A ciliopathy complex builds distal appendages to initiate ciliogenesis

Abstract

Cells inherit two centrioles, the older of which is uniquely capable of generating a cilium. We identified that three evolutionarily conserved proteins that underlie human ciliopathies, CEP90, MNR and OFD1, form a complex. This complex localized to both distal centrioles and centriolar satellites, proteinaceous granules surrounding centrioles. Cells and mice lacking CEP90 or MNR did not generate cilia, failed to assemble distal appendages, and did not transduce Hedgehog signals. Disrupting the satellite pools did not affect distal appendage assembly, indicating that it is the centriolar populations of MNR and CEP90 that are critical for ciliogenesis. CEP90 recruited the most proximal known distal appendage component, CEP83, to root distal appendages formation, an early step in ciliogenesis. In addition to distal appendage formation, MNR, but not CEP90, restricted centriolar length by recruiting OFD1. We conclude that a complex of disease-associated proteins, MNR, OFD1 and CEP90, acts at the distal centriole to support ciliogenesis by restraining centriole length and assembling distal appendages.

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

“…The search of proximity partners of FOPNL in mammalian cells led us to identify CEP90. As expected from previous results, we identified in our mass spectrometry MNR/OFIP in proximity of FOPNL (Chevrier et al, 2016), (Kumar et al, 2021). Interestingly, these two proteins are working in a complex with OFD1 to build a cilium (Lopes et al, 2011a).…”

“…This discrepancy might be due to the fact that these authors used 5-ethynyl-29-deoxyuridine (EdU) to distinguish the different phases of the cell cycle, while we used unsynchronized U2OS cells. Another possibility is that the recruitment of the complex differs between cell types causing this difference between our study (Kumar et al, 2021) which used RPE1 cells. Consistent with our findings, numerous distal end proteins such as C2CD3, CP110, Centrin2 (Thauvin-Robinet et al, 2014), (Kleylein-Sohn et al, 2007), (Paoletti et al, 1996) have already been observed on newly born procentrioles.…”

“…POC1B (Chang et al, 2016) and POC5 (Azimzadeh et al, 2009) are then recruited to allow centriole elongation. Centrin2 (Ruiz et al, 2005), (Aubusson-Fleury et al, 2012), OFD1 (Singla et al, 2010) and MNR (Kumar et al, 2021) have been shown to participate in the regulation of microtubule wall length, since their absence lead to elongated centrioles.…”

“…The ternary complex composed of OFD1 (Lopes et al, 2011), FOPNL/FOR20 (Sedjaï et al, 2010) and OFIP/MNR/KIAA0753 (Kodani et al, 2015), (Kumar et al, 2021) has been localized in mammalian cells at the centriole distal end and at the centriolar satellites, membrane-less cytoplasmic granules that concentrate in the vicinity of the centrosome (Kubo & Tsukita, 2003). OFIP was shown to interact directly with FOPNL and OFD1 (Chevrier et al, 2016), two proteins required for building the distal end of the basal bodies and for the anchoring process in both mammalian cells (Singla et al, 2010), (Thauvin-Robinet et al, 2013) and Paramecium (Aubusson-Fleury et al, 2012), (Bengueddach et al, 2017).…”

“…In mammalian cells, the dual location of these proteins at both distal end and centriolar satellites (Sedjaï et al, 2010), (Singla et al, 2010) (Chevrier et al, 2016) prevents from determining, which pool is involved in BB anchoring process, since centriolar satellites are also involved in cilia formation (Sedjaï et al, 2010), (Stowe et al, 2012). Interestingly, a recent study using satellites-less PCM1-/-cells demonstrated that the centriolar pool of the complex composed of MNR, OFD1 and CEP90 is crucial for ciliogenesis (Kumar et al 2021). In this paper, we turn to Paramecium as a physiological model, devoid of centriolar satellites, as far as we can tell from electron microscopy studies and by the absence of PCM1 orthologues, to further demonstrate the requirement and the evolutionary conservation of the BB distal end proteins FOPNL/FOR20 together with OFD1 and CEP90 in the BB anchoring process (Aubusson-Fleury et al, 2012), (Bengueddach et al, 2017).…”