pnp4a Is the Causal Gene of the Medaka Iridophore Mutant guanineless

G3 (Bethesda). 2017 Apr 3;7(4):1357-1363. doi: 10.1534/g3.117.040675.


See-through medaka lines are suitable for observing internal organs throughout life. They were bred by crossing multiple color mutants. However, some of the causal genes for these mutants have not been identified. The medaka has four pigment cell types: black melanophores, yellow xanthophores, white leucophores, and silvery iridophores. The causal genes of melanophore, xanthophore, and leucophore mutants have been elucidated, but the causal gene for the iridophore mutant remains unknown. Here, we describe the iridophore mutant, guanineless (gu), which exhibits a strong reduction in visible iridophores throughout its larval to adult stages. The gu locus was previously mapped to chromosome 5, but was located near the telomeric region, making it difficult to integrate into the chromosome. We sought the causal gene of gu using synteny analysis with the zebrafish genome and found a strong candidate, purine nucleoside phosphorylase 4a (pnp4a). Gene targeting and complementation testing showed that pnp4a is the causal gene of gu This result will allow the establishment of inbred medaka strains or other useful strains with see-through phenotypes without major disruption in the genetic background of each strain.

Keywords: guanineless; iridophore; medaka; pigment mutant; pnp4a.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • CRISPR-Cas Systems / genetics
  • Exons / genetics
  • Fish Proteins / chemistry
  • Fish Proteins / genetics*
  • Gene Expression Regulation, Developmental
  • Gene Targeting
  • Genetic Loci
  • Heterozygote
  • Melanophores / metabolism*
  • Mutation / genetics*
  • Oryzias / embryology
  • Oryzias / genetics
  • Oryzias / metabolism*
  • Phenotype
  • Phylogeny
  • Pigmentation
  • Synteny / genetics


  • Fish Proteins