Urotensin II-Related Peptides, Urp1 and Urp2, Control Zebrafish Spine Morphology

Abstract

The spine provides structure and support to the body, yet how it develops its characteristic morphology as the organism grows is little understood. This is underscored by the commonality of conditions in which the spine curves abnormally such as scoliosis, kyphosis and lordosis. Understanding the origin of such spinal curves has been challenging in part due to the lack of appropriate animal models. Recently, zebrafish have emerged as promising tools with which to understand the origin of spinal curves. Using zebrafish, we demonstrate that the Urotensin II-related peptides (URPs), Urp1 and Urp2, are essential for maintaining spine morphology. Urp1 and Urp2 are 10-amino acid cyclic peptides expressed by neurons lining the central canal of the spinal cord. Upon combined genetic loss of Urp1 and Urp2, adolescent-onset planar curves manifested in the caudal region of the spine, akin to a lordosis-like condition. Highly similar curves were caused by mutation of Uts2r3, an URP receptor. Quantitative comparisons revealed that Urotensin-associated curves were distinct from other zebrafish spinal curve mutants that more closely reflected idiopathic scoliosis or kyphosis. Last, we found that the Reissner fiber, a proteinaceous thread that sits in the central canal and has been implicated in the control of spine morphology, breaks down prior to curve formation in an idiopathic scoliosis model but was unperturbed by loss of Uts2r3. This suggests a Reissner fiber-independent mechanism of curvature in Urotensin-deficient mutants. Overall, our results show that Urp1 and Urp2 control zebrafish spine morphology and establish new animal models of lordosis-like curves.

MicroCT scanning and analysis in the zebrafish skeleton

“…Segmentation of individual sh and generation of .DCM les can also be performed manually. A protocol for this described in [14].…”

“…There is also free, open-source software (e.g., 3D Slicer) for this purpose. Details on the use of some of these applications for the analysis of bones in zebra sh and small rodents have been described in previously published protocols [14,15]. Second, our discussion of key considerations for microCT scanning and analysis is not meant to be exhaustive as further details can be attained from published resources [6,16].…”

Advances in genetic factors of adolescent idiopathic scoliosis: a bibliometric analysis

“…Zebrafish, genetically similar to humans, are ideal subjects for studying scoliosis due to their inherent susceptibility to the condition (19,20). The circulation of cerebrospinal fluid (CSF) is associated with spinal development and can result in zebrafish developing spinal deformities (21)(22)(23). When CSF flows through neurons in contact with CSF(CSF-cNs) in the central canal, these neurons produce the urotensin-related peptides Urp1 and Urp2 (24-26).…”

“…Reducing these peptides during zebrafish growth causes spinal deformities similar to human spinal dysplasia (27,28). Bearce et al found that zebrafish lacking Uts2r3 have scoliosis in adulthood; and that Uts2r3, as a receptor of the urotensin family, may regulate spinal morphology (21). Research on Chinese Han patients with AIS has additionally verified a substantial correlation between UTS2R gene mutation and AIS (29).…”

“…Abnormal ciliary movement may also lead to scoliosis. Zebrafish cilia contribute to Reissner fiber aggregation and straightening of the body axis; and knockout of the ciliary polarity and movementrelated gene cfap298 (35) and ciliary dynamic protein axonal heavy chain 10 genes may affect Reissner fiber aggregation and lead to zebrafish spinal deformity (21,36). Variants in genes dnaaf1 and zmynd10 related to cilia structure and function were also found in AIS patients in southern China by whole exome sequencing (37).…”