From a fertilized embryo to a fully developed human body cells divide about 32 trillion times – not accounting for the additional 30 billion cell divisions that cells undergo every single day in order to replenish blood and other tissues. Errors during these cell divisions can result in the gain or loss of genomic information and drive disease development, such as cancer.
Over the last 50 years, researchers have gained incredible insights into the process of cell division. However, the complexity of cell division can be overwhelming. Hundreds – if not thousands – of proteins are involved in ensuring error-free cell division. Until now, studying the cell cycle has often meant to investigate the consequences of removing or interfering with certain parts of this highly complex network and inferring the underlying network structures and functions. However, the various layers of complexity obstruct our view onto the fundamental processes underlying cell cycle regulation.
Our current knowledge suggests that the most basic (and probably most ancient) cell division cycle – stripped of all additional regulatory layers – comprises three essential components – a protein called cyclin B, a protein called cyclin-dependent kinase (Cdk) and a large multi-subunit protein complex called the anaphase-promoting complex/cyclosome (APC/C). These three regulators build a negative feedback loop. Cyclin synthesis activates the cyclin-dependent kinase. The cyclin-dependent kinase activates the APC/C. And finally, the APC/C inactivates cyclin by flagging cyclin for destruction. Thereby the system is reset for a new round of the cell cycle. It is thought, that this time-delayed negative feedback constitutes the core cell cycle clock in every eukaryotic cell and drives cell cycle-dependent processes in an orderly temporal manner. However, whether this simple biological design is indeed capable of producing sustained oscillations has never been tested.
Therefore, we aim to engineer a functional core cell cycle oscillator using the minimal necessary building blocks. Combining state-of-the-art biochemistry, including the powerful frog egg extract system, with synthetic and computational biology we aim to
(1) design novel fluorescence assays that will enable us to follow and optimize the enzymatic reactions of the cell cycle clock in real-time.
(2) develop computational models of the minimal cell cycle clock to efficiently identify the right experimental conditions to make the clock ‘tick’.
(3) eventually purify and assemble all necessary parts of the cell cycle clock to achieve sustained oscillations.
If we can indeed demonstrate that it is possible to build the core cell cycle oscillator from isolated components in the test tube, it will open up numerous possibilities to subsequently carefully construct additional layers of regulation and directly study their impact on the characteristics of cell cycle oscillations, e.g. amplitude, frequency, and robustness, thereby answering longstanding questions about the cell cycle clock. But more than this, in developing a novel in vitro experimental platform and biosensors for the study of cell division, we will provide powerful new tools with applications ranging from synthetic biology to the development of new therapeutics targeting uncontrolled cell proliferation.
