The effect of puromycin on the early cleavage cycles and morphogenesis of the pond snailLymnaea stagnalis.

The susceptibility of eggs ofLymnaea to puromycin was investigated during the first four cleavage cycles.The eggs are susceptible with respect to cleavage delay during the first half of the cell cycle, including cytokinesis, the phase of DNA replication, and early G2. The effect is reversible. Puromycin reduces the incorporation of3H-lysine to about 50%. The data suggest that puromycin interferes with the synthesis of specific proteins necessary for normal progression through the cleavage cycle.Later development of the treated eggs is normal, except for extension of the fourth cleavage cycle. At this stage the parallel cycles of first macro- and micromeres are lengthened to different degrees. Some eggs showed an abnormal chronology of division and developed into embryos with head malformations. The disturbed division chronology is thought to be the cause of abnormal morphogenesis. The significance for morphogenesis of the cleavage sequence and of the normal process of nuclear reduplication and cellular division during cleavage is discussed.