Formation of the eye field

Introduction Vertebrate eyes originate from a single field of neuroectodermal cells in the anterior region of the neural plate called the eye field (sometimes referred to as the eye anlage, eye primordia or presumptive eye). The origins of the eye field can be traced back to the 32-cell-stage blastula in which a subset of blastomeres is competent, but not yet committed, to form retina. This chapter begins with a discussion of retinal competence and the maternal molecules and cell–cell interactions that take place in and bias early blastomeres toward a retinal fate. Transplantation experiments have shown that the entire presumptive neural plate of midgastrula embryos can form retina, demonstrating the remarkable coordination of neural development with eye formation. Neural induction and the neural patterning events critical for defining where the eye field forms in the developing nervous system will be addressed. Cultured amphibian anterior neural plates form eyes demonstrating that the eye field is specified (committed to form the eye) by the neural plate stage. A conserved set of transcription factors collectively referred to as eye field transcription factors are required for normal eye formation and are expressed in the eye field of the neural plate stage embryo. These genes and their functional interactions, which are required for and under some circumstances sufficient to drive eye field and eye formation will be described. A description of how the single vertebrate eye field separates to form the eye primordia that eventually give rise to the two eyes concludes this chapter.