TM14 is a new member of the fibulin family (fibulin-7) that interacts with extracellular matrix molecules and is active for cell binding.
We identified a new extracellular protein, TM14, by differential hybridization using mouse tooth germ cDNA microarrays. TM14 cDNA encodes 440 amino acids containing a signal peptide. The protein contains 3 EGF modules at the center, a C-terminal domain homologous to the fibulin module, and a unique Sushi domain at the N terminus. In situ hybridization revealed that TM14 mRNA was expressed by preodontoblasts and odontoblasts in developing teeth. TM14 mRNA was also expressed in cartilage, hair follicles, and extraembryonic tissues of the placenta. Immunostaining revealed that TM14 was localized at the apical pericellular regions of preodontoblasts. When the dentin matrix was fully formed and dentin mineralization occurred, TM14 was present in the predentin matrix and along the dentinal tubules. We found that the recombinant TM14 protein was glycosylated with N-linked oligosaccharides and interacted with heparin, fibronectin, fibulin-1, and dentin sialophosphoprotein. We also found that TM14 preferentially bound dental mesenchyme cells and odontoblasts but not dental epithelial cells or nondental cells such as HeLa, COS7, or NIH3T3 cells. Heparin, EDTA, and anti-integrin beta1 antibody inhibited TM14 binding to dental mesenchyme cells, suggesting that both a heparan sulfate-containing cell surface receptor and an integrin are involved in TM14 cell binding. Our findings indicate that TM14 is a cell adhesion molecule that interacts with extracellular matrix molecules in teeth and suggest that TM14 plays important roles in both the differentiation and maintenance of odontoblasts as well as in dentin formation. Because of its protein characteristics, TM14 can be classified as a new member of the fibulin family: fibulin-7.
de Vega
Susana
S
Laboratory of Cell and Developmental Biology, NIDCR, National Institutes of Health, Bethesda, Maryland 20892-4370, USA.
Iwamoto
Tsutomu
T
Nakamura
Takashi
T
Hozumi
Kentaro
K
McKnight
Dianalee A
DA
Fisher
Larry W
LW
Fukumoto
Satoshi
S
Yamada
Yoshihiko
Y
D000818:Animals; D019556:COS Cells; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D002522:Chlorocebus aethiops; D018076:DNA, Complementary / Q000235:genetics / Q000378:metabolism; D003804:Dentin / Q000196:embryology / Q000378:metabolism*; D005109:Extracellular Matrix / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D006031:Glycosylation; D006367:HeLa Cells; D006801:Humans; D017403:In Situ Hybridization; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D005810:Multigene Family / Q000502:physiology; D041681:NIH 3T3 Cells; D009804:Odontoblasts / Q000166:cytology / Q000378:metabolism*; D009928:Organ Specificity / Q000502:physiology; D046188:Protein Modification, Translational / Q000502:physiology*; D021382:Protein Sorting Signals / Q000502:physiology; D017434:Protein Structure, Tertiary / Q000502:physiology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014070:Tooth / Q000166:cytology / Q000196:embryology / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D018076:DNA, Complementary; C524759:FBLN7 protein, human; D019012:Integrin beta1; D021382:Protein Sorting Signals; D012333:RNA, Messenger; D011994:Recombinant Proteins; C060820:fibulin