What is the function of δ-crystallin in the lens?
Delta-crystallin, first crystallin characterized in chick lens, is a major structural protein highly expressed in lens fiber cells providing transparency, high refractive index, and protective stability. Recruited as metabolic enzyme argininosuccinate lyase with gene sharing property, delta-crystallin accumulates at high concentration in fiber cytoplasm increasing protein density and minimizing light scattering while lacking organelles. It does not form retina, promote corneal differentiation, or inhibit Wnt signaling. L-Maf transcription factor directly activates delta-crystallin enhancer downstream of Pax6-Sox2 cascade, establishing lens optical clarity essential for focusing light onto retina and vision.
Ref: Gilbert, Developmental Biology, 12th ed., Chapter 12: Delta-crystallin structural role and transparency function.