Primary cilium tip

The primary cilium tip is at the tip of the primary cilium. Knowledge on the primary cilium tip is extremely sparse. However, the tip of the primary cilium is a place where multiple processes related to cilia and ciliary signaling have been observed to occur or suspected to occur, such as, (1) the processing of GLI transcription factors in hedgehog signaling, (2) shedding of extracellular vesicles, appearing as big blobs in the image, (3) continuous turn-over of the axoneme by continuous addition and removal of tubulin proteins, (4) reloading of kinesin motor proteins, which lead intraflagellar transport (IFT) along the axoneme to the tip, onto dynein motor proteins, which transport them back to the ciliary base, etc.

Immunofluorescent staining

The primary cilium tip can be seen as a spot staining at the distal end, remote from the basal body, of the primary cilium. To clearly detect the primary cilium tip, a co-staining with a ciliary marker and a basal body marker is required, to be able to clearly discern it from a transition zone staining.

Read more about the proteome of the primary cilium tip as a substructure of the primary cilium.