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Fig. 7 The Engrailed domain of Lbx2 is required for myofilament gene expression. A-H: Expression of acta1 (A-D) and mybpc1 (E-H). Embryos express acta1at 24 hpf (A: 93% with normal expression, n = 15). Injection of lbx2-MO results in decreased acta1 expression (B: 20% with normal expression, n = 20), whereas acta1 expression partially recovers in embryos injected with lbx2-MO + lbx2 mRNA (C: 42% with normal expression, n = 50). In contrast, embryos injected with lbx2-MO + lbx Δ En mRNA fail to express acta1 (D: 14% with normal expression, n = 37). mybpc1 (E: 94%, n = 18; F: 43%, n = 23; G: 81%, n = 31; H: 42%, n = 38). I-P: Expression of mef2ca (I-L) and myogenin (M-P). Embryos express mef2ca at 24 hpf (I: n = 11). Injection of lbx2-MO results in increased mef2ca expression (J: 72% with increased expression, n = 11), whereas mef2ca expression partially recovers in embryos injected with lbx2-MO + lbx2 mRNA (K: 21% with increased expression, n = 19). In contrast, embryos injected with lbx2-MO + lbx Δ En mRNA fail to express mef2ca (L: 61% with increased expression, n = 21). myogenin (M: n = 7, N: 78% with increased expression, n = 9, O: 23%, n = 13, P: 67%, n = 14). (A-P) Whole mounts, lateral views, rostral toward the left, dorsal toward the top. Scale bar: 100 μm.