RC/BTB2 is essential for formation of primary cilia in mammalian cells

Abstract

RC/BTB2 is a binding partner of sperm associated antigen 16S (SPAG16S), which is regulator of spermiogenesis in mice, a process during which sperm flagella are formed. The expression of Rc/btb2 is also regulated by multicilin, a protein that controls ciliogenesis. Given that mouse Rc/btb2 mRNA is not only expressed in tissues bearing motile cilia, but also in tissues without motile cilia, we investigated whether RC/BTB2 plays a role in the general process of ciliogenesis by studying two somatic cells lines that have primary cilia, NIH3T3 and IMCD3. We discovered that the subcellular localization of RT/BTB2 in the NIH3T3 and IMCD3 cells encompasses the pathway for ciliogenesis. RC/BTB2 was found in the Golgi bodies and centrosomes, two key structures essential for normal ciliogenesis. Knockdown of Rc/btb2 gene expression in these cell lines disrupted ciliogenesis. The percentage of cells with primary cilia was significantly reduced in stable cell lines transduced with specific Rc/btb2 shRNA viruses compared to the control cells. When cilia were formed in the knockdown cells, they were significantly shorter than those in the control cells. Knockdown of Rc/btb2 expression did not affect cell proliferation and the cell cycle. Exogenous expression of RC/BTB2 in these stable knockdown cells restored ciliogenesis. These findings suggest that RC/BTB2 is a necessary component of the process of formation of primary cilia in somatic cells, perhaps through the transportation of cargos from Golgi bodies to centrosomes for cilia assembling.

The flagellar germ‐line hypothesis: How flagellate and ciliate gametes significantly shaped the evolution of organismal complexity

“…[66] Perhaps most impressive, another sperm associated protein RC/BTB 2 , that is the interaction partner of SPAG 16S, is essential in the genesis of primary cilia. [67] As we will see shortly, primary cilia are the key to much of the development of complexity.…”

Primary cilia proteins: ciliary and extraciliary sites and functions

“…Importantly, KIF7 (JBTS12) is implicated in JBTS [198]. In a more direct manner, many proteins have now been identified that localize to the Golgi apparatus and to centrioles and/or primary cilia axonemes: IFT20 [192], RC/BTB2 [199], retinitis pigmentosa protein (RP2) [200], HOOK2 [201], CCDC41 [202], and VPS15 [203]. In light of these studies, the Golgi apparatus appears to be an important extraciliary site for cilia proteins.…”

Ovarian dysfunction following prenatal exposure to an insecticide, chlordecone, associates with altered epigenetic features

“…To identify whether these genes are affected in female mice, we analyzed the expression of some of these genes in E15.5 embryonic ovaries. We found that the expression of Rcbtb2 (regulator of chromosome condensation [33]) and Rbpms (RNA-binding protein critical repressor of AP-1 signaling [34]) was totally absent in E15.5-treated ovaries (Additional file 1: Fig. S3), which implies that CD targets similar genes in ovaries as well.…”

“…We also found a dramatic decrease in the expression of genes such as Rcbtb2 and Rbpms in embryonic ovaries. Rcbtb2 is essential for the formation of primary cilia in mammalian cells [33]. The presence of primary cilia has been documented in granulosa cells, antral follicles and ovarian surface epithelium [54, 55].…”