ABSTRACT
Occluding cell-cell junctions are pivotal during the development of many organs. One example is septate junction (SJ) strands, which are found in vertebrates and invertebrates. Although several proteins have been identified that are responsible for septate junction formation in Drosophila, it is presently unclear how these structures are formed or how they are positioned in a coordinated manner between two neighboring cells and within the tissue. Here, we identified a GPI-anchored protein called Undicht required for septate junction formation. Clonal analysis and rescue experiments show that Undicht acts in a non-cell-autonomous manner. It can be released from the plasma membrane by the proteolytic activity of two related ADAM10-like proteases, Kuzbanian and Kuzbanian-like. We propose that juxtacrine function of Undicht coordinates the formation of septate junction strands on two directly neighboring cells, whereas paracrine activity of Undicht controls the formation of occluding junctions within a tissue.
Subject(s)
Drosophila Proteins/genetics , Drosophila melanogaster/genetics , Endothelial Cells/metabolism , GPI-Linked Proteins/genetics , Intercellular Junctions/metabolism , ADAM Proteins/genetics , ADAM Proteins/metabolism , Animals , Cell Adhesion Molecules, Neuronal/genetics , Cell Adhesion Molecules, Neuronal/metabolism , Cell Membrane/chemistry , Cell Membrane/metabolism , Disintegrins/genetics , Disintegrins/metabolism , Drosophila Proteins/metabolism , Drosophila melanogaster/enzymology , Drosophila melanogaster/metabolism , Embryo, Nonmammalian , Endothelial Cells/cytology , GPI-Linked Proteins/metabolism , Gene Expression Regulation, Developmental , Intercellular Junctions/genetics , Metalloendopeptidases/genetics , Metalloendopeptidases/metabolism , Paracrine Communication , Proteolysis , Trachea/cytology , Trachea/growth & development , Trachea/metabolismABSTRACT
Glial cells constitute without any dispute an essential element in providing an efficiently operating nervous system. Work in many labs over the last decades has demonstrated that neuronal function, from action potential generation to its propagation, from eliciting synaptic responses to the subsequent postsynaptic integration, is evolutionarily highly conserved. Likewise, the biology of glial cells appears conserved in its core elements and therefore, a deeper understanding of glial cells is expected to benefit from analyzing model organisms such as Drosophila melanogaster. Drosophila is particularly well suited for studying glial biology since in the fly nervous system only a limited number of glial cells exists, which can be individually identified based on position and a set of molecular markers. In combination with the well-known genetic tool box an unprecedented level of analysis is feasible, that not only can help to identify novel molecules and principles governing glial cell function but also will help to better understand glial functions first identified in the mammalian nervous system. Here we review the current knowledge on Drosophila glia to spark interest in using this system to analyze complex glial traits in the future.
