Practice question

Vertebrate eye development exemplifies reciprocal induction where two tissues sequentially induce each other. Initially the optic vesicle evaginating from diencephalon contacts head ectoderm, inducing lens placode via BMP4 and FGF8 signaling. Once induced, the lens placode secretes factors including BMP7 and FGFs that feedback to promote invagination of distal optic vesicle into bilayered optic cup, specifying neural retina and retinal pigment epithelium. Interrupting either signal aborts both structures, demonstrating mutual dependence rather than single-direction or autonomous differentiation, crucial for coordinated eye morphogenesis.