Fig. 1. Identification and structural analysis of cup/pkd2. (A) Mapping of the cup mutation to a genetic interval on chromosome 1. The number of recombinants at each marker is shown. (B) pkd2 encodes a six-pass transmembrane calcium-activated non-specific cation channel [structure modified from Hayashi et al. (Hayashi et al., 1997)]. Sequencing of pkd2 in tc321 mutants revealed a nonsense mutation at nucleotide position 407 and ty30b showed a missense mutation at nucleotide position 1052, resulting in an amino acid substitution from a leucine to proline. (C) Lateral image of wild-type, cup^tc321, and cup^ty30b embryos at 48 hpf. Both alleles have a curly tail upward phenotype, but ty30b has a milder curvature than that of tc321.