SUMMARY S6K1 has been implicated in a number of key metabolic responses, which contribute to obesity. Critical among these is the control of a transcriptional program required for the commitment of mesenchymal stem cells to the adipocytic lineage. However, in contrast to its role in the cytosol, the functions and targets of nuclear S6K1 are unknown. Here, we show that adipogenic stimuli trigger nuclear translocation of S6K1, leading to H2BS36 phosphorylation and recruitment of EZH2 to H3, which mediates H3K27 trimethylation. This blocks Wnt gene expression, inducing the upregulation of PPARγ and Cebpa and driving increased adipogenesis. Consistent with this finding, white adipose tissue from S6K1-deficient mice exhibits no detectable H2BS36 phosphorylation or H3K27 trimethylation, whereas both responses are highly elevated in obese humans or in mice fed a high-fat diet. These findings define an S6K1-dependent mechanism in early adipogenesis, contributing to the promotion of obesity.

Novel therapeutic strategies are needed to overcome cancer recurrence, metastasis, and resistance to chemo- and radiotherapy. Cancer stem cells (CSCs) are major contributors to the malignant transformation of cells due to their capacity for self-renewal. Although various CSC markers have been identified in several types of tumors, they are primarily used as cancer-prediction markers and for the isolation of CSC populations. CD133, one of the best-characterized CSC markers in distinct solid tumor types, was shown to be correlated with CSC tumor-initiating capacity; however, the regulation of CD133 expression and its function in cancer are poorly understood. Here, we show that CD133 expression is negatively regulated by direct binding of the p53 tumor suppressor protein to a noncanonical p53-binding sequence in the CD133 promoter. Binding of p53 recruits Histone Deacetylase 1 (HDAC1) to the CD133 promoter and subsequently suppresses CD133 expression by reducing histone H3 acetylation. Furthermore, CD133 depletion suppresses tumor cell proliferation, colony formation, and the expression of core stemness transcription factors including NANOG, octamer-binding transcription factor 4 (OCT4), SOX2, and c-MYC. Critically, the anti-proliferative effects of p53 are antagonized by rescue of CD133 expression in a p53 overexpressing cell line, indicating that the tumor suppressive activity of p53 might be mediated by CD133 suppression. Taken together, our results suggest that p53-mediated transcriptional regulation of CD133 is a key underlying mechanism for controlling the growth and tumor-initiating capacity of CSCs and provide a novel perspective on targeting CSCs for cancer therapy.

organoids should exhibit essential features, including organ-specific multiple cell types, functions of the organ, and spatially organized structures. The emergence and progression of organoid technologies have resulted from several important discoveries (Figure 1). The formation of actual tissuelike colonies in vitro was firstly observed from a co-culture system of keratinocytes and 3T3 fibroblasts. [4] Self-organization, one of the fundamental aspects of organogenesis, was first observed via two distinct approaches, namely reaggregation and structural patterning of dissociated single cells. [5,6] The establishment of 3D culture methods for the structural organization began with the development of extracellular matrices (ECM).In the late 1980s, Bissell and colleagues observed that a laminin-rich gel could function as a basement membrane to differentiate and morphogenesis of mammary epithelial cells. [7,8] In the 1990s, it was reported that in addition to their primary role in physical support, ECM components could regulate gene expression by interacting with integrin-based focal adhesion pathways. [9] Finally, in 2009, Clevers group reported that embedding single intestinal stem cells in ECM substitute had created crypt-like structures similar to the epithelium of the native intestinal tissues, which were the first organoids. [10] Based on these recognitions, biochemical cues that include the initiation of lineage-specific genetic programs have been incorporated in 3D organoid cultures. Through exposure to morphogens, growth factors, or morphogen inhibitors, multiple research groups rapidly developed various organoid models using embryonic stem cells (ESCs) or adult stem cells (ASCs); these include intestine, [10] stomach, [11] liver, [12] pancreas, [13] prostate, [14] and brain [15] organoids. At the same time, vascularization techniques were devised by several groups to embody microenvironments that are physiologically close to their actual counterparts. Microfluidic systems, [16] endothelial cell-coated modules, [17] and vascular endothelial growth factor delivery systems [18] have been demonstrated as in vitro vasculature systems that can facilitate oxygen or nutrients transport to the inner mass of organoids.In the late 2010s, owing to the accumulated information on mechanisms underlying organogenesis and the remarkable advancements in the fields of biomaterial and bioengineering, the era of "organoid customization" has begun. Customizable hydrogel matrices have been proposed to form intestinal organoids whose internal networks recapitulate the Recent advances in 3D cell culture technology have enabled scientists to generate stem cell derived organoids that recapitulate the structural and functional characteristics of native organs. Current organoid technologies have been striding toward identifying the essential factors for controlling the processes involved in organoid development, including physical cues and biochemical signaling. There is a growing demand for engineering dynamic niches characterized by ...

Since the global outbreak of SARS-CoV-2 (COVID-19), infections of diverse human organs along with multiple symptoms continue to be reported. However, the susceptibility of the brain to SARS-CoV-2, and the mechanisms underlying neurological infection are still elusive. Here, we utilized human embryonic stem cell-derived brain organoids and monolayer cortical neurons to investigate infection of brain with pseudotyped SARS-CoV-2 viral particles. Spike-containing SARS-CoV-2 pseudovirus infected neural layers within brain organoids. The expression of ACE2, a host cell receptor for SARS-CoV-2, was sustained during the development of brain organoids, especially in the somas of mature neurons, while remaining rare in neural stem cells. However, pseudotyped SARS-CoV-2 was observed in the axon of neurons, which lack ACE2. Neural infectivity of SARS-CoV-2 pseudovirus did not increase in proportion to viral load, but only 10% of neurons were infected. Our findings demonstrate that brain organoids provide a useful model for investigating SARS-CoV-2 entry into the human brain and elucidating the susceptibility of the brain to SARS-CoV-2.