Shot and Patronin polarise microtubules to direct membrane traffic and biogenesis of microvilli in epithelia

In epithelial tissues, polarisation of microtubules and actin microvilli occurs along the apical-basal axis of each cell, yet how these cytoskeletal polarisation events are coordinated remains unclear. Here, we examine the hierarchy of events during cytoskeletal polarisation in Drosophila melanogaster epithelia. Core apical-basal polarity determinants polarise the spectrin cytoskeleton to recruit the microtubule-binding proteins Patronin (CAMSAP1, CAMSAP2 and CAMPSAP3 in humans) and Shortstop [Shot; MACF1 and BPAG1 (also known as DST) in humans] to the apical membrane domain. Patronin and Shot then act to polarise microtubules along the apical-basal axis to enable apical transport of Rab11 endosomes by the Nuf–Dynein microtubule motor complex. Finally, Rab11 endosomes are transferred to the MyoV (also known as Didum in Drosophila) actin motor to deliver the key microvillar determinant Cadherin 99C to the apical membrane to organise the biogenesis of actin microvilli

Microtubule-dependent apical restriction of recycling endosomes sustains adherens junctions during morphogenesis of the Drosophila tracheal system

International audienceEpithelial remodelling is an essential mechanism for organogenesis, during which cells change shape and position while maintaining contact with each other. Adherens junctions (AJs) mediate stable intercellular cohesion but must be actively reorganised to allow morphogenesis. Vesicle trafficking and the microtubule (MT) cytoskeleton contribute to regulating AJs but their interrelationship remains elusive. We carried out a detailed analysis of the role of MTs in cell remodelling during formation of the tracheal system in the Drosophila embryo. Induction of MT depolymerisation specifically in tracheal cells shows that MTs are essential during a specific time frame of tracheal cell elongation while the branch extends. In the absence of MTs, one tracheal cell per branch overelongates, ultimately leading to branch break. Three-dimensional quantifications revealed that MTs are crucial to sustain E-Cadherin (Shotgun) and Par-3 (Bazooka) levels at AJs. Maintaining E-Cadherin/Par-3 levels at the apical domain requires de novo synthesis rather than internalisation and recycling from and to the apical plasma membrane. However, apical targeting of E-Cadherin and Par-3 requires functional recycling endosomes, suggesting an intermediate role for this compartment in targeting de novo synthesized E-Cadherin to the plasma membrane. We demonstrate that apical enrichment of recycling endosomes is dependent on the MT motor Dynein and essential for the function of this vesicular compartment. In addition, we establish that E-Cadherin dynamics and MT requirement differ in remodelling tracheal cells versus planar epithelial cells. Altogether, our results uncover an MT-Dynein-dependent apical restriction of recycling endosomes that controls adhesion by sustaining Par-3 and E-Cadherin levels at AJs during morphogenesis

A Developmentally Regulated Two-Step Process Generates a Noncentrosomal Microtubule Network in Drosophila Tracheal Cells

International audienceMicrotubules (MTs) are essential for many cell features, such as polarity, motility, shape, and vesicle trafficking. Therefore, in a multicellular organism, their organization differs between cell types and during development; however, the control of this process remains elusive. Here, we show that during Drosophila tracheal morphogenesis, MT reorganization is coupled to relocalization of the microtubule organizing centers (MTOC) components from the centrosome to the apical cell domain from where MTs then grow. We reveal that this process is controlled by the trachealess patterning gene in a two-step mechanism. MTOC components are first released from the centrosome by the activity of the MT-severing protein Spastin, and then anchored apically through the transmembrane protein Piopio. We further show that these changes are essential for tracheal development, thus stressing the functional relevance of MT reorganization for morphogenesis

A developmentally regulated two-step process generates a noncentrosomal microtubule network in Drosophila tracheal cells

Microtubules (MTs) are essential for many cell features, such as polarity, motility, shape, and vesicle trafficking. Therefore, in a multicellular organism, their organization differs between cell types and during development; however, the control of this process remains elusive. Here, we show that during Drosophila tracheal morphogenesis, MT reorganization is coupled to relocalization of the microtubule organizing centers (MTOC) components from the centrosome to the apical cell domain from where MTs then grow. We reveal that this process is controlled by the trachealess patterning gene in a two-step mechanism. MTOC components are first released from the centrosome by the activity of the MT-severing protein Spastin, and then anchored apically through the transmembrane protein Piopio. We further show that these changes are essential for tracheal development, thus stressing the functional relevance of MT reorganization for morphogenesis. © 2010 Elsevier Inc.Este trabajo ha sido financiado por las conceciones del CNRS y ANR « Blanche » (subvención Cymempol, Blan06-3-139786). Jordi Casanova ha sido financiado por la Generalitat de Catalunya, el Ministerio de España de Ciencia e Innovación, y su programa Consolider-Ingenio 2010.Peer Reviewe