Normal embryogenesis occurs in starfish eggs induced to mature by microinjection of cytoplasm containing maturation- promoting factor (MPF)

Oocytes arrested at the first meiotic prophase reinitiate meiosis under the influence of a variety of signals, including hormones. These signals are thought to act indirectly to produce a maturation-promoting factor (MPF) which triggers transition to the metaphase. We show here that non-hormone-stimulated starfish oocytes, induced to mature by microinjection of MPF- containing cytosol taken from hormone-stimulated oocytes, produce normal bipinnaria larvae once fertilized. The same result was obtained when donor oocytes were induced to mature by microinjecting heterologous MPF partially purified from amphibian oocytes. These results argue against the hypothesis that maturation events essential for normal embryogenesis occur independently of MPF, at least in starfish.