Evolution of the intermuscular bones in the Cyprinidae (Pisces) from a phylogenetic perspective

Molecular mechanisms and softening effects of edible acids on the intermuscular bones of grass carp (Ctenopharyngodon idella)

This study aimed to mitigate the health threats posed by intermuscular bones (IMBs) of grass carp (Ctenopharyngodon idella) by immersing them in dilute acetic acid (AA) and citric acid (CA). The hardness of AA-immersed IMBs reduced from 44.60 ± 0.25 N to 4.65 ± 0.34 N and CA-immersed IMBs from 44.27 ± 0.23 N to 3.58 ± 0.36 N. The reduction in IMBs hardness was attributed to the partial denaturation of collagen and hydroxyapatite, as shown by multispectral analysis and microstructural changes. Furthermore, sensory analysis confirmed that AA 0.75 mmol/L and CA 0.50 mmol/L significantly reduced IMBs hardness in the fish fillets (P < 0.05). Additionally, the use of these edible acids not only reduced IMBs hardness but also enhanced the textural and sensory attributes of the fish fillets, as demonstrated by textural parameters, color analysis, TVBN, and TBARS analysis. It is recommended that AA 0.75 mmol/L and CA 0.50 mmol/L can be used for IMBs softening and improving the acceptability of grass carp (C. idella) fillets in terms of texture, flavor, and aroma.

Integrated transcriptomic analysis reveals evolutionary and developmental characteristics of tendon ossification in teleost

BACKGROUND

Intermuscular bones (IBs) are segmental intramembranous ossifications located within myosepta. They share similarities with tendon ossification, a form of heterotopic ossification (HO). The mechanisms underlying IB formation remain incompletely understood.

RESULTS

In this study, we systematically analyzed transcriptome data across multiple tissues, species, time points, and resolutions in teleosts. First, we identified IB-specific expression genes using the tau index method. Through cross-species comparisons of the tendon development process, we discovered that candidate genes were primarily enriched in extracellular matrix organization, ossification, regulation of angiogenesis, and other related processes. We also revealed that some of these candidate genes are abnormally expressed in runx2b-/- zebrafish, which lack IBs. To clarify the trajectory of cell differentiation during IB formation, we demonstrated that myoseptal stem cells differentiate into osteoblasts, fibroblasts, and tenocytes in runx2b+/+ zebrafish. However, in runx2b-/- zebrafish, the differentiation of myoseptal stem cell into osteoblast was inhibited, while differentiation into clec3bb + tenocyte and fibroblast was enhanced. Additionally, runx2b deficiency led to the upregulation of clec3bb expression in the clec3bb + tenocyte cluster. Notably, a compensatory effect was observed in cell differentiation and gene expression in runx2b-/- zebrafish, suggesting that runx2b and the candidate genes, such as clec3bb, were involved in the gene network of IB development.

CONCLUSIONS

The results elucidate cell differentiation process during tendon ossification in teleosts and identify the key factor clec3bb involved in this process. These findings provide a foundation for understanding tendon ossification in teleosts and for further research on tendon ossification in mammals.

Transcriptomic analysis of intermuscular bone development in barbel steed (Hemibarbus labeo)

Intermuscular bones (IBs), which are little, bony spicules in muscle, are embedded in lower teleosts' myosepta. Despite the importance of studying IB development in freshwater aquaculture species, the genes associated with IB development need to be further explored. In the present study, we identified four stages of IB development in barbel steed (Hemibarbus labeo), namely stage 1: IBs have not emerged, stage 2: a few small IBs have emerged in the tail, stage 3: longer IBs gradually emerged in the tail and stage 4: all of the IBs in the tail are mature and long, via Alizarin red staining. Subsequently, we used the HiseqXTen platform to sequence and de novo assemble the transcriptome of epaxial muscle (between 35th and 40th myomere) of barbel steed at 29 days (stage 1) and 42 days (stage 3) after hatching. A total of 190,814 unigenes were obtained with an average length and N50 of 648 bp and 1027 bp, respectively. We found 2174 differentially expressed genes (DEGs) between stages 1 and 3, of which 378 and 1796 were up- and down-regulated, respectively. Functional enrichment analysis showed that several DEGs functioned in ossification, positive regulation of osteoblast differentiation, osteoblast differentiation, and BMP signaling pathway, and were further enriched in signal pathway, including osteoclast differentiation, TGF-β signaling pathway, cytokine-cytokine receptor interaction, Jak-STAT signaling pathway, and other KEEG pathways. In conclusion, we identified genes that may be related to IB development, such as kazal type serine peptidase inhibitor domain 1 (KAZALD1), extracellular matrix protein 1 (ECM1), tetranectin, bone morphogenetic protein 1 (bmp1), acid phosphatase 5 (ACP5), collagen type XI alpha 1 chain (COL11A1), matrix metallopeptidase 9 (MMP9), pannexin-3 (PANX3), sp7 transcription factor (Sp7), and c-x-c motif chemokine ligand 8 (CXCL8), by comparing the transcriptomes of epaxial muscle before and after IB ossification. This study provided a theoretical basis for identifying the molecular mechanisms underlying IB development in fish.

Bulked Segregant Analysis and Association Analysis Identified the Polymorphisms Related to the Intermuscular Bones in Common Carp (Cyprinus carpio)

Simple Summary

Many widely cultured freshwater fish species, such as common carp, belong to the Cyprinidae family. However, most cyprinids have numerous and complex intermuscular bones (IBs), resulting in an adverse effect on cyprinid fish meat processing and consumption. Numerous studies have been trying to understand the development mechanism of IBs and to identify the SNPs associated with the total IB number. However, the SNPs associated with different forms of IBs have been studied less thoroughly. The joint effects of the SNPs on IB development also remain poorly understood. The common carp has numerous geographical populations and domesticated strains, diversifying its phenotypes. The question of whether consensus IB-related SNPs or genes exist among multiple strains of common carp has also not yet been answered. Selective breeding of IB-reduced common carp has been hindered due to a lack of effective molecular markers. To answer these questions, we performed bulked segregant analysis (BSA) to detect the consensus SNPs in three strains. The consensus BSA-SNPs and the other SNPs in their flanking regions were validated in additional individuals. The SNPs associated with the frequency of different IB types were identified. We examined the joint effects of significant SNPs on the numbers of different types of IBs. The identified genetic markers may benefit future selective breeding and reduce the IB number in common carp.

Abstract

The allotetraploid common carp is one of the most important freshwater food fish. However, the IBs found in allotetraploid common carp increase the difficulty in fish meat processing and consumption. Although candidate genes associated with the total IB number have been identified, the SNPs associated with the numbers of the total IBs and different forms of IBs have not yet been identified, hindering the breeding of IB-reduced common carp. Herein, the numbers of different types of IBs in three common carp strains were measured. Using whole-genome resequencing and bulked segregant analysis in three pairs of IB-more and IB-less groups, we identified the consensus nonsynonymous SNPs in three strains of common carp. Screening the flanking regions of these SNPs led to the detection of other SNPs. Association study detected 21 SNPs significantly associated with the number of total IBs, epineural-IBs, and ten detailed types of IBs. We observed the joint effects of multiple SNPs on each associated IB number with an improved explained percentage of phenotypic variation. The resulting dataset provides a resource to understand the molecular mechanisms of IB development in different common carp strains. These SNPs are potential markers for future selection to generate IB-reduced common carp.

Molecular mechanisms of intermuscular bone development in fish: a review

Intermuscular bones (IBs) are slender linear bones embedded in muscle, which ossify from tendons through a process of intramembranous ossification, and only exist in basal teleosts. IBs are essential for fish swimming, but they present a choking risk during human consumption, especially in children, which can lead to commercial risks that have a negative impact on the aquaculture of these fish. In this review, we discuss the morphogenesis and functions of IBs, including their underlying molecular mechanisms, as well as the advantages and disadvantages of different methods for IB studies and techniques for breeding and generating IB-free fish lines. This review reveals that the many key genes involved in tendon development, osteoblast differentiation, and bone formation, e.g., scxa, msxC, sost, twist, bmps, and osterix, also play roles in IB development. Thus, this paper provides useful information for the breeding of new fish strains without IBs via genome editing and artificial selection.

Bones of teleost fish demonstrate high fracture strain

The endoskeleton of teleosts (bony fish) includes a vertebral spine with articulating rib bones (RBs) similar to humans and further encompasses mineralized tissues that are not found in mammals, including intermuscular bones (IBs). RBs form through endochondral ossification and protect the inner organs, and IBs form through intramembranous ossification within the myosepta and play a role in force transmission and propulsion during locomotion. Based on previous findings suggesting that IBs show a much higher ability for fracture strain compared to mammalian bones, this study aims to investigate whether this ability is general to teleost bones or specific to IBs. We analyzed RBs and IBs of 25 North Atlantic Herring fish. RBs were analyzed using micro-mechanical tensile testing and micro-computed tomography, and both RB and IB were additionally analyzed with Raman spectroscopy. Based on our previous results from IB, we found that RBs are more elastically deformable (on average, 50% higher yield strain and 115% higher elastic work) and stronger (55% higher fracture stress) than values reported for IBs. However, these differences were neither associated with a higher Young's modulus nor a higher degree of mineralization in RBs. Astonishingly, RBs and IBs showed similar fracture strains (12-15% on average, reaching up to 20%), reflecting a much higher ability for tensile deformation than reported for mammalian bone, and further highlighting the biomimetic potential of teleost fish bones for inspiring innovative biomaterials.