Embryonic stem cells dynamically fluctuate between phenotypic states, as defined by expression levels of genes such as Nanog, while remaining pluripotent. The dynamic phenotype of stem cells is in part determined by gene expression control and dictated by various signaling pathways and transcriptional regulators. We sought to define the activities of two TGF-beta-related signaling pathways, Bone morphogenetic protein (BMP) and Nodal signaling, in modulating mouse embryonic stem cell heterogeneity in undifferentiated culture conditions. Both BMP and Nodal signaling pathways were seen to be active in distinct Nanog subpopulations, with subtle quantitative differences in activity. Pharmacological and genetic modulation of BMP or Nodal signaling strongly influenced the heterogeneous state of undifferentiated ES cells, as assessed by dynamic expression of Nanog reporters. Inhibition of Nodal signaling enhanced BMP activity, which through the downstream target Id factors, enhanced the capacity of ES cells to remain in the Nanog-high epigenetic state. The combined inhibition of Nodal and BMP signaling resulted the accumulation of Nanog-negative cells, even in the presence of LIF, uncovering a shared role for BMP and Nodal signaling in maintaining Nanog expression and repression of differentiation. These results demonstrate a complex requirement for both arms of TGF-beta-related signaling to influence the dynamic cellular phenotype of undifferentiated ES cells in serum-based media, and that differing subpopulations of ES cells in heterogeneous culture have distinct responses to these signaling pathways. Several pathways, including BMP, Nodal, and FGF signaling, have important regulatory function in defining the steady-state distribution of heterogeneity of stem cells.

Members of the transforming growth factor-␤ superfamily play essential roles in both the pluripotency and differentiation of embryonic stem (ES) cells. Although bone morphogenic proteins (BMPs) maintain pluripotency of undifferentiated mouse ES cells, the role of autocrine Nodal signaling is less clear. Pharmacological, molecular, and genetic methods were used to further understand the roles and potential interactions of these pathways. Treatment of undifferentiated ES cells with SB431542, a pharmacological inhibitor of Smad2 signaling, resulted in a rapid reduction of phosphorylated Smad2 and altered the expression of several putative downstream targets. Unexpectedly, inhibition of the Nodal signaling pathway resulted in enhanced BMP signaling, as assessed by Smad1/5 phosphorylation. SB431542-treated cells also demonstrated significant induction of the Id genes, which are known direct targets of BMP signaling and important factors in ES cell pluripotency. Inhibition of BMP signaling decreased the SB431542-mediated phosphorylation of Smad1/5 and induction of Id genes, suggesting that BMP signaling is necessary for some Smad2-mediated activity. Because Smad7, a known inhibitory factor to both Nodal and BMP signaling, was down-regulated following inhibition of Nodal-Smad2 signaling, the contribution of Smad7 to the cross-talk between the transforming growth factor-␤ pathways in ES cells was examined. Biochemical manipulation of Smad7 expression, through shRNA knockdown or inducible gene expression, significantly reduced the SB431542-mediated phosphorylation of Smad1/5 and induction of the Id genes. We conclude that autocrine Nodal signaling in undifferentiated mouse ES cells modulates the vital pluripotency pathway of BMP signaling. Mouse embryonic stem (ES)2 cells are derived from the inner cell mass of the early blastocyst. It is from the inner cell mass that the germ layers arise to produce all cell types of the adult. The capacity of ES cells to either self-renew or differentiate into cells of the three germ layers provides an excellent tool for studying early embryonic development, including self-renewal and pluripotency (1). Some of the essential factors controlling ES cell pluripotency have been identified; however, additional work is necessary to identify other functional signaling pathways that impinge upon the ES cell phenotype, to determine genes that are regulated by these pathways, and to discover how the various pathways interact. Applications of this work will yield insights into the promising use of stem cells for regenerative therapies.ES cells can be maintained as pluripotent cells when grown on mitotically inactivated embryonic fibroblasts or when grown in media supplemented with leukemia inhibitory factor (LIF (2, 3)). Additionally, under serum-free culture conditions, signaling through the bone morphogenetic protein (BMP) pathway is essential for maintaining mouse ES cell pluripotency (4, 5). The combination of LIF and BMP4 inhibits multiple differentiation-inductive signals, a capability that...

Objective Adolescents and young adults with cancer face unique psychosocial and practical issues. However, patients across this group encounter different life experiences, cancer diagnoses and treatment settings given the tailored services for patients ages 15 to 24. Here, we qualitatively explore the psychosocial experiences and practical challenges of young adults (YAs) with cancer diagnosed between ages 25 and 39 in the United Kingdom. Methods We invited YAs diagnosed with cancer in the 5 years prior to enrolment at participating sites to take part in semi‐structured interviews or focus groups. Transcripts were analysed using inductive thematic analysis. Two YA patients reviewed the results to ensure robustness. Results Sixty‐five YAs with varied diagnoses participated. Participants struggled to balance work, childcare and financial solvency with treatment. The halt in family and work life as well as changes in image and ability threatened participants’ identity and perceived ‘normality’ as a YA, however, these also stimulated positive changes. YAs experienced social isolation from friends and family, including children. Many struggled to cope with uncertainty around treatment outcomes and disease recurrence. Conclusion The disruption of family and work life can lead to age‐specific issues in YAs diagnosed with cancer. Age‐tailored psychological and practical services must be considered.

BackgroundThe maintenance of stem cell pluripotency is controlled by a core cluster of transcription factors, NANOG, OCT4 and SOX2 – genes that jointly regulate each other’s expression. The expression of some of these genes, especially of Nanog, is heterogeneous in a population of undifferentiated stem cells in culture. Transient changes in expression levels, as well as heterogeneity of the population is not restricted to this core regulator, but involve a large number of other genes that include growth factors, transcription factors or signal transduction proteins.ResultsAs the molecular mechanisms behind NANOG expression heterogeneity is not yet understood, we explore by computational modeling the core transcriptional regulatory circuit and its input from autocrine FGF signals that act through the MAP kinase cascade. We argue that instead of negative feedbacks within the core NANOG-OCT4-SOX2 transcriptional regulatory circuit, autocrine signaling loops such as the Esrrb - FGF - ERK feedback considered here are likely to generate distinct sub-states within the “ON” state of the core Nanog switch. Thus, the experimentally observed fluctuations in Nanog transcription levels are best explained as noise-induced transitions between negative feedback-generated sub-states. We also demonstrate that ERK phosphorilation is altered and being anti-correlated with fluctuating Nanog expression – in accord with model simulations. Our modeling approach assigns an empirically testable function to the transcriptional regulators Klf4 and Esrrb, and predict differential regulation of FGF family members.ConclusionsWe argue that slow fluctuations in Nanog expression likely reflect individual cell-specific changes in parameters of an autocrine feedback loop, such as changes in ligand capture efficiency, receptor numbers or the presence of crosstalks within the MAPK signal transduction pathway. We proposed a model that operates with binding affinities of multiple transcriptional regulators of pluripotency, and the activity of an autocrine signaling pathway. The resulting model produces varied expression levels of several components of pluripotency regulation, largely consistent with empirical observations reported previously and in this present work.Electronic supplementary materialThe online version of this article (doi:10.1186/s12918-014-0112-4) contains supplementary material, which is available to authorized users.