Morphogenetic molecules are made and released by specialized cells in the developing embryo and instruct cells they act upon to adopt a particular fate. Two such molecules, Sonic hedgehog (Shh) and fibroblast growth factor 8 (Fgf8), cooperate to induce neuroepithelial cells in the developing midbrain to differentiate into dopaminergic (DA) neurons.
Shh is expressed by notochord and later floor plate along the entire ventral surface of the developing neural tube. Fgf8 is expressed by a discrete population of cells found on the dorsal surface at midbrain/hindbrain boundary called isthmic organizer.
What is the correct outcome of experimental manipulation testing cooperation of Shh and Fgf8 in specifying DA neuron fate? Select ALL that apply.