Actin-based deformations of the nucleus control multiciliated ependymal cell differentiation

Abstract

Ependymal cells (ECs) are multi-ciliated cells in the brain that contribute to cerebrospinal fluid flow. ECs are specified at embryonic stages but differentiate and grow cilia later in development. Differentiation depends on genes such as GEMC1 and MCIDAS with E2F4/5 but also on cell cycle related factors. In the mouse brain, we observe that nuclear deformation accompanies EC differentiation. Tampering with these deformations either by decreasing F-actin levels or by severing the link between the nucleus and the actin cytoskeleton blocks differentiation. Conversely, increasing F-actin by knocking out the Arp2/3 complex inhibitor Arpin activates differentiation. Thus, actin polymerization triggers nuclear deformation and jump-starts the signaling that produce differentiated ECs. We show evidence that one of the players in this process is the retinoblastoma 1 (RB1) protein whose phosphorylation prompts MCIDAS activation. Overall, this study reveals an important role for actin-based mechanical inputs to the nucleus as controlling factors in cell differentiation.

Cyclin O controls entry into the cell-cycle variant required for multiciliated cell differentiation

“…4C and D ). We also stained WT and Cena KO cultures for retinoblastoma protein phosphorylation (pRB pSer807/811), another hallmark of cycling cells entering S-phase (Zhou et al, 2022), which was recently shown to also turn positive during early MCC differentiation (Basso et al, 2023; Ortiz-Alvarez et al, 2022). Consistent with the p27 observations, while the proportion of pRB+ cells begins to increase in FOXJ1+ WT cells entering A-stage (:: 26%), very few cells are pRB+ in FOXJ1+ Cena KO cells (:: 3%), a proportion comparable to the proportion observed in WT FOXJ1+ cells at the centrosome stage (:: 4%) ( Fig.…”