**5. Intraflagellar transport protein system (IFT)**

During ciliogenesis, cilia elongate from the basal body by the addition of new axonemal subunits to the distal tip. As protein synthesis does not occur in cilia, axonemal and membrane components are conveyed in non-membrane-bound macromolecular particles by intraflagellar transport (IFT) along the axonemal microtubule doublets [24].

The proteins are transported as convoys, bringing together several proteins called *"IFT particles".* IFT have 2 transport routes [25, 26]:


At the tip of the cilium there is a particular structure where there is a change in intraciliar transport direction [27 a 29]. Large IFT particles move between the axoneme microtubule doublets and ciliary membrane, transported by specific Golgi vesicles directed toward the ciliary pore complex using cytoplasmic dynein. These vesicles exocyst at the base of the cilium, where kinesin II transports the particles up to the tip. By shortening or recycling of the cilium, the IFT descend to the base by means of dynein 2 for recycling [31]. IFT play a key role in ciliogenesis, taking axoneme components synthesized in the cytoplasm to the tip of the cilium.

Intraciliar or intraflagellar transport is responsible for cilia growth, for renewal of its components and for the particular formation of the cilium membrane that distinguishes it from the rest of the plasma membrane [30].
