title: The RhoGEF trio functions in sculpting class specific dendrite morphogenesis in Drosophila sensory neurons.
abstract: BACKGROUND
  As the primary sites of synaptic or sensory input in the nervous system, dendrites play an essential role in processing neuronal and sensory information. Moreover, the specification of class specific dendrite arborization is critically important in establishing neural connectivity and the formation of functional networks. Cytoskeletal modulation provides a key mechanism for establishing, as well as reorganizing, dendritic morphology among distinct neuronal subtypes. While previous studies have established differential roles for the small GTPases Rac and Rho in mediating dendrite morphogenesis, little is known regarding the direct regulators of these genes in mediating distinct dendritic architectures.
  
  
  RESULTS
  Here we demonstrate that the RhoGEF Trio is required for the specification of class specific dendritic morphology in dendritic arborization (da) sensory neurons of the Drosophila peripheral nervous system (PNS). Trio is expressed in all da neuron subclasses and loss-of-function analyses indicate that Trio functions cell-autonomously in promoting dendritic branching, field coverage, and refining dendritic outgrowth in various da neuron subtypes. Moreover, overexpression studies demonstrate that Trio acts to promote higher order dendritic branching, including the formation of dendritic filopodia, through Trio GEF1-dependent interactions with Rac1, whereas Trio GEF-2-dependent interactions with Rho1 serve to restrict dendritic extension and higher order branching in da neurons. Finally, we show that de novo dendritic branching, induced by the homeodomain transcription factor Cut, requires Trio activity suggesting these molecules may act in a pathway to mediate dendrite morphogenesis.
  
  
  CONCLUSIONS
  Collectively, our analyses implicate Trio as an important regulator of class specific da neuron dendrite morphogenesis via interactions with Rac1 and Rho1 and indicate that Trio is required as downstream effector in Cut-mediated regulation of dendrite branching and filopodia formation.
authors.affiliation: School of Systems Biology, George Mason University, Manassas, Virginia, United States of America.
authors.forename: Srividya Chandramouli
authors.initials: SC
authors.lastname: Iyer
authors.forename: Dennis
authors.initials: D
authors.lastname: Wang
authors.forename: Eswar Prasad R
authors.initials: EP
authors.lastname: Iyer
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Trunnell
authors.forename: Ramakrishna
authors.initials: R
authors.lastname: Meduri
authors.forename: Riaz
authors.initials: R
authors.lastname: Shinwari
authors.forename: Mikolaj J
authors.initials: MJ
authors.lastname: Sulkowski
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Cox
mesh_terms: D000818:Animals; D003712:Dendrites / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D009024:Morphogenesis / Q000502:physiology; D064067:Rho Guanine Nucleotide Exchange Factors; D011984:Sensory Receptor Cells / Q000378:metabolism*; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029721:Drosophila Proteins; D020662:Guanine Nucleotide Exchange Factors; C090146:Rac1 protein, Drosophila; D064067:Rho Guanine Nucleotide Exchange Factors; C511153:Rho1 protein, Drosophila; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins