Nanotubes Make Big Science
نویسنده
چکیده
D uring development, cells need to communicate with each other to establish properly organised and functional tissues. Cells communicate with each other in various ways, such as by secreting and receiving diffusible molecules (morphogens, hormones, and neurotransmitters) or by establishing intercellular connections (gap junctions and cell protrusions) to allow a direct exchange of instructive factors. A recent paper has shown that communication via tiny cell protrusions might be a more common mechanism than previously expected (Rustom et al. 2004). Many different types of cell extensions have been described in a variety of developmental processes Rorth 2003), and for most of them a role in cell-to-cell communication has been hypothesized. For example, in the mouse, Salas-Vidal and Lomeli (2004) have described long processes (fi lopodia) that connect tissues in early embryos. Because these protrusions contain receptors for some well-known signalling molecules, it is thought that they might be responsible for receiving signals from neighbouring cells. Similarly, it has been proposed in the development of the Drosophila wing and eye imaginal discs (precursors of adult structures) that signals modulating the growth and patterning of one epithelial layer of cells are received through microtubule-based cell extensions arising from the apposing epithelium (Cho et al. 2000; Gibson and Schubiger 2000). Furthermore, in the wing imaginal disc, planar extensions called cytonemes arise from the periphery of the epithelium and grow towards a central area in the wing disc that produces the signalling molecule Decapentaplegic. This directionality of growth, and the observation of vesicles inside cytonemes, led Ramirez-Weber and Kornberg (1999) to propose that cells meant to receive a signal were searching actively for it, extending long cell protrusions towards the region from which signals were emanating. Although cell protrusions have been described in different developmental processes, tissues, and organisms, their potential role in cell signalling has been diffi cult to pin down. Most cell processes are very fragile, and their study is mainly limited to live tissues; in these conditions it is technically challenging to defi ne how the signalling is mediated via protrusions. Possibly, it could occur through the release of free molecules, in a similar manner to synaptic neurotransmission, or shedding of vesicles as exosomes followed by endocytosis by the recipient cell. Alternatively, membrane-tethered ligands (such as Delta) on the protrusion could bind and activate receptors displayed on the surface of the receiving cell (De Joussineau et al. 2003). The paper by Rustom …
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ورودعنوان ژورنال:
- PLoS Biology
دوره 2 شماره
صفحات -
تاریخ انتشار 2004