Essential basal cytonemes take up Hedgehog in the Drosophila wing imaginal disc

Abstract

Morphogen concentration gradients that extend across developmental fields form by dispersion from source cells. In the Drosophila wing disc, Hedgehog (Hh) produced by posterior compartment cells distributes in a concentration gradient to adjacent cells of the anterior compartment. We monitored Hh:GFP after pulsed expression, and analyzed the movement and colocalization of Hh, Patched (Ptc) and Smoothened (Smo) proteins tagged with GFP or mCherry and expressed at physiological levels from bacterial artificial chromosome transgenes. Hh:GFP moved to basal subcellular locations prior to release from posterior compartment cells that express it, and was taken up by basal cytonemes that extend to the source cells. Hh and Ptc were present in puncta that moved along the basal cytonemes and formed characteristic apical-basal distributions in the anterior compartment cells. The basal cytonemes required diaphanous, SCAR, Neuroglian and Synaptobrevin, and both the Hh gradient and Hh signaling declined under conditions in which the cytonemes were compromised. These findings show that in the wing disc, Hh distributions and signaling are dependent upon basal release and uptake, and on cytoneme-mediated movement. No evidence for apical dispersion was obtained.

Cytoneme-mediated signaling essential for tumorigenesis

“…1 and 2). This is consistent with previous studies that reported increased signaling between tumor and stromal cells in this model (Herranz et al, 2014), and with the presence of cytonemes in many other contexts of paracrine signaling (Bischoff et al, 2013;Chen et al, 2017;Eom et al, 2015;Inaba et al, 2015;Roy et al, 2014;Sanders et al, 2013;Stanganello et al, 2015). We confirmed that Dpp is expressed by the tumor cells ( Fig.…”

“…Downregulation of diaphanous (dia), Neuroglian (Nrg), SCAR or Capricious (Caps) reduces the number and length of cytonemes, and reduces signaling in tracheal cells, myoblasts and wing disc cells (Bischoff et al, 2013;Huang and Kornberg, 2015;Roy et al, 2014). We expressed RNAi constructs to lower Dia, Nrg, SCAR and Caps levels in tumor cells, using conditions that represent partial loss-of-function and do not perturb cell polarity, cell viability, or cell cycle during normal development (Chen et al, 2017;Kornberg, 2015, 2016;Roy et al, 2014). We monitored wing discs for morphology, Cut expression, and pMAD.…”

Glutamate signaling at cytoneme synapses

“…n-Syb is functionally interchangeable with the other (Syb) (48), which is expressed ubiquitously and has a general role in membrane trafficking (Chin et al, 1993). In the wing pouch primordium of the wing disc, Syb is required for Wingless signaling (49) and by the cytonemes of the Hh-producing cells of the wing disc (8). Wing disc expression of the sybRNAi used by Yamazaki et al (49) stunted ASP growth and reduced Dpp signal transduction, and reduced the number of ASP cytonemes (Figs.…”

“…In addition to the ASP, cytoneme-mediated signaling has been implicated in Drosophila tissues such as the wing disc epithelium (4–8), abdominal histoblasts (6), testis (9), and the hematopoietic stem cell niche (10), and in zebrafish embryos (11–13), chick embryos (14), mouse embryos (15), and cultured cell systems (16). In signal producing cells, cytoneme-mediated signaling is dependent on the signaling proteins and requires proteins that process and prepare the signaling proteins for release (17).…”

Imaging Cytonemes in Drosophila Embryos

“…Earlier studies used CherryCAAX, CD8:Cherry, CD4:IFP2, CD2:GFP, and CD8:GFP to image cytonemes from larval tissues [21,23,24, 39,41]. We successfully imaged the embryonic cytonemes using all these constructs.…”