Directed cardiac differentiation of human pluripotent stem cells (hPSCs) enables disease modeling, investigation of human cardiogenesis, as well as large-scale production of cardiomyocytes (CMs) for translational purposes. Multiple CM differentiation protocols have been developed to individually address specific requirements of these diverse applications, such as enhanced purity at a small scale or mass production at a larger scale. However, there is no universal highefficiency procedure for generating CMs both in two-dimensional (2D) and three-dimensional (3D) culture formats, and undefined or complex media additives compromise functional analysis or cost-efficient upscaling. Using systematic combinatorial optimization, we have narrowed down the key requirements for efficient cardiac induction of hPSCs. This implied differentiation in simple serum and serum albumin-free basal media, mediated by a minimal set of signaling pathway manipulations at moderate factor concentrations. The method was applicable both to 2D and 3D culture formats as well as to independent hPSC lines. Global time-course gene expression analyses over extended time periods and in comparison with human heart tissue were used to monitor culture-induced maturation of the resulting CMs. This suggested that hPSC-CMs obtained with our procedure reach a rather stable transcriptomic state after approximately 4 weeks of culture. The underlying gene expression changes correlated well with a decline of immature characteristics as well as with a gain of structural and physiological maturation features within this time frame. These data link gene expression patterns of hPSC-CMs to functional readouts and thus define the cornerstones of culture-induced maturation. STEM

To elucidate the function of Omega class glutathione transferases (GSTs) (EC 2.5.1.18) in multicellular organisms, the GSTO-1 from Caenorhabditis elegans (GSTO-1; C29E4.7) was investigated. Disc diffusion assays using Escherichia coli overexpressing GSTO-1 provided a test of resistance to long-term exposure under oxidative stress. After affinity purification, the recombinant GSTO-1 had minimal catalytic activity toward classic GST substrates but displayed significant thiol oxidoreductase and dehydroascorbate reductase activity. Microinjection of the GSTO-1-promoter green fluorescent protein construct and immunolocalization by electron microscopy localized the protein exclusively in the intestine of all postembryonic stages of C. elegans. Deletion analysis identified an approximately 300-nucleotide sequence upstream of the ATG start site necessary for GSTO-1 expression. Site-specific mutagenesis of a GATA transcription factor binding motif in the minimal promoter led to the loss of reporter expression. Similarly, RNA interference (RNAi) of Elt-2 indicated the involvement of this gut-specific transcription factor in GSTO-1 expression. Transcriptional up-regulation under stress conditions of GSTO-1 was confirmed by analyzing promoter-reporter constructs in transgenic C. elegans strains. To investigate the function of GSTO-1 in vivo, transgenic animals overexpressing GSTO-1 were generated exhibiting an increased resistance to juglone-, paraquat-, and cumene hydroperoxide-induced oxidative stress. Specific silencing of the GSTO-1 by RNAi created worms with an increased sensitivity to several prooxidants, arsenite, and heat shock. We conclude that the stress-responsive GSTO-1 plays a key role in counteracting environmental stress.

The mitogen-activated protein kinase (MAPK) pathways and insulin-like signaling play pivotal roles in cellular stress response. Using an anti-phospho-SAPK/JNK antibody and a daf-16::GFP-based reporter assay, the present study shows in Caenorhabditis elegans that ambient temperature (1-37 degrees C) specifically influences the activation (phosphorylation) of the MAP kinase JNK-1 as well as the nuclear translocation of DAF-16, the main downstream target of insulin-like signaling. Activated JNK-1 was detected only in neuronal cells, and JNK-1 was found to be controlled by the MAPK JKK-1 under heat stress. Comparative analyses on the wildtype and a jnk-1 deletion mutant revealed a promoting influence of JNK-1 on both nuclear DAF-16 translocations and DAF-16 target gene (superoxide dismutase 3, sod-3) expressions within peripheral, non-neuronal tissue. Consequently, the mutant exhibited a reduced thermal tolerance and reproductive fitness at higher temperatures. These results provide evidence of indirect interactions between neuronal MAPK and peripheral insulin-like signaling in response to environmental stimuli (temperature, H2O2).

Background: PP2A activity and intracellular targeting are regulated by post-translational modifications of B56 phosphoprotein subunits. Results: PP2A is inhibited by a PKC␣-dependent phosphorylation of B56␣ at Ser 41 leading to downstream functional effects. Conclusion: This inhibition may represent an important signaling pathway regulated by stimuli that activate PKC␣. Significance: Our data focus B56␣ on a dynamic role in the interplay between protein kinases and PP2A.