title: Both the RGS domain and the six C-terminal amino acids of mouse Axin are required for normal embryogenesis.
abstract: Axin is a negative regulator of canonical Wnt signaling, which promotes the degradation of beta-catenin, the major effector in this signaling cascade. While many protein-binding domains of Axin have been identified, their significance has not been evaluated in vivo. Here, we report the generation and analysis of mice carrying modified Axin alleles in which either the RGS domain or the six C-terminal amino acids (C6 motif) were deleted. The RGS domain is required for APC-binding, while the C6 motif has been implicated in the activation of c-Jun N-terminal kinase, but is not required for the effects of Axin on the Wnt/beta-catenin pathway, in vitro. Both mutant Axin alleles caused recessive embryonic lethality at E9.5-E10.5, with defects indistinguishable from those caused by a null allele. As Axin-DeltaRGS protein was produced at normal levels, its inability to support embryogenesis confirms the importance of interactions between Axin and APC. In contrast, Axin-DeltaC6 protein was expressed at only 25-30% of the normal level, which may account for the recessive lethality of this allele. Furthermore, many Axin(DeltaC6/DeltaC6) embryos that were heterozygous for a beta-catenin null mutation survived to term, demonstrating that early lethality was due to failure to negatively regulate beta-catenin.
authors.affiliation: Department of Genetics and Development, Columbia University Medical Center, New York, NY 10032, USA.
authors.forename: Ian V
authors.initials: IV
authors.lastname: Chia
authors.forename: Min Jung
authors.initials: MJ
authors.lastname: Kim
authors.forename: Keiji
authors.initials: K
authors.lastname: Itoh
authors.forename: Sergei Y
authors.initials: SY
authors.lastname: Sokol
authors.forename: Frank
authors.initials: F
authors.lastname: Costantini
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D060466:Axin Protein; D001483:Base Sequence; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000235:genetics*; D005328:Fetal Viability / Q000235:genetics; D017353:Gene Deletion; D005804:Genes, Lethal; D051379:Mice; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000235:genetics / Q000502:physiology; D020710:RGS Proteins / Q000737:chemistry / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D051153:Wnt Proteins / Q000502:physiology; D014981:Xenopus / Q000196:embryology; D029867:Xenopus Proteins
chemical_list: D060466:Axin Protein; D050505:Mutant Proteins; D020710:RGS Proteins; D012097:Repressor Proteins; D051153:Wnt Proteins; D029867:Xenopus Proteins; C555454:axin1 protein, Xenopus