Axis formation in hydra

Annu Rev Genet. 2011;45:105-17. doi: 10.1146/annurev-genet-102209-163540. Epub 2011 Aug 4.


A hydra has a simple structure consisting of a head, body column, and foot along a single axis called the oral-aboral axis. The tissue dynamics of a hydra consist of a steady state of production and loss of tissue involving the entire animal. Axis formation and its maintenance is controlled by the head organizer, which is located at the apex of the animal. The head organizer produces two signals, the head activator and head inhibitor, which are transmitted to, and are distributed in, descending gradients among the epithelial cells along the body column. The two gradients control axial patterning along the oral-aboral axis. In the context of the tissue dynamics of the adult hydra, these three elements controlling axis formation and axial patterning are in a steady state of production and loss. The canonical Wnt pathway plays a major role in setting up and maintaining the head organizer.

Publication types

  • Review

MeSH terms

  • Animals
  • Body Patterning*
  • Cell Differentiation
  • Cell Lineage
  • Endoderm / physiology
  • Epithelial Cells / physiology
  • Gene Expression Regulation, Developmental
  • Head / physiology*
  • Hydra / genetics
  • Hydra / physiology*
  • Regeneration
  • TCF Transcription Factors / physiology
  • Wnt Proteins / genetics
  • Wnt Proteins / physiology
  • Wnt Signaling Pathway*
  • beta Catenin / physiology


  • TCF Transcription Factors
  • Wnt Proteins
  • beta Catenin