Induced stem cell neoplasia in a cnidarian by ectopic expression of a POU domain transcription factor

Abstract

SUMMARYThe evolutionary origin of stem cell pluripotency is an unresolved question. In mammals, pluripotency is limited to early embryos and is induced and maintained by a small number of key transcription factors, of which the POU domain protein Oct4 is considered central. Clonal invertebrates, by contrast, possess pluripotent stem cells throughout their life, but the molecular mechanisms that control their pluripotency are poorly defined. To address this problem, we analyzed the expression pattern and function of Polynem (Pln), a POU domain gene from the marine cnidarian Hydractinia echinata. We show that Pln is expressed in the embryo and adult stem cells of the animal and that ectopic expression in epithelial cells induces stem cell neoplasms and loss of epithelial tissue. Neoplasm cells downregulated the transgene but expressed the endogenous Pln gene and also Nanos, Vasa, Piwi and Myc, which are all known cnidarian stem cell markers. Retinoic acid treatment caused downregulation of Pln and the differentiation of neoplasm cells to neurosensory and epithelial cells. Pln downregulation by RNAi led to differentiation. Collectively, our results suggest an ancient role of POU proteins as key regulators of animal stem cells.

GSK3 Inhibitors Regulate MYCN mRNA Levels and Reduce Neuroblastoma Cell Viability through Multiple Mechanisms, Including p53 and Wnt Signaling

“…As a control to show that the ectopic MYCN is not responsive to stimuli that alter endogenous MYCN levels through direct transcriptional regulation, we treated SY5Y-MYCN cells with retinoic acid. Retinoic acid is used in neuroblastoma treatment as it has an evolutionarily conserved role in neuronal cell differentiation (31,32). Retinoic acid reduced endogenous MYCN mRNA levels in parental SY5Y cells and other neuroblastoma cell lines as expected.…”

Hydractinia, a pioneering model for stem cell biology and reprogramming somatic cells to pluripotency

“…Most observations and investigations on stem cells in Cnidaria have been made in Hydra (reviewed by Bode, 1996;Bosch, 2007Bosch, , 2009Bosch et al, 2010;Watanabe et al, 2009;David 2012;Hobmayer 2012 in this issue) and in Hydractinia (Weismann, 1883;Hoffmann and Kroiher, 2001;Müller et al, 2004a;Teo et al, 2006;Rebscher et al, 2008;Künzel et al, 2010;Millane et al, 2011). The stem cells are also known as interstitial cells (i-cells) as they reside in interstitial spaces at the bases of the epithelia (Weismann, 1883).…”

“…Reprogramming of epithelial cells into stem cells in Hydractinia Millane et al, 2011) analyzed the expression and function of a POU-domain gene from Hydractinia echinata with high sequence similarity to the mammalian Oct4. Oct4 is a well-known pluripotency factor expressed in the inner cell mass, epiblast and germ line of mammals.…”

The Hydra genome: insights, puzzles and opportunities for Developmental Biologists

“…An Oct4 homologue appears to be absent from Hydra. However, Polynem, a POU family gene in Hydractinia, has been shown to have a role in stem cell development (Millane et al, 2011;Plickert et al, 2012). Phylogenetic analysis does not resolve the relationship of Polynem to other members of the POU family (Millane et al, 2011).…”

“…However, Polynem, a POU family gene in Hydractinia, has been shown to have a role in stem cell development (Millane et al, 2011;Plickert et al, 2012). Phylogenetic analysis does not resolve the relationship of Polynem to other members of the POU family (Millane et al, 2011). Additional studies of the POU family in cnidarians are clearly warranted to clarify the evolutionary history of members of this family and their role in stem cell biology.…”