Practice question

Reciprocal induction describes sequentially interdependent signaling where two tissues mutually induce and refine each other. In eye development optic vesicle first secretes BMP4 and FGF inducing head surface ectoderm to form lens placode expressing Pax6, Sox2, L-Maf. Lens placode then secretes FGFs inducing optic vesicle to invaginate into optic cup and differentiate into neural retina and retinal pigment epithelium. Lens does not differentiate autonomously, Pax6 activation still requires BMP, FGF8 does not suppress L-Maf. This bidirectional dependency exemplifies classic reciprocal induction ensuring coordinated eye assembly and lens-retina alignment and function.