Lineage specificity of primary cilia in the mouse embryo

Abstract

Primary cilia are required for vertebrate cells to respond to specific intercellular signals. Here we define when and where primary cilia appear in the mouse embryo using a transgenic line that expresses ARL13B-mCherry in cilia and Centrin2-GFP in centrosomes. Primary cilia first appear on cells of the epiblast at e6.0 and are subsequently present on all derivatives of the epiblast. In contrast, extraembryonic cells of the visceral endoderm and trophectoderm lineages have centrosomes but no cilia. Stem cell lines derived from embryonic lineages recapitulate the in vivo pattern: epiblast stem cells are ciliated, whereas trophoblast stem cells and extraembryonic endoderm stem (XEN) cells lack cilia. Basal bodies in XEN cells are mature and can form cilia when the AURKA/HDAC6 cilia disassembly pathway is inhibited. The lineage-dependent distribution of cilia is stable throughout much of gestation, defining which cells in the placenta and yolk sac are able respond to Hedgehog ligands.