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Single-Cell Biophysics: Measurement, Modulation, and Modeling
Monday Speaker Abstracts
28
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.