Early transcriptional similarities between two distinct neural lineages during ascidian embryogenesis
Résumé
Abstract
In chordates, the central nervous system arises from precursors that have distinct developmental and
transcriptional trajectories. Anterior nervous systems are ontogenically associated with ectodermal
lineages while posterior nervous systems are associated with mesoderm. Taking advantage of the welldocumented
cell lineage of ascidian embryos, we asked to what extent the transcriptional states of the
different neural lineages become similar during the course of progressive lineage restriction. We
performed single-cell RNA sequencing (scRNA-seq) analyses on hand-dissected neural precursor cells
of the two distinct lineages, together with those of their sister cell lineages, with a high temporal
resolution covering five successive cell cycles from the 16-cell to neural plate stages. A transcription
factor binding site enrichment analysis of neural specific genes at the neural plate stage revealed limited
evidence for shared transcriptional control between the two neural lineages, consistent with their
different ontogenies. Nevertheless, PCA analysis and hierarchical clustering showed that, by neural
plate stages, the two neural lineages cluster together. Consistent with this, we identified a set of genes
enriched in both neural lineages at the neural plate stage, including miR-124, Celf3.a, Zic.r-b, and Ets1/2.
Altogether, the current study has revealed genome-wide transcriptional dynamics of neural progenitor
cells of two distinct developmental origins. Our scRNA-seq dataset is unique and provides a valuable
resource for future analyses, enabling a precise temporal resolution of cell types not previously described
from dissociated embryos.