脊椎动物和模型无脊椎动物(例如果蝇)中的成体干细胞(ASC)通常是长寿命的,血统限制,具有体细胞后代和组织/器官限制活动的克隆和静止细胞。这样的ASC大多是罕见的,形态未分化,并经历不对称的细胞分裂。以基因表达为特征,它们可以调节组织/器官的稳态,修复和再生。相比之下,对其他动物门的分析表明,ASCs出现在不同的生命阶段,呈现分化和未分化表型,并且可能具有变形虫运动。通常是多能/全能,它们可能表达生殖细胞标记,但通常缺乏种系隔离,并且通常不位于离散的生态位。ASCs可能占动物细胞的40%,参与一系列生物现象,从全身再生,休眠,和无性繁殖,不确定的增长。他们被认为是合法的选择单位。概念化这种分歧,我们提出了沃丁顿景观的另一种干性隐喻:“摇摆的彭罗斯”景观。这里,全能性ASC采用“Escherian楼梯间”的上升/下降路线,终身全能性途径。ASC还可以沿着较低的干性梯队行进以达到完全分化的状态。然而,从任何起始状态,细胞可以改变它们的干细胞状态,强调了它们动态的细胞效力。因此,脊椎动物ASCs可能仅反映一种后生动物ASC原型。
Adult stem cells (ASCs) in vertebrates and model invertebrates (e.g. Drosophila melanogaster) are typically long-lived, lineage-restricted, clonogenic and quiescent cells with somatic descendants and tissue/organ-restricted activities. Such ASCs are mostly rare, morphologically undifferentiated, and undergo asymmetric cell division. Characterized by \'stemness\' gene expression, they can regulate tissue/organ homeostasis, repair and regeneration. By contrast, analysis of other animal phyla shows that ASCs emerge at different life stages, present both differentiated and undifferentiated phenotypes, and may possess amoeboid movement. Usually pluri/totipotent, they may express germ-cell markers, but often lack germ-line sequestering, and typically do not reside in discrete niches. ASCs may constitute up to 40% of animal cells, and participate in a range of biological phenomena, from whole-body regeneration, dormancy, and agametic asexual reproduction, to indeterminate growth. They are considered legitimate units of selection. Conceptualizing this divergence, we present an alternative stemness metaphor to the Waddington landscape: the \'wobbling Penrose\' landscape. Here, totipotent ASCs adopt ascending/descending courses of an \'Escherian stairwell\', in a lifelong totipotency pathway. ASCs may also travel along lower stemness echelons to reach fully differentiated states. However, from any starting state, cells can change their stemness status, underscoring their dynamic cellular potencies. Thus, vertebrate ASCs may reflect just one metazoan ASC archetype.