title: Fibulin-4 E57K Knock-in Mice Recapitulate Cutaneous, Vascular and Skeletal Defects of Recessive Cutis Laxa 1B with both Elastic Fiber and Collagen Fibril Abnormalities.
abstract: Fibulin-4 is an extracellular matrix protein essential for elastic fiber formation. Frameshift and missense mutations in the fibulin-4 gene (EFEMP2/FBLN4) cause autosomal recessive cutis laxa (ARCL) 1B, characterized by loose skin, aortic aneurysm, arterial tortuosity, lung emphysema, and skeletal abnormalities. Homozygous missense mutations in FBLN4 are a prevalent cause of ARCL 1B. Here we generated a knock-in mouse strain bearing a recurrent fibulin-4 E57K homozygous missense mutation. The mutant mice survived into adulthood and displayed abnormalities in multiple organ systems, including loose skin, bent forelimb, aortic aneurysm, tortuous artery, and pulmonary emphysema. Biochemical studies of dermal fibroblasts showed that fibulin-4 E57K mutant protein was produced but was prone to dimer formation and inefficiently secreted, thereby triggering an endoplasmic reticulum stress response. Immunohistochemistry detected a low level of fibulin-4 E57K protein in the knock-in skin along with altered expression of selected elastic fiber components. Processing of a precursor to mature lysyl oxidase, an enzyme involved in cross-linking of elastin and collagen, was compromised. The knock-in skin had a reduced level of desmosine, an elastin-specific cross-link compound, and ultrastructurally abnormal elastic fibers. Surprisingly, structurally aberrant collagen fibrils and altered organization into fibers were characteristics of the knock-in dermis and forelimb tendons. Type I collagen extracted from the knock-in skin had decreased amounts of covalent intermolecular cross-links, which could contribute to the collagen fibril abnormalities. Our studies provide the first evidence that fibulin-4 plays a role in regulating collagen fibril assembly and offer a preclinical platform for developing treatments for ARCL 1B.
authors.affiliation: From the Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Olga
authors.initials: O
authors.lastname: Igoucheva
authors.affiliation: From the Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Vitali
authors.initials: V
authors.lastname: Alexeev
authors.affiliation: the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: Carmen M
authors.initials: CM
authors.lastname: Halabi
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida, Morsani College of Medicine, Tampa, Florida 33612, and.
authors.forename: Sheila M
authors.initials: SM
authors.lastname: Adams
authors.affiliation: the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: Ivan
authors.initials: I
authors.lastname: Stoilov
authors.affiliation: the Department of Biochemistry, Faculty of Medicine, Oita University, Yufu, Oita 879-5593, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Sasaki
authors.affiliation: From the Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Machiko
authors.initials: M
authors.lastname: Arita
authors.affiliation: From the Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107.
authors.forename: Adele
authors.initials: A
authors.lastname: Donahue
authors.affiliation: the Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: Robert P
authors.initials: RP
authors.lastname: Mecham
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida, Morsani College of Medicine, Tampa, Florida 33612, and.
authors.forename: David E
authors.initials: DE
authors.lastname: Birk
authors.affiliation: From the Department of Dermatology and Cutaneous Biology, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, mon-li.chu@jefferson.edu.
authors.forename: Mon-Li
authors.initials: ML
authors.lastname: Chu
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D001808:Blood Vessels / Q000002:abnormalities* / Q000473:pathology; D001842:Bone and Bones / Q000002:abnormalities* / Q000473:pathology; D024042:Collagen Type I / Q000378:metabolism* / Q000648:ultrastructure; D003432:Cross-Linking Reagents / Q000378:metabolism; D003483:Cutis Laxa / Q000378:metabolism / Q000473:pathology*; D004195:Disease Models, Animal; D004547:Elastic Tissue / Q000002:abnormalities* / Q000473:pathology / Q000648:ultrastructure; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000201:enzymology / Q000473:pathology; D005552:Forelimb / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000473:pathology; D055879:Gene Knock-In Techniques; D057809:HEK293 Cells; D006801:Humans; D008810:Mice, Inbred C57BL; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D014176:Protein Biosynthesis; D055503:Protein Multimerization; D008249:Protein-Lysine 6-Oxidase / Q000378:metabolism; D011859:Radiography; D012867:Skin / Q000473:pathology*; D013710:Tendons / Q000002:abnormalities / Q000473:pathology / Q000648:ultrastructure
chemical_list: D024042:Collagen Type I; D003432:Cross-Linking Reagents; C403672:EFEMP2 protein, human; D016326:Extracellular Matrix Proteins; D008249:Protein-Lysine 6-Oxidase
keywords: aneurysm; aorta; collagen; connective tissue; elastin; extracellular matrix; forelimb; lysyl oxidase; skin; tendon