The active stem cell specific expression of sponge Musashi homolog EflMsiA suggests its involvement in maintaining the stem cell state
The active stem cell specific expression of sponge Musashi homolog EflMsiA suggests its involvement in maintaining the stem cell state
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海绵 Musashi 同源物 EflMsiA 的活性干细胞特异性表达表明其参与维持干细胞状态
DOI：
10.1016/j.mod.2012.03.001
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
and Funayama N
中科院分区：
文献类型：
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作者：
Okamoto K;Nakatsukasa M;Alie A;Masuda Y;Agata A;and Funayama N
干细胞的一个标志是能够可持续地产生干细胞本身（自我更新）以及分化的细胞。虽然对这种能力的全面理解需要澄清原始分子和细胞机制，但干细胞如何在进化上最古老的现存多细胞生物海绵中保持其干细胞状态和数量，人们知之甚少。在这里，我们报告的第一个干细胞特异性基因的识别demosponges，Musashi（一种进化保守的RNA结合蛋白，调节各种生物体中的干细胞状态）的同源物。EflMsiA是一种Musashi parasi，在淡水海绵Ephydatia fluviatilis的干细胞（原始细胞）中特异性表达。EflMsiA蛋白主要定位于古细胞的细胞核中，小部分位于细胞质中。当古细胞进入M期时，EflMsiA蛋白扩散到细胞质中，可能是由于核膜的破裂。在本研究中，通过精确分析EflMsiA mRNA和蛋白质的表达水平，揭示了两种类型的M期原始细胞[（M）-原始细胞]的存在。在I型（M）-原始细胞（推测为经历自我更新的原始细胞）中，EflMsiA mRNA和蛋白质的表达水平高。在II型（M）-原始细胞中，推测为定向分化的原始细胞（定向原始细胞），EflMsiA mRNA和蛋白质的表达水平比I型（M）-原始细胞中的表达水平低约60%和30%。根据这些结果，古细胞可以首次在分子上被定义为EflMsiA-mRNA表达细胞。此外，这些研究结果揭示了原始细胞的细胞分裂模式，并建议原始细胞分裂对称的自我更新和分化。
A hallmark of stem cells is the ability to sustainably generate stem cells themselves (self-renew) as well as differentiated cells. Although a full understanding of this ability will require clarifying underlying the primordial molecular and cellular mechanisms, how stem cells maintain their stem state and their population in the evolutionarily oldest extant multicellular organisms, sponges, is poorly understood. Here, we report the identification of the first stem cell-specific gene in demosponges, a homolog of Musashi (an evolutionarily conserved RNA binding protein that regulates the stem cell state in various organisms). EflMsiA, a Musashi paralog, is specifically expressed in stem cells (archeocytes) in the freshwater sponge Ephydatia fluviatilis. EflMsiA protein is localized predominantly in the nucleus, with a small fraction in the cytoplasm, in archeocytes. When archeocytes enter M-phase, EflMsiA protein diffuses into the cytoplasm, probably because of the breakdown of the nuclear membrane. In the present study, the existence of two types of M-phase archeocytes [(M)-archeocytes] was revealed by a precise analysis of the expression levels of EflMsiA mRNA and protein. In Type I (M)-archeocytes, presumably archeocytes undergoing self-renewal, the expression levels of EflMsiA mRNA and protein were high. In Type II (M)-archeocytes, presumably archeocytes committed to differentiate (committed archeocytes), the expression levels of EflMsiA mRNA and protein were about 60% and 30% lower than those in Type I (M)-archeocytes. From these results, archeocytes can be molecularly defined for the first time as EflMsiA-mRNA-expressing cells. Furthermore, these findings shed light on the mode of cell division of archeocytes and suggest that archeocytes divide symmetrically for both self-renewal and differentiation.