Homologies between vertebrate and invertebrate eyes.

Abstract

The eye of vertebrates derives from the eye field, an unpaired anlage that is located in the anterior part of the neural plate (Adelmann 1936; Li et al. 1997; Bernier et al. 2000). Together with the anlagen of the dorsal forebrain, mid-brain, olfactory system and pituitary, the eye field forms the anterior neural plate, a neurectodermal domain that differs in its molecular properties from the posterior neural plate that gives rise to hindbrain and spinal cord. The anterior neural plate with its above-listed derivatives will be referred to as the anterior brain/eye anlage in the following. Molecularly, this anlage is characterized by the overlapping expression of several regulatory proteins, including Otx1/2 (Simeone et al. 1993; Kablar et al. 1996) and Tlx (Yu et al. 1994; Hollemann et al. 1998). Hox genes, which provide the posterior part of the neural primordium with specific antero-posterior “identities”, are not expressed in the anterior brain/eye anlage (reviewed in Holland and Graham 1995). Another characteristic that sets the anterior brain/eye anlage apart from the caudal neural plate is its reliance on different signals during neural induction. In mouse, for example, signals (including cerberus and dickkopf) emanate from the anterior endoderm and induce anterior brain/eye structures, whereas the posterior neural plate is induced by noggin, chordin and follistatin that originate from the dorsal mesoderm (reviewed in Brewster and Dahmane 1999).KeywordsGanglion CellRetinal Ganglion CellOptic LobeNeural PlateNeural RetinaThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.