Kürn Ulrich, Rendulic Snjezana, Tiozzo Stefano, Lauzon Robert J
Zoological Institute, Christian-Albrechts-University Kiel, Olshausenstrasse, Germany.
Biol Bull. 2011 Aug;221(1):43-61. doi: 10.1086/BBLv221n1p43.
Regeneration is widely distributed among the metazoans. However, clear differences exist as to the degree of regenerative capacity: some phyla can only replace missing body parts, whereas others can generate entirely new individuals. Ascidians are animals that possess a remarkable regenerative plasticity and exhibit a great diversity of mechanisms for asexual propagation and survival. They are marine invertebrate members of the subphylum Tunicata and represent modern-day descendants of the chordate ancestor; in their tadpole stage they exhibit a chordate body plan that is resorbed during metamorphosis. Solitary species grow into an adult that can reach several centimeters in length, whereas colonial species grow by asexual propagation, creating a colony of genetically identical individuals. In this review, we present an overview of the biology of colonial ascidians as a paradigm for study in stem cell and regenerative biology. Focusing on botryllid ascidians, we introduce the potential roles played by multipotent epithelia and multipotent/pluripotent stem cells as source of asexual propagation and regenerative plasticity in the different budding mechanisms, and consider the putative mechanism of body repatterning in a non-embryonic scenario. We also discuss the involvement of intra-colony homeostatic processes in regulating budding potential, and the functional link between allorecognition, chimerism, and regenerative potential.
再生现象在多细胞动物中广泛存在。然而，不同物种的再生能力程度存在明显差异：有些门类只能替换缺失的身体部位，而其他一些门类则能够产生全新的个体。海鞘是一类具有显著再生可塑性的动物，展现出多种无性繁殖和生存机制。它们是被囊亚门的海洋无脊椎动物成员，代表着脊索动物祖先的现代后裔；在蝌蚪阶段，它们呈现出脊索动物的身体结构，在变态过程中会被吸收。独居物种成长为成年个体，长度可达数厘米，而群体物种则通过无性繁殖生长，形成由基因相同的个体组成的群体。在这篇综述中，我们概述了群体海鞘的生物学特性，将其作为干细胞和再生生物学研究的范例。以葡萄海鞘为例，我们介绍了多能上皮细胞和多能/多潜能干细胞在不同出芽机制中作为无性繁殖和再生可塑性来源所发挥的潜在作用，并探讨了在非胚胎环境下身体重新模式化的假定机制。我们还讨论了群体内稳态过程在调节出芽潜能中的作用，以及异体识别、嵌合现象和再生潜能之间的功能联系。
