Fig. 1

Fig. 1 npas4l is expressed at the medial and lateral boundaries of the IM. In situ hybridization chain reaction (A,C: npas4l, hand2; B,D: npas4l, osr1) and immunohistochemistry (Pax2a) label components of the wild-type posterior lateral mesoderm in dorsal views, anterior to the left, of three-dimensional reconstructions at 2 som (A,B) and 12 som (C,D). (A?-D?) Magnification of boxed regions in A-D. (A-A?) At 2 som, npas4l is expressed in bilateral territories (green, arrowhead) medial to the IM marker Pax2a (magenta) and hand2 (blue). There is overlap between npas4l expression and Pax2a localization (yellow arrows) seen in A'. (B-B?) At 2 som, npas4l is expressed in bilateral territories (arrowhead) medial to Pax2a and osr1. There is overlap between osr1 expression and Pax2a localization (yellow arrowheads), as well as overlap of between npas4l expression and Pax2a localization (yellow arrows) in B'. (C-C?) At 12 som, npas4l-expressing lateral vessel progenitors (arrow) have arisen lateral to Pax2a and medial to hand2. Faint npas4l expression remains in the medial territory (arrowhead). (D-D?) At 12 som, npas4l-expressing lateral vessel progenitors (arrow) are lateral to Pax2a and medial to osr1. Faint npas4l expression remains in the medial territory (arrowhead). Unlike at 2 som (B?), no substantial osr1 expression is detected in the Pax2a territory, but osr1 expression is still present lateral to Pax2a. Scale bars: A?D: 200 ?m; A?-D?: 50 ?m.