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- Detection and localization of osteocalcin (BGP or Bone Gla Protein) in teleosts by in situ hybridization and immunohistochemistryPublication . Gavaia, Paulo J.; Viegas, C. A.; Pinto, Jorge; Sarasquete, C.; Cancela, LeonorAlthough the presence of osteocalcin (BGP) has been known for a number years, little knowledge on the regulation of expression and tissue localization of this protein in lower vertebrate organisms. In this site we have investigated the site of BGP mRNA expression by in situ hybridization using radiolabeled riboprobes and the tissue localization of the mature protein by immunohistochemistry in the Senegal sole (Solea senegalensis), zebrafish (Danio rerio), and gilthead sea bream (Sparus aurata) using fish BGP polyclonal antibodies.
- Phox2b function in the enteric nervous system is conserved in zebrafish and is sox10-dependentPublication . Elworthy, S.; P Pinto, Jorge; Pettifer, A.; Leonor Cancela, M.; Kelsh, R. N.Zebrafish lacking functional sox10 have defects in non-ectomesenchymal neural crest derivatives including the enteric nervous system (ENS) and as such provide an animal model for human Waardenburg Syndrome IV. Here, we characterize zebrafish phox2b as a functionally conserved marker of the developing ENS. We show that morpholino-mediated knockdown of Phox2b generates fish modeling Hirschsprung disease. Using markers, including phox2b, we investigate the ontogeny of the sox10 ENS phenotype. As previously shown for melanophore development, ENS progenitor fate specification fails in these mutant fish. However, in addition, we trace back the sox10 mutant ENS defect to an even earlier time point, finding that most neural crest cells fail to migrate ventrally to the gut primordium. (c) 2005 Elsevier Ireland Ltd. All rights reserved.
- Characterization of specific antibodies for fish osteocalcin and its usefulness to investigate osteocalcin tissue distribution in lower vertebrates.Publication . Simes, D; Gavaia, Paulo J.; Ortiz-Delgado, J. B.; Pinto, Jorge; Cancela, LeonorOsteocalcin (BGP or Bone Gla protein) is a small acidic protein with 46-50 residues (pI»4.0) that belongs to the family of the vitamin K dependent, Gla containing proteins. This protein is the most abundant non-collagenous bone protein in mammals and has been isolated only from bone and dentine suggesting that it may be expressed only in hydroxyapatite-containing bone tissue. Previous studies suggest that in mammals BGP is an ossification regulator, but its mode of action at the molecular level, in particular in non-mammalian organisms, remains unclear
- Identification of a promoter element within the zebrafish Collagen X¿1 gene responsive to Runx2 isoforms Osf2/Cbfa1 and til-1 but not to pebp2aA2Publication . Simões, B.; Conceição, N.; S B Viegas, Carla; Pinto, Jorge; Gavaia, Paulo J.; Kelsh, R. N.; Cancela, LeonorType X collagen is a short chain collagen specifically expressed by hypertrophic chondrocytes during endochondral ossification. We report here the functional analysis of the zebrafish (Danio rerio) collagen Xa1 gene (colXa1) promoter with the identification of a region responsive to two isoforms of the runt domain transcription factor runx2.
- Localization of osteocalcin (BGP) during fish (Sparus aurata) development by in situ hybridization and immunohistochemistry: comparison between gene expression/protein distribution and skeletal mineralizationPublication . Pinto, Jorge; Gavaia, Paulo J.; Simes, D; Kelsh, R. N.; Cancela, LeonorOsteocalcin (Bone Gla protein, BGP) is a small noncollagenous protein which is synthesized by osteoblasts and odontoblasts and is found exlusively in mineralized bony tissues. Although isolated for the first time in 1978, only recently has a function for this protein been suggested, specifically in controlling hydroxyapatite crystal growth. Appearance of osteocalcin could be linked to the presence of an hydroxyapatite-containing bony skeleton, since the protein was never found in cartilaginous fishes. Furthermore, within its primary sequence the amino acid residues known to be essential for its function are present in fish as well as in mammals, suggesting that function has been conserved over 400 million years of evolution. Taken totgether, these findings prompted us to study in detail the localization of osteocalcin gene expression in fish.
- Identification of a new pebp2 alpha A2 isoform from zebrafish runx2 capable of inducing osteocalcin gene expression in vitroPublication . Pinto, Jorge; Conceição, Natércia; S B Viegas, Carla; Leite, Ricardo; Hurst, L. D.; Kelsh, R. N.; Leonor Cancela, M.Introduction: RUNX2 (also known as CBFA1/Osf2/AML3/PEBP2 alpha A) is a transcription factor essential for bone formation in mammals, as well as for osteoblast and chondrocyte differentiation, through regulation of expression of several bone- and cartilage-related genes. Since its discovery, Runx2 has been the subject of intense studies, mainly focused in unveiling regulatory targets of this transcription factor in high vertebrates. However, no single study has been published addressing the role of Runx2 in bone metabolism of low vertebrates. While analyzing the zebrafish (Danio rerio) runx2 gene, we identified the presence of two orthologs of RUNX2, which we named runx2a and runx2b and cloned a pebp2 alpha A-like transcript of the runx2b gene, which we named pebp2 alpha A2. Materials and Methods: Zebrafish runx2b gene and cDNA were isolated by RT-PCR and sequence data mining. The 3D structure of runx2b runt domain was modeled using mouse Runx1 runt as template. The regulatory effect of pebp2 alpha A2 on osteocalcin expression was analyzed by transient co-transfection experiments using a luciferase reporter gene. Phylogenetic analysis of available Runx sequences was performed with TREE-PUZZLE 5.2. and MrBayes. Results and Conclusions: We showed that the runx2b gene structure is highly conserved between mammals and fish. Zebrafish runx2b has two promoter regions separated by a large intron. Sequence analysis suggested that the runx2b gene encodes three distinct isoforms, by a combination of alternative splicing and differential promoter activation, as described for the human gene. We have cloned a pebp2 alpha A-like transcript of the runx2b gene, which we named pebp2 alpha A2, and showed its high degree of sequence similarity with the mammalian pebp2 alpha A. The cloned zebrafish osteocalcin promoter was found to contain three putative runx2-binding elements, and one of them, located at -221 from the ATG, was capable of mediating pebp2 alpha A2 transactivation. In addition, cross-species transactivation was also confirmed because the mouse Cbfa1 was able to induce the zebrafish osteocalcin promoter, whereas the zebrafish pebp2 alpha A2 activated the murine osteocalcin promoter. These results are consistent with the high degree of evolutionary conservation of these proteins. The 3D structure of the runx2b runt domain was modeled based on the runt domain of mouse Runx1. Results show a high degree of similarity in the 3D configuration of the DNA binding regions from both domains, with significant differences only observed in non-DNA binding regions or in DNA-binding regions known to accommodate considerable structure flexibility. Phylogenetic analysis was used to clarify the relationship between the isoforms of each of the two zebrafish Runx2 orthologs and other Runx proteins. Both zebrafish runx2 genes clustered with other Runx2 sequences. The duplication event seemed, however, to be so old that, whereas Runx2b clearly clusters with the other fish sequences, it is unclear whether Runx2a clusters with Runx2 from higher vertebrates or from other fish.
- Matrix Gla protein gene expression and protein accumulation co-localize with cartilage distribution during development of the teleost fish Sparus aurataPublication . Pinto, Jorge; Conceição, N.; Gavaia, Paulo J.; Cancela, LeonorMatrix Gla protein (MGP) is a member of the family of extracellular mineral-binding Gla proteins, expressed in several tissues with high accumulation in bone and cartilage. Although the precise molecular mechanism of action of this protein remains unknown, all available evidence indicates that MGP plays a role as an inhibitor of mineralization. We investigated the sites of gene expression and protein accumulation of MGP throughout development of the bony fish Sparus aurata, by in situ hybridization, Northern and RT-PCR Southern hybridization, and immunohistochemistry. The results obtained were compared with the patterns of developmental appearance of cartilaginous and mineralized structures in this species, identified by histological techniques and by detection of mRNA presence and protein accumulation of osteocalcin (Bone Gla protein), a marker for osteoblasts known to accumulate in bone mineralized extracellular matrix.
- Osteocalcin and Matrix Gla Protein in zebrafish (Danio rerio) and Senegal sole (Solea senegalensis): comparative gene and protein expression during larval development through adulthoodPublication . Gavaia, Paulo J.; Simes, D; Ortiz-Delgado, J. B.; S B Viegas, Carla; Pinto, Jorge; Kelsh, R. N.; Sarasquete, C.; Cancela, LeonorBone Gla protein (Bgp or osteocalcin) and matrix Gla protein (Mgp) are important in calcium metabolism and skeletal development, but their precise roles at the molecular level remain poorly understood. Here, we compare the tissue distribution and accumulation of Bgp and Mgp during larval development and in adult tissues of zebrafish (Danio rerio) and throughout metamorphosis in Senegal sole (Solea senegalensis), two fish species with contrasting environmental calcium levels and degrees of skeletal reorganization at metamorphosis. Mineral deposition was investigated in parallel using a modified Alizarin red/Alcian blue protocol allowing sensitive simultaneous detection of bone and cartilage. In zebrafish, bgp and mgp mRNAs were localized in all mineralized tissues during and after calcification including bone and calcified cartilage of branchial arches. Through immunohistochemistry we demonstrated that these proteins accumulate mainly in the matrix of skeletal structures already calcified or under calcification, confirming in situ hybridization results. Interestingly, some accumulation of Bgp was also observed in kidney, possibly due to the presence of a related protein, nephrocalcin. Chromosomal localization of bgp and mgp using a zebrafish radiation hybrid panel indicated that both genes are located on the same chromosome, in contrast to mammals where they map to different chromosomes, albeit in regions showing synteny with the zebrafish location. Results in Senegal sole further indicate that, during metamorphosis, there is an increase in expression of both bgp and mgp, paralleling calcification of axial skeleton structures. In contrast with results obtained for previously studied marine fishes, in zebrafish and Senegal sole Mgp accumulates in both calcified tissues and non-mineralized vessel walls of the vascular system. These results suggest different patterns of Mgp accumulation between fish and mammals.