Urotensin II-related peptides, Urp1 and Urp2, control zebrafish spine morphology.
Urotensin II-related peptides, Urp1 and Urp2, control zebrafish spine morphology.
复制标题
DOI：
10.7554/elife.83883
复制
发表时间：
2022-12-01
期刊：
影响因子：
7.7
通讯作者：
Grimes DT
中科院分区：
文献类型：
--
作者：
Bearce EA;Irons ZH;O'Hara-Smith JR;Kuhns CJ;Fisher SI;Crow WE;Grimes DT
脊柱为身体提供结构和支撑，然而，随着生物体的生长，它是如何形成其特征形态的，人们知之甚少。脊柱异常弯曲的共性，如脊柱侧凸、后凸和前凸，强调了这一点。由于缺乏适当的动物模型，了解这些脊柱弯曲的起源一直具有挑战性。最近，斑马鱼已经成为了解脊柱弯曲起源的有前途的工具。利用斑马鱼，我们证明了尿紧张素ii相关肽（URPs）， Urp1和Urp2对维持脊柱形态至关重要。Urp1和Urp2是由脊髓中央管内衬的神经元表达的10个氨基酸的环状肽。在Urp1和Urp2基因缺失的情况下，青春期发病的平面曲线出现在脊柱的尾侧区域。高度相似的曲线是由URP受体Uts2r3突变引起的。定量比较表明，尾紧张素相关曲线在曲线位置和方向上与其他斑马鱼脊柱曲线突变体不同。最后，我们发现Reissner纤维（位于中央椎管中的一种蛋白线，与脊柱形态的控制有关）在纤毛运动紊乱的突变体中，在曲线形成之前就会断裂，但不受Uts2r3缺失的影响。这表明在尿紧张素缺陷突变体中存在一种不依赖赖斯纳纤维的弯曲机制。总之，我们的研究结果表明，Urp1和Urp2控制着斑马鱼脊柱形态，并建立了新的脊柱畸形动物模型。脊椎骨是人体不可分割的一部分，为我们的躯干提供支撑，使我们可以坐、站、弯曲和扭动。如果这种结构不能正确形成，就会导致疼痛、神经问题和行动不便。脊柱通常是弯曲的，但由于多种原因，包括遗传和肌肉因素，脊柱会变形。也有一些病例导致脊柱扭曲的原因不明，如脊柱侧凸（脊柱向一侧扭曲）、脊柱前凸（脊柱下部过度弯曲）和脊柱后凸（脊柱上部极度弯曲）。脊柱的结构是在胚胎发育期间形成的，并在一生中保持不变。在斑马鱼身上进行的实验表明，保持脊柱形状的一个关键因素是脑脊液或CSF的流动。在特殊细胞表面的小“毛发”运动的推动下，这种液体沿着布满神经元的腔体流经我们的中枢神经系统。这些神经细胞产生Urp1和Urp2，这两种短分子（或肽）由与蛋白质相同的成分构成。在斑马鱼胚胎中，降低这些肽的水平已经被证明会导致早期身体畸形。但是Urp1和Urp2在维持成年斑马鱼脊柱形状方面起什么作用，如果有的话？Bearce等人着手回答这个问题。首先，他们培育出不携带Urp1、Urp2或两种肽的斑马鱼突变体。与之前的发现相反，这三种突变体都在胚胎时期正常发育。成年后，缺乏Urp1的斑马鱼表现出正常的脊柱，而缺乏Urp2的斑马鱼的脊柱曲线略有变形。然而，缺乏这两种肽的斑马鱼在其脊柱的尾部区域有明显的曲线，有点类似于人类的脊柱前凸。这表明这两种肽对成人脊柱结构都是必要的，但以半冗余的方式工作。有趣的是，观察到的缺陷首先出现在青春期的鱼身上，随着它们的成长逐渐恶化；许多形式的人类脊柱异常都遵循类似的轨迹。Bearce等人还测试了Uts2r3蛋白的作用，这是一种属于尿紧张素家族的肽受体（如Urp1和Urp2）。缺乏这种蛋白的鱼在胚胎时脊柱结构正常，但在成年后脊柱曲线扭曲，这表明Urp1和Urp2可能通过Uts2r3受体的信号传导来控制脊柱形态。总之，Bearce等人的观察表明，不安的尿紧张素信号会导致成年斑马鱼出现类似前凸的状况，脊柱尾部区域出现明显的畸形。考虑到斑马鱼和人类脊柱在结构上的广泛相似性，这些结果表明，人类脊柱扭曲可能与尿紧张素信号有关。更多使用斑马鱼的研究可能会进一步深入了解控制脊柱形状的原理，以及脊柱断裂时出现的问题。
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 these 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. 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 in curve position and direction. 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 mutants with perturbed cilia motility but was unaffected 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 spine deformity. The backbone, or spine, is an integral part of the human body, providing support to our torsos so that we can sit, stand, bend and twist. If this structure does not form correctly, it can lead to pain, neurologic problems, and mobility issues. The spine normally has curves, but these can become deformed for many reasons, including genetic and muscular factors. There are also cases in which the cause of a spine distortion is unknown, such as in scoliosis (where the spine twists to the side), lordosis (where the lower part of the spine curves excessively), and kyphosis (where the upper part of the spine shows extreme curvature). The structure of the spine is laid out during embryonic development and maintained throughout life. Experiments in zebrafish have shown that a crucial element in preserving the shape of the spine is the flow of cerebrospinal fluid or CSF. Propelled by the movement of little ‘hairs’ at the surface of specialized cells, this liquid runs through our central nervous system along a cavity lined with neurons. These nerve cells produce Urp1 and Urp2, two short molecules (or peptides) built from the same components as proteins. In zebrafish embryos, lowering the levels of these peptides had previously been shown to cause early body deformities. But what role, if any, do Urp1 and Urp2 play in maintaining the shape of the spine in adult zebrafish? Bearce et al. set out to answer this question. First, they generated mutant zebrafish which did not carry either Urp1, Urp2 or both peptides. Contrary to previous findings, all three of these mutants developed normally as embryos. Once they were adults, zebrafish lacking Urp1 exhibited normal spines, while those lacking Urp2 had slightly deformed curves. However, zebrafish lacking both peptides had prominent curves in the tail-region of their spines, somewhat akin to lordosis in humans. This indicates that both peptides are necessary for adult spine structure, but work in a semi-redundant manner. Interestingly, the defects observed first appeared in adolescent fish and gradually worsened as they grew; many forms of human spinal abnormalities follow a similar trajectory. Bearce et al. also tested the role of the protein Uts2r3, a receptor for peptides which belong to the urotensin family (such as Urp1 and Urp2). Fish lacking this protein showed normal spine structure as embryos, but distorted spinal curves as adults, suggesting that Urp1 and Urp2 might control spine morphology by signaling via the Uts2r3 receptor. Together, Bearce et al.’s observations show that disturbing urotensin signaling leads to a lordosis-like condition in adult zebrafish, with evident deformities in the tail-region of the spine. Considering the broad similarities in structures between the zebrafish and the human spine, these results point to a possible involvement of urotensin signaling in spine distortion in humans. More studies using zebrafish will likely provide further insights into the principles that control the shape of the spine and what goes wrong when it breaks down.