Septate junctions in insects: Comparison between intercellular and intramembranous structures

Noirot-Timothée, C.; Smith, David S.; Cayer, Marilyn L.; Noirot, Ch.

doi:10.1016/0040-8166(78)90011-3

Cited by 77 publications

(18 citation statements)

References 15 publications

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“…Septate junctions are the primary occluding junction in invertebrates, and are thought to be functionally equivalent to vertebrate tight junctions [19], [20], [21], [22]. Gap junctions were not observed between these cells.…”

Section: Resultsmentioning

confidence: 99%

Adult Neurogenesis: Ultrastructure of a Neurogenic Niche and Neurovascular Relationships

et al. 2012

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The first-generation precursors producing adult-born neurons in the crayfish (Procambarus clarkii) brain reside in a specialized niche located on the ventral surface of the brain. In the present work, we have explored the organization and ultrastructure of this neurogenic niche, using light-level, confocal and electron microscopic approaches. Our goals were to define characteristics of the niche microenvironment, examine the morphological relationships between the niche and the vasculature and observe specializations at the boundary between the vascular cavity located centrally in the niche. Our results show that the niche is almost fully encapsulated by blood vessels, and that cells in the vasculature come into contact with the niche. This analysis also characterizes the ultrastructure of the cell types in the niche. The Type I niche cells are by far the most numerous, and are the only cell type present superficially in the most ventral cell layers of the niche. More dorsally, Type I cells are intermingled with Types II, III and IV cells, which are observed far less frequently. Type I cells have microvilli on their apical cell surfaces facing the vascular cavity, as well as junctional complexes between adjacent cells, suggesting a role in regulating transport from the blood into the niche cells. These studies demonstrate a close relationship between the neurogenic niche and vascular system in P. clarkii. Furthermore, the specializations of niche cells contacting the vascular cavity are also typical of the interface between the blood/cerebrospinal fluid (CSF)-brain barriers of vertebrates, including cells of the subventricular zone (SVZ) producing new olfactory interneurons in mammals. These data indicate that tissues involved in producing adult-born neurons in the crayfish brain use strategies that may reflect fundamental mechanisms preserved in an evolutionarily broad range of species, as proposed previously. The studies described here extend our understanding of neurovascular relationships in the brain of P. clarkii by characterizing the organization and ultrastructure of the neurogenic niche and associated vascular tissues.

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Section: Resultsmentioning

confidence: 99%

Adult Neurogenesis: Ultrastructure of a Neurogenic Niche and Neurovascular Relationships

et al. 2012

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“…By contrast, the pleated SJs found in invertebrate epithelia localize basal to the adherens junction and are characterized by uniformly spaced rows of electron-dense septa between the plasma membranes of adjacent cells (Noirot-timothée et al, 1978). Despite these differences in subcellular localization and ultrastructure, the functional similarity and molecular conservation of key proteins, including members of the claudin and membrane-associated guanylate kinase (MAGUK) families, suggest that TJs and SJs are analogous structures.…”

mentioning

confidence: 94%

Macroglobulin complement-relatedencodes a protein required for septate junction organization and paracellular barrier function inDrosophila

et al. 2014

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Polarized epithelia play crucial roles as barriers to the outside environment and enable the formation of specialized compartments for organs to carry out essential functions. Barrier functions are mediated by cellular junctions that line the lateral plasma membrane between cells, principally tight junctions in vertebrates and septate junctions (SJs) KEY WORDS: Septate junction, Epithelia, Innate immunity INTRODUCTIONPolarized epithelia play crucial roles as barriers to the outside world and in providing distinct compartments for organs to carry out essential metabolic functions in all metazoans. These functions require a physiologically tight epithelium to provide a barrier to the flow of small molecules between the apical and basal sides of the epithelium. This paracellular barrier is established and maintained by tight junctions (TJs) in the epithelia of vertebrate organisms, and by septate junctions (SJs) in invertebrate organisms. TJs localize

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“…Typically, one or two or as many as eight rows of particles may run parallel to a three-cell intersection at any given point. Because there is good evidence that the rows of P-face particles correspond to the position of intercellular septa (13,14), one can conclude that individual septa approach but never cross a three-cell intersection. When septa meet an intersection they turn abruptly towards the basal surface and run close to and parallel to the lateral cell boundary, as shown schematically in Fig.…”

Section: The Organization Of the Septate Junction In Disksmentioning

confidence: 99%

Septate junctions in imaginal disks of Drosophila: a model for the redistribution of septa during cell rearrangement.

Fristrom¹

1982

The Journal of Cell Biology

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The organization of septate junctions during morphogenesis of imaginal disks is described from freeze-fracture replicas and thin sections with a view to understanding junction modulation during rearrangements of cells in epithelia. The septate junctions of each epithelial cell of the disk are distributed in a number of discrete domains equal to the number of neighboring cells. Individual septa traverse domains of contact between pairs of adjacent cells, turn downwards at the lateral boundary of the domain and run parallel to the intersection with a third cell. This arrangement leaves small channels at three-cell intersections that are occupied by specialized structures termed "tricellular plugs." Cell rearrangement involves a progressive change in the width of contact domains between adjacent cells, until old contacts are broken and new ones established. It is proposed that the septate junction adjusts to the changing width of domains by the compaction or extension of existing septa. This redistribution of septa theoretically allows a transepithelial barrier to be maintained during cell rearrangements. The applicability of this model to other epithelial tissues is discussed.The morphogenesis of an epithelium has previously been assumed to be limited to movements of entire epithelial sheets, with each cell within the epithelium retaining its immediate neighbors (1, 2). The presence of specialized connections between adjacent epithelial cells and the absence of morphological evidence of locomotion undoubtedly contributed to this view. However, rearrangements of cells (i.e., cell movements involving change of neighbors within a contiguous epithelial sheet) have recently been described during the evagination of imagined disks in Drosophila (3,4), neurulation in newts (5), gastrulation in Xenopus (6), regeneration in Hydra (7), and epiboly in teleosts (8). Thus, cell rearrangement appears to be a widespread phenomenon in epithelial morphogenesis.In most of the examples cited above, intercellular junctions persist during cell rearrangement (3,(6)(7)(8). Because junctions are sites of intercellular adhesion between pairs of adjacent cells, the exchange of neighbors requires some form ofjnnction modulation (9). Tight junctions of vertebrates and septate junctions of invertebrates present particularly formidable bartiers to cell rearrangement because they bridge or close off the intercellular space between a given cell and all of its neighbors, ensuring contiguity of the epithelial layer and providing a barrier to the extracellular movement of molecules across the epithelium (10-12). Thus, each cell appears to be fixed with respect to its neighbors. This paper focuses on the distribution of septa and the potentially dynamic organization of the septate junction during cell rearrangement in imagined disks. The detailed structure of the septate junction is well known. Rows of septa connect adjacent ceils and separate the apical from the basal intercellular space. The plasma membranes on both sides of a septum conta...

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Septate junctions in insects: Comparison between intercellular and intramembranous structures

Cited by 77 publications

References 15 publications

Adult Neurogenesis: Ultrastructure of a Neurogenic Niche and Neurovascular Relationships

Adult Neurogenesis: Ultrastructure of a Neurogenic Niche and Neurovascular Relationships

Macroglobulin complement-relatedencodes a protein required for septate junction organization and paracellular barrier function inDrosophila

Septate junctions in imaginal disks of Drosophila: a model for the redistribution of septa during cell rearrangement.

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