High Epha1 expression is a potential cell surface marker for embryonic neuro-mesodermal progenitors

The basic layout of the vertebrate body is built during the initial stages of embryonic development by the sequential addition of new tissue as the embryo grows at its caudal end. During this process the neuro-mesodermal progenitors (NMPs) are thought to generate the postcranial neural tube and paraxial mesoderm. In recent years, several approaches have been designed to determine the NMP molecular fingerprint but a simple method to isolate them from embryos without the need of transgenic markers is still missing. We wanted to identify a suitable cell surface marker allowing isolation of NMPs from the embryo without the need of previous genetic modifications. We used a genetic strategy to recover NMPs on the basis of their ability to populate the tail bud and searched their transcriptome for cell surface markers specifically enriched in these cells. We found a distinct Epha1 expression profile in progenitor-containing areas of the mouse embryo, consisting in at least two subpopulations of Epha1-positive cells according to their Epha1 expression levels. We show that double Sox2/T(Bra) positive cells are preferentially associated with the Epha1High compartment, indicating that NMPs might be contained within this cell pool. Transcriptional profiling of Epha1-positive tail bud cells also showed enrichment of Epha1High cells in known NMP markers. Interestingly, the Epha1Low compartment contains a molecular signature compatible with notochord progenitor identity. Our results thus indicate that Epha1 could represent a valuable cell surface marker for different subsets of mouse embryonic axial progenitors.