six1a loss-of-function affects the expression of muscle-specific mRNAs in the regions of fast muscle formation. Lateral views of embryos after WISH for myhz1 (A, A′, B, B′), tpma (C, C′, D, and D′), mylz2 (K) at 13 s and for mylz2 at 24 h (L). Anterior somites of control embryos (A, C) and UM morphants (B, D). In panel K, control (wt) and morphant (UM) embryos were placed together for comparison of mylz2 expression levels on the same picture. Three somites indicated by brackets in panels A, B, C, and D are shown at higher magnification in panels A′, B′, C′, and D′, correspondingly. Note that transcripts of tpma and myhz1 genes were excluded from posterior and dorsal regions of somites in morphants (arrowheads in panels B′ and D′). Bright field (E, G) and fluorescent (F, H) images of trunk somites of control embryos and UM morphants of mylz2-gfp transgenic line at 30 h. Some of the melanophores are out of focus due to the slight undulation of the trunk of the morphant (G). Equal numbers of control embryos and UM morphants were grown and half of embryos were collected for RNA isolation. Remaining embryos were grown until 30 h and analyzed. Note the low level of GFP fluorescence in the trunk muscle of morphants. Semiquantitative RT-PCR of gfp mRNA (I) and mylz2 mRNA (J) isolated from uninjected control embryos (wt) and UM morphants (UM) of mylz2-gfp line. Note the weaker band intensity of product amplified from gfp RNA isolated from UM morphants at 24 h. Also, note down-regulation of mylz2 mRNA at 14 h and recovery of expression at 24 h. Down-regulation (K) and recovery (L) of mylz2 mRNA at 13 s and 24 h, correspondingly. Scale bars, 100 μm in panels A, B, C, D, E–H and K; 50 μm in panels A′, B′, C′, and D′; 200 μm in panel L.
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