Practice question

L-Maf, member of large Maf family containing bZIP domain, executes terminal lens fiber differentiation after early Pax6/Sox2 specification. It accumulates in equatorial lens epithelium where FGF gradient is high, binding MARE sequences in delta-crystallin enhancer and alphaA-crystallin promoter, strongly transactivating them. L-Maf knockout chick lacks crystallin accumulation and shows defective fiber elongation. It works synergistically with Sox2 and Prox1 to drive cytoskeletal changes and gap junction formation for transparency. Thus L-Maf links extracellular FGF signal to structural gene output essential for refractive properties of lens, not vesicle induction itself.