**10. Conclusion**

Recent studies provide evidence for novel functions of primary cilia ranging from mechanosensory and cellular homeostasis, to signal transduction pathways that regulate intracellular Ca2+levels. Their importance in key developmental pathways such as Sonic Hedgehog and Wnt is beginning to emerge. Defects in cilia formation or function have profound effects on the development of body pattern and the physiology of multiple organ systems. Thus, impairment of ciliar function is involved in organ specific diseases (e.g. polycystic kidney disease, retinitis pigmentosa) as well as pleiotropic syndromes (e.g. Bardet-Biedl, Alstrom, Meckel-Gruber and orofaciodigital syndromes) of unknown origin until recently. Increasing knowledge of the ciliar role in morphogenesis pathways in conjunction with genetic studies is helping to characterize a new group of diseases, previously unconnected to each other.
