Wnt5 is required for tail formation in the zebrafish embryo.

Intercellular signaling molecules, such as those encoded by the Wnt gene family, have a fundamental role in various aspects of pattern formation in the developing embryo. The zebrafish wnt5 gene encodes a member of a subfamily of Wnt molecules thought to be involved in modulating cell behavior during vertebrate development. Here, we show that the zebrafish pipetail gene is identical to wnt5. The pipetail mutant phenotype is characterized by defects in tail formation and impaired maturation of the cells that contribute to cartilaginous elements of the head skeleton. This suggests a major role for wnt5 in morphogenetic processes underlying tail outgrowth and cartilage differentiation in the head. To investigate the function of maternally derived wnt5 mRNA, we generated females that were homozygous for pipetail. The lack of a maternal effect phenotype in the progeny of these females suggests that no obvious function for the maternal wnt5 expression can be deduced.