De Mulder Katrien, Pfister Daniela, Kuales Georg, Egger Bernhard, Salvenmoser Willi, Willems Maxime, Steger Jessica, Fauster Katja, Micura Ronald, Borgonie Gaetan, Ladurner Peter
University of Innsbruck, Institute of Zoology and CMBI, Technikerstrasse 25, A-6020 Innsbruck, Austria.
Dev Biol. 2009 Oct 1;334(1):198-212. doi: 10.1016/j.ydbio.2009.07.019. Epub 2009 Jul 23.
The flatworm stem cell system is exceptional within the animal kingdom, as totipotent stem cells (neoblasts) are the only dividing cells within the organism. In contrast to most organisms, piwi-like gene expression in flatworms is extended from germ cells to somatic stem cells. We describe the isolation and characterization of the piwi homologue macpiwi in the flatworm Macrostomum lignano. We use in situ hybridization, antibody staining and RNA interference to study macpiwi expression and function in adults, during postembryonic development, regeneration and upon starvation. We found novelties regarding piwi function and observed differences to current piwi functions in flatworms. First, macpiwi was essential for the maintenance of somatic stem cells in adult animals. A knock-down of macpiwi led to a complete elimination of stem cells and death of the animals. Second, the regulation of stem cells was different in adults and regenerates compared to postembryonic development. Third, sexual reproduction of M. lignano allowed to follow germline formation during postembryonic development, regeneration, and starvation. Fourth, piwi expression in hatchlings further supports an embryonic formation of the germline in M. lignano. Our findings address new questions in flatworm stem cell research and provide a basis for comparison with higher organisms.
扁虫干细胞系统在动物界中是独特的，因为全能干细胞（新细胞）是该生物体中唯一进行分裂的细胞。与大多数生物体不同，扁虫中类Piwi基因的表达从生殖细胞扩展到了体细胞干细胞。我们描述了扁虫曼氏大口涡虫（Macrostomum lignano）中Piwi同源物macpiwi的分离和特性。我们使用原位杂交、抗体染色和RNA干扰来研究macpiwi在成虫、胚后发育、再生和饥饿期间的表达及功能。我们发现了关于Piwi功能的新情况，并观察到其与扁虫当前Piwi功能的差异。首先，macpiwi对成年动物体细胞干细胞的维持至关重要。敲低macpiwi会导致干细胞完全消失以及动物死亡。其次，与胚后发育相比，成虫和再生体中干细胞的调控有所不同。第三，曼氏大口涡虫的有性生殖使得在胚后发育、再生和饥饿期间能够追踪生殖系的形成。第四，幼体中Piwi的表达进一步支持了曼氏大口涡虫生殖系的胚胎形成。我们的研究结果提出了扁虫干细胞研究中的新问题，并为与高等生物进行比较提供了基础。
