Forms the apical lamina, a component of the extracellular matrix. Homotetramer. In vesicles in the cytoplasm of unfertilized eggs, then to the base of the hyaline layer throughout development and finally in the apical lamina in late embryos and early larvae. Moderate levels in unfertilized eggs and during early cleavage, then rapidly increases in abundance between late morula and mesenchyme blastula stages to maximal levels maintained through subsequent stages. Expressed both maternally and zygotically.