title: Expression of inactive glutathione peroxidase 4 leads to embryonic lethality, and inactivation of the Alox15 gene does not rescue such knock-in mice.
abstract: OBJECTIVE
  Glutathione peroxidases (Gpx) and lipoxygenases (Alox) are functional counterplayers in the metabolism of hydroperoxy lipids that regulate cellular redox homeostasis. Gpx4 is a moonlighting protein that has been implicated not only as an enzyme in anti-oxidative defense, gene expression regulation, and programmed cell death, but also as a structural protein in spermatogenesis. Homozygous Gpx4 knock-out mice are not viable, but molecular reasons for intrauterine lethality are not completely understood. This study was aimed at investigating whether the lack of catalytic activity or the impaired function as structural protein is the dominant reason for embryonic lethality. We further explored whether the pro-oxidative enzyme mouse 12/15 lipoxygenase (Alox15) plays a major role in embryonic lethality of Gpx4-deficient mice.
  
  
  RESULTS
  To achieve these goals, we first created knock-in mice, which express a catalytically inactive Gpx4 mutant (Sec46Ala). As homozygous Gpx4-knock-out mice Sec46Ala-Gpx4(+/+) knock-in animals are not viable but undergo intrauterine resorption between embryonic day 6 and 7 (E6-7). In contrast, heterozygous knock-in mice (Sec46Ala-Gpx4(-/+)) are viable, fertile and do not show major phenotypic alterations. Interestingly, homozygous Alox15 deficiency did not rescue the U46A-Gpx4(+/+) mice from embryonic lethality. In fact, when heterozygous U46A-Gpx4(-/+) mice were stepwise crossed into an Alox15-deficent background, no viable U46A-Gpx4(+/+)+Alox15(-/-) individuals were obtained. However, we were able to identify U46A-Gpx4(+/+)+Alox15(-/-) embryos in the state of resorption around E7.
  
  
  CONCLUSIONS
  These data suggest that the lack of catalytic activity is the major reason for the embryonic lethality of Gpx4(-/-) mice and that systemic inactivation of the Alox15 gene does not rescue homozygous knock-in mice expressing catalytically silent Gpx4.
authors.affiliation: 1 Institute of Biochemistry, Charite-University Medicine Berlin , Berlin, Germany .
authors.forename: Simone Hanna
authors.initials: SH
authors.lastname: Brütsch
authors.forename: Chi Chiu
authors.initials: CC
authors.lastname: Wang
authors.forename: Lu
authors.initials: L
authors.lastname: Li
authors.forename: Hannelore
authors.initials: H
authors.lastname: Stender
authors.forename: Nilgün
authors.initials: N
authors.lastname: Neziroglu
authors.forename: Constanze
authors.initials: C
authors.lastname: Richter
authors.forename: Hartmut
authors.initials: H
authors.lastname: Kuhn
authors.forename: Astrid
authors.initials: A
authors.lastname: Borchert
mesh_terms: D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000235:genetics*; D001093:Arachidonate 15-Lipoxygenase / Q000235:genetics*; D016718:Arachidonic Acid / Q000378:metabolism; D005260:Female; D015870:Gene Expression; D055879:Gene Knock-In Techniques; D005804:Genes, Lethal; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism*; D006579:Heterozygote; D008297:Male; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010084:Oxidation-Reduction; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase
chemical_list: D016718:Arachidonic Acid; D000080662:Phospholipid Hydroperoxide Glutathione Peroxidase; D005979:Glutathione Peroxidase; C521960:Alox15 protein, mouse; D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase