The Cilium
A primary cilium consists of a central axoneme made of microtubules enclosed by a distinct cell membrane.
Several structural elements such as the periciliary membrane, the transition fibers and basal bodies form a selective barrier at the entrance of the cilium and create a unique environment that allows for compartmentalization.
Cilia are sensory organelles that can scan the extracellular environment, but they also act as signaling centers. Bending of the cilium by renal tubular flow causes an intracellular Ca2+ influx that sets off a variety of signaling cascades. Components of the Hedgehog (and other) signal transduction pathway(s) have been shown to depend on ciliary localization. GLI and GLIS transcription factors can move from there to the nucleus to regulate gene expression.
Schematic drawing of a cilium transmitting an extra-cellular signal to the nucleus
A primary cilium consists of a central axoneme made of microtubules enclosed by a distinct cell membrane.
Several structural elements such as the periciliary membrane, the transition fibers and basal bodies form a selective barrier at the entrance of the cilium and create a unique environment that allows for compartmentalization.
Cilia are sensory organelles that can scan the extracellular environment, but they also act as signaling centers. Bending of the cilium by renal tubular flow causes an intracellular Ca2+ influx that sets off a variety of signaling cascades. Components of the Hedgehog (and other) signal transduction pathway(s) have been shown to depend on ciliary localization. GLI and GLIS transcription factors can move from there to the nucleus to regulate gene expression.