The Pax6b homeodomain is dispensable for pancreatic endocrine cell differentiation in zebrafish

Verbruggen, V., Ek, O., Georlette, D., Delporte, F., Von Berg, V., Detry, N., Biemar, F., Coutinho, P., Martial, J.A., Voz, M.L., Manfroid, I., and Peers, B.
The Journal of biological chemistry   285(18): 13863-13873 (Journal)
Registered Authors
Biemar, Frédéric, Coutinho, Pedro, Delporte, Francois, Ek, Olivier, Georlette, Daphne, Manfroid, Isabelle, Martial, Joseph A., Peers, Bernard, Verbruggen, Vincianne, Voz, Marianne
Cell differentiation, Development, Homeobox, Insulin, Pancreas, Transcription factors, Pax6
MeSH Terms
  • Animals
  • Cell Differentiation/physiology*
  • Endocrine Cells/cytology
  • Endocrine Cells/metabolism*
  • Eye Proteins/genetics
  • Eye Proteins/metabolism*
  • Glucagon/biosynthesis
  • Glucagon/genetics
  • Homeodomain Proteins/genetics
  • Homeodomain Proteins/metabolism*
  • Mutation
  • Paired Box Transcription Factors/genetics
  • Paired Box Transcription Factors/metabolism*
  • Pancreas/cytology
  • Pancreas/embryology*
  • RNA Splicing/physiology
  • Repressor Proteins/genetics
  • Repressor Proteins/metabolism*
  • Zebrafish/embryology*
  • Zebrafish/genetics
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism*
20177065 Full text @ J. Biol. Chem.
Pax6 is a well conserved transcription factor that contains two DNA binding domains, a paired domain and a homeodomain, and plays a key role in the development of eye, brain and pancreas in vertebrates. The recent identification of the zebrafish sunrise mutant, harbouring a mutation in pax6b homeobox and presenting eye abnormalities but no obvious pancreatic defects, raised the question about the role of pax6b in zebrafish pancreas. We show here that pax6b does play an essential role in pancreatic endocrine cell differentiation as revealed by the phenotype of a novel zebrafish pax6b null mutant and of embryos injected with pax6b morpholinos. Pax6b-depleted embryos have almost no beta cells, a strongly reduced number of delta cells, and a significant increase of epsilon cells. Through the use of various morpholinos targetting intron-exon junctions, pax6b RNA splicing was perturbed at several sites leading either to retention of intronic sequences or to deletion of exonic sequences in pax6b transcript. By this strategy, we show that deletion of Pax6b homeodomain in zebrafish embryos does not disturb pancreas development while lens formation is strongly affected. These data thus provide the explanation for the lack of pancreatic defects in the sunrise pax6b mutants. In addition, partial reduction of Pax6b function in zebrafish embryos performed by injection of small amounts of pax6b morpholinos caused a clear rise in alpha cell number and in glucagon expression, emphasizing the importance of the fine tuning of Pax6b level on its biological activity.
Genes / Markers
Mutation and Transgenics
Human Disease / Model Data
Sequence Targeting Reagents
Engineered Foreign Genes
Errata and Notes