DEFINING NOVEL MECHANISMS REQUIRED FOR THE FORMATION AND MORPHOGENESIS OF A POLARIZED EPITHELIUM

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Drosophila protein kinase N (Pkn) is a negative regulator of actin-myosin activity during oogenesis

Publication . Ferreira, Tania; Prudencio, Pedro; Martinho, Rui Goncalo

Nurse cell dumping is an actin-myosin based process, where 15 nurse cells of a given egg chamber contract and transfer their cytoplasmic content through the ring canals into the growing oocyte. We isolated two mutant alleles of protein kinase N (pkn) and showed that Pkn negatively-regulates activation of the actin-myosin cytoskeleton during the onset of dumping. Using live-cell imaging analysis we observed that nurse cell dumping rates sharply increase during the onset of fast dumping. Such rate increase was severely impaired in pkn mutant nurse cells due to excessive nurse cell actin-myosin activity and/or loss of tissue integrity. Our work demonstrates that the transition between slow and fast dumping is a discrete event, with at least a five to six-fold dumping rate increase. We show that Pkn negatively regulates nurse cell actin-myosin activity. This is likely to be important for directional cytoplasmic flow. We propose Pim provides a negative feedback loop to help avoid excessive contractility after local activation of Rho GTPase. (C) 2014 Elsevier Inc. All rights reserved.

2014-10Journal article

Open access

Drosophila aPKC is required for mitotic spindle orientation during symmetric division of epithelial cells

Publication . Guilgur, Leonardo G.; Prudencio, Pedro; Ferreira, Tania; Pimenta-Marques, Ana Rita; Goncalo Martinho, Rui

Epithelial cells mostly orient the spindle along the plane of the epithelium (planar orientation) for mitosis to produce two identical daughter cells. The correct orientation of the spindle relies on the interaction between cortical polarity components and astral microtubules. Recent studies in mammalian tissue culture cells suggest that the apically localised atypical protein kinase C (aPKC) is important for the planar orientation of the mitotic spindle in dividing epithelial cells. Yet, in chicken neuroepithelial cells, aPKC is not required in vivo for spindle orientation, and it has been proposed that the polarization cues vary between different epithelial cell types and/or developmental processes. In order to investigate whether Drosophila aPKC is required for spindle orientation during symmetric division of epithelial cells, we took advantage of a previously isolated temperature-sensitive allele of aPKC. We showed that Drosophila aPKC is required in vivo for spindle planar orientation and apical exclusion of Pins (Raps). This suggests that the cortical cues necessary for spindle orientation are not only conserved between Drosophila and mammalian cells, but are also similar to those required for spindle apicobasal orientation during asymmetric cell division.

2012-02Journal article

Open access