Posterior specification of multi-lineage axial assembloids from human pluripotent stem cells.

Elongation of the posterior body axis is driven by multi-potent neuromesodermal progenitors (NMPs), which both self-renew and simultaneously generate neural tube, neural crest, and presomitc mesoderm lineages at successive anterior posterior (A-P) levels. The ensuing diversification of these three NMP lineages is remarkably extensive, and also essential for an immense range of clinically important adult posterior body tissues. Here, we describe a human pluripotent stem cell protocol that successfully specifies authentic NMPs using a cocktail of seven factors (7F). 7F-NMPs express requisite markers, exhibit co-linear HOX activation, and can be purposely specified into each of the three NMP daughter lineages, demonstrating genuine multi-potency. 3D assembly of neural tube, neural crest, and presomitic mesoderm spheroids followed by long-term floating culture derives mature, multi-compartment Posterior Axial Assembloids, or PAXAs. PAXAs constitute a complex heterogeneous tissue containing spinal motor neurons and interneurons, central and peripheral glia, connective tissues, muscle satellite cells and contractile muscle fibres. Together, 7F-NMP and PAXA protocols establish a versatile in vitro platform to model mechanisms of human posterior body axis development, and for the study of a wide range of human diseases.