Colloquium on May 30th, 2005

Hans-Peter Herzel
Humboldt Universität zu Berlin

Feedbacks, oscillations and synchronization in mammalian cells

Signaling cascades and gene regulation exhibit various positive and negative feedback loops leading to bistability or oscillations. As examples the MAPK cascade, cell cycle regulation and the somitic oscillator are discussed briefly. Then the mammalian circadian clock located in the SCN is discussed in detail. These cell-autonomous oscillations are due to delayed transcriptional/translational feedback loops. The cells are synchronized effectively via unknown coupling mechanisms and entrained by light. A synchronization mechanism is proposed based on a global coupling via neurotransmitters. The corresponding computer simulations are consistent with recent experimental findings regarding periods and phases of SCN cells.