Du SJ , Devoto SH , Westerfield M , Moon RT .

P01 HD022486 NICHD NIH HHS , HD22486 NICHD NIH HHS , HD29360 NICHD NIH HHS

	Figure 2. Induction of slow muscle cells by zebrafish Sonic hedgehog (Shh) and Tiggy-winkle hedgehog (Twhh). (A, B, and C) Sections (dorsal to the top) showing fluorescence localization of slow muscle cells labeled with F59, an anti–myosin heavy chain antibody, in embryos injected with frame shifted sonic hedgehog (Shhfs) (A), Shh (B), or Twhh (C). (D, E, and F) Sections (dorsal to the top) showing fluorescence localization of muscle pioneer cells labeled with 4D9, an anti-engrailed antibody, in embryos injected with Shhfs (D), Shh (E), or Twhh (F). (G, H, and I) Whole-mount Nomarski images showing muscle pioneer cells labeled with the 4D9 antibody in embryos injected with Shhfs (G), Shh (H), or Twhh (I). Embryos in G, H, and I are oriented in side views, with anterior to the left and dorsal to the top. Bars, 50 μm.
	Figure 3. Inhibition of slow muscle cells by a constitutively active isoform of PKA. (A) Whole-mount Nomarski images showing slow muscle cells labeled with the F59 antibody in a representative control embryo. (B) Whole-mount Nomarski images showing slow muscle cells labeled with the F59 antibody in a representative embryo injected with a constitutively active form of PKA. (C) Section (dorsal to the top) showing localization of slow muscle cells labeled with F59 in a control embryo. (D) Sections (dorsal to the top) showing local loss of slow muscle cells in an embryo injected with a constitutively active form of PKA.
	Figure 4. Dorsalin-1 blocks the development of muscle pioneer cells. (A) β-gal expression in embryos injected with twhh-β-gal was monitored by enzyme activity and Nomarski microscopy at early pharyngula stage (∼24 h). At this stage, the expression of β-galactosidase was notochord specific in >90% (n = 120) of the injected embryos that expressed the construct. We first detected β-galactosidase expression in the early segmentation stage (∼12 h), specifically in notochord cells of injected embryos (84%, n = 57, data not shown). (B) Immunolocalization with anti– c-myc antibody in embryos injected with the DNA construct twhh-dsl-1myc. The twhh promoter drives expression of dsl-1myc in notochord cells (arrowheads). (C and D) Double labeling with anti–c-myc antibody and anti-engrailed antibody, 4D9, in embryos injected with either the DNA construct twhh-bGFP (C) or twhh-dsl-1myc (D). The bracket in D marks the region affected by Dorsalin-1. The dsl-1myc expressing notochord cells in D are indicated by the arrowheads. Muscle pioneer cells in C and D are indicated by arrows. Cells in only some regions of the embryos expressed the transgenes (B and D, arrowheads), consistent with the mosaic expression of other injected DNAs (Westerfield et al., 1992). In 93% (n = 54) of the embryos lacking muscle pioneer cells in some of their somites, nearby notochord cells expressed Dorsalin-1. Embryos are oriented in side views, with anterior to the left and dorsal to the top. Bar, 50 μm.
	Figure 5. Dorsalin-1 specifically affects the development of muscle pioneer cells but not the non–muscle pioneer slow muscle cells. (A) Whole-mount staining of embryo injected with DNA construct twhh-dsl-1myc using F59 to monitor slow muscle cells. The bracket marks the region affected by Dorsalin-1. (B) Section through an unaffected region with both muscle pioneer cells (arrows) and non–muscle pioneer slow muscle cells (arrowhead) labeled with F59. (C) Section through an affected region with normal non–muscle pioneer slow muscle cells labeled with F59 antibody (arrowhead) but no muscle pioneer cells. The orientation is anterior to the left (A) and dorsal to the top (A–C). Bars: (A) 100 μm; (B and C) 50 μm.
	Figure 6. Ectopic Dorsalin-1 represses muscle pioneer cell induction by Hedgehogs. Embryos were double labeled with anti-myc antibody to monitor expression of dsl-1myc and with the 4D9 antibody to monitor muscle pioneer cells. (A) Embryos injected with Shhfs RNA as control. (B) Embryos coinjected with twhh-bGFP DNA and zebrafish Shh RNA show induction of extra muscle pioneer cells. (C) Embryos coinjected with twhh-dsl-1myc DNA and zebrafish Shh RNA also show induction of extra muscle pioneer cells, but not in the region (bracket) near the notochord cell expressing Dorsalin-1 (arrowhead). Embryos are oriented in side views, with anterior to the left and dorsal to the top. Bar, 50 μm.
	Figure 7. dnPKA induces slow muscle cells. (A–C) Sections showing slow muscle cells labeled with F59 in embryos injected with Shhfs (A), dnPKA (B), or dnPKA/twhh-dsl-1myc (C). Extra slow muscle cells are induced in both B and C. (D–F) Sections showing muscle pioneer cells labeled with 4D9 in embryos injected with Shhfs (D), dnPKA (E), or dnPKA/twhh-dsl-1myc (F). Muscle pioneer cells are induced by dnPKA (E) but are repressed by dsl-1 (F). (G–I) Whole-mount labeling with anti–c-myc and 4D9 antibodies in embryos injected with Shhfs (G), dnPKA (H), or dnPKA/twhh-dsl-1myc (I). The bracket in I marks the region affected by Dorsalin-1. The dsl-1myc expressing cell in I is indicated by the arrowhead. The orientation is dorsal to the top (A–I) and anterior to the left (G–I). Bar, 50 μm.
	Figure 8. Opposing actions of Hedgehog and BMP4-like proteins regulate slow muscle cell identity. (A) At the tail bud stage, paraxial mesoderm cells are induced by Hedgehog secreted from notochord precursor cells to become adaxial cells, the slow muscle precursors. A subset of the adaxial cells located adjacent to the notochord are induced to become muscle pioneer cells by continued Hedgehog signal from the notochord cells and floor plate cells. In contrast, other slow muscle precursors migrate to the lateral surface of the myotome and differentiate into non–muscle pioneer slow muscle cells. BMP4-like inhibitory signal antagonizes the hedgehog signals in dorsal and ventral regions of the somite and blocks the induction of muscle pioneer cells in these regions. (B) Schematic illustration of this model in cross section at the tailbud stage (upper embryo, arrow denotes Hedgehog signal), and at the somitogenesis stage (lower embryo, arrow denotes Hedgehog signal and stippling denotes the BMP4-like signal). The distribution of muscle pioneers is determined by the distribution of these competing signals.

Basler, Control of cell pattern in the neural tube: regulation of cell differentiation by dorsalin-1, a novel TGF beta family member. 1993, Pubmed

Basler, Control of cell pattern in the neural tube: regulation of cell differentiation by dorsalin-1, a novel TGF beta family member. 1993, Pubmed
Butler, Differentiation of muscle fiber types in aneurogenic brachial muscles of the chick embryo. 1982, Pubmed
Christ, Early stages of chick somite development. 1995, Pubmed
Concordet, Spatial regulation of a zebrafish patched homologue reflects the roles of sonic hedgehog and protein kinase A in neural tube and somite patterning. 1996, Pubmed
Crow, Myosin expression and specialization among the earliest muscle fibers of the developing avian limb. 1986, Pubmed
Currie, Induction of a specific muscle cell type by a hedgehog-like protein in zebrafish. 1996, Pubmed
Devoto, Identification of separate slow and fast muscle precursor cells in vivo, prior to somite formation. 1996, Pubmed
Ekker, Patterning activities of vertebrate hedgehog proteins in the developing eye and brain. 1995, Pubmed
Ekker, Distinct expression and shared activities of members of the hedgehog gene family of Xenopus laevis. 1995, Pubmed , Xenbase
Ekker, Coordinate embryonic expression of three zebrafish engrailed genes. 1992, Pubmed
Ericson, Two critical periods of Sonic Hedgehog signaling required for the specification of motor neuron identity. 1996, Pubmed
Fan, Patterning of mammalian somites by surface ectoderm and notochord: evidence for sclerotome induction by a hedgehog homolog. 1994, Pubmed
Fan, Long-range sclerotome induction by sonic hedgehog: direct role of the amino-terminal cleavage product and modulation by the cyclic AMP signaling pathway. 1995, Pubmed
Felsenfeld, The fub-1 mutation blocks initial myofibril formation in zebrafish muscle pioneer cells. 1991, Pubmed
Fredette, A reevaluation of the role of innervation in primary and secondary myogenesis in developing chick muscle. 1991, Pubmed
Fredette, Relationship of primary and secondary myogenesis to fiber type development in embryonic chick muscle. 1991, Pubmed
Hammerschmidt, Genetic analysis of dorsoventral pattern formation in the zebrafish: requirement of a BMP-like ventralizing activity and its dorsal repressor. 1996, Pubmed
Hammerschmidt, Protein kinase A is a common negative regulator of Hedgehog signaling in the vertebrate embryo. 1996, Pubmed
Harris, Neural control of the sequence of expression of myosin heavy chain isoforms in foetal mammalian muscles. 1989, Pubmed
Hatta, Diversity of expression of engrailed-like antigens in zebrafish. 1991, Pubmed
Heim, Improved green fluorescence. 1995, Pubmed
Hemmati-Brivanlou, Follistatin, an antagonist of activin, is expressed in the Spemann organizer and displays direct neuralizing activity. 1994, Pubmed , Xenbase
Hughes, Three slow myosin heavy chains sequentially expressed in developing mammalian skeletal muscle. 1993, Pubmed
Jiang, Protein kinase A and hedgehog signaling in Drosophila limb development. 1995, Pubmed
Johnson, Ectopic expression of Sonic hedgehog alters dorsal-ventral patterning of somites. 1994, Pubmed
Kimmel, Stages of embryonic development of the zebrafish. 1995, Pubmed , Xenbase
Krauss, A functionally conserved homolog of the Drosophila segment polarity gene hh is expressed in tissues with polarizing activity in zebrafish embryos. 1993, Pubmed
Kroll, Transgenic Xenopus embryos from sperm nuclear transplantations reveal FGF signaling requirements during gastrulation. 1996, Pubmed , Xenbase
Lassar, The role of positive and negative signals in somite patterning. 1996, Pubmed
Li, Function of protein kinase A in hedgehog signal transduction and Drosophila imaginal disc development. 1995, Pubmed
Liem, Dorsal differentiation of neural plate cells induced by BMP-mediated signals from epidermal ectoderm. 1995, Pubmed , Xenbase
Miller, Developmental origins of skeletal muscle fibers: clonal analysis of myogenic cell lineages based on expression of fast and slow myosin heavy chains. 1986, Pubmed
Miller, Developmental regulation of the multiple myogenic cell lineages of the avian embryo. 1986, Pubmed
Miller, Evolutionarily conserved sequences of striated muscle myosin heavy chain isoforms. Epitope mapping by cDNA expression. 1989, Pubmed
Münsterberg, Combinatorial signaling by Sonic hedgehog and Wnt family members induces myogenic bHLH gene expression in the somite. 1995, Pubmed
Nikaido, Conservation of BMP signaling in zebrafish mesoderm patterning. 1997, Pubmed , Xenbase
Orellana, Mutations in the catalytic subunit of cAMP-dependent protein kinase result in unregulated biological activity. 1992, Pubmed
Pan, cAMP-dependent protein kinase and hedgehog act antagonistically in regulating decapentaplegic transcription in Drosophila imaginal discs. 1995, Pubmed
Patel, Expression of engrailed proteins in arthropods, annelids, and chordates. 1989, Pubmed , Xenbase
Perrimon, Hedgehog and beyond. 1995, Pubmed
Piccolo, Dorsoventral patterning in Xenopus: inhibition of ventral signals by direct binding of chordin to BMP-4. 1996, Pubmed , Xenbase
Pourquié, Lateral and axial signals involved in avian somite patterning: a role for BMP4. 1996, Pubmed
Raamsdonk, Differentiation of the musculature of the teleost Brachydanio rerio. I. Myotome shape and movements in the embryo. 1974, Pubmed
Rissi, Zebrafish Radar: a new member of the TGF-beta superfamily defines dorsal regions of the neural plate and the embryonic retina. 1995, Pubmed
Roelink, Floor plate and motor neuron induction by vhh-1, a vertebrate homolog of hedgehog expressed by the notochord. 1994, Pubmed , Xenbase
Sasai, Xenopus chordin: a novel dorsalizing factor activated by organizer-specific homeobox genes. 1994, Pubmed , Xenbase
Smith, Expression cloning of noggin, a new dorsalizing factor localized to the Spemann organizer in Xenopus embryos. 1992, Pubmed , Xenbase
Talbot, A homeobox gene essential for zebrafish notochord development. 1995, Pubmed , Xenbase
Thornell, Development of fiber types in human fetal muscle. An immunocytochemical study. 1984, Pubmed
Trevarrow, Organization of hindbrain segments in the zebrafish embryo. 1990, Pubmed , Xenbase
Ungar, Inhibition of protein kinase A phenocopies ectopic expression of hedgehog in the CNS of wild-type and cyclops mutant embryos. 1996, Pubmed
Van Swearingen, Slow and fast muscle fibers are preferentially derived from myoblasts migrating into the chick limb bud at different developmental times. 1995, Pubmed
Waterman, Development of the lateral musculature in the teleost, Brachydanio rerio: a fine structural study. 1969, Pubmed
Weinberg, Developmental regulation of zebrafish MyoD in wild-type, no tail and spadetail embryos. 1996, Pubmed
Westerfield, Specific activation of mammalian Hox promoters in mosaic transgenic zebrafish. 1992, Pubmed
Zimmerman, The Spemann organizer signal noggin binds and inactivates bone morphogenetic protein 4. 1996, Pubmed , Xenbase