Du S J, Dienhart M
Center of Marine Biotechnology, University of Maryland Biotechnology Institute, 710 E. Pratt St., Baltimore, MD 21202, USA.
Differentiation. 2001 Mar;67(3):84-91. doi: 10.1046/j.1432-0436.2001.067003084.x.
Zebrafish skeletal muscles are composed of two major types of muscle fibers, broadly classified as fast or slow fibers. Recent studies have demonstrated that members of the Hedgehog (Hh) family induce the formation of slow muscle fibers. Hedgehog signals are secreted proteins that function through the transcription factor Glis. We report here the characterization of a zebrafish Gli2 expression in slow and fast muscle cells and the study of the roles of Hedgehogs and Gli2 in zebrafish muscle development using two mutant strains; sonic-you (syu) and you-too (yot), respective for sonic hedgehog (shh) and Gli2 mutation. We have demonstrated that Shh and Gli2 mutation causes similar defects in slow muscle formation. There is, however, a difference in the degree of defect between these two mutants. In yot mutant embryos, development of slow muscles was completely blocked, whereas in syu mutant embryos, a small number of slow muscle cells could still form, suggesting that other Hhs were also involved in slow muscle induction. Induction of slow muscles by other Hhs appeared to require Gli2, because ectopic expression of Echidna hedgehog (Ehh) and Tiggy-winkle hedgehog (Twhh) failed to induce slow muscles in yot mutant embryos. Together, these data suggest that further Hhs, other than Shh, are also involved in the induction and differentiation of slow muscle cells and that Gli2 is required by Shh, Twhh, and Ehh, thus playing a key role in the induction and differentiation of slow muscle cells.
斑马鱼的骨骼肌由两种主要类型的肌纤维组成，大致可分为快肌纤维或慢肌纤维。最近的研究表明，刺猬（Hh）家族的成员可诱导慢肌纤维的形成。刺猬信号是通过转录因子Gli发挥作用的分泌蛋白。我们在此报告斑马鱼Gli2在慢肌和快肌细胞中的表达特征，并使用两种突变株；sonic-you（syu）和you-too（yot），分别针对音猬因子（shh）和Gli2突变，研究刺猬因子和Gli2在斑马鱼肌肉发育中的作用。我们已经证明，Shh和Gli2突变在慢肌形成中会导致类似的缺陷。然而，这两种突变体在缺陷程度上存在差异。在yot突变体胚胎中，慢肌的发育完全受阻，而在syu突变体胚胎中，仍有少量慢肌细胞能够形成，这表明其他Hh因子也参与了慢肌的诱导。其他Hh因子对慢肌的诱导似乎需要Gli2，因为在yot突变体胚胎中，刺猬索尼克（Ehh）和刺猬汀克（Twhh）的异位表达未能诱导慢肌形成。总之，这些数据表明，除了Shh之外，其他Hh因子也参与了慢肌细胞的诱导和分化，并且Shh、Twhh和Ehh都需要Gli2，因此Gli2在慢肌细胞的诱导和分化中起关键作用。
