The binding of LARP6 and DNAAF6 in biomolecular condensates influences ciliogenesis of multiciliated cells

Abstract

Motile cilia on the cell surface produce fluid flows in the body and abnormalities in motile cilia cause primary ciliary dyskinesia (PCD). Dynein axonemal assembly factors 6 (DNAAF6), a causative gene of PCD, was isolated as an interacting protein with La ribonucleoprotein 6 (LARP6) that regulates ciliogenesis in multi-ciliated cells (MCCs). In MCCs of Xenopus embryos, LARP6 and DNAAF6 were co-localized in biomolecular condensates termed dynein axonemal particles (DynAPs) and synergized to control ciliogenesis. Moreover, Tubulin alpha 1c like (TUBA1CL) mRNA encoding α-Tubulin protein that is a major component of ciliary axoneme was identified as a target mRNA regulated by binding LARP6. While DNAAF6 was necessary for high α-Tubulin protein expression near the apical side of Xenopus MCCs during ciliogenesis, its mutant, which abolishes binding with LARP6, was unable to restore the expression of α-Tubulin protein near the apical side of MCCs in Xenopus DNAAF6 morphant. These results indicated that the binding of LARP6 and DNAAF6 in DynAPs regulates highly expressed α-Tubulin protein near the apical side of Xenopus MCCs during ciliogenesis.