title: Fluorosed mouse ameloblasts have increased SATB1 retention and Gαq activity.
abstract: Dental fluorosis is characterized by subsurface hypomineralization and increased porosity of enamel, associated with a delay in the removal of enamel matrix proteins. To investigate the effects of fluoride on ameloblasts, A/J mice were given 50 ppm sodium fluoride in drinking water for four weeks, resulting serum fluoride levels of 4.5 µM, a four-fold increase over control mice with no fluoride added to drinking water. MicroCT analyses showed delayed and incomplete mineralization of fluorosed incisor enamel as compared to control enamel. A microarray analysis of secretory and maturation stage ameloblasts microdissected from control and fluorosed mouse incisors showed that genes clustered with Mmp20 appeared to be less downregulated in maturation stage ameloblasts of fluorosed incisors as compared to control maturation ameloblasts. One of these Mmp20 co-regulated genes was the global chromatin organizer, special AT-rich sequence-binding protein-1 (SATB1). Immunohistochemical analysis showed increased SATB1 protein present in fluorosed ameloblasts compared to controls. In vitro, exposure of human ameloblast-lineage cells to micromolar levels of both NaF and AlF3 led to a significantly increase in SATB1 protein content, but not levels of Satb1 mRNA, suggesting a fluoride-induced mechanism protecting SABT1 from degradation. Consistent with this possibility, we used immunohistochemistry and Western blot to show that fluoride exposed ameloblasts had increased phosphorylated PKCα both in vivo and in vitro. This kinase is known to phosphorylate SATB1, and phosphorylation is known to protect SATB1 from degradation by caspase-6. In addition, production of cellular diacylglycerol (DAG) was significantly increased in fluorosed ameloblasts, suggesting that the increased phosphorylation of SATB1 may be related to an effect of fluoride to enhance Gαq activity of secretory ameloblasts.
authors.affiliation: Department of Orofacial Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Pediatric Dentistry, Dental Research Institute, Pusan National University, Pusan, Korea.
authors.forename: Ji-Yeon
authors.initials: JY
authors.lastname: Kim
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Orapin
authors.initials: O
authors.lastname: Horst
authors.affiliation: Department of Orofacial Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nakano
authors.affiliation: Department of Orofacial Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Li
authors.initials: L
authors.lastname: Zhu
authors.affiliation: Charité - Campus Benjamin Franklin at Freie Universität Berlin, Center for Dental and Craniofacial Sciences, Department of Craniofacial Developmental Biology, Berlin, Germany.
authors.forename: Ralf J
authors.initials: RJ
authors.lastname: Radlanski
authors.affiliation: Department of Preventive and Restorative Dental Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Sunita
authors.initials: S
authors.lastname: Ho
authors.affiliation: Department of Orofacial Sciences, University of California San Francisco, San Francisco, California, United States of America.
authors.forename: Pamela K
authors.initials: PK
authors.lastname: Den Besten
mesh_terms: D000565:Ameloblasts / Q000378:metabolism* / Q000473:pathology; D000566:Amelogenesis / Q000187:drug effects* / Q000235:genetics; D000818:Animals; D053178:Caspase 6 / Q000235:genetics / Q000378:metabolism; D003743:Dental Enamel / Q000378:metabolism / Q000473:pathology; D004075:Diglycerides / Q000378:metabolism; D005260:Female; D009050:Fluorosis, Dental / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000235:genetics* / Q000378:metabolism; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006801:Humans; D007180:Incisor / Q000378:metabolism / Q000473:pathology; D008297:Male; D036961:Matrix Attachment Region Binding Proteins / Q000235:genetics* / Q000378:metabolism; D053519:Matrix Metalloproteinase 20 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D020411:Oligonucleotide Array Sequence Analysis; D010766:Phosphorylation; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D012969:Sodium Fluoride / Q000494:pharmacology*
chemical_list: D004075:Diglycerides; D036961:Matrix Attachment Region Binding Proteins; D012333:RNA, Messenger; C469541:Satb1 protein, mouse; D012969:Sodium Fluoride; D051571:Protein Kinase C-alpha; D053178:Caspase 6; D053519:Matrix Metalloproteinase 20; C507113:Mmp20 protein, mouse; D043802:GTP-Binding Protein alpha Subunits, Gq-G11
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