Transient synthesis of a specific set of proteins during the rapid cleavage phase of sea urchin development.

The rapid cleavage stage of early sea urchin development is characterized by the transient synthesis of a specific set of proteins. These proteins were identified by comparing the pattern of newly synthesized proteins from fully grown sea urchin oocytes, unfertilized and fertilized eggs, several embryonic stages, and adult tissues by one- and two-dimensional gel electrophoresis. We found that, in contrast to fertilization, meiotic maturation results in major changes in the relative amounts and types of proteins synthesized. The synthesis of many proteins in the oocyte, including actin, tubulin, and other proteins which have accumulated during oogenesis, appears to be greatly reduced or eliminated in the unfertilized and newly fertilized egg. An examination of the proteins synthesized in unfertilized and fertilized eggs reveals several proteins that are synthesized only during this phase of development and may be required for the rapid cell divisions which occur during this period. At the midblastula stage, when the cell-doubling time shows down, the pattern of synthesis changes to resemble that of the oocyte. These results imply that many of the changes in the pattern of protein synthesis seen around the blastula stage may be associated with the return of the cell cycle to a normal length rather than synthetic changes associated with differentiation.