Practice question

Hindlimb field positioning and maintenance require Wnt8c signaling in caudal lateral plate mesoderm acting upstream of FGF10. Wnt8c activates canonical beta-catenin cascade inducing and stabilizing FGF10 transcription and supporting Islet1 Pitx1 expression, analogous to Wnt3 requirement anteriorly for forelimb initiation. Wnt8c expression colocalizes with forming hindlimb bud mesenchyme, preceding FGF10 upregulation and marking hindlimb competence. Wnt3a induces AER via beta-catenin primarily in forelimb region, beta-catenin common mediator, RA influences proximal-distal patterning rather than hindlimb stabilization. Thus Wnt8c anchors hindlimb formation and prevents regression.