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Abstract
The tips of cilia play key roles in the assembly and maintenance of cilia and in cell-cellsignaling. Dysfunction of cilia can result in severe diseases (ciliopathies) such as Joubert Syndrome (JS), a debilitating neurodevelopmental disorder. In recent years, several proteins mutated in JS have been shown to localize to the ciliary tip. We show that another JS protein,KIAA0556, localizes to the tips of short, assembling cilia in in the protist model Tetrahymena thermophila. KIAA0556 is enriched at the tips of cilia during times of both de novo ciliogenesis and ciliation, and KIAA0556 consistently appeared at the tips of growing cilia. Cells lackingKIAA0556 possessed an elongated distal segment with abnormal organization of posttranslationally modified microtubules. To our knowledge, these data are the first to show thatKIAA0556 functions at the tips of growing cilia and organizes the ciliary distal segment.