The mTOR pathway is a critical determinant of cell persistence and growth wherein mTOR complex 1 (mTORC1) mediates a balance between growth factor stimuli and nutrient availability. Amino acids or glucose facilitates mTORC1 activation by inducing RagA GTPase recruitment of mTORC1 to the lysosomal outer surface, enabling activation of mTOR by the Ras homolog Rheb. Thereby, RagA alters mTORC1-driven growth in times of nutrient abundance or scarcity. Here, we have evaluated differential nutrient-sensing dependence through RagA and mTORC1 in hematopoietic progenitors, which dynamically drive mature cell production, and hematopoietic stem cells (HSC), which provide a quiescent cellular reserve. In nutrient-abundant conditions, RagA-deficient HSC were functionally unimpaired and upregulated mTORC1 via nutrient-insensitive mechanisms. RagA was also dispensable for HSC function under nutritional stress conditions. Similarly, hyperactivation of RagA did not affect HSC function. In contrast, RagA deficiency markedly altered progenitor population function and mature cell output. Therefore, RagA is a molecular mechanism that distinguishes the functional attributes of reactive progenitors from a reserve stem cell pool. The indifference of HSC to nutrient sensing through RagA contributes to their molecular resilience to nutritional stress, a characteristic that is relevant to organismal viability in evolution and in modern HSC transplantation approaches.
Demetrios Kalaitzidis, Dongjun Lee, Alejo Efeyan, Youmna Kfoury, Naema Nayyar, David B. Sykes, Francois E. Mercier, Ani Papazian, Ninib Baryawno, Gabriel D. Victora, Donna Neuberg, David M. Sabatini, David T. Scadden
A hallmark of aged mesenchymal stem/progenitor cells (MSCs) in bone marrow is the pivot of differentiation potency from osteoblast to adipocyte coupled with a decrease in self-renewal capacity. However, how these cellular events are orchestrated in the aging progress is not fully understood. In this study, we have used molecular and genetic approaches to investigate the role of forkhead box P1 (FOXP1) in transcriptional control of MSC senescence. In bone marrow MSCs, FOXP1 expression levels declined with age in an inverse manner with those of the senescence marker
Hanjun Li, Pei Liu, Shuqin Xu, Yinghua Li, Joseph D. Dekker, Baojie Li, Ying Fan, Zhenlin Zhang, Yang Hong, Gong Yang, Tingting Tang, Yongxin Ren, Haley O. Tucker, Zhengju Yao, Xizhi Guo
The BM niche comprises a tightly controlled microenvironment formed by specific tissue and cells that regulates the behavior of hematopoietic stem cells (HSCs). Here, we have provided a 3D model that is tunable in different BM niche components and useful, both in vitro and in vivo, for studying the maintenance of normal and malignant hematopoiesis. Using scaffolds, we tested the capacity of different stromal cell types to support human HSCs. Scaffolds coated with human mesenchymal stromal cells (hMSCs) proved to be superior in terms of HSC engraftment and long-term maintenance when implanted in vivo. Moreover, we found that hMSC-coated scaffolds can be modulated to form humanized bone tissue, which was also able to support human HSC engraftment. Importantly, hMSC-coated humanized scaffolds were able to support the growth of leukemia patient cells in vivo, including the growth of samples that would not engraft the BM of immunodeficient mice. These results demonstrate that an s.c. implantation approach in a 3D carrier scaffold seeded with stromal cells is an effective in vivo niche model for studying human hematopoiesis. The various niche components of this model can be changed depending on the context to improve the engraftment of nonengrafting acute myeloid leukemia (AML) samples.
Ander Abarrategi, Katie Foster, Ashley Hamilton, Syed A. Mian, Diana Passaro, John Gribben, Ghulam Mufti, Dominique Bonnet
Certain secretory proteins are known to be critical for maintaining the stemness of stem cells through autocrine signaling. However, the processes underlying the biogenesis, maturation, and secretion of these proteins remain largely unknown. Here we demonstrate that many secretory proteins produced by hematopoietic stem cells (HSCs) undergo exosomal maturation and release that is controlled by vacuolar protein sorting protein 33b (VPS33B). Deletion of
Hao Gu, Chiqi Chen, Xiaoxin Hao, Conghui Wang, Xiaocui Zhang, Zhen Li, Hongfang Shao, Hongxiang Zeng, Zhuo Yu, Li Xie, Fangzhen Xia, Feifei Zhang, Xiaoye Liu, Yaping Zhang, Haishan Jiang, Jun Zhu, Jiangbo Wan, Chun Wang, Wei Weng, Jingjing Xie, Minfang Tao, Cheng Cheng Zhang, Junling Liu, Guo-Qiang Chen, Junke Zheng
Current chemotherapies for T cell acute lymphoblastic leukemia (T-ALL) efficiently reduce tumor mass. Nonetheless, disease relapse attributed to survival of preleukemic stem cells (pre-LSCs) is associated with poor prognosis. Herein, we provide direct evidence that pre-LSCs are much less chemosensitive to existing chemotherapy drugs than leukemic blasts because of a distinctive lower proliferative state. Improving therapies for T-ALL requires the development of strategies to target pre-LSCs that are absolutely dependent on their microenvironment. Therefore, we designed a robust protocol for high-throughput screening of compounds that target primary pre-LSCs maintained in a niche-like environment, on stromal cells that were engineered for optimal NOTCH1 activation. The multiparametric readout takes into account the intrinsic complexity of primary cells in order to specifically monitor pre-LSCs, which were induced here by the
Bastien Gerby, Diogo F.T. Veiga, Jana Krosl, Sami Nourreddine, Julianne Ouellette, André Haman, Geneviève Lavoie, Iman Fares, Mathieu Tremblay, Véronique Litalien, Elizabeth Ottoni, Milena Kosic, Dominique Geoffrion, Joël Ryan, Paul S. Maddox, Jalila Chagraoui, Anne Marinier, Josée Hébert, Guy Sauvageau, Benjamin H. Kwok, Philippe P. Roux, Trang Hoang
Radiotherapy causes dose-limiting toxicity and long-term complications in rapidly renewing tissues, including the gastrointestinal tract. Currently, there is no FDA-approved agent for the prevention or treatment of radiation-induced intestinal injury. In this study, we have shown that PD 0332991 (PD), an FDA-approved selective inhibitor of cyclin-dependent kinase 4/6 (CDK4/6), prevents radiation-induced lethal intestinal injury in mice. Treating mice with PD or a structurally distinct CDK4/6 inhibitor prior to radiation blocked proliferation and crypt apoptosis and improved crypt regeneration. PD treatment also enhanced LGR5+ stem cell survival and regeneration after radiation. PD was an on-target inhibitor of RB phosphorylation and blocked G1/S transition in the intestinal crypts. PD treatment strongly but reversibly inhibited radiation-induced p53 activation, which blocked p53-upregulated modulator of apoptosis–dependent (PUMA-dependent) apoptosis without affecting p21-dependent suppression of DNA damage accumulation, with a repair bias toward nonhomologous end joining. Further, deletion of
Liang Wei, Brian J. Leibowitz, Xinwei Wang, Michael Epperly, Joel Greenberger, Lin Zhang, Jian Yu
Duchenne muscular dystrophy (DMD) is a severe and progressive muscle-wasting disease caused by mutations in the dystrophin gene. Although dystrophin deficiency in myofiber triggers the disease’s pathological changes, the degree of satellite cell (SC) dysfunction defines disease progression. Here, we have identified chicken ovalbumin upstream promoter–transcription factor II (COUP-TFII) hyperactivity as a contributing factor underlying muscular dystrophy in a dystrophin-deficient murine model of DMD. Ectopic expression of COUP-TFII in murine SCs led to Duchenne-like dystrophy in the muscles of control animals and exacerbated degenerative myopathies in dystrophin-deficient mice. COUP-TFII–overexpressing mice exhibited regenerative failure that was attributed to deficient SC proliferation and myoblast fusion. Mechanistically, we determined that COUP-TFII coordinated a regenerative program through combined regulation of multiple promyogenic factors. Furthermore, inhibition of COUP-TFII preserved SC function and counteracted the muscle weakness associated with Duchenne-like dystrophy in the murine model, suggesting that targeting COUP-TFII is a potential treatment for DMD. Together, our findings reveal a regulatory role of COUP-TFII in the development of muscular dystrophy and open up a potential therapeutic opportunity for managing disease progression in patients with DMD.
Xin Xie, Sophia Y. Tsai, Ming-Jer Tsai
Hematopoietic stem cells (HSCs) serve as a life-long reservoir for all blood cell types and are clinically useful for a variety of HSC transplantation-based therapies. Understanding the role of chromatin organization and regulation in HSC homeostasis may provide important insights into HSC development. Bromodomain- and PHD finger–containing protein 1 (BRPF1) is a multivalent chromatin regulator that possesses 4 nucleosome-binding domains and activates 3 lysine acetyltransferases (KAT6A, KAT6B, and KAT7), suggesting that this protein has the potential to stimulate crosstalk between different chromatin modifications. Here, we investigated the function of BRPF1 in hematopoiesis by selectively deleting its gene in murine blood cells.
Linya You, Lin Li, Jinfeng Zou, Kezhi Yan, Jad Belle, Anastasia Nijnik, Edwin Wang, Xiang-Jiao Yang
Vision impairments and blindness caused by retinitis pigmentosa result from severe neurodegeneration that leads to a loss of photoreceptors, the specialized light-sensitive neurons that enable vision. Although the mammalian nervous system is unable to replace neurons lost due to degeneration, therapeutic approaches to reprogram resident glial cells to replace retinal neurons have been proposed. Here, we demonstrate that retinal Müller glia can be reprogrammed in vivo into retinal precursors that then differentiate into photoreceptors. We transplanted hematopoietic stem and progenitor cells (HSPCs) into retinas affected by photoreceptor degeneration and observed spontaneous cell fusion events between Müller glia and the transplanted cells. Activation of Wnt signaling in the transplanted HSPCs enhanced survival and proliferation of Müller-HSPC hybrids as well as their reprogramming into intermediate photoreceptor precursors. This suggests that Wnt signaling drives the reprogrammed cells toward a photoreceptor progenitor fate. Finally, Müller-HSPC hybrids differentiated into photoreceptors. Transplantation of HSPCs with activated Wnt functionally rescued the retinal degeneration phenotype in
Daniela Sanges, Giacoma Simonte, Umberto Di Vicino, Neus Romo, Isabel Pinilla, Marta Nicolás Farrés, Maria Pia Cosma
Glioblastomas co-opt stem cell regulatory pathways to maintain brain tumor–initiating cells (BTICs), also known as cancer stem cells. NOTCH signaling has been a molecular target in BTICs, but NOTCH antagonists have demonstrated limited efficacy in clinical trials. Recombining binding protein suppressor of hairless (RBPJ) is considered a central transcriptional mediator of NOTCH activity. Here, we report that pharmacologic NOTCH inhibitors were less effective than targeting RBPJ in suppressing tumor growth. While NOTCH inhibitors decreased canonical NOTCH gene expression, RBPJ regulated a distinct profile of genes critical to BTIC stemness and cell cycle progression. RBPJ was preferentially expressed by BTICs and required for BTIC self-renewal and tumor growth. MYC, a key BTIC regulator, bound the
Qi Xie, Qiulian Wu, Leo Kim, Tyler E. Miller, Brian B. Liau, Stephen C. Mack, Kailin Yang, Daniel C. Factor, Xiaoguang Fang, Zhi Huang, Wenchao Zhou, Kareem Alazem, Xiuxing Wang, Bradley E. Bernstein, Shideng Bao, Jeremy N. Rich