Abstract
In the present study, the distribution of sulphated glycosaminoglycans (GAGs) in the developing vertebral column of Atlantic salmon (Salmo salar) at 700, 900, 1100 and 1400 d° was examined by light microscopy. The mineralization pattern was outlined by Alizarin red S and soft structures by Alcian blue. The temporal and spatial distribution patterns of different types of GAGs: chondroitin-4-sulphate/dermatan sulphate, chondroitin-6-sulphate, chondroitin-0-sulphate and keratan sulphate were addressed by immunohistochemistry using monoclonal antibodies against the different GAGs. The specific pattern obtained with the different antibodies suggests a unique role of the different GAG types in pattern formation and mineralization. In addition, the distribution of the different GAG types in normal and malformed vertebral columns from 15 g salmon was compared. A changed expression pattern of GAGs was found in the malformed vertebrae, indicating the involvement of these molecules during the pathogenesis. The molecular size of proteoglycans (PGs) in the vertebrae carrying GAGs was analysed with western blotting, and mRNA transcription of the PGs aggrecan, decorin, biglycan, fibromodulin and lumican by real-time qPCR. Our study reveals the importance of GAGs in development of vertebral column also in Atlantic salmon and indicates that a more comprehensive approach is necessary to completely understand the processes involved.
Highlights
The vertebral column is the defining character of all vertebrates
The architecture of the notochord and the vertebral column in the time span studied was outlined by HE staining-added saffron, here illustrated with longitudinal and transverse sections of salmons obtained at 700 and 1100 d° (Fig. 1a–d)
The results showed a persistent spatial distribution pattern of the GAGs from 1100 d° to 15 g, indicating similar functions for the different GAGs both in the juvenile and in the mature spine
Summary
The vertebral column is the defining character of all vertebrates It consists of an alternating pattern of vertebral bodies (centra), providing strength and support, and intervertebral regions (IVR), providing flexibility and resistance to compression. The vertebral column develops from notochord, a flexible rodlike structure derived from the mesoderm. During the embryonic and larval stages, the notochord is the main axial support playing essential roles in the development of the vertebral column by serving structural as well as signalling roles for patterning, of surrounding tissue. Throughout the early yolksac stage, the notochord of Atlantic salmon is unsegmented with a uniform notochord sheath of even thickness surrounded by the sclerotome (Grotmol et al 2003, 2005). During the growth period from 800 to 1400 d°, the main events have occurred, resulting in the architecture of the adult salmon vertebral column (Nordvik et al 2005)
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