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Fig. 7 MRFs act to suppress Pax3/7 expression during somite development. Immunodetection of MyHC or Pax3/7 or in situ mRNA hybridisation for pax3 or pax7 in embryos injected with MRF MOs viewed in dorsal flatmount (A-D 15 s anterior to top), lateral confocal short stack of yolk extension somites at 24 hpf (E, magnified in insets) and confocal stack in lateral view (F, 24 hpf, DAPI). (A insets) Injection of both myf5 and myod MOs ablates muscle, whereas each MO alone has no effect on MyHC. (A-C) Myod MO or double MO up-regulate pax3 both in anterior (som 8-10, A) and posterior (som 11-13, B) somites and pax7 (C) mRNA. Green arrowheads indicate adaxial cell rows. Insets show the normal timing of pax7 accumulation after pax3 (arrows). Brackets show somites in which pax3 is widely expressed. Black arrowheads indicate posterior region of more mature somites in which pax3/7 mRNA is low relative to the anterior region. Myf5 MO is like controls. (D) Dual immunodetection of pax3 mRNA and Pax3/7 protein. (E) Pax3/7 protein is up-regulated in many lateral somite cells by either myod MO alone or double MO, but is little affected by myf5 MO. Insets show a single region at higher magnification. (F) DAPI reveals numerous somite nuclei with condensed chromatin (arrowhead), suggesting apoptosis in double MO embryos. Note that the apparent reduction in tissue mass may lead to an underestimate of the extent of the Pax3/7 increase. (G) Counts at 24 hpf represent mean ± standard deviation of four somites in 4–6 embryos. Asterisks indicate significant difference from control, P < 0.001.
Reprinted from Developmental Biology, 302(2), Hammond, C.L., Hinits, Y., Osborn, D.P., Minchin, J.E., Tettamanti, G., and Hughes, S.M., Signals and myogenic regulatory factors restrict pax3 and pax7 expression to dermomyotome-like tissue in zebrafish, 504-521, Copyright (2007) with permission from Elsevier. Full text @ Dev. Biol.