Centrin2 regulates CP110 removal in primary cilium formation

Primary cilia are antenna-like sensory microtubule structures that extend from basal bodies, plasma membrane-docked mother centrioles. Cellular quiescence potentiates ciliogenesis, but the regulation of basal body formation is not fully understood. We used reverse genetics to test the role of the small calcium-binding protein, centrin2, in ciliogenesis. Primary cilia arise in most cell types but have not been described in lymphocytes. We show here that serum starvation of transformed, cultured B and T cells caused primary ciliogenesis. Efficient ciliogenesis in chicken DT40 B lymphocytes required centrin2. We disrupted CETN2 in human retinal pigmented epithelial cells, and despite having intact centrioles, they were unable to make cilia upon serum starvation, showing abnormal localization of distal appendage proteins and failing to remove the ciliation inhibitor CP110. Knockdown of CP110 rescued ciliation in CETN2-deficient cells. Thus, centrin2 regulates primary ciliogenesis through controlling CP110 levels.