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  • Prickle isoforms determine handedness of helical morphogenesis. eLife Cho, B., Song, S., Axelrod, J. D. 2020; 9

    Abstract

    Subcellular asymmetry directed by the planar cell polarity (PCP) signaling pathway orients numerous morphogenetic events in both invertebrates and vertebrates. Here, we describe a morphogenetic movement in which the intertwined socket and shaft cells of the Drosophila anterior wing margin mechanosensory bristles undergo PCP-directed apical rotation, inducing twisting that results in a helical structure of defined chirality. We show that the Frizzled/Vang PCP signaling module coordinates polarity among and between bristles and surrounding cells to direct this rotation. Furthermore, we show that dynamic interplay between two isoforms of the Prickle protein determines right- or left-handed bristle morphogenesis. We provide evidence that, Frizzled/Vang signaling couples to the Fat/Dachsous PCP directional signal in opposite directions depending on whether Pkpk or Pksple predominates. Dynamic interplay between Pk isoforms is likely to be an important determinant of PCP outcomes in diverse contexts. Similar mechanisms may orient other lateralizing morphogenetic processes.

    View details for DOI 10.7554/eLife.51456

    View details for PubMedID 31934858

  • Endosomal Wnt signaling proteins control microtubule nucleation in dendrites. PLoS biology Weiner, A. T., Seebold, D. Y., Torres-Gutierrez, P., Folker, C., Swope, R. D., Kothe, G. O., Stoltz, J. G., Zalenski, M. K., Kozlowski, C., Barbera, D. J., Patel, M. A., Thyagarajan, P., Shorey, M., Nye, D. M., Keegan, M., Behari, K., Song, S., Axelrod, J. D., Rolls, M. M. 2020; 18 (3): e3000647

    Abstract

    Dendrite microtubules are polarized with minus-end-out orientation in Drosophila neurons. Nucleation sites concentrate at dendrite branch points, but how they localize is not known. Using Drosophila, we found that canonical Wnt signaling proteins regulate localization of the core nucleation protein γTubulin (γTub). Reduction of frizzleds (fz), arrow (low-density lipoprotein receptor-related protein [LRP] 5/6), dishevelled (dsh), casein kinase Iγ, G proteins, and Axin reduced γTub-green fluorescent protein (GFP) at branch points, and two functional readouts of dendritic nucleation confirmed a role for Wnt signaling proteins. Both dsh and Axin localized to branch points, with dsh upstream of Axin. Moreover, tethering Axin to mitochondria was sufficient to recruit ectopic γTub-GFP and increase microtubule dynamics in dendrites. At dendrite branch points, Axin and dsh colocalized with early endosomal marker Rab5, and new microtubule growth initiated at puncta marked with fz, dsh, Axin, and Rab5. We propose that in dendrites, canonical Wnt signaling proteins are housed on early endosomes and recruit nucleation sites to branch points.

    View details for DOI 10.1371/journal.pbio.3000647

    View details for PubMedID 32163403

  • TRIM-9 functions in the UNC-6/UNC-40 pathway to regulate ventral guidance JOURNAL OF GENETICS AND GENOMICS Song, S., Ge, Q., Wang, J., Chen, H., Tang, S., Bi, J., Li, X., Xie, Q., Huang, X. 2011; 38 (1): 1-11

    Abstract

    TRIpartite Motif (TRIM) family proteins are ring finger domain-containing, multi-domain proteins implicated in many biological processes. Members of the TRIM-9/C-I subfamily of TRIM proteins, including TRIM-9, MID1 and MID2, have neuronal functions and are associated with neurological diseases. To explore whether the functions of C-I TRIM proteins are conserved in invertebrates, we analyzed Caenorhabditis elegans and Drosophila trim-9 mutants. C. elegans trim-9 mutants exhibit defects in the ventral guidance of hermaphrodite specific neuron (HSN) and the touch neuron AVM. Further genetic analyses indicate that TRIM-9 participates in the UNC-6-UNC-40 attraction pathway. Asymmetric distribution of UNC-40 during HSN development is normal in trim-9 mutants. However, the asymmetric localization of MIG-10, a downstream effector of UNC-40, is abolished in trim-9 mutants. These results suggest that TRIM-9 functions upstream of MIG-10 in the UNC-40 pathway. Moreover, we showed that TRIM-9 exhibits E3 ubiquitin ligase activity in vitro and this activity is important for TRIM-9 function in vivo. Additionally, we found that Drosophila trim-9 is required for the midline attraction of a group of sensory neuron axons. Over-expression of the Netrin/UNC-6 receptor Frazzled suppresses the guidance defects in trim-9 mutants. Our study reveals an evolutionarily conserved function of TRIM-9 in the UNC-40/Frazzled-mediated UNC-6/Netrin attraction pathway.

    View details for DOI 10.1016/j.jgg.2011.12.004

    View details for Web of Science ID 000287114300001

    View details for PubMedID 21338947

  • A Wnt-Frz/Ror-Dsh Pathway Regulates Neurite Outgrowth in Caenorhabditis elegans PLOS GENETICS Song, S., Zhang, B., Sun, H., Li, X., Xiang, Y., Liu, Z., Huang, X., Ding, M. 2010; 6 (8)

    Abstract

    One of the challenges to understand the organization of the nervous system has been to determine how axon guidance molecules govern axon outgrowth. Through an unbiased genetic screen, we identified a conserved Wnt pathway which is crucial for anterior-posterior (A/P) outgrowth of neurites from RME head motor neurons in Caenorhabditis elegans. The pathway is composed of the Wnt ligand CWN-2, the Frizzled receptors CFZ-2 and MIG-1, the co-receptor CAM-1/Ror, and the downstream component Dishevelled/DSH-1. Among these, CWN-2 acts as a local attractive cue for neurite outgrowth, and its activity can be partially substituted with other Wnts, suggesting that spatial distribution plays a role in the functional specificity of Wnts. As a co-receptor, CAM-1 functions cell-autonomously in neurons and, together with CFZ-2 and MIG-1, transmits the Wnt signal to downstream effectors. Yeast two-hybrid screening identified DSH-1 as a binding partner for CAM-1, indicating that CAM-1 could facilitate CWN-2/Wnt signaling by its physical association with DSH-1. Our study reveals an important role of a Wnt-Frz/Ror-Dsh pathway in regulating neurite A/P outgrowth.

    View details for DOI 10.1371/journal.pgen.1001056

    View details for Web of Science ID 000281383800012

    View details for PubMedID 20711352

  • Lysosome Biogenesis Mediated by vps-18 Affects Apoptotic Cell Degradation in Caenorhabditis elegans MOLECULAR BIOLOGY OF THE CELL Xiao, H., Chen, D., Fang, Z., Xu, J., Sun, X., Song, S., Liu, J., Yang, C. 2009; 20 (1): 21-32

    Abstract

    Appropriate clearance of apoptotic cells (cell corpses) is an important step of programmed cell death. Although genetic and biochemical studies have identified several genes that regulate the engulfment of cell corpses, how these are degraded after being internalized in engulfing cell remains elusive. Here, we show that VPS-18, the Caenorhabditis elegans homologue of yeast Vps18p, is critical to cell corpse degradation. VPS-18 is expressed and functions in engulfing cells. Deletion of vps-18 leads to significant accumulation of cell corpses that are not degraded properly. Furthermore, vps-18 mutation causes strong defects in the biogenesis of endosomes and lysosomes, thus affecting endosomal/lysosomal protein degradation. Importantly, we demonstrate that phagosomes containing internalized cell corpses are unable to fuse with lysosomes in vps-18 mutants. Our findings thus provide direct evidence for the important role of endosomal/lysosomal degradation in proper clearance of apoptotic cells during programmed cell death.

    View details for DOI 10.1091/mbc.E08-04-0441

    View details for Web of Science ID 000262134800003

    View details for PubMedID 18923146

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