title: Positional cloning of the sex-linked giant egg (Ge) locus in the silkworm, Bombyx mori.
abstract: The giant egg (Ge) locus is a Z-linked mutation that leads to the production of large eggs. Cytological observations suggest that an unusual translocation of a large fragment of the W chromosome bearing a putative egg size-determining gene, Esd, gave rise to giant egg mutants. However, there is currently no molecular evidence confirming either a W-Z translocation or the presence of Esd on the W chromosome. To elucidate the origin of giant egg mutants, we performed positional cloning. We observed that the Bombyx mori. orthologue of the human Phytanoyl-CoA dioxygenase domain containing 1 gene (PHYHD1) is disrupted in giant egg mutants. PHYHD1 is highly conserved in eukaryotes and is predicted to be a Fe(II) and 2-oxoglutarate-dependent oxygenase. Exon skipping in one of the two available Ge mutants is probably caused by the insertion of a non-long terminal repeat transposon into intron 4 in the vicinity of the 5' splice site. Segmental duplication in Ge(2) , an independent allele, was caused by unequal recombination between short interspersed elements inserted into introns 3 and 5. Our results indicate that (1) Bombyx PHYHD1 is responsible for the Ge mutants and that (2) the Ge locus is unrelated to the W-linked putative Esd. To our knowledge, this is the first report describing the phenotypic defects caused by mutations in PHYHD1 orthologues.
authors.affiliation: Graduate School of Bioresource and Bioenvironmental Science, Kyushu University, Fukuoka, Japan; Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Fujii
authors.forename: H
authors.initials: H
authors.lastname: Abe
authors.forename: M
authors.initials: M
authors.lastname: Kawamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Banno
authors.forename: T
authors.initials: T
authors.lastname: Shimada
mesh_terms: D000818:Animals; D001483:Base Sequence; D012831:Bombyx / Q000235:genetics*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005260:Female; D056426:Genetic Loci; D005821:Genetic Techniques; D008969:Molecular Sequence Data; D009154:Mutation; D009866:Oogenesis / Q000235:genetics; D010063:Ovum / Q000166:cytology; D012730:Sex Chromosomes / Q000235:genetics*
keywords: 2-oxoglutarate-dependent oxygenase; dosage effect; egg size; oogenesis