A transgenic mouse lacking Wnt7a shows limbs whose dorsal surfaces are converted to ventral identity, with loss of nail formation. This phenotype results from loss of Wnt7a-dependent induction of which factor in the limb mesenchyme?
- A Olig2
- B Lmx1b ✓
- C En1
- D Radical fringe
Correct answer: B. Lmx1b
Explanation
Wnt7a secreted by the dorsal limb ectoderm induces the transcription factor Lmx1b in the underlying mesenchyme; Lmx1b specifies dorsal fate, and its human mutation gives nail-patella syndrome. En1 marks the ventral ectoderm and restricts Wnt7a dorsally, while Radical fringe sets the dorsoventral boundary at the AER, so neither is the induced mesenchymal effector.
Reference: Larsen's Human Embryology, 5th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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