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. 2001 Jul;30(3):170-4.
doi: 10.1002/gene.1057.

Sonic hedgehog and tiggy-winkle hedgehog cooperatively induce zebrafish branchiomotor neurons

S Bingham  1 , A Nasevicius, S C Ekker, A Chandrasekhar
Affiliations

Sonic hedgehog and tiggy-winkle hedgehog cooperatively induce zebrafish branchiomotor neurons

S Bingham et al. Genesis. 2001 Jul.
No abstract available

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Figures

FIG. 1
FIG. 1
Shh and Twhh act cooperatively in branchiomotor neuron (BMN) induction in zebrafish. All panels show dorsal views of the hindbrain with anterior to the left. The images are fluorescent micrographs of live, 48 HPF (Hours Post Fertilization) embryos embedded in 3% methycellulose, and shows the distribution of GFP-expressing BMNs. (A, B) In wild-type embryos injected with either control MO (A) or twhh MO (B), the development of BMNs is unaffected. The nV motor neurons are found in rhombomere 2 (r2) (arrowhead) and r3 (arrow), the nVII motor neurons are found in r6 and r7, and the nX motor neurons (asterisk) are found in the caudal hindbrain. (C, D) In many wild-type embryos injected with shh MO, the nV motor neurons in r3 are either greatly reduced in number (arrow in C) or missing (D), whereas the nV neurons in r2 (arrowheads) are unaffected. The nX neurons (asterisks) are also slightly reduced in number. (E) In syut4 homozygotes injected with control MO, the nV neurons in r3 are greatly reduced or missing, the nV neurons in r2 are unaffected (arrowhead), the nVII neurons are slightly reduced, and the nX neurons are greatly reduced in number (asterisk). This BMN phenotype is identical to that described previously using immunohistochemistry (Chandrasekhar et al., 1998). (F) Many wild-type embryos injected with shh MO exhibit the same BMN phenotype as syu mutant embryos (E). (G, H) Most (95%) syu mutant embryos injected with twhh MO (G) and many (28%) wild-type embryos co-injected with shh MO and twhh MO (H) exhibit an almost complete loss of GFP-expressing BMNs throughout the hindbrain. Scale bar = 100 μm.
FIG. 2
FIG. 2
Hindbrain development and patterning are not affected in “double mutants.” All panels show side views of the hindbrain with anterior to the left. (A, B) Live, 30 HPF embryos were embedded in 3% methylcellulose and photographed using DIC optics and GFP epifluorescence. The fluorescent images of the GFP-expressing cells were subsequently superimposed on the DIC images using Photoshop software. In a twhh MO-injected wild-type embryo (A), the GFP-expressing BMNs (nV, nVII, nX) are found in normal numbers at characteristic locations. In contrast, in a twhh MO-injected syu “double mutant” (B), very few GFP-expressing cells are found in an otherwise healthy hindbrain. (C, D) Twhh MO-injected embryos were examined under epifluorescence at 23 HPF to select wild-type (n = 5) and “double mutant” (n = 3) embryos, which were processed for hoxb1 in situ hybridization. Hoxb1 is expressed normally in rhombomere 4 in twhh MO-injected wild-type (C) and syu mutant embryos (D). Scale bars = 100 μm.
FIG. 3
FIG. 3
Twhh RNA injection rescues the BMN defects caused by twhh MO injection. All panels show dorsal views with anterior to the left. Live, 48 HPF embryos were embedded in methylcellulose and viewed under GFP epifluorescence. (A) In a twhh MO-injected wild-type embryo, BMN development is normal. (B) In a twhh MO; twhh RNA-injected wild-type embryo, BMN numbers are variably increased, and many GFP-expressing cells are located more dorsally (not shown). (C) In a twhh MO-injected syu mutant, BMNs are almost completely missing. (D) In a twhh MO; twhh RNA-injected syu mutant, BMN loss is prevented, and many GFP-expressing cells are located at ectopic, dorsal locations (not shown). Scale bar = 100 μm.
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References

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