Data availability RNA-seq data and ribosomal profiling data that support the findings of this study have been deposited in the Gene Expression Omnibus (GEO) under accession code GSE106858. Mass spectrometry data that support the findings of this study have been deposited in figshare.com under the title of this manuscript (A MYC/GCN2/eIF2a negative feedback loop limits protein synthesis to prevent MYC dependent apoptosis in colorectal cancer) by the author Werner Schmitz (
Recent studies show that combinations of defined key developmental transcription factors (TFs) can reprogram somatic cells to pluripotency or induce cell conversion of one somatic cell type to another. However, it is not clear if single genes can define a cell̀s identity and if the cell fate defining potential of TFs is also operative in pluripotent stem cells in vitro. Here, we show that ectopic expression of the neural TF Neurogenin2 (Ngn2) is sufficient to induce rapid and efficient differentiation of embryonic stem cells (ESCs) into mature glutamatergic neurons. Ngn2-induced neuronal differentiation did not require any additional external or internal factors and occurred even under pluripotency-promoting conditions. Differentiated cells displayed neuron-specific morphology, protein expression, and functional features, most importantly the generation of action potentials and contacts with hippocampal neurons. Gene expression analyses revealed that Ngn2-induced in vitro differentiation partially resembled neurogenesis in vivo, as it included specific activation of Ngn2 target genes and interaction partners. These findings demonstrate that a single gene is sufficient to determine cell fate decisions of uncommitted stem cells thus giving insights into the role of key developmental genes during lineage commitment. Furthermore, we present a promising tool to improve directed differentiation strategies for applications in both stem cell research and regenerative medicine.
The MAPK pathway is activated in the majority of melanomas and is the target of therapeutic approaches. Under normal conditions, it initiates the so-called immediate early response, which encompasses the transient transcription of several genes belonging to the AP-1 transcription factor family. Under pathological conditions, such as continuous MAPK pathway overactivation due to oncogenic alterations occurring in melanoma, these genes are constitutively expressed. The consequences of a permanent expression of these genes are largely unknown. Here, we show that FOSL1 is the main immediate early AP-1 member induced by melanoma oncogenes. We first examined its role in established melanoma cells. We found that FOSL1 is involved in melanoma cell migration as well as cell proliferation and anoikis-independent growth, which is mediated by the gene product of its target gene HMGA1, encoding a multipotent chromatin modifier. As FOSL1 expression is increased in patient melanoma samples compared to nevi, we investigated the effect of enhanced FOSL1 expression on melanocytes. Intriguingly, we found that FOSL1 acts oncogenic and transforms melanocytes, enabling subcutaneous tumor growth in vivo. During the process of transformation, FOSL1 reprogrammed the melanocytes and downregulated MITF in a HMGA1-dependent manner. At the same time, AXL was upregulated, leading to a shift in the MITF/AXL balance. Furthermore, FOSL1 re-enforced pro-tumorigenic transcription factors MYC, E2F3 and AP-1. Together, this led to the enhancement of several growth-promoting processes, such as ribosome biogenesis, cellular detachment and pyrimidine metabolism. Overall, we demonstrate that FOSL1 is a novel reprogramming factor for melanocytes with potent tumor transformation potential.
Primary cutaneous marginal zone lymphoma (PCMZL) represents an indolent subtype of non-Hodgkin lymphoma that is clinically characterized by slowly growing skin tumors with a very low propensity for systemic dissemination. The underlying genetic basis of PCMZL has not been comprehensively elucidated. To gain deeper insight into the molecular pathogenesis of PCMZL, we performed hybridization-based panel sequencing of 38 patients with well-characterized PCMZL. In 32 of the 38 patients, we identified genetic alterations within 39 selected target genes. The most frequently detected alterations (24/38 patients, 63.2%) affected the FAS gene, of which 22 patients harbored alterations, which affect the functionally relevant death domain of the apoptosis-regulating FAS/CD95 protein in a dominant-negative manner. In addition, we identified highly recurrent mutations in three other genes, namely SLAMF1, SPEN, and NCOR2. Our molecular data suggest that apoptosis defects provide the molecular basis of the observed clinical features of PCMZL, which commonly presents with only slowly growing skin tumors, reflecting its invariably indolent behavior. From a diagnostic point of view, highly recurrent FAS mutations in PCMZL presumably separate this indolent lymphoma entity from pseudolymphoma, and this adds adjunctive discriminatory features at a molecular level.
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