Fig. 1.
Experiments and setup illustration. (A) MKs imaged in vitro grow long tubular extensions (proplatelets) which after some time form periodic swellings along their shaft as shown in B and C. MKs are trapped in the bottom part of a microfluidic bioreactor by small gaps (15, 16) and remain fixed during proplatelet extension and fragmentation. To illustrate the periodic arrangement of MKs as shown in SI Appendix, Fig. S21, the marked area on the right-hand side has been copied and reinserted on the left of the image. Fluid flows with a maximum velocity of 2.2 mm/s and the complete width of the experimental image is m. (D) Illustration of the computational model for the proplatelet membrane. Plasma membrane and cortex (Inset) are treated together as an active, elastic thin shell. The shell is endowed with bending and shear elasticity as well as actomyosin contractility in concert with microtubule sliding. We model the proplatelet as an initially cylindrical membrane with one fixed end and one free end according to the experimental situation. The proplatelet is subject to external flow.