Epha1 is a cell surface marker for neuromesodermal progenitors and their early mesoderm derivatives

The vertebrate body is built during 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) generate the postcranial neural tube and paraxial mesoderm. Recently, several approaches have been designed to determine their molecular fingerprint but a simple method to isolate NMPs from embryos without the need for transgenic markers is still missing. We isolated NMPs using a genetic strategy that exploits their self-renew properties, and searched their transcriptome for cell surface markers. We found a distinct Epha1 expression profile in progenitor-containing areas of the mouse embryo, consisting of two cell subpopulations with different Epha1 expression levels. We show that Sox2+/T+ cells are preferentially associated with the Epha1 compartment, indicating that NMPs might be contained within this cell pool. Transcriptional profiling showed enrichment of high Epha1-expressing cells in known NMP and early mesoderm markers. Also, tail bud cells with lower Epha1 levels contained a molecular signature suggesting the presence of notochord progenitors. Our results thus indicate that Epha1 could represent a valuable cell surface marker for different subsets of axial progenitors, most particularly for NMPs taking mesodermal fates.