Hormonal Regulation During Growth and Limb Regeneration in Crustacea: Ecdysteroid and Retinoid Receptors

在动物中，类固醇激素长期以来被认为在调节从钙平衡到生长发育的许多生理过程中起重要作用。 同样，维生素A及其类似维生素A的衍生物，类维生素A，对正常发育至关重要。 人类饮食中维生素A缺乏可导致不育、视力丧失和皮肤病。 过量的维甲酸同样具有破坏性，导致发育中的胚胎严重畸形。 最近已经清楚，类固醇和类维生素A在无脊椎动物发育过程中起着重要作用，作为信号分子影响导致正常体型和组织分化的过程。 类固醇和类维生素A发挥其生理作用的基本机制尚不清楚。 这项研究将研究招潮蟹生长周期中存在的信号分子的类型和分布，并研究信号分子如何与特定的细胞受体蛋白相互作用，以调节一种特殊类型的发育再生甲壳类动物肢体的基因表达;一种适合实验操作的系统。已知类维生素A和类固醇通过使用特异性细胞受体来调节基因表达。 可能存在于给定细胞中的受体的数量和类型太小而无法直接测量。 然而，重组DNA技术可用于开发分子探针，可以在亚细胞水平上标记特定受体的存在，并且微生物可以被工程化以产生大量的受体蛋白。 这些方法将用于检测哪些细胞含有受体，并通过推断，鉴定可能对类固醇/类维生素A信号传导有反应的特定细胞。 重组蛋白还将用于检测受体的物理特性，例如它们与特定信号分子和基因序列结合的能力。肢体的再生必须与动物的生长和生殖活动相一致。 一个“共同的”信号如何调节这些不同的生理事件还不清楚。 在生长和再生的特定阶段存在的信号分子的类型和数量的知识，再加上受体的物理特性和分布的信息，将阐述类固醇/类维生素A信号的作用，并帮助我们更好地了解基本发育过程的演变。

In animals, the steroid hormones have long been recognized as playing important roles in regulating many physiological processes, from calcium balance to growth and development. Similarly, vitamin A and its hormone-like derivatives, the retinoids, are essential for normal development. Dietary vitamin A deficiencies in humans can lead to sterility, loss of vision and skin pathologies. Retinoid excess can be equally damaging, causing profound deformities in developing embryos. It has recently become clear that both steroids and retinoids play a major role during invertebrate animal development, serving as signaling molecules which influence the processes that result in normal body shape and tissue differentiation. The basic mechanisms through which steroids and retinoids exert their physiological effects remain unclear. This research will examine the type and distribution of signaling molecules present during the growth cycle of the fiddler crab, and investigate how signaling molecules interact with specific cell receptor proteins to regulate gene expression in a special type of development-regenerating crustacean limbs; a system amenable to experimental manipulation. Retinoids and steroids are known to modulate gene expression through the use of specific cellular receptor. The amount and type of receptor that may be present in a given cell is too small to measure directly. Recombinant DNA techniques, however, can be used to develop molecular probes that can mark the presence of specific receptors at the subcellular level, and microbes can be engineered to produce large amounts of receptor protein. These methodologies will be employed to detect which cells contain receptors, and by inference, identify particular cells that may be responding to steroid/retinoid signaling. The recombinant proteins will also be used to examine the physical characteristics of the receptors, such as their ability to bind to specific signaling molecules and gene sequences.The regeneration of limbs must occur in concert with the animal's growth and reproductive activities. How a "common" signal might modulate these varied physiological events is unclear. Knowledge of the type and amounts of signaling molecules present at specific stages of growth and regeneration, coupled with information on the physical properties and distribution of receptors, will elaborate the role of steroid/retinoid signaling and help us to better understand the evolution of basic developmental processes.