the exact function of these proteins in terms of sensory cilia has not been elucidated in these studies.Therefore, the discovery by Shah etal.(2009) was one of the landmarks in cilia biology and has completely rearranged the authentic view that in vertebrates conventional cilia with a 9+2 axoneme are specialized solely for motility,whereas primary cilia are non-motile and mostly sensory.We recently showed that choroid plexus epithelial cell(CPEC) cilia constitute a unique category of ciliary subtype,as they
exhibit a 9+0 axonemal configuration, but are found multiple times (afewdozen)on a single cell, showing an intermediate nature between conventional motileand primary
cilia. While they express neuropeptide FF(NPFF)receptors and therefore have a sensory function, they have also been reported as motile with very low frequencies of beating
compared with those in the trachea. In this sense,CPEC cilia are similar to
tracheal epithelialcilia(Shah etal.,2009) thatpossessboth
mechanical and sensory function; however,the structure of the axoneme in CPECs mimics that of primary cilia.