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Rhomboid 3 orchestrates Slit-independent repulsion of tracheal branches at the CNS midline
Södertörn University, School of Chemistry, Biology, Geography and Environmental Science. Stockholm University / Karolinska Institute.
Stockholm University / Umeå University.
Södertörn University, School of Chemistry, Biology, Geography and Environmental Science.
Stockholm University.
2004 (English)In: Development, ISSN 0950-1991, E-ISSN 1477-9129, Vol. 131, no 15, 3605-3614 p.Article in journal (Refereed) Published
Abstract [en]

EGF-receptor ligands act as chemoattractants for migrating epithelial cells during organogenesis and wound healing. We present evidence that Rhomboid 3/EGF signalling, which originates from the midline of the Drosophila ventral nerve cord, repels tracheal ganglionic branches and prevents them from crossing it. rho3 acts independently from the main midline repellent Slit, and originates from a different sub-population of midline cells: the VUM neurons. Expression of dominant-negative Egfr or Ras induces midline crosses, whereas activation of the Egfr or Ras in the leading cell of the ganglionic branch can induce premature turns away from the midline. This suggests that the level of Egfr intracellular signalling, rather than the asymmetric activation of the receptor on the cell surface, is an important determinant in ganglionic branch repulsion. We propose that Egfr activation provides a necessary switch for the interpretation of a yet unknown repellent function of the midline.

Place, publisher, year, edition, pages
2004. Vol. 131, no 15, 3605-3614 p.
National Category
Developmental Biology
URN: urn:nbn:se:sh:diva-15472DOI: 10.1242/dev.01242ISI: 000223517400010PubMedID: 15229181ScopusID: 2-s2.0-4444361021OAI: diva2:504678
Available from: 2012-02-21 Created: 2012-02-20 Last updated: 2017-02-15Bibliographically approved
In thesis
1. The Rhomboid family of intramembrane proteases, conserved regulators of cell communication
Open this publication in new window or tab >>The Rhomboid family of intramembrane proteases, conserved regulators of cell communication
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The development of multicellular organisms relies heavily on cell communication. Cells send and receive complex sets of signals, harmonising their growth and differentiation with that of other, often distant, cell populations. In animals, the Epidermal Growth Factor Receptor (EGFR) is an important mediator of cell communication. EGFR activation regulates various developmental events in nematodes, insects and vertebrates. In addition, mutations in human EGFRs have been associated with a number of cancers. In Drosophila, a key event triggering EGFR signalling is the regulated release of the extracellular portion of EGFR ligands. Rhomboid (Rho), an unusual polytopic protease, cleaves the transmembrane, inactive ligand precursor into an active, soluble form. Both the target sequence and Rho s catalytic site are embedded within the membrane bilayer and for this reason the reaction has been described as regulated intramembrane proteolysis. The work presented in this thesis begins with the characterisation of a classical fly mutation, roughoid (ru). Our results indicate that ru acts as a novel, positive regulator of EGFR signalling during eye development in Drosophila. ru was subsequently identified as rhomboid-3, one of seven rhomboid related genes encoded in the fly genome. Unexpectedly, we found that sequences related to Rhomboid are also common in unicellular organisms. A single microbial Rho has been previously studied, the aarA gene from the human pathogen Providencia stuartii. Strikingly, AarA appears to have a corresponding function to that of the Drosophila Rho: it is necessary for the release of a peptide-signal, which mediates cell communication in P. stuartii. AarA was indeed capable of substituting for the fly Rho in vivo. Vice versa, the fly Rho-1 restored the ability of aarA mutant bacteria to produce the extracellular signal mediating cell communication. These results suggest that Rho-mediated proteolysis might represent a very ancient mechanism for cell communication. The Drosophila genome contains seven Rhomboids. We began to investigate the possibility of additional substrates by analyzing the respiratory system phenotype observed in ru/rho-3 mutant embryos. During embryogenesis, specialised tracheal branches target and invade the ventral nerve cord, part of the central nervous system (CNS). In ru/rho-3 mutants, these branches are misrouted, and inappropriately cross the CNS midline. Also in this context Rho-3 functions to activate an EGFR ligand. Yet, the results reveal an unusual role for the pathway in the repulsion of migrating epithelial cells. EGFR ligands act as chemoattractants for a variety of cells in vivo and in vitro, including tumors. Our results provide a proof of principle that the EGFR can also mediate repulsion from the signal source.

Place, publisher, year, edition, pages
Stockholm: Karolinska Instiutet, 2004. 61 p.
National Category
Biological Sciences
urn:nbn:se:sh:diva-32067 (URN)91-7349-951-X (ISBN)
Public defence
2004-06-04, MB 503, Alfred Nobels allé 7, Huddinge, 11:00 (English)
Available from: 2017-02-15 Created: 2017-02-15 Last updated: 2017-02-15Bibliographically approved

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