Small leucine-rich proteoglycans in the vertebrae of Atlantic salmon Salmo salar

Abstract

We analysed the distribution and expression of the small leucine-rich proteoglycans (SLRPs) decorin, biglycan and lumican in vertebral columns of Atlantic salmon Salmo salar L. with and without radiographically detectable deformities. Vertebral deformities are a reoccurring problem in salmon and other intensively farmed species, and an understanding of the components involved in the pathologic development of the vertebrae is important in order to find adequate solutions to this problem. Using immunohistology and light microscopy, we found that in nondeformed vertebrae biglycan, lumican and decorin were all expressed in osteoblasts at the vertebral growth zones and at the ossification front of the chondrocytic arches. Hence, the SLRPs are expressed in regions where intramembranous and endochondral ossification take place. In addition, mRNA expression of biglycan, decorin and lumican was demonstrated in a primary osteoblast culture established from Atlantic salmon, supporting the in vivo findings. Transcription of the SLRPs increased during differentiation of the osteoblasts in vitro and where lumican mRNA expression increased later in the differentiation compared with decorin and biglycan. Intriguingly, in vertebral fusions, biglycan, decorin and lumican protein expression was extended to transdifferentiating cells at the border between arch centra and osteoblast growth zones. In addition, mRNA expression of biglycan, decorin and lumican differed between non-deformed and fused vertebrae, as shown by quantitative PCR (qPCR). Western blotting revealed an additional band of biglycan in fused vertebrae which had a higher molecular weight than in non-deformed vertebrae. Fourier-transform infrared (FTIR) spectroscopy revealed more spectral focality in the endplates of vertebral fusions and significantly more non-reducible collagen crosslinks compared with non-deformed vertebrae, thus identifying differences in bone structure. KEY WORDS: Atlantic salmon · Bone development · Skeletal deformities · SLRP · VertebraeResale or republication not permitted without written consent of the publisher FREE REE ACCESS CCESS

Transcriptional dynamics of a conserved gene expression network associated with craniofacial divergence in Arctic charr

“…As with many of the other network genes, Lum is an ECM component and affects collagen fibril formation [89]. In Atlantic salmon, Lum is expressed at sites of endochondral and intramembranous ossification [90] and is a component of developing bone tissue in other vertebrate species [89], similarly to many of the other network genes. However, Lum is also a major proteoglycan in the cornea and sclera [91, 92], where it is likely to be independently regulated.…”

Sulphated glycosaminoglycans and proteoglycans in the developing vertebral column of juvenile Atlantic salmon (Salmo salar)

“…In the present study, we demonstrated an up-regulation of biglycan mRNA during development from 2 to 15 g. Biglycan is reported to control signalling pathways regulating the osteogenic program (Berendsen et al 2011 ), and in vitro studies have demonstrated a different influence of biglycan and decorin on mineralization (Mochida et al 2003 ). A changed mRNA expression of decorin and biglycan has previous been demonstrated in salmon of 15 g size with vertebral deformities (Pedersen et al 2013 ). Thus, the presence of four sulphated DS in the notochord during growth and development of salmon is most likely a prerequisite for proper development, but further studies are needed to explore the consequences of the differences in biglycan and decorin expression in vertebral development.…”

“…In our study, C-6-S did not co-localize with KS in the chordocytes, suggesting the presence of other KS PGs. In a recent study, we immunolocalized lumican in the chordocytes of Atlantic salmon (Pedersen et al 2013 ). Lumican is reported to carry KS also in teleosts such as Atlantic cod (Tingbo et al 2012 ) and zebrafish (Souza et al 2007 ).…”

“…We also compared the distribution of the GAG types in salmon with normal and pathologic vertebral development collected at a later stage of development and approached the number and size of the macromolecules carrying the GAG epitopes by western blotting. We have previously reported the transcription of proteoglycans in salmon with malformations (Pedersen et al 2013 ). In the present study, the transcription of PGs known to carry the C-0-S, C-4-S, C-6-S, DS and KS epitopes was analysed in salmon with healthy development with real-time qPCR.…”