribbled, Discs large, Lgl) domains of epithelial cells (1, 2). Because these conserved factors mark equivalent domains in diverse vertebrate and invertebrate epithelial types, it is generally assumed that this system organises polarity in all epithelia. Here we show that this is not the case, as none of these canonical factors are required for the polarisation of the endodermal epithelium of the Drosophila adult midgut. Furthermore, unlike other Drosophila epithelia, the midgut forms occluding junctions above adherens junctions, as in vertebrates, and requires the integrin adhesion complex for polarity (3, 4).Thus, Drosophila contains two types of epithelia that polarise by different mechanisms. Since knock-outs of canonical polarity factors often have little effect on the polarity of vertebrate epithelia, this diversity of polarity mechanisms is likely to be conserved in other animals (5-8).

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Section: Main Textmentioning

confidence: 99%

Section: Main Textmentioning

confidence: 99%

An alternative mode of epithelial polarity in the Drosophila midgut

Chen

Sayadian

Lowe

et al. 2018

Preprint

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“…Tsp2A belongs to the tetraspanin family (Izumi et al, 2016). Zygotic loss of any of these proteins results in embryonic lethality just before hatching or at the 1st instar larva stage with impairment of sSJ formation as well as epithelial barrier function, suggesting critical roles of sSJs (Yanagihashi et al, 2012, Izumi et al, 2012, Izumi et al, 2016, Izumi and Furuse, 2014, Furuse and Izumi, 2017).…”

Section: Introductionmentioning

confidence: 99%

Septate junctions regulate gut homeostasis through regulation of stem cell proliferation and enterocyte behavior inDrosophila

Izumi

Furuse

2019

Preprint

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24Smooth septate junctions (sSJs) contribute to the epithelial barrier, which restricts 25 leakage of solutes through the paracellular route of epithelial cells in the Drosophila 26 midgut. We previously identified three sSJ-associated membrane proteins, Ssk, Mesh, 27and Tsp2A, and showed that these proteins were required for sSJ formation and 28 intestinal barrier function in the larval midgut. Here, we investigated the roles of sSJs in 29 the Drosophila adult midgut. Depletion of any of the sSJ-proteins from enterocytes 30 resulted in remarkably shortened lifespan and intestinal barrier dysfunction in flies. 31 Interestingly, the sSJ protein-deficient flies showed intestinal hypertrophy accompanied 32 by accumulation of morphologically abnormal enterocytes. The phenotype was 33 associated with increased stem cell proliferation and activation of the MAP kinase and 34 Jak-Stat pathways in stem cells. Loss of cytokines Unpaired2 and Unpaired3, which are 35 involved in Jak-Stat pathway activation, suppressed the intestinal hypertrophy, but not 36 the increased stem cell proliferation, in flies lacking Mesh. The present findings suggest 37

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“…Electron microscopy was performed as described previously (Furuse & Izumi, ). Wild‐type or Ripply3 mutant embryos were fixed overnight with a fixative containing 2.5% glutaraldehyde and 2% paraformaldehyde in 0.1M cacodylate buffer.…”

Section: Methodsmentioning

confidence: 99%

Ripply3 is required for the maintenance of epithelial sheets in the morphogenesis of pharyngeal pouches

et al. 2018

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During tissue development, the morphogenesis of epithelial sheets is regulated by many factors, including mechanical force, although the underlying mechanisms remain largely unknown. In the pharyngeal region of the vertebrate embryo, endodermal epithelium is reiteratively folded outward to form pharyngeal pouches, making partitions between the pharyngeal arches. Ripply3, encoding a member of the Ripply family of adaptor proteins, is required for the pouch formation posterior to the 2nd pharyngeal pouch. In this study, we found that the expression of mouse Ripply3 was specifically activated in accordance with the bending of the endodermal epithelium during the pouch formation. In Ripply3-deficient embryos, a continuous monolayer of the endodermal epithelium was not maintained posterior to the 2nd pharyngeal pouch. Corresponding to the endodermal region of the deformed epithelium, the activated form of Integrin β1, which was localized at the basal side of the epithelial cells in the wild-type embryos, was not persistently observed in the mutants. On the other hand, cell proliferation and apoptotic cell death in the endoderm were not obviously affected by the Ripply3 deficiency. Significantly, Ripply3 expressed in cultured cells was found to be preferentially accumulated in the focal adhesions, which are Integrin-mediated adhesive contact sites transmitting mechanical force between the extracellular matrix and attached cells. Furthermore, Ripply3 promoted the maturation of focal adhesions in these cells. Thus, Ripply3 appears to have been activated to enhance the connection between the extracellular matrix and endodermal epithelial cells, as a mechanism to resist the mechanical stress generated during the bending of the epithelial sheets.

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Molecular dissection of smooth septate junctions: understanding their roles in arthropod physiology

Cited by 30 publications

References 31 publications

An alternative mode of epithelial polarity in the Drosophila midgut

An alternative mode of epithelial polarity in the Drosophila midgut

Septate junctions regulate gut homeostasis through regulation of stem cell proliferation and enterocyte behavior inDrosophila

Ripply3 is required for the maintenance of epithelial sheets in the morphogenesis of pharyngeal pouches

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