The ciliary marginal zone (CMZ) in development and regeneration of the vertebrate eye

- We define the ciliary marginal zone (CMZ), its development and organization.
- We summarize the literature concerning the CMZ in fish, frogs, and birds.
- We discuss the role of the CMZ in regeneration in fish and frogs.
- We review the mechanisms of CMZ activation in chickens.
- We question the existence of a CMZ in mammals.

The ciliary marginal zone (CMZ) is a circumferential ring of cells found at the extreme periphery of the maturing and mature neural retina that consists of retinal stem and progenitor cells. It functions to add retinal neurons to the periphery of the neural retina in larval and adult fish, larval frogs, and birds. Additionally, the CMZ may contribute to regeneration of the damaged retina in frogs and fish. In mammals, cells from the ciliary epithelium can be induced to express retinal stem cell-like characteristics in culture but may not comprise a classically defined CMZ.