Biomedical subjects

Satoru Toyosawa

Publications and source records attributed to Satoru Toyosawa.

11 recordsLinked to original sources

PubMed2006

Identification and characterization of matrix metalloproteinase-20 (MMP20; enamelysin) genes in reptile and amphibian.

Matrix metalloproteinase-20 (MMP20; enamelysin) is important for proteolytic processing of extracellular matrix (ECM) proteins during the formation of enamel and plays a critical role in proteolytic processing of amelogenin (AMEL), the most abundant enamel ECM protein. MMP20 might have played a role in the emergence of teeth, because jawless vertebrates with primordial teeth on their external skeletons may have possessed the MMP20 gene, and MMP20 and enamel ECM proteins are thought to have evolved together in a special relationship over time. Thus, an understanding of the molecular evolution of the MMP20 gene is important for elucidating the evolution of enamel and it is necessary to identify the orthologs of the MMP20 gene in non-mammals, as it has been identified in mammals. In the present study, orthologs of the MMP20 genes from a reptile (caiman) and an amphibian (African clawed toad) were cloned and characterized. Comparisons of the orthologs revealed that the MMP20 proteins were highly conserved throughout the evolution of tetrapods. Further, the caiman, toad, and mammalian MMP20 shared several unique features specific for MMP20, but not for other matrix metalloproteinases. In addition, the toad MMP20 gene was transcribed only in the upper jaw, presumably in teeth. These results suggest that MMP20 in a common ancestor of tetrapods might have been recruited for the processing of AMEL and conserved over 350 million years of evolution.

Alligators and Crocodiles↗

PubMed2006

Cbf beta regulates Runx2 function isoform-dependently in postnatal bone development.

Runx2 and Cbfbeta are essential for skeletal development during the embryonic stage. Runx2 has two isoforms with different N-termini. We examined the functions of the Runx2 isoforms and Cbfbeta in postnatal bone development. On luciferase and electrophoretic mobility shift assays, Runx2-I was less active than Runx2-II in the absence of Cbfb, but the two Runx2 isoforms had similar activity levels in the presence of Cbfb. We generated Runx2-I transgenic mice under the control of Col1a1 promoter and Runx2-I/Cbfb and Runx2-II/Cbfb double transgenic mice. Runx2-I transgenic mice showed less severe osteopenia and fragility than Runx2-II transgenic mice due to milder inhibition of both osteoblast maturation and transition to osteocytes, even though the former mice showed higher transgene expression. However, Runx2-I/Cbfb and Runx2-II/Cbfb double transgenic mice had enhanced inhibition of osteoblast maturation, resulting in similar severity of osteopenia and fragility, although the latter mice had less osteocytes. These findings indicate that (1) Runx2-II more strongly inhibits osteoblast maturation and transition to osteocytes than Runx2-I; (2) Cbfbeta regulates Runx2 function isoform-dependently; and (3) Runx2-I activity is highly dependent on Cbfbeta. These findings demonstrate that Runx2 isoforms exert their functions through at least partly different mechanisms and Cbfbeta regulates bone development by regulating Runx2 function isoform-dependently.

Animals↗

PubMed2006

Expression of ameloblastin during enamel formation in a crocodile.

Ameloblastin is an enamel-specific protein that plays critical roles in enamel formation, as well as adhesion between ameloblasts and the enamel matrix, as shown by analyses of ameloblastin-null mice. In the present study, we produced two distinct antibodies that recognize the N-terminus and C-terminus regions of caiman ameloblastin, in order to elucidate the fate of ameloblastin peptides during tooth development. An immunohistochemical study using the antibodies showed that caiman ameloblastin was a tooth-specific matrix protein that may initially be cleaved into two groups, N- and C-terminal peptides, as shown in mammals. The distribution of the N-terminal peptides was much different from that of the C-terminal peptides during enamel formation; however, it was similar to that of mammalian ameloblastin. Although ameloblastin is thought to have a relationship with the enamel prismatic structure in mammals, in the caiman, which has non-prismatic enamel, functional ameloblastin has no relationship with any enamel structure. Consequently, it is suggested that ameloblastin has kept its original functions during the evolutionary transition from reptiles to mammals and that it has been conserved in both lineages during more than 200 million years of evolution. Our results support the notion that ameloblastin acts as a factor for ameloblast adhesion to enamel matrix, because distribution of the C-terminal peptides was consistently restricted on the surface layers of enamel matrix specimens ranging from immature to nearly completely mature. The principal molecules that provide the adhesive function are presumably C-terminal peptides.

Alligators and Crocodiles↗

PubMed2006

Multiple osseous dysplasia arising from impacted teeth: report of a case associated with odontogenic lesions.

We report a case of osseous dysplasia (OD) showing extremely rare clinical features. A 37-year-old Japanese woman was referred to our clinic complaining of a left alveolar bony swelling at an impacted canine. Radiographic examinations revealed a mixed radiopaque lesion involving the impacted left canine and also revealed an impacted left wisdom tooth with a cystic change and a clear radiopaque lesion suspected to be odontoma. All the extracted upper teeth and odontoma showed hypercementosis and the canine was fully involved in it. Histopathologically, they showed the same features and were diagnosed as OD. The findings of multiple OD from incompletely erupted teeth and odontoma in our case may well show that OD can arise from any tooth with periodontal ligaments and that focal OD can show expansive growth like the ossifying fibroma.

Adult↗

PubMed2005

Benign fibrous histiocytoma of the mandible.

A very rare case of benign fibrous histiocytoma of the mandible is presented. A 49-year-old woman was admitted because of left buccal swelling and pain. Panoramic radiograph showed well-demarcated soap-bubble appearance without sclerotic rim in the left mandibular bone. A yellowish-white and partly brown solid tumor was noted in the excised mandibular bone specimen. The tumor histologically consisted of spindle cells, in which areas showing a storiform pattern and other areas composed of histiocytic cells with erythrophagocytosis and foam cells were mixed. Immunohistochemically, the tumor cells were positive for vimentin, CD68, alpha-1-antichymotrypsin and alpha-1-antitrypsin. From these findings the tumor was diagnosed as a primary BFH of the mandible. No recurrence has been noted 2 years and 11 months after surgery.

Antigens, CD↗

PubMed2004

Expression of dentin matrix protein 1 in tumors causing oncogenic osteomalacia.

Oncogenic osteomalacia, which is characterized by renal phosphate wasting, low serum 1, 25-dihydroxyvitamin D, and osteomalacia, is caused by mesenchymal neoplasms that are termed phosphaturic mesenchymal tumors (PMTs). As PMTs are usually small and lack specific histological features, the pathological identification of PMTs is difficult. Dentin matrix protein 1 (DMP1) is an acidic phosphoprotein expressed in mineralized tissues including bone, tooth, and hypertrophic cartilage. Increased expression of DMP1 gene in PMTs has been reported by using differential cDNA screening. In the present study, DMP1 expression in PMTs and other soft tissue tumors was analyzed immunohistochemically to verify its utility in the differential diagnosis of PMTs. Anti-DMP1 polyclonal antibody was raised against the C-terminal sequence of DMP1. Three cases with PMTs and 11 other soft tissue tumors (two malignant hemangiopericytomas, three solitary fibrous tumors, three synovial sarcomas, and three malignant peripheral nerve sheath tumors) were analyzed for DMP1 expression. DMP1 expression was observed in all of the three cases with PMTs, but never found in other soft tissue tumors examined. DMP1 was detected in the extracellular matrix with myxomatous features or around capillary vessels, and in dystrophic calcified sites. Paranuclear DMP1 staining in the tumor cells was also observed. These findings indicate that DMP1 immunohistochemistry is a useful tool for identifying PMTs.

Adult↗

PubMed2004

Eccentric localization of osteocytes expressing enzymatic activities, protein, and mRNA signals for type 5 tartrate-resistant acid phosphatase (TRAP).

Enzymatic activity of type 5 tartrate-resistant acid phosphatase (TRAP) has been regarded as one of the reliable markers for osteoclasts and their precursors. The presence of TRAP activity in osteocytes near the bone resorbing surface has also been pointed out in some reports. However, the significance of TRAP reactions in osteocytes remains controversial and, in fact, there is no agreement as to whether the histochemical enzyme reactions in osteocytes represent the TRAP enzyme generated by the respective osteocytes or is a mere diffusion artifact of the reaction products derived from the nearby osteoclasts. Current histochemical, immunohistochemical, and in situ hybridization studies of rat and canine bones confirmed TRAP enzyme activity, TRAP immunoreactivity, and the expression of Trap mRNA signals in osteocytes located close to the bone-resorbing surface. TRAP/Trap- positive osteocytes thus identified were confined to the areas no further than 200 microm from the bone-resorbing surface and showed apparent upregulation of TRAP/Trap expression toward the active osteoclasts. Spatial and temporal patterns of TRAP/Trap expression in the osteocytes should serve as a valuable parameter for further analyses of biological interactions between the osteocytes and the osteoclasts associated with bone remodeling.

Acid Phosphatase↗

PubMed2003

Identification and characterization of ameloblastin gene in an amphibian, Xenopus laevis.

Ameloblastin (AMBN) is an enamel sheath protein that presumably has a role in determining the prismatic structure of growing enamel crystals. To investigate the relationship between the molecular evolution of the AMBN gene and development of enamel prismatic structures, it is considered to be of great significance in the identification of homologues of the AMBN genes in nonmammals whose teeth lack an enamel prismatic structure. Several clones containing AMBN cDNA were isolated from an African clawed toad tooth cDNA library by screening with a polymerase chain reaction (PCR) method. Sequence analysis of the clones revealed that they were derived from different genes (toad-A and toad-B), which were found to contain ORFs encoding 408- and 352-amino-acid proteins, respectively. The N-terminal part of the toad AMBN proteins and the phosphorylation motif for casein kinase II, as well as several features, were found to be highly conserved throughout the evolution of tetrapods. Exon-intron boundaries were shared by toad and caiman genes with the exception of exons 6, 7 and 10 while human and caiman genes shared them exclusive of exons 8 and 9 which have been found only in the human. As for exon 7, it was absent in both toad genes. Moreover, the AMBN genes were transcribed only in the upper jaw, presumably in teeth. These results may provide useful information for investigation of the evolution of enamel.

Amino Acid Sequence↗

PubMed2003

[Not Available].

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Journal Article↗

PubMed2002

Identification and characterization of ameloblastin gene in a reptile.

Ameloblastin (AMBN) is one of the enamel sheath proteins which presumably has a role in determining the prismatic structure of growing enamel crystals. There may therefore be a relationship between the molecular evolution of the AMBN gene and the development of enamel prismatic structures. To investigate whether such a relationship exists, it was necessary to identify the homologues of the AMBN gene in a reptile whose teeth lack an enamel prismatic structure. To this end, several clones containing AMBN cDNA were isolated from caiman jaws using the reverse transcription-polymerase chain reaction (RT-PCR) method. Sequence analysis of the AMBN cDNA revealed an open reading frame of 1221 bp encoding a 407-amino-acid protein. Translation of the caiman cDNA starts at the methionine corresponding to the second of two putative start codons conserved in mammalian AMBN genes. The N-terminal part of the caiman AMBN shows high amino acid sequence similarities to human, pig, cattle, rat and mouse AMBN sequences, as well as several other features that have been conserved throughout the evolution of reptiles and mammals. Unexpectedly, the nucleotide sequences of the 3' untranslated region (UTR) are also conserved, not only within mammalian genes but also between reptilian and mammalian genes. The caiman AMBN gene is a single-copy gene, transcribed only in the jaws, presumably in teeth.

Alligators and Crocodiles↗

PubMed2002

Persistence of Mhc heterozygosity in homozygous clonal killifish, Rivulus marmoratus: implications for the origin of hermaphroditism.

The mangrove killifish Rivulus marmoratus, a neotropical fish in the order Cyprinodontiformes, is the only known obligatorily selfing, synchronous hermaphroditic vertebrate. To shed light on its population structure and the origin of hermaphroditism, major histocompatibility complex (Mhc) class I genes of the killifish from seven different localities in Florida, Belize, and the Bahamas were cloned and sequenced. Thirteen loci and their alleles were identified and classified into eight groups. The loci apparently arose approximately 20 million years ago (MYA) by gene duplications from a single common progenitor in the ancestors of R. marmoratus and its closest relatives. Distinct loci were found to be restricted to different populations and different individuals in the same population. Up to 44% of the fish were heterozygotes at Mhc loci, as compared to near homozygosity at non-Mhc loci. Large genetic distances between some of the Mhc alleles revealed the presence of ancestral allelic lineages. Computer simulation designed to explain these findings indicated that selfing is incomplete in R. marmoratus populations, that Mhc allelic lineages must have diverged before the onset of selfing, and that the hermaphroditism arose in a population containing multiple ancestral Mhc lineages. A model is proposed in which hermaphroditism arose stage-wise by mutations, each of which spread through the entire population and was fixed independently in the emerging clones.

Alleles↗