An endogenous calcium oscillator may control early embryonic division

摘要: Transient elevations in the concentration of free cytosolic calcium ion ([Ca2+]i) promote cell phase transitions early embryonic division and persist even if these are blocked. These observations suggest that a [Ca2+]i oscillator is an essential timing element “master clock.” We explore this possibility by coupling model to cycle based on protein interactions govern activity M-phase-promoting factor (MPF). hypothesize three dynamical states MPF system choose parameter sets represent each. then investigate how dynamics may control both sea urchin Xenopus embryos. To systems, distinct profiles matching those observed embryos (in which exhibits sharp transients) elevated oscillates sinusoidally) imposed each hypothesized MPF. In first hypothesis, oscillations entrain autonomous oscillator. second third hypotheses, where rests excitatory bistable states, respectively, drive activation cycles. Simulation results show hypotheses two three, fundamental master clock, best account for key experimental questions they raise. Finally, we propose experiments elucidate further regulation components clock.