Airway branching has conserved needs for local parasympathetic innervation but not neurotransmission.
BACKGROUND
Parasympathetic signaling has been inferred to regulate epithelial branching as well as organ regeneration and tumor development. However, the relative contribution of local nerve contact versus secreted signals remains unclear. Here, we show a conserved (vertebrates to invertebrates) requirement for intact local nerves in airway branching, persisting even when cholinergic neurotransmission is blocked.


RESULTS
In the vertebrate lung, deleting enhanced green fluorescent protein (eGFP)-labeled intrinsic neurons using a two-photon laser leaves adjacent cells intact, but abolishes branching. Branching is unaffected by similar laser power delivered to the immediately adjacent non-neural mesodermal tissue, by blocking cholinergic receptors or by blocking synaptic transmission with botulinum toxin A. Because adjacent vasculature and epithelial proliferation also contribute to branching in the vertebrate lung, the direct dependence on nerves for airway branching was tested by deleting neurons in Drosophila embryos. A specific deletion of neurons in the Drosophila embryo by driving cell-autonomous RicinA under the pan-neuronal elav enhancer perturbed Drosophila airway development. This system confirmed that even in the absence of a vasculature or epithelial proliferation, airway branching is still disrupted by neural lesioning.


CONCLUSIONS
Together, this shows that airway morphogenesis requires local innervation in vertebrates and invertebrates, yet neurotransmission is dispensable. The need for innervation persists in the fly, wherein adjacent vasculature and epithelial proliferation are absent. Our novel, targeted laser ablation technique permitted the local function of parasympathetic innervation to be distinguished from neurotransmission.
Division of Biological Sciences, California Institute of Technology, Pasadena, USA. dvbrown@post.harvard.edu.|The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, USA. dvbrown@post.harvard.edu.|Biological Imaging Center, California Institute of Technology, 1200 E. California Blvd, MC 139-74, Pasadena, CA, 91125, USA. dvbrown@post.harvard.edu.
Danielle V
DV
Bower
Division of Biological Sciences, California Institute of Technology, Pasadena, USA. hlee@caltech.edu.
Hyung-Kook
HK
Lee
The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, USA. rlansford@chla.usc.edu.
Rusty
R
Lansford
Division of Biological Sciences, California Institute of Technology, Pasadena, USA. zinnk@caltech.edu.
Kai
K
Zinn
The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, USA. dwarburton@chla.usc.edu.
David
D
Warburton
Division of Biological Sciences, California Institute of Technology, Pasadena, USA. sfraser@provost.usc.edu.|Biological Sciences and Biomedical Engineering, University of Southern California, Los Angeles, USA. sfraser@provost.usc.edu.|Biological Imaging Center, California Institute of Technology, 1200 E. California Blvd, MC 139-74, Pasadena, CA, 91125, USA. sfraser@provost.usc.edu.
Scott E
SE
Fraser
Division of Biological Sciences, California Institute of Technology, Pasadena, USA. ejesudason@caltech.edu.|The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, USA. ejesudason@caltech.edu.|Division of Child Health, University of Liverpool, Liverpool, UK. ejesudason@caltech.edu.|Biological Imaging Center, California Institute of Technology, 1200 E. California Blvd, MC 139-74, Pasadena, CA, 91125, USA. ejesudason@caltech.edu.
Edwin C
EC
Jesudason
D000818:Animals; D049109:Cell Proliferation; D004330:Drosophila / Q000196:embryology; D004847:Epithelial Cells / Q000378:metabolism; D017353:Gene Deletion; D049452:Green Fluorescent Proteins / Q000235:genetics; D007448:Invertebrates / Q000378:metabolism; D008168:Lung / Q000294:innervation* / Q000378:metabolism; D051379:Mice; D009024:Morphogenesis; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D010275:Parasympathetic Nervous System / Q000378:metabolism*; D015398:Signal Transduction; D009435:Synaptic Transmission; D014714:Vertebrates / Q000378:metabolism
C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins