title: A mutation in the tuft mouse disrupts TET1 activity and alters the expression of genes that are crucial for neural tube closure.
abstract: Genetic variations affecting neural tube closure along the head result in malformations of the face and brain. Neural tube defects (NTDs) are among the most common birth defects in humans. We previously reported a mouse mutant called tuft that arose spontaneously in our wild-type 3H1 colony. Adult tuft mice present midline craniofacial malformations with or without an anterior cephalocele. In addition, affected embryos presented neural tube closure defects resulting in insufficient closure of the anterior neuropore or exencephaly. Here, through whole-genome sequencing, we identified a nonsense mutation in the Tet1 gene, which encodes a methylcytosine dioxygenase (TET1), co-segregating with the tuft phenotype. This mutation resulted in premature termination that disrupts the catalytic domain that is involved in the demethylation of cytosine. We detected a significant loss of TET enzyme activity in the heads of tuft embryos that were homozygous for the mutation and had NTDs. RNA-Seq transcriptome analysis indicated that multiple gene pathways associated with neural tube closure were dysregulated in tuft embryo heads. Among them, the expressions of Cecr2, Epha7 and Grhl2 were significantly reduced in some embryos presenting neural tube closure defects, whereas one or more components of the non-canonical WNT signaling pathway mediating planar cell polarity and convergent extension were affected in others. We further show that the recombinant mutant TET1 protein was capable of entering the nucleus and affected the expression of endogenous Grhl2 in IMCD-3 (inner medullary collecting duct) cells. These results indicate that TET1 is an epigenetic determinant for regulating genes that are crucial to closure of the anterior neural tube and its mutation has implications to craniofacial development, as presented by the tuft mouse.
authors.affiliation: Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA ksfong@hawaii.edu.
authors.forename: Keith S K
authors.identifier: 0000-0001-6845-1754
authors.initials: KS
authors.lastname: Fong
authors.affiliation: Department of Pediatrics, Division of Human Genetics, Cincinnati Children's Hospital, College of Medicine, University of Cincinnati, 3333 Burnet Ave, ML 7003, Cincinnati, OH 45229, USA Unit on Pediatric, Development & Genetic Ophthalmology, Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Robert B
authors.identifier: 0000-0003-3015-3545
authors.initials: RB
authors.lastname: Hufnagel
authors.affiliation: Office of Biostatistics and Quantitative Health Sciences, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA.
authors.forename: Vedbar S
authors.initials: VS
authors.lastname: Khadka
authors.affiliation: Epigenomics Research Program, Department of Native Hawaiian Health, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Corley
authors.affiliation: Epigenomics Research Program, Department of Native Hawaiian Health, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA.
authors.forename: Alika K
authors.initials: AK
authors.lastname: Maunakea
authors.affiliation: Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA.
authors.forename: Ben
authors.initials: B
authors.lastname: Fogelgren
authors.affiliation: Department of Pediatrics, Division of Human Genetics, Cincinnati Children's Hospital, College of Medicine, University of Cincinnati, 3333 Burnet Ave, ML 7003, Cincinnati, OH 45229, USA Department of Otorhinolaryngology Head and Neck Surgery, School of Medicine, University of Maryland, BioPark Bldg1, 800 West Baltimore Street, Room 404, Baltimore, MD 21201, USA.
authors.forename: Zubair M
authors.initials: ZM
authors.lastname: Ahmed
authors.affiliation: Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawai'i, Honolulu, HI 96813, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Lozanoff
mesh_terms: D000818:Animals; D049628:Body Size; D016764:Cell Polarity; D018389:Codon, Nonsense / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D004475:Ectoderm / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006720:Homozygote; D051379:Mice; D008954:Models, Biological; D009154:Mutation / Q000235:genetics*; D054259:Neural Tube; D017354:Point Mutation; D011518:Proto-Oncogene Proteins / Q000235:genetics; D012313:RNA / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism; D060449:Wnt Signaling Pathway / Q000235:genetics
chemical_list: D018389:Codon, Nonsense; D004268:DNA-Binding Proteins; D011518:Proto-Oncogene Proteins; C540839:TET1 protein, mouse; D014157:Transcription Factors; C552738:grainy head-like 2 protein, mouse; D012313:RNA
keywords: Anencephaly; Anterior cranial cephalocele; Encephalocele; Epigenetic; Exencephaly; Midfacial cleft; Neural tube defect