A feedforward loop between JAK/STAT downstream target p115 and STAT in germline stem cells.

The maintenance of germline stem cells (GSCs) is essential for tissue homeostasis. JAK/STAT signaling maintains GSC fate in Drosophila testis. However, how JAK/STAT signaling maintains male GSC fate through its downstream targets remains poorly understood. Here, we identify p115, a tER/cis-Golgi golgin protein, as a putative downstream target of JAK/STAT signaling. p115 maintains GSC fate independent of GM130 and GRASP65. p115 localizes in cytosol, the ER and Golgi apparatus in germline cells and is required for the morphology of the ER and Golgi apparatus. Furthermore, depletion of p115 in GSCs results in aberrant spindle orientation. Mechanistically, p115 associates with and stabilizes STAT. Finally, ectopic expression of STAT completely restores GSC loss caused by p115 depletion. Collectively, JAK/STAT signaling and p115 form a feedforward loop to maintain male GSC fate. Our work provides new insights into the regulatory mechanism of how stem cell maintenance is properly controlled by JAK/STAT signaling.

Nanocellulose interface enhanced all-cellulose foam with controllable strength via a facile liquid phase exchange route.

The development of sustainable, biodegradable, non-toxic biomass foams with outstanding physical properties to replace traditional petroleum-based foams is urgent. In this work, we proposed a simple, efficient, and scalable approach to fabricate nanocellulose (NC) interface enhanced all-cellulose foam through ethanol liquid phase exchange and subsequent ambient drying. In this process, NCs served as reinforcer and binder were integrated with pulp fiber to improve cellulose interfibrillar bonding and interface adhesion between NCs and pulp microfibrils. The resultant all-cellulose foam displayed stable microcellular structure (porosity of 91.7-94.5 %), low apparent density (0.08-0.12 g/cm3), and high compression modulus (0.49-2.96 MPa) by regulating the content and size of NCs. Further, the strengthening mechanism of the structure and property of all-cellulose foam were investigated in detail. This proposed process enabled ambient drying, and is simple and feasible for low-cost, practicable, and scalable production of biodegradable, green bio-based foam without special apparatuses and other chemicals.

SZT2 maintains hematopoietic stem cell homeostasis via nutrient-mediated mTORC1 regulation.

The mTORC1 pathway coordinates nutrient and growth factor signals to maintain organismal homeostasis. Whether nutrient signaling to mTORC1 regulates stem cell function remains unknown. Here, we show that SZT2 - a protein required for mTORC1 downregulation upon nutrient deprivation - is critical for hematopoietic stem cell (HSC) homeostasis. Ablation of SZT2 in HSCs decreased the reserve and impaired the repopulating capacity of HSCs. Furthermore, ablation of both SZT2 and TSC1 - 2 repressors of mTORC1 on the nutrient and growth factor arms, respectively - led to rapid HSC depletion, pancytopenia, and premature death of the mice. Mechanistically, loss of either SZT2 or TSC1 in HSCs led to only mild elevation of mTORC1 activity and reactive oxygen species (ROS) production. Loss of both SZT2 and TSC1, on the other hand, simultaneously produced a dramatic synergistic effect, with an approximately 10-fold increase of mTORC1 activity and approximately 100-fold increase of ROS production, which rapidly depleted HSCs. These data demonstrate a critical role of nutrient mTORC1 signaling in HSC homeostasis and uncover a strong synergistic effect between nutrient- and growth factor-mediated mTORC1 regulation in stem cells.

Genome-wide fitness gene identification reveals Roquin as a potent suppressor of CD8 T cell expansion and anti-tumor immunity.

Robust expansion of adoptively transferred T cells is a prerequisite for effective cancer immunotherapy, but how many genes in the genome modulate T cell expansion remains unknown. Here, we perform in vivo and in vitro CRISPR screens to systematically identify genes influencing CD8 T cell expansion. In the mouse genome, ∼2,600 and ∼1,500 genes are required for optimal CD8 T cell expansion in vivo and in vitro, respectively. In vivo-specific CD8 T cell essential genes are enriched in metabolic pathways, including mitochondrial metabolism. The strongest repressor of CD8 T cell expansion is Roquin, the ablation of which drastically boosts T cell proliferation by enhancing cell-cycle progression and upregulation of IRF4. Roquin deficiency or IRF4 overexpression potently enhances anti-tumor immunity. These data provide a functional catalog of CD8 T cell fitness genes and suggest that targeting the Roquin-IRF4 axis is an effective strategy to enhance efficacy of adoptive transfer therapy for cancer.

Wildtype adult stem cells, unlike tumor cells, are resistant to cellular damages in Drosophila.

Adult stem cells or residential progenitor cells are critical to maintain the structure and function of adult tissues (homeostasis) throughout the lifetime of an individual. Mis-regulation of stem cell proliferation and differentiation often leads to diseases including cancer, however, how wildtype adult stem cells and cancer cells respond to cellular damages remains unclear. We find that in the adult Drosophila midgut, intestinal stem cells (ISCs), unlike tumor intestinal cells, are resistant to various cellular damages. Tumor intestinal cells, unlike wildtype ISCs, are easily eliminated by apoptosis. Further, their proliferation is inhibited upon autophagy induction, and autophagy-mediated tumor inhibition is independent of caspase-dependent apoptosis. Interestingly, inhibition of tumorigenesis by autophagy is likely through the sequestration and degradation of mitochondria, as compromising mitochondria activity in these tumor models mimics the induction of autophagy and increasing the production of mitochondria alleviates the tumor-suppression capacity of autophagy. Together, these data demonstrate that wildtype adult stem cells and tumor cells show dramatic differences in sensitivity to cellular damages, thus providing potential therapeutic implications targeting tumorigenesis.