Transcription factors SP5 and SP8 drive primary cilia formation in mammalian embryos

Although specific transcription factors (TFs) are known to regulate cell fate decisions, the degree to which they can stimulate formation of specific cell organelles is less clear. We used a multiomics comparison of the transcriptomes of ciliated and unciliated embryonic cells to identify TFs up-regulated in ciliated cells. We also used conditional genetics in mouse embryos and stem cells and found that the TFs SP5 and SP8 regulate cilia formation and gene expression. In embryos lacking Sp5 and Sp8, primary and motile cilia were shorter than normal and reduced in number across cell types, contributing to situs inversus and hydrocephalus. Moreover, expression of SP8 was sufficient to induce primary cilia in unciliated cells. This work will facilitate the study of cilia assembly using stem cell models and promote further understanding of human ciliopathies. To investigate transcriptome differences of ciliated cell types versus unciliated visceral endoderm lineage cell types in yolk sac tissue, we performed scRNA-seq analysis of yolk sac tissue of E8.75 mouse embryos.3 yolk sac tissues from 3 embryos at E8.75 stages were dissected out and dissassoicated into single cells, multiplexed and pooled for single cell sequencing.