Ocular dominance stripe formation by regenerated isogenic double temporal retina in Xenopus laevis.

In lower vertebrates such as frogs and fish, long ocular dominance stripes with anterior-posterior (A-P) orientation can be produced by causing both eyes to innervate one optic tectum during the course of development. Similar experiments on adult animals usually produce patches rather than stripes. During development, new retinal fibers from the nasal retina segregate into appropriate stripes at the growing edge of the posterior (P) tectum while new temporal fibers segregate at the non-growing anterior (A) tectal edge. Fiber segregation into long A-P oriented stripes might depend upon a template produced by new nasal fibers initiating stripe orientation in the vicinity of new tectal cells; new nasal fibers would orient to the nascent (posterior) edge of the template while temporal fibers would orient to the anterior (non-growing) end of the template. To test the dependence of stripe formation on the matching of nascent retinal cells with nascent tectal cells, we compared stripe orientation in animals with isogenic double nasal innervation and isogenic double temporal innervation of the tectum. In double nasal innervation, the oldest retinal cells innervate the anterior tectum; new fibers from the entire retinal periphery always innervate the newest tectal cells at the posterior tectum. Stripes are oriented A-P, consistent with a maturation front model. In contrast, the oldest retinal cells innervate the newest (posterior) tectal cells in double temporal innervation of the tectum; the growing retinal periphery innervates the non-growing anterior tectum. Stripes are also oriented A-P, indicating that the production of long stripes does not depend upon maturation front matching of nascent retinal fibers and nascent tectal cells.