title: Lhx6 and Lhx8 promote palate development through negative regulation of a cell cycle inhibitor gene, p57Kip2.
abstract: Cleft palate is a common birth defect in humans. Therefore, understanding the molecular genetics of palate development is important from both scientific and medical perspectives. Lhx6 and Lhx8 encode LIM homeodomain transcription factors, and inactivation of both genes in mice resulted in profound craniofacial defects including cleft secondary palate. The initial outgrowth of the palate was severely impaired in the mutant embryos, due to decreased cell proliferation. Through genome-wide transcriptional profiling, we discovered that p57(Kip2) (Cdkn1c), encoding a cell cycle inhibitor, was up-regulated in the prospective palate of Lhx6(-/-);Lhx8(-/-) mutants. p57(Kip2) has been linked to Beckwith-Wiedemann syndrome and IMAGe syndrome in humans, which are developmental disorders with increased incidents of palate defects among the patients. To determine the molecular mechanism underlying the regulation of p57(Kip2) by the Lhx genes, we combined chromatin immunoprecipitation, in silico search for transcription factor-binding motifs, and in vitro reporter assays with putative cis-regulatory elements. The results of these experiments indicated that LHX6 and LHX8 regulated p57(Kip2) via both direct and indirect mechanisms, with the latter mediated by Forkhead box (FOX) family transcription factors. Together, our findings uncovered a novel connection between the initiation of palate development and a cell cycle inhibitor via LHX. We propose a model in which Lhx6 and Lhx8 negatively regulate p57(Kip2) expression in the prospective palate area to allow adequate levels of cell proliferation and thereby promote normal palate development. This is the first report elucidating a molecular genetic pathway downstream of Lhx in palate development.
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010, USA.
authors.forename: Jeffry M
authors.initials: JM
authors.lastname: Cesario
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: Landin Malt
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010, USA.
authors.forename: Lindsay J
authors.initials: LJ
authors.lastname: Deacon
authors.affiliation: Department of Psychiatry, Nina Ireland Laboratory of Developmental Neurobiology, University of California, San Francisco, CA 94158, USA.
authors.forename: Magnus
authors.initials: M
authors.lastname: Sandberg
authors.affiliation: Department of Psychiatry, Nina Ireland Laboratory of Developmental Neurobiology, University of California, San Francisco, CA 94158, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Vogt
authors.affiliation: Center for Health Informatics and Bioinformatics, New York University School of Medicine, New York, NY 10016, USA and.
authors.forename: Zuojian
authors.initials: Z
authors.lastname: Tang
authors.affiliation: Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Yangu
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Center for Health Informatics and Bioinformatics, New York University School of Medicine, New York, NY 10016, USA and.
authors.forename: Stuart
authors.initials: S
authors.lastname: Brown
authors.affiliation: Department of Psychiatry, Nina Ireland Laboratory of Developmental Neurobiology, University of California, San Francisco, CA 94158, USA.
authors.forename: John L
authors.initials: JL
authors.lastname: Rubenstein
authors.affiliation: Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, NY 10010, USA, jj78@nyu.edu.
authors.forename: Juhee
authors.initials: J
authors.lastname: Jeong
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D050761:Cyclin-Dependent Kinase Inhibitor p57 / Q000235:genetics* / Q000378:metabolism; D051858:Forkhead Transcription Factors / Q000235:genetics / Q000378:metabolism; D015870:Gene Expression; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D055106:Genome-Wide Association Study; D005838:Genotype; D006801:Humans; D060850:LIM-Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D008437:Maxilla / Q000196:embryology / Q000378:metabolism; D051379:Mice; D009154:Mutation; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D038081:Organogenesis / Q000235:genetics; D010159:Palate / Q000196:embryology* / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D050761:Cyclin-Dependent Kinase Inhibitor p57; D051858:Forkhead Transcription Factors; C498504:LHX6 protein, mouse; C112960:LIM homeobox protein 8; D060850:LIM-Homeodomain Proteins; D009419:Nerve Tissue Proteins; D012097:Repressor Proteins; D014157:Transcription Factors