Premature Stem Research Articles

480 Induction of tissue-specific premature stem cell aging via DNA damage response dysregulation promotes senescence-like phenotypes in remote multiple organs

480 Induction of tissue-specific premature stem cell aging via DNA damage response dysregulation promotes senescence-like phenotypes in remote multiple organs

A new variety of Chinese radish (loba) Serdtse Podmoskovya for the Central region of Russia

The article presents the results of the selection work of the laboratory of breeding and seed production of table root crops of the Federal Scientific Vegetable Center for the culture of Chinese radish (loba). From the collection material (a total of 23 samples were studied), a promising material was selected under the number No. 600 for a complex of economically valuable features. The purpose of the research is to create a variety of Chinese radish – loba for open and protected ground. Based on this goal, the objectives of the research included: to evaluate a promising variety of loba in a nursery of competitive variety testing in open and protected ground conditions, to assess alignment according to the main morphobiological parameters, as well as to assess the safety and resistance to diseases during storage.Results. As a result of repeated individual and family selection in the direction of productivity, resistance to premature stem formation and diseases of vegetation and storage, as well as improvement of taste qualities, a new variety of Chinese radish Serdtse Podmoskovya was bred. The new variety belongs to the pink-red rounded varietal type. The root crop is flat-rounded, large in size. The flesh is white, juicy, with a slightly spicy taste. The variety is medium-ripened, the growing season is 65-75 days, suitable for use in early summer, autumn and winter, resistant to longterm storage (95-96% preservation) and low light. The yield of the variety in protected ground is 2.7 kg/m2, marketability – 88.7%, root crop weight – 533 g; dry matter content – 6.26%, sugars – 2.56%, ascorbic acid – 19.36 mg%. The variety on this background was distinguished by the absence of flowering and diseased plants. The yield in the open ground was 31.2 t/ha (3.12 kg/m2), marketability – 81.2%, root crop weight – 281 g. The variety under these conditions was characterized by a higher content of dry matter –11.0%, sugars – 3.2% and ascorbic acid – 20.13 mg%; a small percentage of flowering (9.4%) and affected plants (6.3%) was noted. For this variety, a technology has been developed for obtaining original and elite seeds according to a one-year development cycle in the conditions of the Central region ща Russia.

Hereditary spastic paraplegia-like presentation with the unique “ear of lynx” sign in dyskeratosis congenita

Abstract Dyskeratosis congenita (DC) is a rare inherited syndrome with an incidence of less than one in a million. It is characterized by reticular skin pigmentation, dystrophic nails, oral leukoplakia, and later bone marrow failure. Neurological manifestations in DC are rare, and our patient who fulfilled criteria for DC had a hereditary spastic paraplegia-like presentation with the unique “ear of lynx” sign on brain magnetic resonance imaging; this is an unreported phenotype to date. Callosal thinning, cerebellar atrophy, enlarged diploic marrow space of the skull bones, and spine magnetic resonance imaging showing high signals on T1- and T2-weighted images affecting the vertebrae, suggesting pathological fatty replacement of the bone marrow, are other diagnostic clues. DC is a disease caused by defective telomere maintenance. Affected patients have premature telomere shortening and subsequent replicative senescence, leading to premature stem cell exhaustion and bone marrow failure. Awareness is the key to identify such unique presentations of rare diseases as patients require follow-up due to their predisposition to cancer.

559 Induction of tissue-specific premature stem cell aging promotes senescence-like phenotypes in remote multiple organs

Adult tissue stem cells (SCs) play an important role in tissue homeostasis and regeneration in multicellular organisms. With aging, these cells decline in their capacities such as regeneration, proliferation, and differentiation, leading to disruption of tissue homeostasis in systemic organs. The senescence-associated secretory phenotype (SASP), that is, senescent cells secrete various inflammatory factors, has been implicated in the promotion of chronic inflammation and organismal aging. However, little is known about the common molecular mechanisms underlying SC aging and their influence on systemic aging.

Novel intrinsic factor Yun maintains female germline stem cell fate through Thickveins.

SummaryGermline stem cells (GSCs) are critical for the reproduction of an organism. The self-renewal and differentiation of GSCs must be tightly controlled to avoid uncontrolled stem cell proliferation or premature stem cell differentiation. However, how the self-renewal and differentiation of GSCs are properly controlled is not fully understood. Here, we find that the novel intrinsic factor Yun is required for female GSC maintenance in Drosophila. GSCs undergo precocious differentiation due to de-repression of differentiation factor Bam by defective BMP/Dpp signaling in the absence of yun. Mechanistically, Yun associates with and stabilizes Thickveins (Tkv), the type I receptor of Dpp/BMP signaling. Finally, ectopic expression of a constitutively active Tkv (TkvQD) completely suppresses GSC loss caused by yun depletion. Collectively, these data demonstrate that Yun functions through Tkv to maintain GSC fate. Our results provide new insight into the regulatory mechanisms of how stem cell maintenance is properly controlled.

Centrosome linker protein C‐Nap1 maintains stem cells in mouse testes

The centrosome linker component C‐Nap1 (encoded by CEP250) anchors filaments to centrioles that provide centrosome cohesion by connecting the two centrosomes of an interphase cell into a single microtubule organizing unit. The role of the centrosome linker during development of an animal remains enigmatic. Here, we show that male CEP250−/− mice are sterile because sperm production is abolished. Premature centrosome separation means that germ stem cells in CEP250−/− mice fail to establish an E‐cadherin polarity mark and are unable to maintain the older mother centrosome on the basal site of the seminiferous tubules. This failure prompts premature stem cell differentiation in expense of germ stem cell expansion. The concomitant induction of apoptosis triggers the complete depletion of germ stem cells and consequently infertility. Our study reveals a role for centrosome cohesion in asymmetric cell division, stem cell maintenance, and fertility.

ATR activity controls stem cell quiescence via the cyclin F–SCF complex

A key property of adult stem cells is their ability to persist in a quiescent state for prolonged periods of time. The quiescent state is thought to contribute to stem cell resilience by limiting accumulation of DNA replication–associated mutations. Moreover, cellular stress response factors are thought to play a role in maintaining quiescence and stem cell integrity. We utilized muscle stem cells (MuSCs) as a model of quiescent stem cells and find that the replication stress response protein, ATR (Ataxia Telangiectasia and Rad3-Related), is abundant and active in quiescent but not activated MuSCs. Concurrently, MuSCs display punctate RPA (replication protein A) and R-loop foci, both key triggers for ATR activation. To discern the role of ATR in MuSCs, we generated MuSC-specific ATR conditional knockout (ATRcKO) mice. Surprisingly, ATR ablation results in increased MuSC quiescence exit. Phosphoproteomic analysis of ATRcKO MuSCs reveals enrichment of phosphorylated cyclin F, a key component of the Skp1–Cul1–F-box protein (SCF) ubiquitin ligase complex and regulator of key cell-cycle transition factors, such as the E2F family of transcription factors. Knocking down cyclin F or inhibiting the SCF complex results in E2F1 accumulation and in MuSCs exiting quiescence, similar to ATR-deficient MuSCs. The loss of ATR could be counteracted by inhibiting casein kinase 2 (CK2), the kinase responsible for phosphorylating cyclin F. We propose a model in which MuSCs express cell-cycle progression factors but ATR, in coordination with the cyclin F–SCF complex, represses premature stem cell quiescence exit via ubiquitin–proteasome degradation of these factors.

Prospects for the use of a multi-tier narrow-stack installation in the selection of European radish

Relevance. Growing European radishes in protected soil on hydroponics provides year-round fresh vitamin production. For the autumn-winter turnover shade-tolerant varieties with a short growing season are necessary. For the spring-summer turnover, the resistance of the variety to high temperatures and premature stem formation is of particular importance. Selection of targeted radish varieties is an energy-consuming process, which can be optimized by using an open-type multi-tier narrow-stack hydroponics installation with a different combination of limiting factors for tiers (light, heat).Methods and results. In Federal Scientific Vegetable Center radish varieties were tested in different conditions. The informativeness of the tiers on the installation as backgrounds for selection for adaptability and specificity is determined. It was found that the assessment and selection of productivity and large-fruited is effectively carried out on 1-2 tiers; for resistance to premature stem formation – on 1 tier; for shade tolerance, early ripening, with a stable manifestation of the marketable mass of the root crop – on 4-5 tiers. Radish varieties were selected as the starting material for the suitability for hydroponic cultivation of intensive type and highly adaptive. The uniqueness of the use of a multi-level narrow column hydroponics for the purpose of radish breeding is shown.

METTL3 counteracts premature aging via m6A-dependent stabilization of MIS12 mRNA.

N6-Methyladenosine (m6A) messenger RNA methylation is a well-known epitranscriptional regulatory mechanism affecting central biological processes, but its function in human cellular senescence remains uninvestigated. Here, we found that levels of both m6A RNA methylation and the methyltransferase METTL3 were reduced in prematurely senescent human mesenchymal stem cell (hMSC) models of progeroid syndromes. Transcriptional profiling of m6A modifications further identified MIS12, for which m6A modifications were reduced in both prematurely senescent hMSCs and METTL3-deficient hMSCs. Knockout of METTL3 accelerated hMSC senescence whereas overexpression of METTL3 rescued the senescent phenotypes. Mechanistically, loss of m6A modifications accelerated the turnover and decreased the expression of MIS12 mRNA while knockout of MIS12 accelerated cellular senescence. Furthermore, m6A reader IGF2BP2 was identified as a key player in recognizing and stabilizing m6A-modified MIS12 mRNA. Taken together, we discovered that METTL3 alleviates hMSC senescence through m6A modification-dependent stabilization of the MIS12 transcript, representing a novel epitranscriptional mechanism in premature stem cell senescence.

Id4 promotes the elimination of the pro-activation factor Ascl1 to maintain quiescence of adult hippocampal stem cells.

Quiescence is essential for the long-term maintenance of adult stem cells but how stem cells maintain quiescence is poorly understood. Here, we show that neural stem cells (NSCs) in the adult mouse hippocampus actively transcribe the pro-activation factor Ascl1 regardless of their activated or quiescent states. We found that the inhibitor of DNA binding protein Id4 is enriched in quiescent NSCs and that elimination of Id4 results in abnormal accumulation of Ascl1 protein and premature stem cell activation. Accordingly, Id4 and other Id proteins promote elimination of Ascl1 protein in NSC cultures. Id4 sequesters Ascl1 heterodimerization partner E47, promoting Ascl1 protein degradation and stem cell quiescence. Our results highlight the importance of non-transcriptional mechanisms for the maintenance of NSC quiescence and reveal a role for Id4 as a quiescence-inducing factor, in contrast with its role of promoting the proliferation of embryonic neural progenitors.

Id4 Eliminates the Pro-Activation Factor Ascl1 to Maintain Quiescence of Adult Hippocampal Stem Cells

Quiescence is essential for the long-term maintenance of adult stem cells and tissue homeostasis. However, how stem cells maintain quiescence is still poorly understood. Here we show that stem cells in the dentate gyrus of the adult hippocampus actively transcribe the pro-activation factor Ascl1 regardless of their activation state. We found that the inhibitor of DNA binding protein Id4 suppresses Ascl1 activity in neural stem cell cultures. Id4 sequesters Ascl1 heterodimerisation partner E47, promoting Ascl1 protein degradation and neural stem cell quiescence. Accordingly, elimination of Id4 from stem cells in the adult hippocampus results in abnormal accumulation of Ascl1 protein and premature stem cell activation. We also found that multiple signalling pathways converge on the regulation of Id4 to reduce the activity of hippocampal stem cells. Id4 therefore maintains quiescence of adult neural stem cells, in sharp contrast with its role of promoting the proliferation of embryonic neural progenitors.

Stem Cell Aging and Sex: Are We Missing Something?

Longevity differs between sexes, with females being longer-lived in most mammals, including humans. One hallmark of aging is the functional decline of stem cells. Thus, a key question is whether the aging of stem cells differs between males and females and whether this has consequences for disease and lifespan.

Single-cell telomere-length quantification couples telomere length to meristem activity and stem cell development in Arabidopsis.

SummaryTelomeres are specialized nucleoprotein caps that protect chromosome ends assuring cell division. Single-cell telomere quantification in animals established a critical role for telomerase in stem cells, yet, in plants, telomere-length quantification has been reported only at the organ level. Here, a quantitative analysis of telomere length of single cells in Arabidopsis root apex uncovered a heterogeneous telomere-length distribution of different cell lineages showing the longest telomeres at the stem cells. The defects in meristem and stem cell renewal observed in tert mutants demonstrate that telomere lengthening by TERT sets a replicative limit in the root meristem. Conversely, the long telomeres of the columella cells and the premature stem cell differentiation plt1,2 mutants suggest that differentiation can prevent telomere erosion. Overall, our results indicate that telomere dynamics are coupled to meristem activity and continuous growth, disclosing a critical association between telomere length, stem cell function, and the extended lifespan of plants.

PRL1 modulates root stem cell niche activity and meristem size through WOX5 and PLTs in Arabidopsis.

The stem cell niche in the root meristem maintains pluripotent stem cells to ensure a constant supply of cells for root growth. Despite extensive progress, the molecular mechanisms through which root stem cell fates and stem cell niche activity are determined remain largely unknown. In Arabidopsis thaliana, the Pleiotropic Regulatory Locus 1 (PRL1) encodes a WD40-repeat protein subunit of the spliceosome-activating Nineteen Complex (NTC) that plays a role in multiple stress, hormone and developmental signaling pathways. Here, we show that PRL1 is involved in the control of root meristem size and root stem cell niche activity. PRL1 is strongly expressed in the root meristem and its loss of function mutation results in disorganization of the quiescent center (QC), premature stem cell differentiation, aberrant cell division, and reduced root meristem size. Our genetic studies indicate that PRL1 is required for confined expression of the homeodomain transcription factor WOX5 in the QC and acts upstream of the transcription factor PLETHORA (PLT) in modulating stem cell niche activity and root meristem size. These findings define a role for PRL1 as an important determinant of PLT signaling that modulates maintenance of the stem cell niche and root meristem size.

CHD7 maintains neural stem cell quiescence and prevents premature stem cell depletion in the adult hippocampus.

Neural stem/progenitor cells (NSCs) in the hippocampus produce new neurons throughout adult life. NSCs are maintained in a state of reversible quiescence and the failure to maintain the quiescent state can result in the premature depletion of the stem cell pool. The epigenetic mechanisms that maintain this quiescent state have not been identified. Using an inducible knockout mouse model, we show that the chromatin remodeling factor chromodomain–helicase‐DNA‐binding protein 7 (CHD7) is essential for maintaining NSC quiescence. CHD7 inactivation in adult NSCs results in a loss of stem cell quiescence in the hippocampus, a transient increase in cell divisions, followed by a significant decline in neurogenesis. This loss of NSC quiescence is associated with the premature loss of NSCs in middle‐aged mice. We find that CHD7 represses the transcription of several positive regulators of cell cycle progression and is required for full induction of the Notch target gene Hes5 in quiescent NSCs. These findings directly link CHD7 to pathways involved in NSC quiescence and identify the first chromatin‐remodeling factor with a role in NSC quiescence and maintenance. As CHD7 haplo‐insufficiency is associated with a range of cognitive disabilities in CHARGE syndrome, our observations may have implications for understanding the basis of these deficits. Stem Cells 2015;33:196–210

DNMT3L promotes quiescence in postnatal spermatogonial progenitor cells.

The ability of adult stem cells to reside in a quiescent state is crucial for preventing premature exhaustion of the stem cell pool. However, the intrinsic epigenetic factors that regulate spermatogonial stem cell quiescence are largely unknown. Here, we investigate in mice how DNA methyltransferase 3-like (DNMT3L), an epigenetic regulator important for interpreting chromatin context and facilitating de novo DNA methylation, sustains the long-term male germ cell pool. We demonstrated that stem cell-enriched THY1(+) spermatogonial stem/progenitor cells (SPCs) constituted a DNMT3L-expressing population in postnatal testes. DNMT3L influenced the stability of promyelocytic leukemia zinc finger (PLZF), potentially by downregulating Cdk2/CDK2 expression, which sequestered CDK2-mediated PLZF degradation. Reduced PLZF in Dnmt3l KO THY1(+) cells released its antagonist, Sal-like protein 4A (SALL4A), which is associated with overactivated ERK and AKT signaling cascades. Furthermore, DNMT3L was required to suppress the cell proliferation-promoting factor SALL4B in THY1(+) SPCs and to prevent premature stem cell exhaustion. Our results indicate that DNMT3L is required to delicately balance the cycling and quiescence of SPCs. These findings reveal a novel role for DNMT3L in modulating postnatal SPC cell fate decisions.

Epigenetic Regulation of Stem Cell Maintenance in the Drosophila Testis via the Nucleosome-Remodeling Factor NURF

Regulation of stem cells depends on both tissue-specific transcriptional regulators and changes in chromatin organization, yet the coordination of these events in endogenous niches is poorly understood. In the Drosophila testis, local JAK-STAT signaling maintains germline and somatic stem cells (GSCs and cyst progenitor cells, or CPCs) in a single niche. Here we show that epigenetic regulation via the nucleosome-remodeling factor (NURF) complex ensures GSC and CPC maintenance by positively regulating JAK-STAT signaling, thereby preventing premature differentiation. Conversely, NURF is not required in early differentiating daughter cells of either lineage. Because three additional ATP-dependent chromatin remodelers (ACF, CHRAC, and dMi-2/NuRD) are dispensable for stem cell maintenance in the testis, epigenetic regulation of stem cells within this niche may rely primarily on NURF. Thus, local signals cooperate with specific chromatin-remodeling complexes in intact niches to coordinately regulate a common set of target genes to prevent premature stem cell differentiation.

Proximate Analysis of Dragon Fruit (Hylecereus polyhizus)

Problem statement: Dragon fruit (Hylecereus polyhizus ) is well known for the rich nutrient contents and it is commercially available worldwide for improving many health problems. Several studies show the proximity value of red pitaya frui ts but the nutrient composition of the stem has not been extensively studied. Approach: This study was carried out to measure the proximat e analysis of moisture content, water activity, ash, crude protei n, crude fat, crude fiber, glucose and ascorbic aci ds content in premature and mature of dragon fruit. Th e dried powder was produced from the stem of dragon fruit and the proximate analysis of dragon f ruit stem was compared between freeze drying process and drying oven process. Results: Results of this study showed that 96% moisture; 0. 270 g of protein; 0.552 g L -1 glucose and 132.95 mg L -1 ascorbic acid of dragon fruit stem found higher th an the fruit flesh of the dragon fruit. Conclusion: The premature stem had higher values than the mature stem of the dragon fruit which may helpful in preve nting the risk factors of certain diseases.

Parity-induced mouse mammary epithelial cells are pluripotent, self-renewing and sensitive to TGF-β1 expression

A parity-induced mammary population, marked by beta-galactosidase expression conditionally activated through cre-lox recombinase originates in WAP-Cre/Rosa-lox-STOP-lox-LacZ (WAP-Cre/Rosa-LacZ) female mice during pregnancy, lactation and involution. During subsequent pregnancies, these parity-induced mammary epithelial cells (PI-MEC) proliferated to produce new secretory acini composed of secretory luminal cells and myoepithelium. In serial transplantation assays, PI-MEC were able to self-renew over several transplant generations and to contribute significantly to the resulting mammary outgrowths. In limiting dilution transplantation, they proliferated to produce both luminal and myoepithelial cells, comprised both lobule-limited and duct-limited epithelial outgrowths, and differentiated into all the cellular subtypes recognized in murine mammary epithelium. TGF-beta1 expression from the whey acidic protein promoter (WAP) in triply transgenic females did not prevent the appearance of PI-MEC after pregnancy despite the absence of full lactation or their ability to proliferate and produce progeny with diverse cellular fates in situ upon subsequent pregnancies. However, in transplants from triple transgenic parous females, the WAP-TGF-beta1-positive PI-MEC did not contribute to the newly recapitulated mammary outgrowths, suggesting that they were incapable of expansive cellular proliferation (self-renewal). This result is consistent with our earlier publication that WAP-TGF-beta1 expression in mammary epithelium induces premature stem cell senescence in mammary transplants and decreases mammary cancer risk in mouse mammary tumor virus (MMTV)-infected females even after multiple pregnancies.

Reducing mammary cancer risk through premature stem cell senescence

The reproductive capacity of the mammary epithelial stem cell is reduced coincident with the number of symmetric divisions it must perform. In a study of FVB/N mice with the transgene, WAP-TGFbeta1, we discovered that mammary epithelial stem cells were prematurely aged due to ectopic expression of TGF-beta1. To test whether premature aging of mammary epithelial stem cells would have an impact on susceptibility or resistance to mammary cancer, female littermates from FVB/N x WAP-TGF-beta1 mating were injected with mouse mammary tumor virus (MMTV) at 8-10 weeks of age. A total of 44 females were inoculated, maintained as breeders and observed for tumor development for up to 18 months. Only one mammary tumor appeared in 17 TGF-beta1 females while 15 were collected from 29 wild type sisters. Premalignant mammary epithelial cells in infected glands were identified by transplantation of single cell (1 x 10(5)) suspensions into nulliparous hosts and testing for hyperplastic outgrowth. Although the number of positive takes was significantly reduced with TGF-beta1 cells, both MMTV-infected TGF-beta1 and wild type cells produced hyperplastic outgrowths suggesting that premalignant transformation was achieved in each group. The results suggest a positive correlation between the procreative life-span of mammary epithelial stem cells and mammary cancer risk.