Stem cells in reproductive strategy of asexually reproducing invertebrates

Pluripotent Gametogenic Stem Cells of Asexually Reproducing Invertebrates

“…In animals with asexual reproduction, the differentiation of "primary" stem cells into germ and somatic cells is delayed, the germ lineage in these animals is not segregated (Tuzet, 1964;Buss, 1987Buss, , 1999Sköld et al, 2009); these stem cells serve as the cellular source of asexual and sexual reproduction as well as of regeneration (Isaeva et al, 2008b(Isaeva et al, , 2009Frank et al, 2009). Pluripotent stem cells can differentiate into a very wide spectrum of somatic cells in adult organisms.…”

“…Pluripotent stem cells can differentiate into a very wide spectrum of somatic cells in adult organisms. Depending on the width of the potential range of cell differentiation, totipotent, pluripotent, multipotent, oligopotent, and unipotent stem cells are distinguished, but the usage of this terminology is not unified (Müller, 2006;Newton, 2006;Isaeva et al, 2008bIsaeva et al, , 2009Rinkevich et al, 2009;Sköld et al, 2009). Totipotent cells can give rise to all cell types of a developing organism; the zygote and the cells of the early mammalian embryo are totipotent.…”

“…We have found stem cells, morphologically similar to hemoblasts in B. leachi (Cima et al, 2001) and other studied ascidians (Burighel & Cloney, 1997), in the early buds and vascular system of the colonial ascidian Botryllus tuberatus (Akhmadieva et al, 2007). The data of our team showed that studied pluripotent reserve stem cells serve as the predecessors of germ and somatic cells and display some evolutionarily conserved features of the morphological and functional organization typical also for cells of the germ line and embryonic stem cells (Isaeva et al, 2003(Isaeva et al, , 2008b(Isaeva et al, , 2009Akhmadieva et al, 2007;Shukalyuk et al, , 2007Shukalyuk et al, , 2011Isaeva, 2010;.…”

“…In animals with asexual reproduction by somatic embryogenesis, the germ lineage remains non-segregated even in the adult organism, the gametes of which differentiate from stem cells (Blackstone & Jasker, 2003;Rinkevich, 2009;Sköld et al, 2009). Examples of such reserve stem cells, capable of differentiating both into germ and somatic cells, include sponge archaeocytes, cnidarian interstitial cells, planarian neoblasts, and stem cells of colonial ascidians (reviews: Isaeva et al, 2008bIsaeva et al, , 2009Frank et al, 2009;Rinkevich et al, 2009;Sköld et al, 2009;Isaeva, 2010;Srouji, Extavour, 2011). These self-renewing stem cells maintains continuously throughout the life of an individual or a colony, being predecessors of germ cells and all the types (or a wide spectrum) of somatic cells, so ensuring both sexual and asexual reproduction.…”

“…Besides, a third variant of germ cell specification, along with preformation and epigenesis, is recognized as somatic embryogenesis, in asexually reproducing animals, which have stem cells able to differentiate into germ and somatic cells throughout the life of an individual or a colony (Buss, 1987(Buss, , 1999Blackstone & Jasker, 2003;Frank et al, 2009;Rinckevich et al, 2009). Pluri/totipotent stem cells of these animals provide a cell source for gametogenesis, asexual reproduction and regeneration (Isaeva et al, 2008b(Isaeva et al, , 2009Frank et al, 2009;Sköld et al, 2009). Stem cells that have the potential to become both somatic and primary germ cells and are morphologically indistinguishable from the latter were defined as "primary stem cells" (Sköld et al, 2009).…”