Practice question

Stylopod and zeugopod regionalization integrates Hox genes, RA-FGF antagonism and Meis cofactors controlling progenitor allocation. Hoxa11 and Hoxd11 activities are crucial for zeugopod specification while also overlapping with Hox9-10 to pattern stylopod via Meis regulation and proximal boundary maintenance through chromatin looping. Genetic analyses show Hox11 paralogs single mutants show mild shortening but combined with Hox10 produce stylopod defects, indicating overlapping regulation across junction. Hoxa11 expression boundary straddles stylopod-zeugopod transition, controlling growth, condensation and patterning of proximal segments through integration of FGF-dependent distalization and RA clearance.