Fig. 1

PFR models for zebrafish pigment cell development from neural crest.

Models show early NCCS (eNCCs) generating multipotent (MIX) and bipotent (MI) intermediates en route to generating melanocytes and iridophores, and distinguish timing of expression and role of Ltk signaling: a Ltk Chromatoblast Model b Ltk Iridoblast Model. In these schema, potency of cells (number of fill colours) at different stages in PFR of the pigment cell lineages decreases down the diagram (i.e. with time), reflecting PFR. Expression of ltk is indicated by italics (ltk); other key marker genes are indicated too. Ltk function (signaling activity) is indicated in Roman script (Ltk, boxed). Thus, in the Ltk Chromatoblast Model, ltk is expressed in all chromatoblasts (MIX) and melanoiridoblasts (MI)(‘Early’), but Ltk signaling is activated only in a subset of them, driving iridophore lineage specification (iridoblast specification). Continuing ltk expression in iridoblasts and iridophores (‘Late’) has late role in iridophore differentiation, proliferation and/or survival. In the Ltk Iridoblast Model, early phase expression represents iridoblasts (‘Early’), where it functions in differentiation or survival. Late expression reflects ongoing expression and ongoing function in differentiated iridophores. Experimental assessment using Ltk inhibitor treatment reveals early role in iridophore fate specification and later role in differentiated cells, supporting Ltk Chromatoblast Model (a) (Supplementary Fig. 9).