Regulator of calcineurin-2 is a centriolar protein with a role in cilia length control

Abstract

Almost every cell in the human body extends a primary cilium. Defective cilia function leads to a set of disorders known as ciliopathies, which are characterised by debilitating developmental defects that affect many tissues. Here, we report a new role for regulator of calcineurin 2 (RCAN2) in primary cilia function. It localises to centrioles and the basal body and is required to maintain normal cilia length. RCAN2 was identified as the most strongly upregulated gene from a comparative RNAseq analysis of cells in which expression of the Golgi matrix protein giantin had been abolished by gene editing. In contrast to previous work where we showed that depletion of giantin by RNAi results in defects in ciliogenesis and in cilia length control, giantin knockout cells generate normal cilia after serum withdrawal. Furthermore, giantin knockout zebrafish show increased expression of RCAN2. Importantly, suppression of RCAN2 expression in giantin knockout cells results in the same defects in the control of cilia length that are seen upon RNAi of giantin itself. Together, these data define RCAN2 as a regulator of cilia function that can compensate for the loss of giantin function.

Calcineurin associates with centrosomes and regulates cilia length maintenance

“…We also discovered that CN regulates cilia length, although the mechanism underlying this effect remains to be determined. Our findings are consistent with previous studies which localized RCAN2, a negative regulator of CN, to centrioles and basal bodies and showed that its depletion resulted in shorter cilia (Stevenson et al, 2018). CN may alter cilia length through effects on POC5 or other structural proteins.…”

“…Both POC5 and CEP97 (another CN-proximal protein, Fig. 1B) are required for cilia assembly, maintenance, signaling and retraction (Hassan et al, 2019; Schweizer et al, 2021; Spektor et al, 2007) High affinity CN-binding partners CaM, FG-repeat nucleoporins and RCAN2 also localize to basal bodies and regulate ciliation (Kee et al, 2012; Plotnikova et al, 2012; Stevenson et al, 2018), suggesting possible CN- dependent modulation of these processes. To examine whether CN regulates ciliation, IMCD3 cells were grown to near confluency (∼20% ciliated) (Figs 4A, B) and then plated at a high density to induce ciliation via contact inhibition (Joly et al, 2006), while simultaneously treating them with DMSO (control) or the CNI FK506.…”

Zebrafish as an Emerging Model for Osteoporosis: A Primary Testing Platform for Screening New Osteo-Active Compounds

“…While concerns have been raised about MO veracity as morphants frequently show more severe phenotypes than stables mutants generated for the same gene (42, 43). This is due to a transcriptional compensation response for chronic loss of a gene as has been shown in mouse, cultured human cell lines, plants, and zebrafish models (44–51). Thus, while MOs have a role, their use has been largely supplanted by use of genome editing strategies.…”

Genetic compensation for cilia defects in cep290 mutants by upregulation of cilia-associated small GTPases

“…Significantly, mutation in the zebrafish giantin gene, which encodes a golgin protein involved in golgi structure and is required for ciliogenesis ( Bergen et al, 2017 ; Stevenson et al, 2017 ), has been shown to be compensated by upregulation of the regulator of the calcineurin 2 (RCAN2) gene. RCAN2 was identified as the gene most highly upregulated by giantin genetic knockout, and was shown by knockdown to suppress ciliopathy phenotypes in giantin mutants ( Stevenson et al, 2018 ).…”