Fig. 7

(A) Two-color ISH of nr2f1a (blue) and tcf21:EGFP (red). Embryo is flat-mounted with anterior leftward. Bracket indicates region of overlap. (B) Schematic of tcf21:Cre^ERT2recombinase and ubiquitous Cre-mediated color-switch transgenic lines used. (C, D) PMs (arrowhead) labeled in nr2f1a-2^ctrl and nr2f1a-2^mut embryos with the tcf21:Cre^ERT2; ubi:CsY transgenes. Labeled PMs–yellow. Muscles (MHC)–blue. Outlines indicate PMs with labeled skeletal muscles. While other cells were labeled within the pharyngeal region, they were not scored as skeletal muscle because they were not located within the muscles or had morphology consistent with skeletal muscle. View is lateral with anterior to the left and dorsal up. (E) Percentage of labeled PMs on each side of the nr2f1a-2^ctrl (n = 74) and nr2f1a-2^mut (n = 104) embryos. The (n) reflects the total number of sides examined, since labeling was not equivalent on both side of an embryo. aPMs—anterior pharyngeal muscles, pp—protractor pectoralis. 44/74 nr2f1a-2^ctrl and 66/104 nr2f1a-2^mut had muscle labeled in aPMs. 23/74 nr2f1a-2^ctrl and 13/104 nr2f1a-2^mut had muscle labeled in the pp. Fisher’s exact test was used to determine if there was a difference between the frequency of anterior and posterior PMs in nr2f1a-2^ctrl and nr2f1a-2^mut embryos.