TH regulated craniofacial muscle development including EOM organization. 96 hpf control embryos demonstrated 6 distinct EOM; medial rectus (MR), lateral rectus (LR), superior rectus (SR), superior oblique (SO), inferior rectus (IR), and inferior oblique (IO) in vivo in Tg(α-actin::EGFP) (A, D) and by in situ hybridization for myzh2 (G, I). In situ hybridization for myoD demonstrated early muscle differentiation in EOM at 60 hpf (K, M). Thraa MO knockdown inhibited jaw and PA muscle development (B, H). Thraa MO knockdown did not disrupt muscle differentiation, but caused indistinct superior (sup) and inferior (inf) EOM complexes (E, H, J). Dio3 MO knockdown inhibited posterior PA development (C, L) and caused thickening and overlapping of EOM insertions (F). At 60 hpf EOMs in Dio3 MO knockdowns showed early muscle differentiation (L), but were clustered together and indistinct in wholemount (L) or on sections (N). AM, anterior mandibulae. Scale bar=50 or 100 µm as indicated.
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