Comparative expression analyses of bone morphogenetic protein 4 (BMP4) expressions in muscles of tilapia and common carp indicate that BMP4 plays a role in the intermuscular bone distribution in a dose-dependent manner

Publication date: Available online 26 November 2017
Source:Gene Expression Patterns
Author(s): Shengyan Su, Zaijie Dong
Intermuscular bones in fish negatively influence both meet processing and attractiveness to consumers. Tilapia (Oreochromis niloticus) and common carp (Cyprinus carpio) are both major farmed fish species globally, but whereas the former does not possess intermuscular bones, the latter does. Therefore, these two species might present a good model to study the genetic control of distribution of intermuscular bones in fish. Bone morphogenetic protein 4 (BMP4) gene is associated with tissue ossification and bone regeneration in mammals, but in fish its role in ossification remains understudied. To study the relationship between BMP4 and bone distribution in fish, we determined the expression of BMP4 in muscle tissues of common carp and tilapia on transcriptional and translational levels. As the gene has been merely predicted in silico from the genome of common carp, we have cloned and characterized it. The gene (GenBank: HQ446455) contains one intron and two exons, which encode a 400-amino acid protein with high homology to other known BMP4 protein sequences. Phylogenetic analysis showed that common carp clustered within the Cypriniformes clade (zebrafish was the closest ortholog) and tilapia within the Percomorpha clade. Using microCT scanning, we confirmed that intermuscular bones could be observed only in common carp (none in tilapia), but only in dorsal and caudal muscles (none in the ventral muscle). Expression levels of BMP4 in the muscles of common carp were in agreement with this observation both on transcriptional (qPCR) and translational (immunohistochemistry) level: higher in dorsal and caudal muscles, and lower in the ventral muscle. In tilapia, expression of BMP4 gene was also detectable in all three muscles, but expression levels in all three muscles were comparable to the one observed in the ventral muscle of carp, i.e., very low. Therefore, among the six studied muscles, the expression of BMP4 was high only in the two that possess intermuscular bones: dorsal and caudal muscles of common carp. The results of this study suggest that BMP4 is likely to play a key role in the determination of intermuscular bone distribution in fish in a dose-dependent manner.



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