THE SEA-URCHIN EGG-YOLK GRANULE IS A STORAGE COMPARTMENT FOR HCL-32, AN EXTRACELLULAR-MATRIX PROTEIN

We have utilized protein gel blot analysis and immunogold labelling to define the intracellular storage compartment for HCL-32, a 32-kDa pro tein component of the sea urchin embryonic extracellular matrices, the hyaline layer and basal lamina. Anti-HCL-32 antiserum specifically la belled yolk granules in unfertilized eggs. Cortical granules, mitochon dria, sparse granules, and lipid vacuoles were not labelled. Label con tinued to be detected in the yolk granules through to the blastula sta ge of development. However, by the gastrula stage no latelling was det ected in the yolk granules. In protein gel blot analysis HCL-32 was de tected in yolk granules prepared from unfertilized eggs. These results clearly define the yolk granule as a storage compartment for HCL-32, an extracellular matrix protein.