Practice question

Ectodermal competence model proposes both neural and epidermal fates possible. BMP4 secreted ventrolaterally binds BMPR inducing Smad1/5/8 phosphorylation, activating epidermal genes like keratin and Xvent while repressing neural genes Sox2, Zic1 and FoxD5. Organizer secretes three BMP antagonists chordin, noggin and follistatin that bind BMPs extracellularly preventing signaling. BMP inhibition dorsalizes ectoderm allowing neural transcription factors to dominate, neural plate forms. FGF and Wnt modulation assist but central switch for neural induction is BMP inhibition demonstrated by neuralization after dominant-negative BMP receptor expression. This illustrates conserved developmental logic of morphogen gradients patterning embryonic axes through Wnt and BMP antagonism.