Kwangjin Park^1,2 and Michel R. Leroux^3,4

¹Terry Fox Laboratory, BC Cancer, Vancouver, British Columbia, Canada; ²Department of Medical Genetics, University of British Columbia, Vancouver, British Columbia, Canada; ³Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada; ⁴Centre for Cell Biology, Development and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.

Correspondence to Michel R. Leroux

Cilia harbor diffusion barriers for soluble and membrane proteins within their proximal-most transition zone (TZ) region and employ an intraflagellar transport (IFT) system to form dynamic motile and signaling compartments. In this issue, De-Castro and colleagues (2021. J. Cell Biol.https://doi.org/10.1083/jcb.202010178) uncover a long-suspected role for the TZ in gating IFT particles.