ZFIN ID: ZDB-PUB-050831-3
The Zebrafish Mutants dre, uki, and lep Encode Negative Regulators of the Hedgehog Signaling Pathway
Koudijs, M.J., den Broeder, M.J., Keijser, A., Wienholds, E., Houwing, S., van Rooijen, E.M., Geisler, R., and van Eeden, F.J.
Date: 2005
Source: PLoS Genetics   1(2): e19 (Journal)
Registered Authors: den Broeder, Marjo, Geisler, Robert, Houwing, Saskia, Koudijs, Marco, van Eeden, Freek, van Rooijen, Ellen, Wienholds, Erno
Keywords: Hedgehog signaling, Phenotypes, Embryos, Chondrocytes, Zebrafish, Ears, Eyes, Nonsense mutation
MeSH Terms:
  • Animals
  • Body Size
  • Cell Proliferation
  • Dwarfism
  • Embryo, Nonmammalian
  • Hedgehog Proteins
  • Mutation*
  • Proliferating Cell Nuclear Antigen/genetics
  • Signal Transduction/genetics*
  • Trans-Activators/genetics*
  • Zebrafish/genetics
  • Zebrafish/growth & development
PubMed: 16121254 Full text @ PLoS Genet.
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ABSTRACT
Proliferation is one of the basic processes that control embryogenesis. To identify factors involved in the regulation of proliferation, we performed a zebrafish genetic screen in which we used proliferating cell nuclear antigen (PCNA) expression as a readout. Two mutants, hu418B and hu540A, show increased PCNA expression. Morphologically both mutants resembled the dre (dreumes), uki (ukkie), and lep (leprechaun) mutant class and both are shown to be additional uki alleles. Surprisingly, although an increased size is detected of multiple structures in these mutant embryos, adults become dwarfs. We show that these mutations disrupt repressors of the Hedgehog (Hh) signaling pathway. The dre, uki, and lep loci encode Su(fu) (suppressor of fused), Hip (Hedgehog interacting protein), and Ptc2 (Patched2) proteins, respectively. This class of mutants is therefore unique compared to previously described Hh mutants from zebrafish genetic screens, which mainly show loss of Hh signaling. Furthermore, su(fu) and ptc2 mutants have not been described in vertebrate model systems before. Inhibiting Hh activity by cyclopamine rescues uki and lep mutants and confirms the overactivation of the Hh signaling pathway in these mutants. Triple uki/dre/lep mutants show neither an additive increase in PCNA expression nor enhanced embryonic phenotypes, suggesting that other negative regulators, possibly Ptc1, prevent further activation of the Hh signaling pathway. The effects of increased Hh signaling resulting from the genetic alterations in the uki, dre, and lep mutants differ from phenotypes described as a result of Hh overexpression and therefore provide additional insight into the role of Hh signaling during vertebrate development.
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