title: Fam83h null mice support a neomorphic mechanism for human ADHCAI.
abstract: Truncation mutations in FAM83H (family with sequence similarity 83, member H) cause autosomal dominant hypocalcified amelogenesis imperfecta (ADHCAI), but little is known about FAM83H function and the pathogenesis of ADHCAI. We recruited three ADHCAI families and identified two novel (p.Gln457*; p.Lys639*) and one previously documented (p.Q452*) disease-causing FAM83H mutations. We generated and characterized Fam83h-knockout/lacZ-knockin mice. Surprisingly, enamel thickness, density, Knoop hardness, morphology, and prism patterns were similar in Fam83h (+/+), Fam83h (+/-), and Fam83h (-/-) mice. The histology of ameloblasts in all stages of development, in both molars and incisors, was virtually identical in all three genotypes and showed no signs of pathology, although the Fam83h (-/-) mice usually died after 2 weeks and rarely survived to 7 weeks. LacZ expression in the knockin mice was used to report Fam83h expression in the epithelial tissues of many organs, notably in skin and hair follicles, which manifested a disease phenotype. Pull-down studies determined that FAM83H dimerizes through its N-terminal phospholipase D-like (PLD-like) domain and identified potential FAM83H interacting proteins. Casein kinase 1 (CK1) interacts with the FAM83H PLD-like domain via an F(270)-X-X-X-F(274)-X-X-X-F(278) motif. CK1 can phosphorylate FAM83H in vitro, and many phosphorylation sites were identified in the FAM83H C-terminus. Truncation of FAM83H alters its subcellular localization and that of CK1. Our results support the conclusion that FAM83H is not necessary for proper dental enamel formation in mice, but may act as a scaffold protein that localizes CK1. ADHCAI is likely caused by gain-of-function effects mediated by truncated FAM83H, which potentially mislocalizes CK1 as part of its pathological mechanism.
authors.affiliation: Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108.
authors.forename: Shih-Kai
authors.initials: SK
authors.lastname: Wang
authors.affiliation: Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Biologic and Materials SciencesUniversity of Michigan School of Dentistry1210 Eisenhower Pl.Ann ArborMichigan48108; Department of Pediatric DentistrySchool and Hospital of StomatologyPeking University22 South Avenue ZhongguancunHaidian DistrictBeijing100081China.
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.affiliation: Facility for Electron Microscopy Research Department of Anatomy and Cell Biology and Faculty of Dentistry McGill University 3640 University Street Montreal Quebec H3A 2C7 Canada.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Smith
authors.affiliation: Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108.
authors.forename: Amelia S
authors.initials: AS
authors.lastname: Richardson
authors.affiliation: Department of Biochemistry and Molecular Biology School of Dental Medicine Tsurumi University 2-1-3 Tsurumi Tsurumi-ku Yokohama 230-8501 Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Yamakoshi
authors.affiliation: Graduate Institute of Clinical Dentistry National Taiwan University No. 1, Chang-Te St Taipei 10048 Taiwan.
authors.forename: Yuan-Ling
authors.initials: YL
authors.lastname: Lee
authors.affiliation: Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey.
authors.forename: Figen
authors.initials: F
authors.lastname: Seymen
authors.affiliation: Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey.
authors.forename: Mine
authors.initials: M
authors.lastname: Koruyucu
authors.affiliation: Department of Pedodontics Faculty of Dentistry Istanbul University Istanbul Turkey.
authors.forename: Koray
authors.initials: K
authors.lastname: Gencay
authors.affiliation: Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea.
authors.forename: Moses
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Biomedical Sciences Seoul National University College of Medicine 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea.
authors.forename: Murim
authors.initials: M
authors.lastname: Choi
authors.affiliation: Department of Pediatric Dentistry & Dental Research Institute School of Dentistry Seoul National University 275-1 Yongon-dong Chongno-gu Seoul 110-768 Korea.
authors.forename: Jung-Wook
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108.
authors.forename: Jan C-C
authors.initials: JC
authors.lastname: Hu
authors.affiliation: Department of Biologic and Materials Sciences University of Michigan School of Dentistry 1210 Eisenhower Pl. Ann Arbor Michigan 48108.
authors.forename: James P
authors.initials: JP
authors.lastname: Simmer
keywords: Amelogenesis imperfecta; gain‐of‐function; hair defects; knockout mouse; skin defects; truncation mutation