1. Academic Validation
  2. Nodal and Hedgehog synergize in gill slit formation during development of the cephalochordate Branchiostoma floridae

Nodal and Hedgehog synergize in gill slit formation during development of the cephalochordate Branchiostoma floridae

  • Development. 2018 Aug 6;145(15):dev162586. doi: 10.1242/dev.162586.
Hiroki Ono 1 Demian Koop 2 Linda Z Holland 3
Affiliations

Affiliations

  • 1 Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202, USA.
  • 2 Discipline of Anatomy and Histology, University of Sydney, Sydney, NSW 2006, Australia.
  • 3 Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0202, USA lzholland@ucsd.edu.
Abstract

The larval pharynx of the cephalochordate Branchiostoma (amphioxus) is asymmetrical. The mouth is on the left, and endostyle and gill slits are on the right. At the neurula, Nodal and Hedgehog (Hh) expression becomes restricted to the left. To dissect their respective roles in gill slit formation, we inhibited each pathway separately for 20 min at intervals during the neurula stage, before gill slits penetrate, and monitored the effects on morphology and expression of pharyngeal markers. The results pinpoint the short interval spanning the gastrula/neurula transition as the critical period for specification and positioning of future gill slits. Thus, reduced Nodal signaling shifts the gill slits ventrally, skews the pharyngeal domains of Hh, Pax1/9, Pax2/5/8, Six1/2 and IrxC towards the left, and reduces Hh and Tbx1/10 expression in endoderm and mesoderm, respectively. Nodal auto-regulates. Decreased Hh signaling does not affect gill slit positions or Hh or Nodal expression, but it does reduce the domain of Gli, the Hh target, in the pharyngeal endoderm. Thus, during the neurula stage, Nodal and Hh cooperate in gill slit development - Hh mediates gill slit formation and Nodal establishes their left-right position.

Keywords

Branchiostoma; Gill slit development; Hedgehog signaling; Nodal signaling; Pharyngeal patterning.

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