During spinal cord development, ventral horn motor neurones are specified by the transcription factor Olig2 in response to a ventral-to-dorsal gradient of which signalling molecule secreted by the notochord and floor plate?

• A Wnt proteins
• B BMP-4
• C Retinoic acid
• D Sonic hedgehog (SHH) ✓

Explanation

SHH is secreted by the notochord and floor plate, creating a ventral-to-dorsal concentration gradient in the neural tube. High SHH concentrations at the ventral pole specify motor neurones and interneurones via a series of homeodomain transcription factors. BMP and Wnt proteins create a dorsal-to-ventral gradient specifying dorsal sensory neurones. Retinoic acid contributes to rostrocaudal (HOX gene) patterning.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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