The development of zebrafish tendon and ligament progenitors

Abstract

Despite the importance of tendons and ligaments for transmitting movement and providing stability to the musculoskeletal system, their development is considerably less well understood than that of the tissues they serve to connect. Zebrafish have been widely used to address questions in muscle and skeletal development, yet few studies describe their tendon and ligament tissues. We have analyzed in zebrafish the expression of several genes known to be enriched in mammalian tendons and ligaments, including scleraxis (scx), collagen 1a2 (col1a2) and tenomodulin (tnmd), or in the tendon-like myosepta of the zebrafish (xirp2a). Co-expression studies with muscle and cartilage markers demonstrate the presence of scxa, col1a2 and tnmd at sites between the developing muscle and cartilage, and xirp2a at the myotendinous junctions. We determined that the zebrafish craniofacial tendon and ligament progenitors are neural crest derived, as in mammals. Cranial and fin tendon progenitors can be induced in the absence of differentiated muscle or cartilage, although neighboring muscle and cartilage are required for tendon cell maintenance and organization, respectively. By contrast, myoseptal scxa expression requires muscle for its initiation. Together, these data suggest a conserved role for muscle in tendon development. Based on the similarities in gene expression, morphology, collagen ultrastructural arrangement and developmental regulation with that of mammalian tendons, we conclude that the zebrafish tendon populations are homologous to their force-transmitting counterparts in higher vertebrates. Within this context, the zebrafish model can be used to provide new avenues for studying tendon biology in a vertebrate genetic system.

CILP1 is dynamically expressed in the developing musculoskeletal system of the trout

“…Skeletogenic cells surrounding the notochord have been shown to originate from the sclerotome compartment ventral to the myotome (Morin-Kensicki and Eisen, 1997). Although awaiting definitive evidence, it is likely that myoseptal/tendon cells originate from a sclerotome derivedcompartment similar to the syndetome of the amniotes (Bricard et al, 2014;Chen and Galloway, 2014;Subramanian and Schilling, 2014). Thus, although myoseptal and skeletogenic cells are likely to share a common sclerotomal origin, they rapidly differ not only by the expression of scleraxis and Osf2/periostin as previously reported (Bricard et al, 2014) but also by that of CILP1.…”

“…CILP1 expression was found to concentrate in myoseptal/tendon cells invading medio-laterally into the space separating adjacent myotomes (Fig.4 D and E). Myoseptal cells have been shown to express scleraxis, tenomodulin and tendon associated collagens and, as such, may be considered homologous to axial tenocytes in amniotes (Bricard et al, 2014;Chen and Galloway, 2014). Using combined fluorescence localization of CILP1 mRNA and osteoblastspecific factor 2 (Osf2)/periostin mRNA, we further observed that CILP1 labelling was excluded from the Osf2/periostin-expressing skeletogenic cells that surround the notochord and are abutted by the most medial CILP1 positive myoseptal cells (Fig.…”

“…In the developing fish embryo, the myosepta are initially acellular and composed of matricial compounds such as fibronectin, laminin and collagens (Henry et al, 2005;Charvet et al, 2011;Bricard et al, 2014 ent in the intersomitic space (Charvet et al, 2011;Bricard et al, 2014;Chen and Galloway., 2014;Subramanian and Schilling., 2014). These myoseptal cells are considered homologous to axial tenocytes in amniotes: they express scleraxis, tenomodulin and tendon associated collagens (Bricard et al, 2014;Chen and Galloway, 2014) and, like axial tenocytes in amniotes (Brent et al, 2003), they probably originate from a somite-derived syndetome compartment (Bricard et al, 2014;Chen and Galloway, 2014;Subramanian and Schilling, 2014). Experimental ablation of the myogenic factors myoD and myf5 in zebrafish results in the loss of scleraxis expression in the myosepta, showing that developing muscle regulates the specification of the myoseptal cell progenitors (Chen and Galloway, 2014).…”

“…These myoseptal cells are considered homologous to axial tenocytes in amniotes: they express scleraxis, tenomodulin and tendon associated collagens (Bricard et al, 2014;Chen and Galloway, 2014) and, like axial tenocytes in amniotes (Brent et al, 2003), they probably originate from a somite-derived syndetome compartment (Bricard et al, 2014;Chen and Galloway, 2014;Subramanian and Schilling, 2014). Experimental ablation of the myogenic factors myoD and myf5 in zebrafish results in the loss of scleraxis expression in the myosepta, showing that developing muscle regulates the specification of the myoseptal cell progenitors (Chen and Galloway, 2014).Cartilage intermediate layer protein 1 (CILP1) is a large secreted glycoprotein present in the extracellular matrix. It was first isolated from extracts of human articular cartilage, and immunocytochemistry revealed that it localizes to the intermediate zone of articular cartilage in the territorial matrix (Lorenzo et al, 1998a).…”

Musculoskeletal integration at the wrist underlies modular development of limb tendons

“…In the developing embryo, the induction of axial tendons in the tenogenic compartment, the syndetome, was shown to depend on signals emanating from the adjacent myotome, as disruption of myotome formation in chick and mouse embryos resulted in failure of tendon progenitor induction (Brent et al, 2005;Brent and Tabin, 2004;Chen and Galloway, 2014). By contrast, induction of cranial tendon progenitors was not disrupted in the absence of muscle, but subsequent differentiation of cranial tendons failed in 'muscle-less' mutants (Chen and Galloway, 2014;Grenier et al, 2009;Grifone et al, 2008).…”