Borg3 controls septin recruitment for primary cilia formation

Abstract

Septin GTPases polymerize into higher-order structures as a part of the cytoskeleton and are involved in vital cellular functions. Among these, they play a role in the formation of primary cilia. However, the regulation of septin assembly in the confined ciliary compartment has not been studied in detail. Here we show, that Borg3 also known as Cdc42EP5, a regulator of septin assembly is involved in the formation of cilia. Borg3 accumulation in cilia is facilitated by switching the Rho-GTPase Cdc42 between an inactive and active state at the base of the primary cilium. Knock out of Borg3 as well as dysregulation of Cdc42 results in reduced septin localization to the primary cilium and reduced formation of cilia.