In cancers with a highly altered genome, distinct genetic alterations drive subsets rather than the majority of individual tumours. Here we use a sequential search across human tumour samples for transcript outlier data points with associated gene copy number variations that correlate with patient's survival to identify genes with pro-invasive functionality. Employing loss and gain of function approaches in vitro and in vivo, we show that one such gene, MTSS1, promotes the ability of melanocytic cells to metastasize and engages actin dynamics via Rho-GTPases and cofilin in this process. Indeed, high MTSS1 expression defines a subgroup of primary melanomas with unfavourable prognosis. These data underscore the biological, clinical and potential therapeutic implications of molecular subsets within genetically complex cancers.
Ever since its description and the generation of its defining antibody some 20 years ago, NeuN (Neural Nuclei) has been an invaluable tool for developmental neuroscientist sand neuropathologists to identify neurons and follow their normal or malignant development [corrected].The recent identification of the splicing factor Rbfox3 as the molecule constituting the genuine NeuN epitope has opened up a novel perspective on NeuN immunostaining and its interpretation. Here, we briefly review these recent developments, and we provide a series of data that allow to rationalize the specificity of the NeuN/A60 antibody on aldehyde-fixed tissues on the one hand, and its cross-reactivity with Synapsin I and R3hdm2 on Western blots on the other. We argue that rather than being considered as a mere marker for mature neurons, Rbfox3-mediated NeuN/A60 immunoreactivity may provide a window onto neuronal biology. Specifically, we hypothesize that the phosphorylation-dependent antigenicity of the Rbfox3/NeuN epitope should allow to visualize neuronal physiology realized through Rbfox3, including splicing, on the single-cell level.
Cultivation of A549 non-small-cell lung carcinoma (NSCLC) cells in the presence of staurosporine (SSP) leads to a reduction or a lack of proliferation in a concentration-dependent manner. This inhibition of proliferation is accompanied by the generation of polyploid giant cancer cells (PGCCs) that are characterized by cell flattening, increased cell size, polyploidy, and polynucleation as determined by crystal violet staining, BrdU and DiI labelling, and flow cytometry as well as video time-lapse analysis. Continuous SSP treatment of A549 cells can preserve PGCCs for at least two months in a resting state. Upon removal of SSP, A549 PGCCs restart to divide and exhibit a proliferation pattern and cellular morphology indistinguishable from cells where PGCCs originally derived from. Thus, SSP-treated A549 cells represent a simple and reliable experimental model for the reversible generation of PGCCs and their subsequent experimental analysis.
The Wingless family of secreted proteins impinges on multiple aspects of vertebrate nervous system development, from early global patterning and cell fate decision to synaptogenesis. Here, we mapped the developmental expression of the Tcf7l2, which is key to the canonical Wingless signaling cascade, in the developing cerebellum. The exclusive and transient expression of Tcf7l2 in ventricular and Olig2-defined precursor cells within the cerebellar anlage, and its predominant expression in postmitotic neurons in the midbrain/inferior colliculus allowed us to ask whether cell type-specific differences are also reflected in splice isoform variability. We also included in this analysis intestinal epithelia, where Tcf7l2 function has been intensively studied. Our data reveal extensive variability of Tcf7l2 splicing in the central nervous system. Additional variability in brain-expressed Tcf7l2 is generated by a length polymorphism of expressed mRNAs in a stretch of normally nine adenines found at the beginning of exon 18, reminiscent of variability observed at the same site in cancers with microsatellite instability. A consensus emerging from our data is that the expression of isoforms comprising or lacking the C-clamp motif, which has been linked by in vitro studies to the regulation of cell growth, is indeed tightly correlated with the proliferative status in vivo.
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