Myostatin and ecdysteroid signaling in crustacean skeletal muscle

甲壳类动物为了生长，必须周期性地脱壳，这个过程称为蜕皮。许多螃蟹和龙虾都有大爪子，当动物蜕皮时，必须通过连接附肢和身体的小关节来拉动爪子。爪肌的减少或萎缩有利于蜕皮时爪的缩回。PI假设肌肉生长抑制素（MSTs）是哺乳动物肌肉生长的负调节因子，介导了类固醇蜕皮激素（蜕皮激素）控制下的爪肌萎缩。该项目的具体目标是（1）确定陆蟹中蜕皮激素对MbR/Smad信号传导的调节和（2）确定龙虾中纤维类型和蜕皮激素对爪肌萎缩的相互作用。对陆地蟹的实验利用了它们操纵蜕皮周期和培养爪肌的能力。对龙虾的实验利用了它们定量肌肉中mRNA和蛋白质的能力，这些肌肉在二形爪中的纤维类型组成不同。这两个物种的一个优点是，只有爪肌对萎缩诱导信号作出反应。对蜕皮激素没有反应的肌肉（陆地蟹的胸肌和龙虾的腹肌）作为内部控制，因为它们暴露在相同的激素环境中。甲壳类动物肌肉中的Mexican的发现表明，肌肉质量的调节在脊椎动物和无脊椎动物之间是高度保守的。它构成了一个全新的和令人兴奋的研究领域。由于甲壳类动物肌肉几乎没有干细胞，因此它们是确定MSPs对成人分化纤维的直接影响的理想模型，因此可以提供对MSPs在人类中作用的见解。了解调节骨骼肌质量的信号通路可能对甲壳类水产养殖产生重大影响。例如，阻断MMPs信号传导可以促进生长并提高产品质量。该项目将为一名美国土著博士后研究员、2名研究生和4-6名本科生提供现代生物化学和分子技术方面的培训。

Crustaceans must shed their shells periodically in order to grow, a process called molting. Many crabs and lobsters have large claws, which must be pulled through the small joints that connect the appendage to the body when the animal molts. A reduction, or atrophy, in the claw muscle facilitates the withdrawal of the claws at molt. The PI hypothesizes that myostatin (Mstn), a negative regulator of muscle growth in mammals, mediates claw muscle atrophy that is under the control of steroid molting hormones (ecdysteroids). The specific aims of the project are to (1) determine the regulation of Mstn/Smad signaling by ecdysteroid in the land crab and (2) determine the interaction of fiber type and ecdysteroid on claw muscle atrophy in lobster. The experiments on land crab take advantage of their ability to manipulate the molt cycle and to culture claw muscle. The experiments on lobster take advantage of their ability to quantify mRNAs and proteins in muscles that differ in fiber type composition in the dimorphic claws. An advantage of both species is that only the claw muscles are responsive to the atrophy-inducing signal. Muscles that do not respond to ecdysteroid (thoracic muscle in land crab and abdominal muscles in lobster) serve as internal controls, as they are exposed to the same hormonal environment. The discovery of Mstn in crustacean muscles suggests that the regulation of muscle mass is highly conserved between vertebrates and invertebrates. It constitutes an entirely novel and exciting area of investigation. As crustacean muscles have few stem cells, they are an ideal model to determine the direct effects of Mstn on differentiated fibers in adults and therefore can provide insights into Mstn action in humans. Understanding the signaling pathway(s) regulating skeletal muscle mass could have significant impacts on crustacean aquaculture. For example, blocking Mstn signaling could enhance growth and improve product quality. The project will provide training in modern biochemical and molecular technologies for a Native American postdoctoral fellow, 2 graduate students, and 4-6 undergraduates.