Role of sonic hedgehog in branchiomotor neuron induction in zebrafish.
The role of zebrafish hedgehog genes in branchiomotor neuron development was analyzed by examining mutations that affect the expression of the hedgehog genes and by overexpressing these genes in embryos. In cyclops mutants, reduction in sonic hedgehog (shh) expression, and elimination of tiggy-winkle hedgehog (twhh) expression, correlated with reductions in branchiomotor neuron populations. Furthermore, branchiomotor neurons were restored in cyclops mutants when shh or twhh was overexpressed. These results suggest that Shh and/or Twhh play an important role in the induction of branchiomotor neurons in vivo. In sonic-you (syu) mutants, where Shh activity was reduced or eliminated due to mutations in shh, branchiomotor neurons were reduced in number in a rhombomere-specific fashion, but never eliminated. Similarly, spinal motor neurons were reduced, but not eliminated, in syu mutants. These results demonstrate that Shh is not solely responsible for inducing branchiomotor and spinal motor neurons, and suggest that Shh and Twhh may function as partially redundant signals for motor neuron induction in zebrafish.
Chandrasekhar
A
A
Department of Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109-1048, USA.
Warren
J T
JT
Takahashi
K
K
Schauerte
H E
HE
van Eeden
F J
FJ
Haffter
P
P
Kuwada
J Y
JY
D000818:Animals; D001934:Branchial Region / Q000294:innervation; D002467:Cell Nucleus / Q000473:pathology; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction; D018507:Gene Expression Regulation, Developmental; D053823:Hedgehog Proteins; D047908:Intracellular Signaling Peptides and Proteins; D009046:Motor Neurons / Q000502:physiology; D009154:Mutation; D009420:Nervous System / Q000196:embryology; D009474:Neurons / Q000502:physiology*; D011506:Proteins / Q000235:genetics* / Q000378:metabolism; D012249:Rhombencephalon / Q000196:embryology / Q000473:pathology; D013116:Spinal Cord; D015534:Trans-Activators; D016212:Transforming Growth Factor beta / Q000235:genetics; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins
D053823:Hedgehog Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D029961:Zebrafish Proteins; C512832:ndr2 protein, zebrafish; C509240:shhb protein, zebrafish