title: Cloning and characterization of three PHEX homologues in Drosophila.
abstract: Inactivating mutations and/or deletions of PHEX ( Phosphate-regulating gene with Homologies to Endopeptidase on the X chromosome) are responsible for X-linked hypophosphatemic rickets in humans. In the present study, three Drosophila PHEX homologues (dPHEX-1, -2, -3) were isolated by the screening of a Drosophila cDNA library and expressed sequence tag (EST) database. The structural region involving motif II: (456)WMXXXTKXXAXXK(468) (numbered according to human PHEX), motif VI: (602)WW(603), and motif VIII: (746)CXLW(749) was conserved in the dPHEX family. Zinc-coordinating motifs (HEFTH and GENIADNGG) were also conserved in the dPHEX family. All three dPHEX genes were expressed during all stages of Drosophila development. The expression of dPHEX-1 was suppressed by dietary phosphate deprivation, but the expression of dPHEX-2 and that of dPHEX-3 were not affected. In-situ hybridization showed a ubiquitous distribution of dPHEX-1 and dPHEX-2, while dPHEX-3 was highly expressed in the larval brain. In an analysis of subcellular localization, dPHEX-1 was localized to intracellular organelles and dPHEX-3 was localized predominately in the plasma membrane of Drosophila embryonic S2 cells. Homozygosity of a dPHEX-1 mutation, a transposon insertion in the dPHEX-1 promoter region, was completely lethal at an early stage of embryonic development. The present study indicates that three homologues are likely involved in the phosphate homeostasis of Drosophila.
authors.affiliation: Nutritional Science, Department of Nutrition, School of Medicine, Tokushima University, Japan.
authors.forename: Mikiko
authors.initials: M
authors.lastname: Ito
authors.forename: Emiko
authors.initials: E
authors.lastname: Akai
authors.forename: Michiyo
authors.initials: M
authors.lastname: Izuka
authors.forename: Hiroko
authors.initials: H
authors.lastname: Segawa
authors.forename: Masashi
authors.initials: M
authors.lastname: Kuwahata
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Miyamoto
mesh_terms: D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002462:Cell Membrane / Q000737:chemistry; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D030561:Databases, Nucleic Acid; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000254:growth & development; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000737:chemistry / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000737:chemistry; D005091:Exons / Q000235:genetics; D040461:Gene Components / Q000235:genetics; D015870:Gene Expression / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental; D005838:Genotype; D006056:Golgi Apparatus / Q000737:chemistry; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional / Q000235:genetics; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; D010710:Phosphates / Q000494:pharmacology; D011506:Proteins / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014162:Transfection
chemical_list: D029721:Drosophila Proteins; D010710:Phosphates; D011506:Proteins; D053402:PHEX Phosphate Regulating Neutral Endopeptidase; C506231:PHEX protein, human