Abstract Notochord progenitors (NotoPs) are a rare, yet vital embryonic cell population that give rise to the cells that form and maintain intervertebral discs. An unlimited access to NotoPs would open new opportunities for basic biomedical research and regenerative medicine of the discs. However, the mechanisms responsible for the specification and the maintenance of NotoPs are not understood. This gap in understanding stems from the fact that NotoPs emerge during the gastrulation to axial elongation transition; an event that is ethically and technically challenging to investigate. Here, to circumvent this issue, we use micropatterning to guide the development of human ESCs into standardised patterns of anterior primitive streak cell fates. We found that endogenous levels of NODAL signalling regulate the balance of axial progenitors and that NotoPs emergence requires the timely inhibition of Nodal signalling. Our work provides insights into the mechanisms driving the patterning of axial progenitors and may inform the development of future strategies aimed at deriving bona-fide NotoPs from hESC.

In vitro modelling of anterior primitive streak patterning with hESC reveals the dynamic of WNT and NODAL signalling required to specify notochord progenitors