The evolutionary conserved complex CEP90, FOPNL and OFD1 specifies the future location of centriolar distal appendages, and promotes their assembly

Abstract

Cilia assembly starts with centriole to basal body maturation, migration to the cell surface and docking to the plasma membrane. The basal body docking process involves the interaction of both the distal end of the basal body and the transition fibers (or mature distal appendages), with the plasma membrane. During this process, the transition zone assembles and forms the structural junction between the basal body and the nascent cilium. Mutations in numerous genes involved in basal body docking and transition zone assembly are associated with the most severe ciliopathies, highlighting the importance of these events in cilium biogenesis. The conservation of this sequence of events across phyla is paralleled by a high conservation of the proteins involved. We identified CEP90 by BioID using FOPNL as a bait. Ultrastructure expansion microscopy showed that CEP90, FOPNL and OFD1 localized at the distal end of both centrioles/basal bodies in Paramecium and mammalian cells. These proteins are recruited early after duplication on the procentriole. Finally, functional analysis performed both in Paramecium and mammalian cells demonstrate the requirement of this complex for distal appendage assembly and basal body docking. Altogether, we propose that this ternary complex is required to determine the future position of distal appendages

DISCO is key to successful centriole maturation

“…Besides OFD1 and MNR proteins, Kumar et al also identified a protein called FGFR1OP N-Terminal Like (FOPNL or FOR20) as a potential CEP90 interactor ( 4 ). Interestingly, this interaction was confirmed in a recent study describing that a complex containing CEP90, OFD1, and FOPNL localizes at the distal end of Paramecium centrioles and is necessary for the recruitment of DA components and centriole docking in Paramecium and human cells ( 9 ). FOPNL was previously found in complex with MNR and OFD1 and shown to facilitate their interaction ( 8 ).…”

Paramecium, a Model to Study Ciliary Beating and Ciliogenesis: Insights From Cutting-Edge Approaches

“…The close observation by EM of these unanchored BBs revealed that their distal ends, which mimic the unciliated TZ, are incomplete. Whereas depletion of Centrin2 leads to long BBs with an almost complete absence of their distal ends ( Figure 7B2 ), the depletion of either OFD1 or FOPNL shows a partially organized TZ ( Figures 7B3,B4 ), compared to Control depleted cells ( Figure 7B1 ) suggesting that Centrin 2 is acting at the distal end, earlier than OFD1, FOPNL and CEP90 ( Ruiz et al, 2005 ; Aubusson-Fleury et al, 2012 ; Bengueddach et al, 2017 ; Borgne et al, 2021 ). Indeed, this has been demonstrated using paramecia expressing Centrin2-GFP and RNAi-depleted for OFD1, FOPNL or CEP90 and vice-versa.…”

“…Thanks to the precise organization pattern of BBs over the cell cortex, defects in their anchoring are easily recognized not only by the presence of some internal BBs, but also by anomalies in the surface pattern by Immunofluorescence (IF) experiments ( Figure 2A , Figure 5A ). Using IF in Paramecium , we have been able to show that depletions of the conserved distal-end BB proteins (Centrin2, OFD1, FOPNL/FOR20 or CEP90) lead to mispositioned and unanchored BBs ( Aubusson-Fleury et al, 2012 ; Bengueddach et al, 2017 ; Borgne et al, 2021 ; Ruiz et al, 2005 Figure 7A1-A4 ). The close observation by EM of these unanchored BBs revealed that their distal ends, which mimic the unciliated TZ, are incomplete.…”

“…These studies demonstrate that proteins that localize at the distal end of BBs early after BB duplication are critical for both the assembly of the distal end and also for the BB docking event. Interestingly, in mammals, these proteins have also been shown to prevent BB docking by preventing distal appendage formation ( Borgne et al, 2021 ; Kumar et al, 2021 ) leading to impaired ciliogenesis and, therefore, to ciliopathies ( Singla et al, 2010 ; Chevrier et al, 2016 ; Bruel et al, 2017 ). These proteins localize in a 9 fold symmetry at the distal end of the BB at a position where the distal appendages are observed by expansion microscopy ( Borgne et al, 2021 ).…”

“…Interestingly, in mammals, these proteins have also been shown to prevent BB docking by preventing distal appendage formation ( Borgne et al, 2021 ; Kumar et al, 2021 ) leading to impaired ciliogenesis and, therefore, to ciliopathies ( Singla et al, 2010 ; Chevrier et al, 2016 ; Bruel et al, 2017 ). These proteins localize in a 9 fold symmetry at the distal end of the BB at a position where the distal appendages are observed by expansion microscopy ( Borgne et al, 2021 ). To support this assumption, Kumar et al ( Kumar et al, 2021 ) showed an interaction between CEP90 and CEP83, the proximal distal appendage protein.…”