title: Entpd5 is essential for skeletal mineralization and regulates phosphate homeostasis in zebrafish.
abstract: Bone mineralization is an essential step during the embryonic development of vertebrates, and bone serves vital functions in human physiology. To systematically identify unique gene functions essential for osteogenesis, we performed a forward genetic screen in zebrafish and isolated a mutant, no bone (nob), that does not form any mineralized bone. Positional cloning of nob identified the causative gene to encode ectonucleoside triphosphate/diphosphohydrolase 5 (entpd5); analysis of its expression pattern demonstrates that entpd5 is specifically expressed in osteoblasts. An additional mutant, dragonfish (dgf), exhibits ectopic mineralization in the craniofacial and axial skeleton and encodes a loss-of-function allele of ectonucleotide pyrophosphatase phosphodiesterase 1 (enpp1). Intriguingly, generation of double-mutant nob/dgf embryos restored skeletal mineralization in nob mutants, indicating that mechanistically, Entpd5 and Enpp1 act as reciprocal regulators of phosphate/pyrophosphate homeostasis in vivo. Consistent with this, entpd5 mutant embryos can be rescued by high levels of inorganic phosphate, and phosphate-regulating factors, such as fgf23 and npt2a, are significantly affected in entpd5 mutant embryos. Our study demonstrates that Entpd5 represents a previously unappreciated essential player in phosphate homeostasis and skeletal mineralization.
authors.affiliation: Hubrecht Institute,  Royal Netherlands Academy of Arts and Sciences and University Medical Centre Utrecht, 3584 CT, Utrecht,  The Netherlands.
authors.forename: Leonie F A
authors.initials: LF
authors.lastname: Huitema
authors.forename: Alexander
authors.initials: A
authors.lastname: Apschner
authors.forename: Ive
authors.initials: I
authors.lastname: Logister
authors.forename: Kirsten M
authors.initials: KM
authors.lastname: Spoorendonk
authors.forename: Jeroen
authors.initials: J
authors.lastname: Bussmann
authors.forename: Chrissy L
authors.initials: CL
authors.lastname: Hammond
authors.forename: Stefan
authors.initials: S
authors.lastname: Schulte-Merker
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001842:Bone and Bones / Q000196:embryology / Q000378:metabolism / Q000473:pathology; D002113:Calcification, Physiologic; D004625:Embryo, Nonmammalian / Q000378:metabolism; D000089703:Fibroblast Growth Factor-23; D006706:Homeostasis; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity; D010006:Osteoblasts / Q000201:enzymology; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism*; D010727:Phosphoric Diester Hydrolases / Q000235:genetics; D011755:Pyrophosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015027:Zebrafish / Q000196:embryology / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C000717427:FGF23 protein, human; D010710:Phosphates; D029961:Zebrafish Proteins; D000089703:Fibroblast Growth Factor-23; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; C578393:entpd5a protein, zebrafish