Neural crest and placodes share a number of important features, pointing to a possible common evolutionary origin. They both arise from the neural plate border, which is the boundary between the non-neural ectoderm and neural plate. The transcription factor Sox9 has been implicated in neural crest and otic placode induction in several species. To investigate the differential regulation of neural crest and otic placode induction by Sox9, a gain of function assay was performed using a hormone-inducible version of the Sox9 construct at different doses and time periods. Sox9 was expressed in both neural crest and otic placode cell populations in the same stage embryos by in situ hybridization. Using a gain of function approach, increased expression of neural crest marker (Snail2) and otic placode marker (Pax8) in Sox9-overexpressed embryos was observed. Higher dose of Sox9 reduced or eliminated both neural crest and placode cells in the embryos. Interestingly, otic placodes cells were more strongly affected as compared to neural crest cells. So, optimal dosage and timing of Sox9 expression are important for the development of the neural crest and otic placode. The development of the neural crest and otic placode are affected by Sox9 in a time- and dose-dependent manner.

Introduction
 Materials and Methods
  Embryo collection and manipulation
  Construct
  Embryo injections and dexamethasone treatment
  Lineage tracing and In situ hybridization
 Results
  Sox9 is expressed in the neural crest and otic placode at neurula stage
  Development of neural crest and otic placode is regulated by Sox9 in time and dose dependent manner
 Discussion
 Acknowledgements
 ORCID
 References

• Byung-Yong Park(Bio-Safety Research Institute, College of Veterinary Medicine, Chonbuk National University, Iksan 570-752, Korea) Corresponding author