title: Expression of SPARC and the osteopontin-like protein during skeletal development in the cichlid fish Oreochromis mossambicus.
abstract: BACKGROUND
  Bones are mainly composed of calcium hydroxyapatite and a proteinous matrix. In this study, we focus on the bone matrix proteins, the fish osteopontin orthologous protein (osteopontin-like protein; OP-L) and SPARC, because the current knowledge regarding their expression is fragmentary or contradictory.
  
  
  RESULTS
  We first provide a comprehensive and detailed description of skeletal development in the cichlid fish Oreochromis mossambicus. Following this, we analyzed the expression pattern of OP-L and SPARC in detail during development. OP-L expression was only found in tissues that undergo ossification (i.e., developing bones and teeth). Furthermore, we show that there is a fundamental difference in cartilage formation of the splanchnocranium and all other cartilages, concerning SPARC expression. Significantly, we show that the initial calcification of cranial bones occurs simultaneously with the expression of OP-L and SPARC in the osteoblast-like cells, which appear early in development.
  
  
  CONCLUSIONS
  The difference in SPARC expression during chondrogenesis of the splanchnocranium is likely based on its different evolutionary history compared with the dermatocranium and chondrocranium. Moreover, our results suggest a co-occurrence of the initial calcium deposition and bone matrix protein expression during osteogenesis. Overall, this study enhances our understanding of fish skeletal development and evolution.
authors.affiliation: Zoological Institute, University of Stuttgart-Hohenheim, Stuttgart, Germany.|Department of Biology, Mount Saint Vincent University, Halifax, Nova Scotia, Canada.
authors.forename: Jochen
authors.initials: J
authors.lastname: Weigele
authors.affiliation: Department of Biology, Mount Saint Vincent University, Halifax, Nova Scotia, Canada.
authors.forename: Tamara A
authors.initials: TA
authors.lastname: Franz-Odendaal
authors.affiliation: Zoological Institute, University of Stuttgart-Hohenheim, Stuttgart, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Hilbig
mesh_terms: D000818:Animals; D023681:Cichlids; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism*; D015676:Osteonectin / Q000235:genetics / Q000378:metabolism*; D012863:Skeleton / Q000196:embryology* / Q000378:metabolism*
chemical_list: D029941:Fish Proteins; D015676:Osteonectin
keywords: Oreochromis mossambicus; SPARC; bone matrix protein; osteopontin-like protein