The ureteric bud fails to grow out from the mesonephric duct in a mouse embryo lacking a glial cell line-derived neurotrophic factor (GDNF) signalling pathway. Which receptor-ligand pair mediates this outgrowth signal?

• A GDNF binding to FGFR2 on the metanephric blastema
• B GDNF binding to RET on the Wolffian duct epithelium ✓
• C RET ligand binding to GFRα1 on the blastema
• D GDNF binding to EDNRB on the mesonephric duct

Explanation

GDNF is secreted by the metanephric blastema and signals through the RET tyrosine kinase receptor, with GFRα1 as co-receptor, on the mesonephric (Wolffian) duct epithelium to trigger ureteric bud outgrowth. Knockout of GDNF or RET produces renal agenesis. EDNRB is the endothelin A receptor involved in enteric neural crest migration, and the blastema expresses the ligand rather than the receptor.

Reference: Langman's Medical Embryology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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