Regulation of vertebrate eye development by Rx genes

Int J Dev Biol. 2004;48(8-9):761-70. doi: 10.1387/ijdb.041878tb.


The paired-like homeobox-containing gene Rx has a critical role in the eye development of several vertebrate species including Xenopus, mouse, chicken, medaka, zebrafish and human. Rx is initially expressed in the anterior neural region of developing embryos, and later in the retina and ventral hypothalamus. Abnormal regulation or function of Rx results in severe abnormalities of eye formation. Overexpression of Rx in Xenopus and zebrafish embryos leads to overproliferation of retinal cells. A targeted elimination of Rx in mice results in a lack of eye formation. Mutations in Rx genes are the cause of the mouse mutation eyeless (ey1), the medaka temperature sensitive mutation eyeless (el) and the zebrafish mutation chokh. In humans, mutations in Rx lead to anophthalmia. All of these studies indicate that Rx genes are key factors in vertebrate eye formation. Because these results cannot be easily reconciled with the most popular dogmas of the field, we offer our interpretation of eye development and evolution.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Chickens
  • Embryo, Mammalian / physiology
  • Embryo, Nonmammalian
  • Evolution, Molecular
  • Eye / embryology*
  • Eye Proteins / biosynthesis
  • Eye Proteins / physiology*
  • Gene Expression Regulation, Developmental*
  • Genes, Homeobox
  • Green Fluorescent Proteins / metabolism
  • Homeodomain Proteins / biosynthesis
  • Homeodomain Proteins / physiology*
  • Humans
  • Mice
  • Microscopy, Fluorescence
  • Models, Biological
  • Mutation
  • Oryzias
  • Phenotype
  • Photoreceptor Cells, Invertebrate / embryology*
  • Retina / metabolism
  • Temperature
  • Transcription Factors / biosynthesis
  • Transcription Factors / physiology*
  • Xenopus


  • Eye Proteins
  • Homeodomain Proteins
  • RAX protein, human
  • Transcription Factors
  • Green Fluorescent Proteins