Browsing by Subject "SELF-RENEWAL"

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  • Narva, Elisa; Stubb, Aki; Guzman, Camilo; Blomqvist, Matias; Balboa, Diego; Lerche, Martina; Saari, Markku; Otonkoski, Timo; Ivaska, Johanna (2017)
    Cell-type-specific functions and identity are tightly regulated by interactions between the cell cytoskeleton and the extracellular matrix (ECM). Human pluripotent stem cells (hPSCs) have ultimate differentiation capacity and exceptionally low-strength ECM contact, yet the organization and function of adhesion sites and associated actin cytoskeleton remain poorly defined. We imaged hPSCs at the cell-ECM interface with total internal reflection fluorescence microscopy and discovered that adhesions at the colony edge were exceptionally large and connected by thick ventral stress fibers. The actin fence encircling the colony was found to exert extensive Rho-ROCK-myosin-dependent mechanical stress to enforce colony morphology, compaction, and pluripotency and to define mitotic spindle orientation. Remarkably, differentiation altered adhesion organization and signaling characterized by a switch from ventral to dorsal stress fibers, reduced mechanical stress, and increased integrin activity and cell-ECM adhesion strength. Thus, pluripotency appears to be linked to unique colony organization and adhesion structure.
  • Vered, Marilena; Shnaiderman-Shapiro, Anna; Zlotogorski-Hurvitz, Ayelet; Salo, Tuula; Yahalom, Ran (2019)
    Objectives: To examine different immunophenotypes of cancer-associated fibroblasts (CAFs) in tongue squamous cell carcinoma (TSCC) and to investigate how they related to clinical outcomes. Methods: Serial sections from 54 cases of TSCC were immunohistochemically stained with a-smooth muscle actin (alpha SMA, CAF marker) to determine CAF density, and double-immunostained with alpha SMA combined with CD80 and CD86 (myeloid/monocytic-derived cell markers), Nanog (mesenchymal stem cell marker) and CD133 (hematopoietic/endothelial stem cell marker). Density of cells co-expressing these marker combinations was semi-quantitatively assessed in 5 randomly selected high power fields within the tumor area and scored as 1 - one-to-five stained cells in each field, 2 - more than 5 stained cells in each field; any finding less than score 1, was allocated a score of 0. Results: There were 26 CAF-poor, 16 CAF-rich and 12 CAF-intermediated cases. CD86(+) alpha SMA(+) cells were the most frequent (80.4%) followed by CD80(+) alpha SMA(+) (72%) and Nanog(+) alpha SMA(+) cells (56%). The CD133(+) alpha SMA(+) phenotype was found only in association with blood vessels. High density of aSMA CAFs was associated with disease recurrence and poor survival (p <0.05). Increased density of CD86(+) alpha SMA(+) cells was significantly associated with CAF-rich tumors and with poor survival (p <0.05). Conclusion: In TSCC, CAFs demonstrate heterogeneous and overlapping phenotypes with the myeloid/monocytic type being the most frequent and having an impact on the clinical outcomes. Further studies are needed in order to further characterize CAF phenotypes in carcinomas of various oral sites, as this may open new frontiers for personalized medicine.
  • Hasegawa, Yuki; Tang, Dave; Takahashi, Naoko; Hayashizaki, Yoshihide; Forrest, Alistair R. R.; Suzuki, Harukazu; FANTOM Consortium; Sajantila, Antti (2014)
  • Lengefeld, Jette; Cheng, Chia-Wei; Maretich, Pema; Blair, Marguerite; Hagen, Hannah; McReynolds, Melanie R.; Sullivan, Emily; Majors, Kyra; Roberts, Christina; Kang, Joon Ho; Steiner, Joachim D.; Miettinen, Teemu P.; Manalis, Scott R.; Antebi, Adam; Morrison, Sean J.; Lees, Jacqueline A.; Boyer, Laurie A.; Yilmaz, Ömer H.; Amon, Angelika (2021)
    Stem cells are remarkably small. Whether small size is important for stem cell function is unknown. We find that hematopoietic stem cells (HSCs) enlarge under conditions known to decrease stem cell function. This decreased fitness of large HSCs is due to reduced proliferation and was accompanied by altered metabolism. Preventing HSC enlargement or reducing large HSCs in size averts the loss of stem cell potential under conditions causing stem cell exhaustion. Last, we show that murine and human HSCs enlarge during aging. Preventing this age-dependent enlargement improves HSC function. We conclude that small cell size is important for stem cell function in vivo and propose that stem cell enlargement contributes to their functional decline during aging.
  • Grey, William; Rio-Machin, Ana; Casado, Pedro; Gronroos, Eva; Ali, Sara; Miettinen, Juho J.; Bewicke-Copley, Findlay; Parsons, Alun; Heckman, Caroline A.; Swanton, Charles; Cutillas, Pedro R.; Gribben, John; Fitzgibbon, Jude; Bonnet, Dominique (2022)
    Acute myeloid leukemia (AML) is an aggressive hematological disorder comprising a hierarchy of quiescent leukemic stem cells (LSCs) and proliferating blasts with limited self-renewal ability. AML has a dismal prognosis, with extremely low 2-year survival rates in the poorest cytogenetic risk patients, primarily due to the failure of intensive chemotherapy protocols to deplete LSCs and toxicity of therapy toward healthy hematopoietic cells. We studied the role of cyclin-dependent kinase regulatory subunit 1 (CKS1)-dependent protein degradation in primary human AML and healthy hematopoiesis xenograft models in vivo. Using a small-molecule inhibitor (CKS1i), we demonstrate a dual role for CKS1-dependent protein degradation in reducing patient-derived AML blasts in vivo and, importantly, depleting LSCs, whereas inhibition of CKS1 has the opposite effect on normal hematopoiesis, protecting normal hematopoietic stem cells from chemotherapeutic toxicity. Proteomic analysis of responses to CKS1i in our patient-derived xenograft mouse model demonstrate that inhibition of CKS1 in AML leads to hyper-activation of RAC1 and accumulation of lethal reactive oxygen species, whereas healthy hematopoietic cells enter quiescence in response to CKS1i, protecting hematopoietic stem cells. Together, these findings demonstrate that CKS1-dependent proteostasis is a key vulnerability in malignant stem cell biology.
  • Kurtzeborn, Kristen; Kwon, Hyuk Nam; Iaroshenko, Vladislav; Faisal, Imrul; Ambroz, Martin; Jin, Xing; Qureshi, Talha; Kupari, Jussi; Ihermann-Hella, Anneliis; Väänänen, Juho; Tyynismaa, Henna; Bousova, Iva; Park, Sunghyouk; Kuure, Satu (2022)
    Background: MAPK/ERK signaling is a well-known mediator of extracellular stimuli controlling intracellular responses to growth factors and mechanical cues. The critical requirement of MAPK/ERK signaling for embryonic stem cell maintenance is demonstrated, but specific functions in progenitor regulation during embryonic development, and in particular kidney development remain largely unexplored. We previously demonstrated MAPK/ERK signaling as a key regulator of kidney growth through branching morphogenesis and normal nephrogenesis where it also regulates progenitor expansion. Here, we performed RNA sequencing-based whole-genome expression analysis to identify transcriptional MAPK/ERK targets in two distinct renal populations: the ureteric bud epithelium and the nephron progenitors. Results: Our analysis revealed a large number (5053) of differentially expressed genes (DEGs) in nephron progenitors and significantly less (1004) in ureteric bud epithelium, reflecting likely heterogenicity of cell types. The data analysis identified high tissue-specificity, as only a fraction (362) of MAPK/ERK targets are shared between the two tissues. Tissue-specific MAPK/ERK targets participate in the regulation of mitochondrial energy metabolism in nephron progenitors, which fail to maintain normal mitochondria numbers in the MAPK/ERK-deficient tissue. In the ureteric bud epithelium, a dramatic decline in progenitor-specific gene expression was detected with a simultaneous increase in differentiation-associated genes, which was not observed in nephron progenitors. Our experiments in the genetic model of MAPK/ERK deficiency provide evidence that MAPK/ERK signaling in the ureteric bud maintains epithelial cells in an undifferentiated state. Interestingly, the transcriptional targets shared between the two tissues studied are over-represented by histone genes, suggesting that MAPK/ERK signaling regulates cell cycle progression and stem cell maintenance through chromosome condensation and nucleosome assembly. Conclusions: Using tissue-specific MAPK/ERK inactivation and RNA sequencing in combination with experimentation in embryonic kidneys, we demonstrate here that MAPK/ERK signaling maintains ureteric bud tip cells, suggesting a regulatory role in collecting duct progenitors. We additionally deliver new mechanistic information on how MAPK/ERK signaling regulates progenitor maintenance through its effects on chromatin accessibility and energy metabolism.
  • Deckwirth, Vivi; Rajakylä, Eeva Kaisa; Cattavarayane, Sandhanakrishnan; Acheva, Anna; Schaible, Niccole; Krishnan, Ramaswamy; Valle-Delgado, Juan Jose; Osterberg, Monika; Björkenheim, Pia; Sukura, Antti; Tojkander, Sari (2021)
    At invasion, transformed mammary epithelial cells expand into the stroma through a disrupted myoepithelial (ME) cell layer and basement membrane (BM). The intact ME cell layer has thus been suggested to act as a barrier against invasion. Here, we investigate the mechanisms behind the disruption of ME cell layer. We show that the expression of basal/ME proteins CK5, CK14, and alpha-SMA altered along increasing grade of malignancy, and their loss affected the maintenance of organotypic 3D mammary architecture. Furthermore, our data suggests that loss of CK5 prior to invasive stage causes decreased levels of Zinc finger protein SNAI2 (SLUG), a key regulator of the mammary epithelial cell lineage determination. Consequently, a differentiation bias toward luminal epithelial cell type was detected with loss of mature, alpha-SMA-expressing ME cells and reduced deposition of basement membrane protein laminin-5. Therefore, our data discloses the central role of CK5 in mammary epithelial differentiation and maintenance of normal ME layer.
  • Mäkitie, R. E.; Niinimäki, R.; Kakko, S.; Honkanen, T.; Kovanen, P. E.; Mäkitie, O. (2018)
    This study explores bone marrow function in patients with defective WNT1 signaling. Bone marrow samples showed increased reticulin and altered granulopoiesis while overall hematopoiesis was normal. Findings did not associate with severity of osteoporosis. These observations provide new insight into the role of WNT signaling in bone marrow homeostasis. WNT signaling regulates bone homeostasis and survival and self-renewal of hematopoietic stem cells. Aberrant activation may lead to osteoporosis and bone marrow pathology. We aimed to explore bone marrow findings in a large family with early-onset osteoporosis due to a heterozygous WNT1 mutation. We analyzed peripheral blood samples, and bone marrow aspirates and biopsies from 10 subjects with WNT1 mutation p.C218G. One subject was previously diagnosed with idiopathic myelofibrosis and others had no previously diagnosed hematologic disorders. The findings were correlated with the skeletal phenotype, as evaluated by number of peripheral and spinal fractures and bone mineral density. Peripheral blood samples showed no abnormalities in cell counts, morphology or distributions but mild increase in platelet count. Bone marrow aspirates (from 8/10 subjects) showed mild decrease in bone marrow iron storages in 6 and variation in cell distributions in 5 subjects. Bone marrow biopsies (from 6/10 subjects) showed increased bone marrow reticulin (grade MF-2 in the myelofibrosis subject and grade MF-1 in 4 others), and an increase in overall, and a shift towards early-phase, granulopoiesis. The bone marrow findings did not associate with the severity of skeletal phenotype. Defective WNT signaling associates with a mild increase in bone marrow reticulin and may predispose to myelofibrosis, while overall hematopoiesis and peripheral blood values are unaltered in individuals with a WNT1 mutation. In this family with WNT1 osteoporosis, bone marrow findings were not related to the severity of osteoporosis.
  • Ihermann-Hella, Anneliis; Hirashima, Tsuyoshi; Kupari, Jussi; Kurtzeborn, Kristen; Li, Hao; Kwon, Hyuk Nam; Cebrian, Cristina; Soofi, Abdul; Dapkunas, Arvydas; Miinalainen, Ilkka; Dressler, Gregory R.; Matsuda, Michiyuki; Kuure, Satu (2018)
    The in vivo niche and basic cellular properties of nephron progenitors are poorly described. Here we studied the cellular organization and function of the MAPK/ERK pathway in nephron progenitors. Live-imaging of ERK activity by a Forster resonance energy transfer biosensor revealed a dynamic activation pattern in progenitors, whereas differentiating precursors exhibited sustained activity. Genetic experiments demonstrate that MAPK/ERK activity controls the thickness, coherence, and integrity of the nephron progenitor niche. Molecularly, MAPK/ERK activity regulates niche organization and communication with extracellular matrix through PAX2 and ITGA8, and is needed for CITED1 expression denoting undifferentiated status. MAPK/ERK activation in nephron precursors propels differentiation by priming cells for distal and proximal fates induced by the Wnt and Notch pathways. Thus, our results demonstrate a mechanism through which MAPK/ERK activity controls both progenitor maintenance and differentiation by regulating a distinct set of targets, which maintain the biomechanical milieu of tissue-residing progenitors and prime precursors for nephrogenesis.
  • Li, Hao; Hohenstein, Peter; Kuure, Satu (2021)
    The adult mammalian kidney is a poorly regenerating organ that lacks the stem cells that could replenish functional homeostasis similarly to, e.g., skin or the hematopoietic system. Unlike a mature kidney, the embryonic kidney hosts at least three types of lineage-specific stem cells that give rise to (a) a ureter and collecting duct system, (b) nephrons, and (c) mesangial cells together with connective tissue of the stroma. Extensive interest has been raised towards these embryonic progenitor cells, which are normally lost before birth in humans but remain part of the undifferentiated nephrogenic rests in the pediatric renal cancer Wilms tumor. Here, we discuss the current understanding of kidney-specific embryonic progenitor regulation in the innate environment of the developing kidney and the types of disruptions in their balanced regulation that lead to the formation of Wilms tumor.
  • Karvonen, Eira; Krohn, Kai J. E.; Ranki, Annamari; Hau, Annika (2022)
    APECED (Autoimmune-Polyendocrinopathy-Candidiasis-Ectodermal-Dystrophy) is a severe and incurable multiorgan autoimmune disease caused by mutations in the AIRE (autoimmune regulator) gene. Without functional AIRE, the development of central and peripheral immune tolerance is severely impaired allowing the accumulation of autoreactive immune cells in the periphery. This leads to multiple endocrine and non-endocrine autoimmune disorders and mucocutaneous candidiasis in APECED patients. Recent studies have suggested that AIRE also has novel functions in stem cells and contributes to the regulatory network of pluripotency. In preparation of therapeutic gene correction, we generated and assessed patient blood cell-derived iPSCs, potentially suitable for cell therapy in APECED. Here, we describe APECED-patient derived iPSCs's properties, expression of AIRE as well as classical stem cell markers by qPCR and immunocytochemistry. We further generated self-aggregated EBs of the iPSCs. We show that APECED patient-derived iPSCs and EBs do not have any major proliferative or apoptotic defects and that they express all the classical pluripotency markers similarly to healthy person iPSCs. The results suggest that the common AIRE R257X truncation mutation does not affect stem cell properties and that APECED iPSCs can be propagated in vitro and used for subsequent gene-correction. This first study on APECED patient-derived iPSCs validates their pluripotency and confirms their ability for differentiation and potential therapeutic use.
  • Kanninen, Liisa K.; Harjumäki, Riina; Peltoniemi, Pasi; Bogacheva, Mariia S.; Salmi, Tuuli; Porola, Pauliina; Niklander, Johanna; Smutny, Tomas; Urtti, Arto; Yliperttula, Marjo L.; Lou, Yan-Ru (2016)
    Human pluripotent stem cells (hPSCs) have gained a solid foothold in basic research and drug industry as they can be used in vitro to study human development and have potential to offer limitless supply of various somatic cell types needed in drug development. Although the hepatic differentiation of hPSCs has been extensively studied, only a little attention has been paid to the role of the extracellular matrix. In this study we used laminin-511, laminin-521, and fibronectin, found in human liver progenitor cells, as culture matrices for hPSC-derived definitive endoderm cells. We observed that laminin-511 and laminin-521 either alone or in combination support the hepatic specification and that fibronectin is not a vital matrix protein for the hPSC-derived definitive endoderm cells. The expression of the laminin-511/521-specific integrins increased during the definitive endoderm induction and hepatic specification. The hepatic cells differentiated on laminin matrices showed the upregulation of liver-specific markers both at mRNA and protein levels, secreted human albumin, stored glycogen, and exhibited cytochrome P450 enzyme activity and inducibility. Altogether, we found that laminin-511 and laminin-521 can be used as stage-specific matrices to guide the hepatic specification of hPSC-derived definitive endoderm cells. 2016 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
  • Allmeroth, Kira; Kim, Christine S.; Annibal, Andrea; Pouikli, Andromachi; Koester, Janis; Derisbourg, Maxime J.; Chacon-Martinez, Carlos Andres; Latza, Christian; Antebi, Adam; Tessarz, Peter; Wickström, Sara A.; Denzel, Martin S. (2021)
    Stem cell differentiation is accompanied by increased mRNA translation. The rate of protein biosynthesis is influenced by the polyamines putrescine, spermidine and spermine, which are essential for cell growth and stem cell maintenance. However, the role of polyamines as endogenous effectors of stem cell fate and whether they act through translational control remains obscure. Here, we investigate the function of polyamines in stem cell fate decisions using hair follicle stem cell (HFSC) organoids. Compared to progenitor cells, HFSCs showed lower translation rates, correlating with reduced polyamine levels. Surprisingly, overall polyamine depletion decreased translation but did not affect cell fate. In contrast, specific depletion of natural polyamines mediated by spermidine/spermine N1-acetyltransferase (SSAT; also known as SAT1) activation did not reduce translation but enhanced stemness. These results suggest a translation-independent role of polyamines in cell fate regulation. Indeed, we identified N1-acetylspermidine as a determinant of cell fate that acted through increasing self-renewal, and observed elevated N1-acetylspermidine levels upon depilation-mediated HFSC proliferation and differentiation in vivo. Overall, this study delineates the diverse routes of polyamine metabolism-mediated regulation of stem cell fate decisions. This article has an associated First Person interview with the first author of the paper.
  • Martin-Lopez, Marta; Maeso-Alonso, Laura; Fuertes-Alvarez, Sandra; Balboa, Diego; Rodriguez-Cortez, Virginia; Weltner, Jere; Diez-Prieto, Inmaculada; Davis, Andrew; Wu, Yaning; Otonkoski, Timo; Flores, Elsa R.; Menendez, Pablo; Marques, Margarita M.; Marin, Maria C. (2017)
    The generation of induced pluripotent stem cells (iPSCs) by somatic cell reprogramming holds great potential for modeling human diseases. However, the reprogramming process remains very inefficient and a better understanding of its basic biology is required. The mesenchymal-to-epithelial transition (MET) has been recognized as a crucial step for the successful reprogramming of fibroblasts into iPSCs. It has been reported that the p53 tumor suppressor gene acts as a barrier of this process, while its homolog p63 acts as an enabling factor. In this regard, the information concerning the role of the third homolog, p73, during cell reprogramming is limited. Here, we derive total Trp73 knockout mouse embryonic fibroblasts, with or without Trp53, and examine their reprogramming capacity. We show that p73 is required for effective reprogramming by the Yamanaka factors, even in the absence of p53. Lack of p73 affects the early stages of reprogramming, impairing the MET and resulting in altered maturation and stabilization phases. Accordingly, the obtained p73-deficient iPSCs have a defective epithelial phenotype and alterations in the expression of pluripotency markers. We demonstrate that p73 deficiency impairs the MET, at least in part, by hindering BMP pathway activation. We report that p73 is a positive modulator of the BMP circuit, enhancing its activation by DNp73 repression of the Smad6 promoter. Collectively, these findings provide mechanistic insight into the MET process, proposing p73 as an enhancer of MET during cellular reprogramming.
  • Piazza, Rocco; Magistroni, Vera; Redaelli, Sara; Mauri, Mario; Massimino, Luca; Sessa, Alessandro; Peronaci, Marco; Lalowski, Maciej; Soliymani, Rabah; Mezzatesta, Caterina; Pirola, Alessandra; Banfi, Federica; Rubio, Alicia; Rea, Delphine; Stagno, Fabio; Usala, Emilio; Martino, Bruno; Campiotti, Leonardo; Merli, Michele; Passamonti, Francesco; Onida, Francesco; Morotti, Alessandro; Pavesi, Francesca; Bregni, Marco; Broccoli, Vania; Baumann, Marc; Gambacorti-Passerini, Carlo (2018)
    SETBP1 variants occur as somatic mutations in several hematological malignancies such as atypical chronic myeloid leukemia and as de novo germline mutations in the Schinzel-Giedion syndrome. Here we show that SETBP1 binds to gDNA in AT-rich promoter regions, causing activation of gene expression through recruitment of a HCF1/KMT2A/PHF8 epigenetic complex. Deletion of two AT-hooks abrogates the binding of SETBP1 to gDNA and impairs target gene upregulation. Genes controlled by SETBP1 such as MECOM are significantly upregulated in leukemias containing SETBP1 mutations. Gene ontology analysis of deregulated SETBP1 target genes indicates that they are also key controllers of visceral organ development and brain morphogenesis. In line with these findings, in utero brain electroporation of mutated SETBP1 causes impairment of mouse neurogenesis with a profound delay in neuronal migration. In summary, this work unveils a SETBP1 function that directly affects gene transcription and clarifies the mechanism operating in myeloid malignancies and in the Schinzel- Giedion syndrome caused by SETBP1 mutations.
  • Getto, Philipp; Gyllenberg, Mats; Nakata, Yukihiko; Scarabel, Francesca (2019)
    We consider a mathematical model describing the maturation process of stem cells up to fully mature cells. The model is formulated as a differential equation with state-dependent delay, where maturity is described as a continuous variable. The maturation rate of cells may be regulated by the amount of mature cells and, moreover, it may depend on cell maturity: we investigate how the stability of equilibria is affected by the choice of the maturation rate. We show that the principle of linearised stability holds for this model, and develop some analytical methods for the investigation of characteristic equations for fixed delays. For a general maturation rate we resort to numerical methods and we extend the pseudospectral discretisation technique to approximate the state-dependent delay equation with a system of ordinary differential equations. This is the first application of the technique to nonlinear state-dependent delay equations, and currently the only method available for studying the stability of equilibria by means of established software packages for bifurcation analysis. The numerical method is validated on some cases when the maturation rate is independent of maturity and the model can be reformulated as a fixed-delay equation via a suitable time transformation. We exploit the analytical and numerical methods to investigate the stability boundary in parameter planes. Our study shows some drastic qualitative changes in the stability boundary under assumptions on the model parameters, which may have important biological implications.
  • Vannini, Nicola; Campos, Vasco; Girotra, Mukul; Trachsel, Vincent; Rojas-Sutterlin, Shanti; Tratwal, Josefine; Ragusa, Simone; Stefanidis, Evangelos; Ryu, Dongryeol; Rainer, Pernille Y.; Nikitin, Gena; Giger, Sonja; Li, Terytty Y.; Semilietof, Aikaterini; Oggier, Aurelien; Yersin, Yannick; Tauzin, Loic; Pirinen, Eija; Cheng, Wan-Chen; Ratajczak, Joanna; Canto, Carles; Ehrbar, Martin; Sizzano, Federico; Petrova, Tatiana V.; Vanhecke, Dominique; Zhang, Lianjun; Romero, Pedro; Nahimana, Aimable; Cherix, Stephane; Duchosal, Michel A.; Ho, Ping-Chih; Deplancke, Bart; Coukos, George; Auwerx, Johan; Lutolf, Matthias P.; Naveiras, Olaia (2019)
    It has been recently shown that increased oxidative phosphorylation, as reflected by increased mitochondrial activity, together with impairment of the mitochondrial stress response, can severely compromise hematopoietic stem cell (HSC) regeneration. Here we show that the NAD(+)-boosting agent nicotinamide riboside (NR) reduces mitochondrial activity within HSCs through increased mitochondrial clearance, leading to increased asymmetric HSC divisions. NR dietary supplementation results in a significantly enlarged pool of progenitors, without concurrent HSC exhaustion, improves survival by 80%, and accelerates blood recovery after murine lethal irradiation and limiting-HSC transplantation. In immune-deficient mice, NR increased the production of human leucocytes from hCD34+ progenitors. Our work demonstrates for the first time a positive effect of NAD(+)-boosting strategies on the most primitive blood stem cells, establishing a link between HSC mitochondrial stress, mitophagy, and stem-cell fate decision, and unveiling the potential of NR to improve recovery of patients suffering from hematological failure including post chemo- and radiotherapy.
  • Faisal, Imrul; Cisneros-Montalvo, Sheyla; Hamer, Geert; Tuominen, Minna M.; Laurila, Pirkka-Pekka; Tumiati, Manuela; Jauhiainen, Matti; Kotaja, Noora; Toppari, Jorma; Mäkelä, Juho-Antti; Kauppi, Liisa (2019)
    A prerequisite for lifelong sperm production is that spermatogonial stem cells (SSCs) balance self-renewal and differentiation, yet factors required for this balance remain largely undefined. Using mouse genetics, we now demonstrate that the ubiquitously expressed transcription factor upstream stimulatory factor (USF)1 is critical for the maintenance of SSCs. We show that USF1 is not only detected in Sertoli cells as previously reported, but also in SSCs. Usf1-deficient mice display progressive spermatogenic decline as a result of age-dependent loss of SSCs. According to our data, the germ cell defect in Usf1(-/-) mice cannot be attributed to impairment of Sertoli cell development, maturation, or function, but instead is likely due to an inability of SSCs to maintain a quiescent state. SSCs of Usf1(-/-) mice undergo continuous proliferation, which provides an explanation for their age-dependent depletion. The proliferation-coupled exhaustion of SSCs in turn results in progressive degeneration of the seminiferous epithelium, gradual decrease in sperm production, and testicular atrophy. We conclude that the general transcription factor USF1 is indispensable for the proper maintenance of mammalian spermatogenesis.
  • Iftakhar-e-Khuda, Imtiaz; Pessia, Alberto; Zheng, Shuyu; Kankainen, Matti; Kontro, Mika; Karikoski, Marika; Laurila, Juha; Gerke, Heidi; Tadayon, Sina; Hollmén, Maija; Tang, Jing; Imhof, Beat A.; Salmi, Marko; Jalkanen, Sirpa (2021)
    Although the development of hematopoietic stem cells (HSC) has been studied in great detail, their heterogeneity and relationships to different cell lineages remain incompletely understood. Moreover, the role of Vascular Adhesion Protein-1 in bone marrow hematopoiesis has remained unknown. Here we show that VAP-1, an adhesin and a primary amine oxidase producing hydrogen peroxide, is expressed on a subset of human HSC and bone marrow vasculature forming a hematogenic niche. Bulk and single-cell RNAseq analyses reveal that VAP-1+ HSC represent a transcriptionally unique small subset of differentiated and proliferating HSC, while VAP-1− HSC are the most primitive HSC. VAP-1 generated hydrogen peroxide acts via the p53 signaling pathway to regulate HSC proliferation. HSC expansion and differentiation into colony-forming units are enhanced by inhibition of VAP-1. Contribution of VAP-1 to HSC proliferation was confirmed with mice deficient of VAP-1, mice expressing mutated VAP-1 and using an enzyme inhibitor. In conclusion, VAP-1 expression allows the characterization and prospective isolation of a new subset of human HSC. Since VAP-1 serves as a check point-like inhibitor in HSC differentiation, the use of VAP-1 inhibitors enables the expansion of HSC.
  • Han, Jinah; Calvo, Charles-Felix; Kang, Tae Hyuk; Baker, Kasey L.; Park, June-Hee; Parras, Carlos; Levittas, Marine; Birba, Ulrick; Pibouin-Fragner, Laurence; Fragner, Pascal; Bilguvar, Kaya; Duman, Ronald S.; Nurmi, Harri Juhani; Alitalo, Kari; Eichmann, Anne C.; Thomas, Jean-Leon (2015)