Signaling by SHH rescues facial defects following blockade in the brain

H. Jonathan Chong, Nathan M. Young, Diane Hu, Juhee Jeong, Andrew P. McMahon, Benedikt Hallgrimsson, Ralph S. Marcucio

Research output: Contribution to journalArticle

Abstract

Background: The Frontonasal Ectodermal Zone (FEZ) is a signaling center in the face that expresses Sonic hedgehog (Shh) and regulates patterned growth of the upper jaw. Blocking SHH in the forebrain blocks Shh expression in the FEZ and creates malformations resembling holoprosencephaly (HPE), while inhibition of BMP signaling in the mesenchyme blocks FEZ formation and causes similar dysmorphology. Thus, the brain could regulate FEZ formation by SHH or BMP signaling, and if so, activating one of these pathways in the face might alleviate the effects of repression of SHH in the brain. Results: We blocked SHH signaling in the brain while adding SHH or BMP between the neural and facial ectoderm of the frontonasal process. When applied early, SHH restored Shh expression in the FEZ and significantly improved shape outcomes, which contrasts with our previous experiments that showed later SHH treatments have no effect. BMP-soaked beads introduced early and late caused apoptosis that exacerbated malformations. Finally, removal of Smoothened from neural crest cells did not inhibit Shh expression in the FEZ. Conclusions: Collectively, this work suggests that a direct, time-sensitive SHH signal from the brain is required for the later induction of Shh in the FEZ. We propose a testable model of FEZ activation and discuss signaling mediators that may regulate these interactions.

Original languageEnglish (US)
Pages (from-to)247-256
Number of pages10
JournalDevelopmental Dynamics
Volume241
Issue number2
DOIs
StatePublished - Feb 2012

Keywords

  • Bone morphogenetic proteins (Bmp)
  • Craniofacial development
  • FFrontonasal process (FNP)
  • Frontonasal ectodermal zone (FEZ)
  • Holoprosencephaly (HPE)
  • Sonic hedgehog (Shh)

ASJC Scopus subject areas

  • Developmental Biology

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    Chong, H. J., Young, N. M., Hu, D., Jeong, J., McMahon, A. P., Hallgrimsson, B., & Marcucio, R. S. (2012). Signaling by SHH rescues facial defects following blockade in the brain. Developmental Dynamics, 241(2), 247-256. https://doi.org/10.1002/dvdy.23726