Localization, quantification, and characterization of tuftelin in soft tissues

Expression of AMELX, AMBN, ENAM, TUFT1, FAM83H and MMP20 Genes in Buccal Epithelial Cells from Patients with Molar Incisor Hypomineralization (MIH)-A Pilot Study

Molar incisor hypomineralization (MIH) is a developmental defect that affects the enamel tissue of permanent teeth. Clinicians may observe a range of opacities in the affected teeth, varying from white to creamy, yellow, and brown. Of particular interest is an etiology of MIH that has not been rigorously elucidated. Researchers believe that there are many potential etiological factors with strong genetic and/or epigenetic influence. The primary factors contributing to the risk of MIH development include specific medical conditions and circumstances. These encompass prematurity, cesarean delivery, perinatal hypoxia, and various health issues such as measles, urinary tract infections, otitis media, gastrointestinal disorders, bronchitis, kidney diseases, pneumonia, and asthma. Although genetic research in this area has received substantial attention, the investigation of epigenetic factors remains comparatively underexplored. Special attention is given to genes and their protein products involved in amelogenesis. Examples of such genes are AMELX, AMBN, ENAM, TUFT1, FAM83H, and MMP20. The median relative FAM83H gene expression in the control group was 0.038 (0.031-0.061) and 0.045 (0.032-0.087) in the study group in buccal swabs. The median relative TUFT1 gene expression in the control group was 0.328 (0.247-0.456) and 0.704 (0.334-1.183) in the study group in buccal swabs. Furthermore, children with MIH had significantly higher TUFT1 expression levels compared to the control group (p-value = 0.0043). Alterations in the expression of the TUFT1 and FAM83H genes could be contributing factors to MIH pathogenesis. Nonetheless, further investigation is essential to comprehensively elucidate the roles of all analyzed genes in the pathogenesis of MIH.

Disruption of TUFT1, a Desmosome-Associated Protein, Causes Skin Fragility, Woolly Hair, and Palmoplantar Keratoderma

Desmosomes are dynamic complex protein structures involved in cellular adhesion. Disruption of these structures by loss-of-function variants in desmosomal genes leads to a variety of skin- and heart-related phenotypes. In this study, we report TUFT1 as a desmosome-associated protein, implicated in epidermal integrity. In two siblings with mild skin fragility, woolly hair, and mild palmoplantar keratoderma but without a cardiac phenotype, we identified a homozygous splice-site variant in the TUFT1 gene, leading to aberrant mRNA splicing and loss of TUFT1 protein. Patients' skin and keratinocytes showed acantholysis, perinuclear retraction of intermediate filaments, and reduced mechanical stress resistance. Immunolabeling and transfection studies showed that TUFT1 is positioned within the desmosome and that its location is dependent on the presence of the desmoplakin carboxy-terminal tail. A Tuft1-knockout mouse model mimicked the patients' phenotypes. Altogether, this study reveals TUFT1 as a desmosome-associated protein, whose absence causes skin fragility, woolly hair, and palmoplantar keratoderma.

In silico screening of non-synonymous SNPs in human TUFT1 gene

BACKGROUND

Tuftelin 1 (TUFT1) gene is important in the development and mineralization of dental enamel. The study aimed to identify potential functionally deleterious non-synonymous SNPs (nsSNPs) in the TUFT1 gene by using different in silico tools. The deleterious missense SNPs were identified from SIFT, PolyPhen-2, PROVEAN, SNPs & GO, PANTHER, and SNAP2. The stabilization, conservation, and three-dimensional modeling of mutant proteins were analyzed by I-Mutant 3.0, Consurf, and Project HOPE, respectively. The protein-protein interaction using STRING, GeneMANIA for gene-gene interaction, and DynaMut for evaluating the impact of the mutation on protein stability, conformation, and flexibility.

RESULTS

Eight deleterious nsSNPs (E242A, R303W, K182N, K123N, R117W, H289Q, R203W, and Q107R) out of 304 were found to have high-risk damaging effects using six in silico tools. Among them, K182N and K123N alone had increased stability, whereas E242A, R303W, R117W, H289Q, Q107R, and R203W exhibited a decrease in protein stability, based on DDG values. Meanwhile, all the eight deleterious nsSNPs altered the size, charge, hydrophobicity, and spatial organization of the amino acids and predominantly had alpha helix domains. These deleterious variants were located in highly conserved regions except R203W. Protein-protein interaction predicted that TUFT1 interacted with ten proteins that are involved in enamel mineralization and odontogenesis. Gene-gene interaction network showed that TUFT1 is involved in physical interactions, gene co-localization, and pathway interactions. DynaMut ΔΔG values predicted that five nsSNPs were destabilizing the protein, ΔΔG ENCoM values showed a destabilizing effect for all mutants, and seven nsSNPs increased the molecular flexibility of TUFT1.

CONCLUSION

Our study predicted eight functional SNPs that had detrimental effects on the structure and function of the TUFT1 gene. This will aid in the development of candidate deleterious markers as a potential target for disease diagnosis and therapeutic interventions.

SUMOylation of TUFT1 is essential for gastric cancer progression through AKT/mTOR signaling pathway activation

Tuftelin (TUFT1) is highly expressed in various tumor types and promotes tumor growth and metastasis by activating AKT and other core signaling pathways. However, the effects of post-translational modifications of TUFT1 on its oncogenic function remain unexplored. In this study, we found that TUFT1 was SUMOylated at K79. SUMOylation deficiency significantly impaired the ability of TUFT1 to promote the proliferation, migration, and invasion of gastric cancer (GC) cells by blocking AKT/mTOR signaling pathway activation. SUMOylation of TUFT1 is mediated by the E3 SUMO ligase tripartite motif-containing protein 27 (TRIM27), and these two proteins regulate the malignant behavior of GC cells and AKT activation in the same pathway. TUFT1 binds to TRIM27 through its N-terminus, and decreased binding affinity of TUFT1 to TRIM27 significantly impairs its oncogenic effect. In addition, data collected from GC clinical samples indicated that the combined detection of TUFT1 and TRIM27 expression reflected tumor malignancy and patient survival with higher precision. In addition, we proved that SUMOylated TUFT1 is not only an upstream signal for AKT activation but also directly activates mTOR by forming a complex with Rab GTPase activating protein 1, which further inhibits Rab GTPases and promotes the perinuclear accumulation of mTORC1. Altogether, these data indicate that SUMOylated TUFT1 is the active form that affects GC progression through the AKT/mTOR signaling pathway and might be a promising therapeutic target or biomarker for GC progression.

Hepatocellular Carcinoma in Non-Alcoholic Fatty Liver Disease: From Epidemiology to Diagnostic Approach

Non-alcoholic fatty liver disease (NAFLD) is becoming the leading cause of liver morbidity worldwide and, as such, represents the pathogenic background for the increasing incidence of hepatocellular carcinoma (HCC). The annual incidence of NAFLD-related HCC is expected to increase by 45-130% by 2030. Diabetes mellitus is the most important risk factor for HCC development in NAFLD, with the risk further increased when associated with other metabolic traits, such as obesity, arterial hypertension and dyslipidemia. The highest risk of HCC exists in patients with advanced fibrosis or cirrhosis, although 20-50% of HCC cases arise in NAFLD patients with an absence of cirrhosis. This calls for further investigation of the pathogenic mechanisms that are involved in hepatocarcinogenesis, including genetics, metabolomics, the influence of the gut microbiota and immunological responses. Early identification of patients with or at risk of NAFLD is of utmost importance to improve outcomes. As NAFLD is highly prevalent in the community, the identification of cases should rely upon simple demographic and clinical characteristics. Once identified, these patients should then be evaluated for the presence of advanced fibrosis or cirrhosis and subsequently enter HCC surveillance programs if appropriate. A significant problem is the early recognition of non-cirrhotic NAFLD patients who will develop HCC, where new biomarkers and scores are potential solutions to tackle this issue.

Tuftelin 1 (TUFT1) Promotes the Proliferation and Migration of Renal Cell Carcinoma via PI3K/AKT Signaling Pathway

Tuftelin 1 (TUFT1), a protein functioning distinctively in different tissues, is reported to be elevated in several types of cancers and the elevation of TUFT1 is correlated with unfavorable clinicopathologic characteristics and poor survival. However, the involvement of TUFT1 in renal cell carcinoma (RCC) remains unknown. In the current study, we investigated the role of TUFT1 in RCC and potential underlying mechanisms. RT-PCR and Western blot analysis showed that both the mRNA and protein levels of TUFT1 were increased in primary RCC tissue and RCC cell lines. TUFT1 overexpression in RCC cells resulted in enhanced cell proliferation and migration while knockdown of TUFT1 by contrast decreased the growth and migration of the RCC cells, indicating TUFT1 expression is involved in RCC cell growth and migration. The involvement of TUFT1 in the epithelial-mesenchymal transition (EMT) of RCC cells was also determined by measuring the expression of EMT-related markers. Our data showed that TUFT1 overexpression promoted RCC cell EMT progression while knockdown of TUFT1 suppressed such process. Further signaling pathway inhibition assay revealed that TUFT1-induced RCC cell growth, migration and EMT was significantly suppressed by PI3K inhibitor, but not JNK or MEK inhibitors. In addition, TUFT1 overexpression enhanced the AKT phosphorylation, a key member of the PI3K signaling pathway, while PI3K inhibitor suppressed such process. Taken together, our study showed that TUFT1 expression was elevated in RCC and such elevation promoted the proliferation, migration and EMT of RCC cells in vitro, through PI3K/AKT signaling pathway. The findings of our current study imply that TUFT1 is involved in RCC tumorigenesis, and it may serve as a biomarker for RCC diagnosis and a potential target for RCC treatment.

Boron as Boric Acid Induces mRNA Expression of the Differentiation Factor Tuftelin in Pre-Osteoblastic MC3T3-E1 Cells

The effects of boron on the formation and maintenance of mineralized structures at the molecular level are still not clearly defined. Thus, a study was conducted using MC3T3-E1 cells to determine whether boron affected mRNA expressions of genes associated with bone/alveolar bone formation around the teethMC3T3-E1 (clone 4) cells were cultured in media treated with boric acid at concentrations of 0, 0.1, 10, 100, or 1000 ng/ml. Total RNAs of each group were isolated on day 3. Gene expression profiles were determined by using RT² Profiler PCR micro-array that included 84 genes associated with osteogenic differentiation. Tuftelin1 mRNA expression was upregulated by all boron treatments. The upregulation was confirmed by quantitative RT-PCR using the tuftelin probe. While 100 ng/ml had no effect on the integrin-α2 (Itga2) transcript and 1 ng/ml boric acid induced Itga2 mRNA expression (2.1-fold), 0.1, 10, and 1000 ng/ml boric acid downregulated the integrin-α2 gene transcript 2.2-, 1.5-, and 2.1-fold respectively. While 0.1 ng/ml boric acid induced BMP6, increased BMP1r mRNA expression (1.5 fold) was observed in 1000 ng/ml boric acid treatment. The findings suggest that boron affects the regulation of the tuftelin1 gene in osteoblastic cells. Further studies are needed to establish that the beneficial actions of boron on alveolar bone and tooth formation and maintenance include an effect on the expression of the tuftelin1 gene.

LncRNA DANCR upregulation induced by TUFT1 promotes malignant progression in triple negative breast cancer via miR-874-3p-SOX2 axis

Triple negative breast cancer (TNBC) is a subtype of breast cancer with poorest survival outcome and is prone to metastasis. TUFT1 and the long non-coding RNA (lncRNA), DANCR, play vital roles in metastasis and progression of various cancers. However, the correlation between TUFT1 and DANCR in TNBC and their downstream molecular mechanisms are still undetermined. We demonstrated that upregulation of TUFT1 in TNBC was related to a worse survival in TNBC patients. The TNBC cells invasiveness was augmented by TUFT1 in a dose-dependent manner, while inhibiting TUFT1 repressed the invasiveness. Particularly, the expression of TUFT1 was positively correlated with the expression of DANCR in TNBC tissues. In addition, TUFT1 increased DANCR expression, while silencing DANCR ameliorated the invasiveness of TNBC cells induced by TUFT1. As demonstrated, TUFT1 interacted with miR-874-3p. Subsequently, qRT-PCR together with luciferase reporter further demonstrated that DANCR acted as competing endogenous (ceRNA) for miR-874-3p, thereby regulating the de-repression of SOX2 and advancing epithelial-mesenchymal transition (EMT) in TNBC. The present research shows that TUFT1 promotes the malignant development in TNBC via enhancing the expression of DANCR. The upregulation of DANCR may contribute to the progression and tumor invasiveness of TNBC, considering that DANCR functions as a miR-874-3p sponge, thus modulating SOX2 positively. Collectively, the present study explored the molecular mechanism underlying TUFT1 in TNBC, raising a TUFT1-mediated therapy for the treatment of patients with TNBC.

Tuftelin and HIFs expression in osteogenesis

Tuftelin was originally discovered and mostly studied in the tooth, but later found also in other organs. Despite its wide distribution among tissues, tuftelin's function has so far been specified only in the formation of enamel crystals. Nevertheless, in many cases, tuftelin was suggested to be associated with cellular adaptation to hypoxia and recently even with cell differentiation. Therefore, we aimed to investigate tuftelin expression along with hypoxia-inducible factors (HIFs) during the early development of the mandibular/alveolar (m/a) bone, when osteoblasts started to differentiate in vivo and to compare their expression levels in undifferentiated versus differentiated osteoblastic cells in vitro. Immunohistochemistry demonstrated the presence of tuftelin already in osteoblastic precursors which were also HIF1-positive, but HIF2-negative. Nevertheless, HIF2 protein appeared when osteoblasts differentiated, one day later. This is in agreement with observations made with MC3T3-E1 cells, where there was no significant difference in tuftelin and Hif1 expression in undifferentiated vs. differentiated cells, although Hif2 increased upon differentiation induction. In differentiated osteoblasts of the m/a bone, all three proteins accumulated, first, prenatally, in the cytoplasm and later, particularly at postnatal stages, they displayed also peri/nuclear localization. Such a dynamic time-space pattern of tuftelin expression has recently been reported in neurons, which, as the m/a bone, differentiate under less hypoxic conditions as indicated also by a prevalent cytoplasmic expression of HIF1 in osteoblasts. However, unlike what was shown in cultured neurons, tuftelin does not seem to participate in final osteoblastic differentiation and its functions, thus, appears to be tissue specific.

Tuftelin's involvement in embryonic development

Little is known about tuftelin expression in the developing embryo, previously it was thought to play a role in tooth enamel mineralization. In this study we show tuftelin's spatio-temporal expression in mineralizing and nonmineralizing tissues of the craniofacial complex in the developing mouse embryo. Embryos aged E10.5-E18.5 and newborns aged P3 were used in this study. Polymerase chain reaction (PCR), Real-time PCR, sequencing, and in-situ hybridization were used to detect and quantify messenger RNA (mRNA) expression in different developmental stages. We applied indirect immunohistochemistry and western-blot analyses to investigate protein expression. Two tuftelin mRNA transcripts and a single 64KDa protein were detected throughout embryonic development. Tuftelin was detected in tissues which develop from different embryonic origins; ectoderm, ectomesenchyme, and mesoderm. Tuftelin mRNA and protein were expressed already at E10.5, before the initiation of tooth formation and earlier than previously described. The expression pattern of tuftelin mRNA and protein exhibits dynamic spatio-temporal changes in various tissues. Tuftelin is expressed in neuronal tissues, thus fitting with its described correlation to nerve growth factor. A shift between cytoplasmatic and perinuclear/nuclear expression implies a possible role in regulation of transcription. Recent studies showed tuftelin is induced under hypoxic conditions in-vitro and in-vivo, through the hypoxia-inducible factor 1-α pathway. These results led to the hypothesis that tuftelin is involved in adaptation to hypoxic conditions. The fact that much of mammalian embryogenesis occurs at O ₂ concentrations of 1-5%, raises the possibility that tuftelin expression throughout development is due to its role in the adaptive mechanisms in response to hypoxia.

Recent Insight into the Role of Fibrosis in Nonalcoholic Steatohepatitis-Related Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most widespread tumors in the world and its prognosis is poor because of lack of effective treatments. Epidemiological studies show that non-alcoholic steatohepatitis (NASH) and advanced fibrosis represent a relevant risk factors to the HCC development. However little is known of pathophysiological mechanisms linking liver fibrogenesis to HCC in NASH. Recent advances in scientific research allowed to discover some mechanisms that may represent potential therapeutic targets. These include the integrin signaling, hepatic stellate cells (HSCs) activation, Hedgehog signaling and alteration of immune system. In the near future, knowledge of fibrosis-dependent carcinogenic mechanisms, will help optimize antifibrotic therapies as an approach to prevent and treat HCC in patients with NASH and advanced fibrosis.

Tuftelin Is Required for NGF-Induced Differentiation of PC12 Cells

Nerve growth factor (NGF) promotes pleiotropic gene transcription-dependent biological effects, in neuronal and non-neuronal cells, including survival, proliferation, differentiation, neuroprotection, pain, and angiogenesis. It is hypothesized that during odontogenesis, NGF may be implicated in morphogenetic and mineralization events by affecting proliferation and/or differentiation of dental cells. Tuftelin belongs to the enamel associated teeth proteins and is thought to play a role in enamel mineralization. We previously reported that tuftelin transcript and protein, which are ubiquitously expressed in various tissues of embryos, adults, and tumors, were significantly upregulated during NGF-induced PC12 differentiation. To further confirm the involvement of tuftelin in the differentiation process, we established a tuftelin-knockdown neuronal PC12 cell model, using a non-cytotoxic siRNA directed towards sequences at the 3' UTR of the tuftelin gene. Using real-time PCR, we quantified tuftelin mRNA expression and found that tuftelin siRNA, but not scrambled siRNA or transfection reagents, efficiently depleted about 60% of NGF-induced tuftelin mRNA transcripts. The effect of tuftelin siRNA was quantified up to 6 days of NGF-induced differentiation. Using immunofluorescence and western blot analyses, we also found a direct correlation between reduction of 60-80% in tuftelin protein expression and inhibition of about 50-70% in NGF-induced differentiation of the cells, as was detected after 3-6 days of treatment. These results demonstrate an important role for tuftelin in NGF-induced differentiation of PC12 cells. Tuftelin could be a useful target for drug development in disease where neurotrophin therapy is required.

Hypoxia-induced TUFT1 promotes the growth and metastasis of hepatocellular carcinoma by activating the Ca2+/PI3K/AKT pathway

Tuftelin1 (TUFT1), an acidic protein constituent of developing and mineralizing tooth tissues, is regulated by hypoxia and the Hedgehog signaling pathway. We investigated the role of TUFT1 in hepatocellular carcinoma (HCC). qRT-PCR, immunohistochemistry and western blot were employed to evaluate TUFT1 level in HCC. MTT, BrdU, 3D culture and Transwell assays were used to assess cell viability, proliferation, in vitro growth, migration, and invasion. Subcutaneous and tail vein injection models were established to investigate in vivo growth and metastasis. Chromatin immunoprecipitation was performed to assess binding of hypoxia-inducible factor 1α (HIF-1α) to TUFT1 promoter. A microRNA array was used to identify hypoxia-related microRNAs. TUFT1 was elevated in HCC, and correlated with unfavorable clinicopathologic characteristics and poor survival. TUFT1 promoted HCC cell growth, metastasis and epithelial-mesenchymal transition in vitro and in vivo via activation of Ca²⁺/PI3K/AKT pathway. Hypoxia induced TUFT1 expression in an HIF-1α dependent manner, and TUFT1 expression was positively correlated with HIF-1α level in HCC tissues. Hypoxiaenhanced TUFT1 expression by downregulating miR-671-5p rather than by directly promoting the binding of HIF-1α to TUFT1 promoter. MiR-671-5p interacted with the 3'-UTR of TUFT1 mRNA and subsequently inhibited TUFT1 expression. Consequently, knockdown of TUFT1 blocked the effects of hypoxia in promoting HCC progression. TUFT1 promoted the growth, metastasis and EMT of HCC cells through activating Ca²⁺/PI3K/AKT pathway. The hypoxic microenvironment increased the expression of TUFT1 via downregulation of miR-671-5p. TUFT1 may function as a potential therapeutic target for the intervention and treatment of HCC.

TUFT1 interacts with RABGAP1 and regulates mTORC1 signaling

The mammalian target of rapamycin (mTOR) pathway is commonly activated in human cancers. The activity of mTOR complex 1 (mTORC1) signaling is supported by the intracellular positioning of cellular compartments and vesicle trafficking, regulated by Rab GTPases. Here we showed that tuftelin 1 (TUFT1) was involved in the activation of mTORC1 through modulating the Rab GTPase-regulated process. TUFT1 promoted tumor growth and metastasis. Consistently, the expression of TUFT1 correlated with poor prognosis in lung, breast and gastric cancers. Mechanistically, TUFT1 physically interacted with RABGAP1, thereby modulating intracellular lysosomal positioning and vesicular trafficking, and promoted mTORC1 signaling. In addition, expression of TUFT1 predicted sensitivity to perifosine, an alkylphospholipid that alters the composition of lipid rafts. Perifosine treatment altered the positioning and trafficking of cellular compartments to inhibit mTORC1. Our observations indicate that TUFT1 is a key regulator of the mTORC1 pathway and suggest that it is a promising therapeutic target or a biomarker for tumor progression.

TUFT1 is expressed in breast cancer and involved in cancer cell proliferation and survival

Tuftelin 1 (TUFT1), which plays an important role in the initial stages of the mineralization of ectodermal enamel, is widely expressed in different embryonic and adult tissues and some tumor cells. However, since the roles of this gene have not been thoroughly investigated in tumors, its function in the development of breast cancer remains unclear. We proved both human specimens studies and cell line studies, that TUFT1 expression levels are increased in breast cancer samples, and the increased expression of TUFT1 was shown to be positively correlated with tumor size, histological grade, lymph node metastasis rate, and poor prognosis. Further in vitro studies showed that the inhibition of TUFT1 expression in T-47D and MDA-MB-231 breast cancer cells significantly affected cell proliferation, induced apoptosis, and led to G1-phase cell cycle arrest. Moreover, reduced TUFT1 expression restrained tumor growth compared with the control group in vivo. Furthermore, microarray and pathway analysis demonstrated that TUFT1 inhibition led to significant changes of several signaling pathways and semi-quantitative western blot analysis showed that a decrease in TUFT1 expression was accompanied by changes in MAPK signaling pathway components. The obtained results suggest that TUFT1 may represent a novel breast cancer marker and a potentially effective therapeutic target.

Evolutionary Analysis of the Mammalian Tuftelin Sequence Reveals Features of Functional Importance

Tuftelin (TUFT1) is an acidic, phosphorylated glycoprotein, initially discovered in developing enamel matrix. TUFT1 is expressed in many mineralized and non-mineralized tissues. We performed an evolutionary analysis of 82 mammalian TUFT1 sequences to identify residues and motifs that were conserved during 220 million years (Ma) of evolution. We showed that 168 residues (out of the 390 residues composing the human TUFT1 sequence) are under purifying selection. Our analyses identified several, new, putatively functional domains and confirmed previously described functional domains, such as the TIP39 interaction domain, which correlates with nuclear localization of the TUFT1 protein, that was demonstrated in several tissues. We also identified several sites under positive selection, which could indicate evolutionary changes possibly related to the functional diversification of TUFT1 during evolution in some lineages. We discovered that TUFT1 and MYZAP (myocardial zonula adherens protein) share a common ancestor that was duplicated circa 500 million years ago. Taken together, these findings expand our knowledge of TUFT1 evolution and provide new information that will be useful for further investigation of TUFT1 functions.

Toward a systems level view of the ECM and related proteins: a framework for the systematic definition and analysis of biological systems

Advances in high throughput 'omic technologies are starting to provide unprecedented insights into how components of biological systems are organized and interact. Key to exploiting these datasets is the definition of the components that comprise the system of interest. Although a variety of knowledge bases exist that capture such information, a major challenge is determining how these resources may be best utilized. Here we present a systematic curation strategy to define a systems-level view of the human extracellular matrix (ECM)--a three-dimensional meshwork of proteins and polysaccharides that impart structure and mechanical stability to tissues. Employing our curation strategy we define a set of 357 proteins that represent core components of the ECM, together with an additional 524 genes that mediate related functional roles, and construct a map of their physical interactions. Topological properties help identify modules of functionally related proteins, including those involved in cell adhesion, bone formation and blood clotting. Because of its major role in cell adhesion, proliferation and morphogenesis, defects in the ECM have been implicated in cancer, atherosclerosis, asthma, fibrosis, and arthritis. We use MeSH annotations to identify modules enriched for specific disease terms that aid to strengthen existing as well as predict novel gene-disease associations. Mapping expression and conservation data onto the network reveal modules evolved in parallel to convey tissue-specific functionality on otherwise broadly expressed units. In addition to demonstrating an effective workflow for defining biological systems, this study crystallizes our current knowledge surrounding the organization of the ECM.

Current knowledge of tooth development: patterning and mineralization of the murine dentition

The integument forms a number of different types of mineralized element, including dermal denticles, scutes, ganoid scales, elasmoid scales, fin rays and osteoderms found in certain fish, reptiles, amphibians and xenarthran mammals. To this list can be added teeth, which are far more widely represented and studied than any of the other mineralized elements mentioned above, and as such can be thought of as a model mineralized system. In recent years the focus for studies on tooth development has been the mouse, with a wealth of genetic information accrued and the availability of cutting edge techniques. It is the mouse dentition that this review will concentrate on. The development of the tooth will be followed, looking at what controls the shape of the tooth and how signals from the mesenchyme and epithelium interact to lead to formation of a molar or incisor. The number of teeth generated will then be investigated, looking at how tooth germ number can be reduced or increased by apoptosis, fusion of tooth germs, creation of new tooth germs, and the generation of additional teeth from existing tooth germs. The development of mineralized tissue will then be detailed, looking at how the asymmetrical deposition of enamel is controlled in the mouse incisor. The continued importance of epithelial-mesenchymal interactions at these later stages of tooth development will also be discussed. Tooth anomalies and human disorders have been well covered by recent reviews, therefore in this paper we wish to present a classical review of current knowledge of tooth development, fitting together data from a large number of recent research papers to draw general conclusions about tooth development.

High yield expression of biologically active recombinant full length human tuftelin protein in baculovirus-infected insect cells

Tuftelin is an acidic protein expressed at very early stages of mouse odontogenesis. It was suggested to play a role during epithelial-mesenchymal interactions, and later, when enamel formation commences, to be involved in enamel mineralization. Tuftelin was also detected in several normal soft tissues of different origins and some of their corresponding cancerous tissues. Tuftelin is expressed in low quantities, and undergoes degradation in the enamel extracellular matrix. To investigate the structure and function of tuftelin, the full length recombinant human tuftelin protein was produced. The full length human tuftelin cDNA was cloned using Gateway recombination into the Bac-to-Bac system compatible transfer vector pDest10. This vector adds a hexahistidine tag to the N-terminus of the expressed protein, enabling one-step affinity purification on nickel column. The recombinant human tuftelin protein was transposed into the bacmid and expressed in Spodoptera frugiperda (Sf9) insect cells. The yield of the purified, his-tagged recombinant full length human Tuftelin (rHTuft+) was 5-8 mg/L culture. rHTuft+ was characterized by SDS-PAGE, Western blot, ESI-TOF spectrometry, restriction mapping and MS/MS sequencing. The availability of the purified, full length recombinant human tuftelin protein opened up the possibility to investigate novel functions of tuftelin. Application of rHTuft+ agarose beads onto embryonic mouse mandibular explants caused changes in the surrounding epithelial cells, including morphology, orientation and spatial organization. Further studies using DiI labeling, revealed that rHTuft+, placed on the tooth germ region, brought about recruitment of adjacent embryonic mesenchymal cells. These findings support the hypothesis that tuftelin plays an important role during embryogenesis.

Type XVII collagen is a key player in tooth enamel formation

Inherited tooth enamel hypoplasia occurs due to mutations in genes that encode major enamel components. Enamel hypoplasia also has been reported in junctional epidermolysis bullosa, caused by mutations in the genes that encode type XVII collagen (COL17), a component of the epithelial-mesenchymal junction. To elucidate the pathological mechanisms of the enamel hypoplasia that arise from the deficiency of epithelial-mesenchymal junction molecules, such as COL17, we investigated tooth formation in our recently established Col17(-/-) and Col17 rescued mice. Compared with wild-type mice, the incisors of the Col17(-/-) mice exhibited reduced yellow pigmentation, diminished iron deposition, delayed calcification, and markedly irregular enamel prisms, indicating the presence of enamel hypoplasia. The molars of the Col17(-/-) mice demonstrated advanced occlusal wear. These abnormalities were corrected in the Col17 rescued humanized mice. Thus, the Col17(-/-) mice clearly reproduced the enamel hypoplasia in human patients with junctional epidermolysis bullosa. We were able to investigate tooth formation in the Col17(-/-) mice because the Col17(-/-) genotype is not lethal. Col17(-/-) mouse incisors had poorly differentiated ameloblasts that lacked enamel protein-secreting Tomes' processes and reduced mRNA expression of amelogenin, ameloblastin, and of other enamel genes. These findings indicated that COL17 regulates ameloblast differentiation and is essential for normal formation of Tomes' processes. In conclusion, COL17 deficiency disrupts the epithelial-mesenchymal interactions, leading to both defective ameloblast differentiation and enamel malformation.