Three-dimensional (3D) UMAP plot of WT (a) and cRE1 dup/+ (b) components of a E9.5E12.5 scRNA-seq object comprising Isl1 + and/or Hoxb1 + FAC-sorted Isl1 MN -GFP cranial motor neurons (MNs) (with GFP cells spiked in) spanning r3r7. Seurat clusters are numbered and annotated according to proposed cellular identity at the right. CN, cranial nucleus. The black dotted arrows trace the proposed pseudotime developmental trajectory of r4MNs from mitotic progenitors of r3r7 neurons (Cluster 1), r4MN mitotic progenitors (Cluster 2) and r4MN precursors (Cluster 3), bipotent r4MNs (Cluster 4), which gave rise to separate populations of IEEs (Cluster 5) defined by Gata2 and Gata3 expression 18 , 19 , and FBMNs (Cluster 6) defined by Syt4, Shox2 and Cdh8 expression and enriched for Nr2f1 (refs. 18 , 19 , 74 , 75 ) (Extended Data Fig. 6c,d ).
