Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Monday Speaker Abstracts

Intraflagellar Transport Proteins Undergo Nonaxonemal Staged Hindrance between the Recruiting Distal Appendages and the Cilium Tony Yang , Minh Nguyet T. Tran, Weng Man Chong, Chia-En Huang, Jung-Chi Liao. Academia Sinica, Taipei, Taiwan. The primary cilium is an essential organelle responsible for multiple sensory and signaling activities. Ciliogenesis is achieved by delivery of precursors such as tubulins along the axoneme through intraflagellar transport (IFT), which is mediated by molecular motors and various IFT particles. Distal appendages (DAPs) are known to serve as the recruiting site of IFT proteins. During ciliogenesis, IFT proteins must go through several different zones in cilia. One of missing links of the IFT dynamics is how IFT particles move between the DAPs and the ciliary axoneme. The major obstacle comes from the tiny volume surrounding the DAPs and TZ and the high density of IFT particles in this region, which is far smaller than the diffraction-limited spot. Here we performed live-cell sptPALM-based superresolution tracking of short trajectories to demonstrate IFT particle dynamics at the ciliary base with the optimization of particle density and trajectory duration suitable for IFT motion speed. Our results revealed the DAPs and TZ accommodate not only axonemal but also transverse IFT88 movement. IFT particles move slower at the base than in the ciliary compartment. Moreover, diffusion analysis revealed that IFT particle movement was confined at the distal TZ while superdiffusive at the proximal TZ. This heterogeneous diffusion characteristics was likely attributed to a complex organization at the DAPs, spatially partitioned into some obstructed regions and some unhindered areas. Together, our live-cell superresolution studies revealed that IFT proteins adopt location- dependent stochastic paths in different regions of the ciliary base, with newly reported dynamic characteristics of IFT particles to shed light on the mechanisms of IFT particle traffic and gating facilitating ciliogenesis.

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