Primary (nonmotile) cilia are currently enjoying a renaissance in light of novel 
ascribed functions ranging from mechanosensory to signal transduction. Their 
importance for key developmental pathways such as Sonic Hedgehog (Shh) and Wnt 
is beginning to emerge. The function of nodal cilia, for example, is vital for 
breaking early embryonic symmetry, Shh signaling is important for tissue 
morphogenesis and successful Wnt signaling for organ growth and differentiation. 
When ciliary function is perturbed, photoreceptors may die, kidney tubules 
develop cysts, limb digits multiply and brains form improperly. The etiology of 
several uncommon disorders has recently been associated with cilia dysfunction. 
The causative genes are often similar and their cognate proteins certainly share 
cellular locations and/or pathways. Animal models of ciliary gene ablation such 
as Ift88, Kif3a, and Bbs have been invaluable for understanding the broad 
function of the cilium. Herein, we describe the wealth of information derived 
from the study of the ciliopathies and their animal models.