|ZFIN ID: ZDB-PUB-080306-8|
Genetic analysis of two zebrafish patched homologues identifies novel roles for the hedgehog signaling pathway
Koudijs, M.J., den Broeder, M.J., Groot, E., and van Eeden, F.J.
|Source:||BMC Developmental Biology 8: 15 (Journal)|
|Registered Authors:||den Broeder, Marjo, Koudijs, Marco, van Eeden, Freek|
|PubMed:||18284698 Full text @ BMC Dev. Biol.|
Koudijs, M.J., den Broeder, M.J., Groot, E., and van Eeden, F.J. (2008) Genetic analysis of two zebrafish patched homologues identifies novel roles for the hedgehog signaling pathway. BMC Developmental Biology. 8:15.
ABSTRACTBACKGROUND: Aberrant activation of the Hedgehog (Hh) signaling pathway in different organisms has shown the importance of this family of morphogens during development. Genetic screens in zebrafish have identified specific roles for Hh in proliferation, differentiation and patterning, mainly as a result of a loss of Hh pathway activity. We attempted to fully activate the Hh pathway by removing both receptors for the Hh proteins, Patched1 and 2, which function as negative regulators of the Hh pathway. RESULTS: Here we describe a splice-donor mutation in Ptc1, called ptc1hu1602, which in a homozygous state results in a subtle eye and somite phenotype. Since we recently positionally cloned a ptc2 mutant, a ptc1;ptc2 double mutant was generated, showing severely increased levels of ptc1, gli1 and nkx2.2a, confirming an aberrant activation of Hh signaling. As a consequence, a number of phenotypes were observed that have not been reported previously using Shh mRNA overexpression. Somites of ptc1;ptc2 double mutants do not express anteroposterior polarity markers, however initial segmentation of the somite itself is not affected. This is the first evidence that segmentation and anterior/posterior (A/P) patterning of the somites are genetically uncoupled processes. Furthermore, we observed a novel negatively regulatory role for Hh signaling in fin field induction. Here Hh acts well before previously reported roles of Shh in fin formation and in a way that is different from the proposed early role of Gli3 in limb/fin bud patterning. CONCLUSIONS: The generation and characterization of the ptc1;ptc2 double mutant assigned novel and unexpected functions to the Hh signaling pathway. Additionally, these mutants will provide a useful system to further investigate the consequences of constitutively activated Hh signaling during vertebrate development.