UCSF

Organelle size control is an interesting problem in Biology. Organelles are often difficult to label or shaped in a way that is difficult to quantify. Chlamydomonas reinhardtii is a single celled alga with two equal length cilia. These cilia represent an ideal case study for organelle size control. Their size is easily quantifiable, as they are essentially one dimensional, only changing in length. The cilia are shed under acid shock, and completely regenerate within two hours. Measurement of length as a function of time during regeneration provides a quantitative insight into the regeneration process, and represents a crucial measurement required to fit predictions of length control models. But obtaining such measurements has proven extremely difficult because Chlamydomonas cells swim rapidly through the media. As a result, regeneration timecourse data usually is obtained at a population level using fixed samples. To enable high-throughput measurements of Chlamydomonas cilia length in living cells, we built a microfluidic device capable of trapping Chlamydomonas and solution exchange. Using this device, we found that instrinsic and extrinsic noise are present in the length control system. We were able to characterize the noise and assess its impact on biological function.