Summary Cell metabolism is adaptive to extrinsic demands, however the intrinsic metabolic demands that drive the induced pluripotent stem cell (iPSC) program remain unclear. While glycolysis increases throughout the reprogramming process, we show that the estrogen related nuclear receptors (ERRα and γ) and their partnered co-factors PGC-1α and β, are transiently induced at an early stage resulting in a burst of oxidative phosphorylation (OXPHOS) activity. Up-regulation of ERRα or γ is required for both the OXPHOS burst in human and mouse cells, respectively, as well as iPSC generation itself. Failure to induce this metabolic switch collapses the reprogramming process. Furthermore, we identify a rare pool of Sca1−/CD34− sortable cells that is highly enriched in bona fide reprogramming progenitors. Transcriptional profiling confirmed that these progenitors are ERRγ and PGC-1β positive and have undergone extensive metabolic reprogramming. These studies characterize a previously unrecognized, ERR-dependent metabolic gate prior to establishment of induced pluripotency.

Cancer-associated fibroblasts (CAFs) are the key components of the densely proliferated stroma in pancreatic ductal adenocarcinoma (PDAC) and contribute to tumor progression and drug resistance. CAFs comprise heterogeneous subpopulations playing unique and vital roles. However, the commonly used mouse models have not been able to fully reproduce the histological and functional characteristics of clinical human CAF. Here, we generated a human cell-derived stroma-rich CDX (Sr-CDX) model, to reproduce the clinical tumor microenvironment. By co-transplanting human adipose-derived mesenchymal stem cells (AD-MSCs) and a human PDAC cell line (Capan-1) into mice, the Sr-CDX model recapitulated the characteristics of clinical pancreatic cancer, such as accelerated tumor growth, abundant stromal proliferation, chemoresistance, and dense stroma formed from the heterogeneous CAFs. Global RNA sequencing, single-cell based RNA sequencing, and histological analysis of CAFs in the Sr-CDX model revealed that the CAFs of the Sr-CDX mice were derived from the transplanted AD-MSCs and composed of heterogeneous subpopulations of CAF, including known and unknown subtypes. These lines of evidences suggest that our new tumor-bearing mouse model has the potential to address an open question in CAF research, that is the mechanism of CAF differentiation.

cThe filamentous, heterocystous cyanobacterium Anabaena sp. strain PCC 7120 is one of the simplest multicellular organisms that show both morphological pattern formation with cell differentiation (heterocyst formation) and circadian rhythms. Therefore, it potentially provides an excellent model in which to analyze the relationship between circadian functions and multicellularity. However, detailed cyanobacterial circadian regulation has been intensively analyzed only in the unicellular species Synechococcus elongatus. In contrast to the highest-amplitude cycle in Synechococcus, we found that none of the kai genes in Anabaena showed high-amplitude expression rhythms. Nevertheless, ϳ80 clock-controlled genes were identified. We constructed luciferase reporter strains to monitor the expression of some high-amplitude genes. The bioluminescence rhythms satisfied the three criteria for circadian oscillations and were nullified by genetic disruption of the kai gene cluster. In heterocysts, in which photosystem II is turned off, the metabolic and redox states are different from those in vegetative cells, although these conditions are thought to be important for circadian entrainment and timekeeping processes. Here, we demonstrate that circadian regulation is active in heterocysts, as shown by the finding that heterocyst-specific genes, such as all1427 and hesAB, are expressed in a robust circadian fashion exclusively without combined nitrogen.

The autonomic nervous system (ANS) regulates tissue homeostasis and remodelling through antagonistic effects of noradrenergic sympathetic and cholinergic parasympathetic signalling. Despite numerous reports on the induction of sympathetic neurons from human pluripotent stem cells (hPSCs), no induction methods have effectively derived cholinergic parasympathetic neurons from hPSCs. Considering the antagonistic effects of noradrenergic and cholinergic inputs on target organs, both sympathetic and parasympathetic neurons are expected to be induced. This study aimed to develop a stepwise chemical induction method to induce sympathetic-like and parasympathetic-like ANS neurons. Autonomic specification was achieved through restricting signals inducing sensory or enteric neurogenesis and activating bone morphogenetic protein (BMP) signals. Global mRNA expression analyses after stepwise induction, including single-cell RNA-seq analysis of induced neurons and functional assays revealed that each induced sympathetic-like or parasympathetic-like neuron acquired pharmacological and electrophysiological functional properties with distinct marker expression. Further, we identified selective induction methods using appropriate seeding cell densities and neurotrophic factor concentrations. Neurons were individually induced, facilitating the regulation of the beating rates of hiPSC-derived cardiomyocytes in an antagonistic manner. The induction methods yield specific neuron types, and their influence on various tissues can be studied by co-cultured assays.

Recently, we reported that bacterial incorporation induces cellular transdifferentiation of human fibroblasts. However, the bacterium-intrinsic cellular- transdifferentiation factor remained unknown. Here, we found that cellular transdifferentiation is caused by ribosomes. Ribosomes, isolated from both prokaryotic and eukaryotic cells, induce the formation of embryoid body-like cell clusters. Numerous ribosomes are incorporated into both the cytoplasm and nucleus through trypsin-activated endocytosis, which leads to cell-cluster formation. Although ribosome-induced cell clusters (RICs) express several stemness markers and differentiate into derivatives of all three germ layers in heterogeneous cell populations, RICs fail to proliferate, alter the methylation states of pluripotent genes, or contribute to teratoma or chimera formation. However, RICs express markers of epithelial–mesenchymal transition without altering the cell cycle, despite their proliferation obstruction. These findings demonstrate that incorporation of ribosomes into host cells induces cell transdifferentiation and alters cellular plasticity.