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. Author manuscript; available in PMC: 2010 Oct 13.
Published in final edited form as: Curr Opin Genet Dev. 2009 May 22;19(3):220–229. doi: 10.1016/j.gde.2009.04.008

Figure 3.

Figure 3

The primary cilium as a signaling hub. (a) Cilia projecting into fluid-filled luminal spaces are positioned to respond to signals and fluid flow within the tubule lumen in order to activate signaling cascades such as calcium signaling, as shown in the inset. (b) The neuronal cilium however appears buried among the dendrites and axons of surrounding neurons implicating an alternative rationale for its presence. One model is that the cilium is positioned next to the nucleus such that components of signaling cascades like the Shh pathway (inset) may be concentrated within the cilium in order to faithfully relay messages. Thus, the cilium acts as a concentrator of signaling components, or a signaling hub. Background images are immunostaining within renal tubules or cultured hippocampal neurons.