In neural tube closure defects, which signaling molecule produced by the notochord induces the overlying ectoderm to become neuroectoderm (neural plate), and what is the process called?
- A Bone Morphogenetic Protein 4 (BMP4); dorsalization
- B Wnt; neuralization
- C Sonic Hedgehog (SHH); neural induction ✓
- D Fibroblast Growth Factor (FGF); caudalization
Explanation
Neural induction is the process by which the notochord (and prechordal plate mesoderm) signals the overlying ectoderm to differentiate into neuroectoderm (neural plate). The key inducing molecule is Sonic Hedgehog (SHH), secreted by the notochord and floor plate cells. SHH inhibits BMP4 signaling (which normally causes epidermal differentiation) in the overlying ectoderm, thus allowing neural fate. BMP4 inhibition by noggin, chordin, and follistatin (secreted by the organizer/Hensen's node) is the mechanistic basis of neural induction. FGF and Wnt also play roles but SHH is specifically the notochordal signal for neural induction and ventral patterning.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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