Rojo Concepción, González Encina
Department of Anatomy and Embryology, Veterinary Faculty, Universidad Complutense of Madrid, Madrid, Spain.
Zebrafish. 2008 Spring;5(1):25-37. doi: 10.1089/zeb.2007.0514.
The purpose of this study was to analyze by transmission electron microscopy the morphology and dynamics of the excess cells remaining in the truncated tail of the zebrafish compound mutant, knypek;no tail (kny;ntl). We mainly focused on two periods during tail extension: first, the stage when the primordia of both notochord and spinal cord should be already formed; second, the stage when morphogenesis of the tail is almost complete. Not only double mutants but also wild-type (wt) embryos were examined to compare with. A massive wave of morphologically normal apoptotic cellular death was detected by 22 h of development in the kny;ntl compound mutants. However, apoptosis was a rare event in the tail of wt embryos. We described the ultrastructural features and possible evolution of the apoptotic cells in the tail region, and also assayed the distribution of apoptotic cells in the different tissues conforming the tail: the covering epithelium or epidermis, the bulk of mesenchymal tissue, and the primordia of the spinal cord and the notochord. Huge amounts of apoptotic bodies were found in the mesenchymal tissue of the double-mutant embryos, just the location where excess cells are erroneously accumulated inside the truncated tail. This fact, together with striking findings regarding both some morphological aspects and the distribution of apoptosis, is discussed and suggested to be an indirect consequence of the genetic defects in kny;ntl mutants.
本研究的目的是通过透射电子显微镜分析斑马鱼复合突变体knypek;no tail（kny;ntl）截断尾部中剩余多余细胞的形态和动态变化。我们主要关注尾部延伸过程中的两个阶段：第一，脊索和脊髓原基均应已形成的阶段；第二，尾部形态发生几乎完成的阶段。不仅对双突变体进行了检查，还检查了野生型（wt）胚胎以作比较。在kny;ntl复合突变体发育至22小时时，检测到大量形态正常的凋亡性细胞死亡。然而，凋亡在野生型胚胎的尾部是罕见事件。我们描述了尾部区域凋亡细胞的超微结构特征和可能的演变过程，还分析了凋亡细胞在构成尾部的不同组织中的分布情况，这些组织包括覆盖上皮或表皮、大量间充质组织以及脊髓和脊索原基。在双突变体胚胎的间充质组织中发现了大量凋亡小体，而间充质组织正是截断尾部内多余细胞错误积聚的位置。结合关于某些形态学方面以及凋亡分布的显著发现，对这一事实进行了讨论，并认为这是kny;ntl突变体基因缺陷的间接后果。
