Tiozzo S, Ballarin L, Burighel P, Zaniolo G
University of Padova, Department of Biology, via U. Bassi 58/B, 35121 Padova, Italy.
Tissue Cell. 2006 Jun;38(3):193-201. doi: 10.1016/j.tice.2006.02.003. Epub 2006 Apr 24.
Programmed cell death (PCD) by apoptosis is a physiological mechanism by which cells are eliminated during embryonic and post-embryonic stages of animal life cycle. During asexual reproduction, the zooids of colonial ascidians originate from an assorted cell population instead of a single zygote, so that we assume that regulation of the equilibrium among proliferation, differentiation and cell death may follow different pathways in comparison to the embryonic development. Here we investigate the presence of apoptotic events throughout the blastogenetic life cycle of the colonial ascidian Botryllus schlosseri, by means of terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL) coupled with histochemical and electron microscopy techniques. The occurrence of low levels of morphogenetic cell death suggests that, in contrast to what happens during sexual development (embryogenesis and metamorphosis), apoptosis does not play a pivotal role during asexual propagation in botryllid ascidian. Nevertheless, PCD emerges as a key force to regulate homeostasis in adult zooids and to shape and modulate the growth of the whole colony.
细胞凋亡介导的程序性细胞死亡（PCD）是一种生理机制，通过该机制，细胞在动物生命周期的胚胎期和胚胎后期被清除。在无性繁殖过程中，群体海鞘的游动孢子来源于多种细胞群体而非单个受精卵，因此我们推测，与胚胎发育相比，增殖、分化和细胞死亡之间平衡的调节可能遵循不同的途径。在这里，我们通过末端脱氧核苷酸转移酶dUTP缺口末端标记法（TUNEL）结合组织化学和电子显微镜技术，研究群体海鞘博氏菊海鞘整个芽殖生命周期中凋亡事件的存在情况。低水平形态发生性细胞死亡的发生表明，与有性发育（胚胎发生和变态）过程中发生的情况相反，凋亡在菊海鞘无性繁殖过程中并不起关键作用。然而，程序性细胞死亡成为调节成年游动孢子内稳态以及塑造和调节整个群体生长的关键力量。
