aPKCλ controls epidermal homeostasis and stem cell fate through regulation of division orientation

The atypical protein kinase C (aPKC) is a key regulator of polarity and cell fate in lower organisms. However, whether mammalian aPKCs control stem cells and fate in vivo is not known. Here we show that loss of aPKCλ in a self-renewing epithelium, the epidermis, disturbed tissue homeostasis, differentiation, and stem cell dynamics, causing progressive changes in this tissue. This was accompanied by a gradual loss of quiescent hair follicle bulge stem cells and a temporary increase in proliferating progenitors. Lineage tracing analysis showed that loss of aPKCλ altered the fate of lower bulge/hair germ stem cells. This ultimately led to loss of proliferative potential, stem cell exhaustion, alopecia, and premature aging. Inactivation of aPKCλ produced more asymmetric divisions in different compartments, including the bulge. Thus, aPKCλ is crucial for homeostasis of self-renewing stratifying epithelia, and for the regulation of cell fate, differentiation, and maintenance of epidermal bulge stem cells likely through its role in balancing symmetric and asymmetric division.

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Alternative polyadenylation of Pax3 controls muscle stem cell fate and muscle function

Science ◽

10.1126/science.aax1694 ◽

2019 ◽

Vol 366 (6466) ◽

pp. 734-738 ◽

Cited By ~ 11

Author(s):

Antoine de Morree ◽

Julian D. D. Klein ◽

Qiang Gan ◽

Jean Farup ◽

Andoni Urtasun ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Messenger Rna ◽

Adult Stem Cells ◽

Alternative Polyadenylation ◽

Quiescent State ◽

Stem Cell Fate ◽

Activation Rate

Adult stem cells are essential for tissue homeostasis. In skeletal muscle, muscle stem cells (MuSCs) reside in a quiescent state, but little is known about the mechanisms that control homeostatic turnover. Here we show that, in mice, the variation in MuSC activation rate among different muscles (for example, limb versus diaphragm muscles) is determined by the levels of the transcription factor Pax3. We further show that Pax3 levels are controlled by alternative polyadenylation of its transcript, which is regulated by the small nucleolar RNA U1. Isoforms of the Pax3 messenger RNA that differ in their 3′ untranslated regions are differentially susceptible to regulation by microRNA miR206, which results in varying levels of the Pax3 protein in vivo. These findings highlight a previously unrecognized mechanism of the homeostatic regulation of stem cell fate by multiple RNA species.

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Effect of the 3D Artificial Nichoid on the Morphology and Mechanobiological Response of Mesenchymal Stem Cells Cultured In Vitro

Cells ◽

10.3390/cells9081873 ◽

2020 ◽

Vol 9 (8) ◽

pp. 1873 ◽

Cited By ~ 3

Author(s):

Andrea Remuzzi ◽

Barbara Bonandrini ◽

Matteo Tironi ◽

Lorena Longaretti ◽

Marina Figliuzzi ◽

...

Keyword(s):

Stem Cells ◽

Mesenchymal Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Cultured Cells ◽

Three Dimensions ◽

Nuclear Pore ◽

Cells Cultured

Stem cell fate and behavior are affected by the bidirectional communication of cells and their local microenvironment (the stem cell niche), which includes biochemical cues, as well as physical and mechanical factors. Stem cells are normally cultured in conventional two-dimensional monolayer, with a mechanical environment very different from the physiological one. Here, we compare culture of rat mesenchymal stem cells on flat culture supports and in the “Nichoid”, an innovative three-dimensional substrate micro-engineered to recapitulate the architecture of the physiological niche in vitro. Two versions of the culture substrates Nichoid (single-layered or “2D Nichoid” and multi-layered or “3D Nichoid”) were fabricated via two-photon laser polymerization in a biocompatible hybrid organic-inorganic photoresist (SZ2080). Mesenchymal stem cells, isolated from rat bone marrow, were seeded on flat substrates and on 2D and 3D Nichoid substrates and maintained in culture up to 2 weeks. During cell culture, we evaluated cell morphology, proliferation, cell motility and the expression of a panel of 89 mesenchymal stem cells’ specific genes, as well as intracellular structures organization. Our results show that mesenchymal stem cells adhered and grew in the 3D Nichoid with a comparable proliferation rate as compared to flat substrates. After seeding on flat substrates, cells displayed large and spread nucleus and cytoplasm, while cells cultured in the 3D Nichoid were spatially organized in three dimensions, with smaller and spherical nuclei. Gene expression analysis revealed the upregulation of genes related to stemness and to mesenchymal stem cells’ features in Nichoid-cultured cells, as compared to flat substrates. The observed changes in cytoskeletal organization of cells cultured on 3D Nichoids were also responsible for a different localization of the mechanotransducer transcription factor YAP, with an increase of the cytoplasmic retention in cells cultured in the 3D Nichoid. This difference could be explained by alterations in the import of transcription factors inside the nucleus due to the observed decrease of mean nuclear pore diameter, by transmission electron microscopy. Our data show that 3D distribution of cell volume has a profound effect on mesenchymal stem cells structure and on their mechanobiological response, and highlight the potential use of the 3D Nichoid substrate to strengthen the potential effects of MSC in vitro and in vivo.

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Constructing stem cell microenvironments using bioengineering approaches

Physiological Genomics ◽

10.1152/physiolgenomics.00099.2013 ◽

2013 ◽

Vol 45 (23) ◽

pp. 1123-1135 ◽

Cited By ~ 29

Author(s):

David A. Brafman

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Disease Modeling ◽

Mechanical Stimuli ◽

Culture Methods ◽

Stem Cell Fate ◽

And Function

Within the adult organism, stem cells reside in defined anatomical microenvironments called niches. These architecturally diverse microenvironments serve to balance stem cell self-renewal and differentiation. Proper regulation of this balance is instrumental to tissue repair and homeostasis, and any imbalance can potentially lead to diseases such as cancer. Within each of these microenvironments, a myriad of chemical and physical stimuli interact in a complex (synergistic or antagonistic) manner to tightly regulate stem cell fate. The in vitro replication of these in vivo microenvironments will be necessary for the application of stem cells for disease modeling, drug discovery, and regenerative medicine purposes. However, traditional reductionist approaches have only led to the generation of cell culture methods that poorly recapitulate the in vivo microenvironment. To that end, novel engineering and systems biology approaches have allowed for the investigation of the biological and mechanical stimuli that govern stem cell fate. In this review, the application of these technologies for the dissection of stem cell microenvironments will be analyzed. Moreover, the use of these engineering approaches to construct in vitro stem cell microenvironments that precisely control stem cell fate and function will be reviewed. Finally, the emerging trend of using high-throughput, combinatorial methods for the stepwise engineering of stem cell microenvironments will be explored.

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CENP-C regulates centromere assembly, asymmetry and epigenetic age in Drosophila germline stem cells

10.1101/2020.11.02.364794 ◽

2020 ◽

Author(s):

Ben L Carty ◽

Anna A Dattoli ◽

Elaine M Dunleavy

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Germ Line ◽

Asymmetric Distribution ◽

Germline Stem Cells ◽

Daughter Cells ◽

Sister Chromatids ◽

Asymmetric Divisions ◽

Centromere Assembly

AbstractGermline stem cells divide asymmetrically to produce one new daughter stem cell and one daughter cell that will subsequently undergo meiosis and differentiate to generate the mature gamete. The silent sister hypothesis proposes that in asymmetric divisions, the selective inheritance of sister chromatids carrying specific epigenetic marks between stem and daughter cells impacts cell fate. To facilitate this selective inheritance, the hypothesis specifically proposes that the centromeric region of each sister chromatid is distinct. In Drosophila germ line stem cells (GSCs), it has recently been shown that the centromeric histone CENP-A (called CID in flies) - the epigenetic determinant of centromere identity - is asymmetrically distributed between sister chromatids. In these cells, CID deposition occurs in G2 phase such that sister chromatids destined to end up in the stem cell harbour more CENP-A, assemble more kinetochore proteins and capture more spindle microtubules. These results suggest a potential mechanism of ‘mitotic drive’ that might bias chromosome segregation. Here we report that the inner kinetochore protein CENP-C, is required for the assembly of CID in G2 phase in GSCs. Moreover, CENP-C is required to maintain a normal asymmetric distribution of CID between stem and daughter cells. In addition, we find that CID is lost from centromeres in aged GSCs and that a reduction in CENP-C accelerates this loss. Finally, we show that CENP-C depletion in GSCs disrupts the balance of stem and daughter cells in the ovary, shifting GSCs toward a self-renewal tendency. Ultimately, we provide evidence that centromere assembly and maintenance via CENP-C is required to sustain asymmetric divisions in female Drosophila GSCs.

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Mathematical modeling of plant cell fate transitions controlled by hormonal signals

10.1101/830190 ◽

2019 ◽

Author(s):

Filip Z. Klawe ◽

Thomas Stiehl ◽

Peter Bastian ◽

Christophe Gaillochet ◽

Jan U. Lohmann ◽

...

Keyword(s):

Stem Cells ◽

Transcription Factor ◽

Stem Cell ◽

Transcription Factors ◽

Cell Division ◽

Cell Fate ◽

Plant Architecture ◽

Two Dimensional ◽

Cell Dynamics ◽

Non Linear

AbstractCoordination of fate transition and cell division is crucial to maintain the plant architecture and to achieve efficient production of plant organs. In this paper, we analysed the stem cell dynamics at the shoot apical meristem (SAM) that is one of the plant stem cells locations. We designed a mathematical model to elucidate the impact of hormonal signaling on the fate transition rates between different zones corresponding to slowly dividing stem cells and fast dividing transit amplifying cells. The model is based on a simplified two-dimensional disc geometry of the SAM and accounts for a continuous displacement towards the periphery of cells produced in the central zone. Coupling growth and hormonal signaling results in a non-linear system of reaction-diffusion equations on a growing domain with the growth velocity depending on the model components. The model is tested by simulating perturbations in the level of key transcription factors that maintain SAM homeostasis. The model provides new insights on how the transcription factor HECATE is integrated in the regulatory network that governs stem cell differentiation.SummaryPlants continuously generate new organs such as leaves, roots and flowers. This process is driven by stem cells which are located in specialized regions, so-called meristems. Dividing stem cells give rise to offspring that, during a process referred to as cell fate transition, become more specialized and give rise to organs. Plant architecture and crop yield crucially depend on the regulation of meristem dynamics. To better understand this regulation, we develop a computational model of the shoot meristem. The model describes the meristem as a two-dimensional disk that can grow and shrink over time, depending on the concentrations of the signalling factors in its interior. This allows studying how the non-linear interaction of multiple transcription factors is linked to cell division and fate-transition. We test the model by simulating perturbations of meristem signals and comparing them to experimental data. The model allows simulating different hypotheses about signal effects. Based on the model we study the specific role of the transcription factor HECATE and provide new insights in its action on cell dynamics and in its interrelation with other known transcription factors in the meristem.

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Encapsulation and recovery of murine hematopoietic stem and progenitor cells in a thiol-crosslinked maleimide-functionalized gelatin hydrogel

10.1101/2021.03.22.436491 ◽

2021 ◽

Author(s):

Aidan E Gilchrist ◽

Julio F. Serrano ◽

Mai T. Ngo ◽

Zona Hrnjak ◽

Sanha Kim ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Click Reaction ◽

Uv Light ◽

3D Culture ◽

Bone Marrow Niche ◽

Hematopoietic Stem ◽

Cell Fate Decisions

Biomaterial platforms are an integral part of stem cell biomanufacturing protocols. The collective biophysical, biochemical, and cellular cues of the stem cell niche microenvironment play an important role in regulating stem cell fate decisions. Three-dimensional (3D) culture of stem cells within biomaterials provides a route to present biophysical and biochemical stimuli such as cell-matrix interactions and cell-cell interactions via secreted biomolecules. Herein, we describe a maleimide-functionalized gelatin (GelMAL) hydrogel that can be crosslinked via thiol-Michael addition click reaction for the encapsulation of sensitive stem cell populations. The maleimide functional units along the gelatin backbone enables gelation via the addition of a dithiol crosslinker without requiring external stimuli (e.g., UV light, photoinitiator), reducing reactive oxide species generation. Additionally, the versatility of crosslinker selection enables easy insertion of thiol-containing bioactive or bioinert motifs. Hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) were encapsulated in GelMAL, with mechanical properties tuned to mimic the in vivo bone marrow niche. We report insertion of a cleavable peptide crosslinker that can be degraded by the proteolytic action of SortaseA, a mammalian-inert enzyme. Notably, SortaseA exposure preserves stem cell surface markers, an essential metric of hematopoietic activity used in immunophenotyping. This novel GelMAL system enables a route to producing artificial stem cell niches with tunable biophysical properties with intrinsic cell-interaction motifs and orthogonal addition of bioactive crosslinks.

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Regulation of ERK basal and pulsatile activity control proliferation and exit from the stem cell compartment in mammalian epidermis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2006965117 ◽

2020 ◽

Vol 117 (30) ◽

pp. 17796-17807 ◽

Cited By ~ 4

Author(s):

Toru Hiratsuka ◽

Ignacio Bordeu ◽

Gunnar Pruessner ◽

Fiona M. Watt

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Basal Cells ◽

Mammalian Development ◽

Down Regulation ◽

Cell Dynamics ◽

Erk Mapk ◽

Differentiated Cells ◽

Erk Activity

Fluctuation in signal transduction pathways is frequently observed during mammalian development. However, its role in regulating stem cells has not been explored. Here we tracked spatiotemporal ERK MAPK dynamics in human epidermal stem cells. While stem cells and differentiated cells were distinguished by high and low stable basal ERK activity, respectively, we also found cells with pulsatile ERK activity. Transitions from Basalhi-Pulselo(stem) to Basalhi-Pulsehi, Basalmid-Pulsehi, and Basallo-Pulselo(differentiated) cells occurred in expanding keratinocyte colonies and in response to differentiation stimuli. Pharmacological inhibition of ERK induced differentiation only when cells were in the Basalmid-Pulsehistate. Basal ERK activity and pulses were differentially regulated by DUSP10 and DUSP6, leading us to speculate that DUSP6-mediated ERK pulse down-regulation promotes initiation of differentiation, whereas DUSP10-mediated down-regulation of mean ERK activity promotes and stabilizes postcommitment differentiation. Levels of MAPK1/MAPK3 transcripts correlated with DUSP6 and DUSP10 transcripts in individual cells, suggesting that ERK activity is negatively regulated by transcriptional and posttranslational mechanisms. When cells were cultured on a topography that mimics the epidermal−dermal interface, spatial segregation of mean ERK activity and pulses was observed. In vivo imaging of mouse epidermis revealed a patterned distribution of basal cells with pulsatile ERK activity, and down-regulation was linked to the onset of differentiation. Our findings demonstrate that ERK MAPK signal fluctuations link kinase activity to stem cell dynamics.

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Cell size is a determinant of stem cell potential during aging

10.1101/2020.10.27.355388 ◽

2020 ◽

Author(s):

Jette Lengefeld ◽

Chia-Wei Cheng ◽

Pema Maretich ◽

Marguerite Blair ◽

Hannah Hagen ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Size ◽

Cell Function ◽

Cell Aging ◽

Proliferative Potential ◽

Cell Potential ◽

Hematopoietic Stem ◽

Stem Cell Potential

AbstractStem cells are remarkably small in size. Whether small size is important for stem cell function is unknown. We find that murine hematopoietic stem cells (HSCs) enlarge under conditions known to decrease stem cell function. This decreased fitness of large HSCs is due to reduced proliferative potential. Preventing HSC enlargement by inhibiting macromolecule biosynthesis or reducing large HSCs size by shortening G1 averts the loss of stem cell potential under conditions causing stem cell exhaustion. Finally, we show that a fraction of 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.One Sentence SummarySize increase drives stem cell aging.

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Mitochondrial Control of Stem Cell State and Fate: Lessons From Drosophila

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.606639 ◽

2021 ◽

Vol 9 ◽

Author(s):

Satish Kumar Tiwari ◽

Sudip Mandal

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Cell Types ◽

Extrinsic Factors ◽

Cell Fate Decisions ◽

Cell State ◽

Resident Stem Cells ◽

Stem Cell State

Over the years, Drosophila has served as a wonderful genetically tractable model system to unravel various facets of tissue-resident stem cells in their microenvironment. Studies in different stem and progenitor cell types of Drosophila have led to the discovery of cell-intrinsic and extrinsic factors crucial for stem cell state and fate. Though initially touted as the ATP generating machines for carrying various cellular processes, it is now increasingly becoming clear that mitochondrial processes alone can override the cellular program of stem cells. The last few years have witnessed a surge in our understanding of mitochondria’s contribution to governing different stem cell properties in their subtissular niches in Drosophila. Through this review, we intend to sum up and highlight the outcome of these in vivo studies that implicate mitochondria as a central regulator of stem cell fate decisions; to find the commonalities and uniqueness associated with these regulatory mechanisms.

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CENP-C functions in centromere assembly, the maintenance of CENP-A asymmetry and epigenetic age in Drosophila germline stem cells

PLoS Genetics ◽

10.1371/journal.pgen.1009247 ◽

2021 ◽

Vol 17 (5) ◽

pp. e1009247

Author(s):

Ben L. Carty ◽

Anna A. Dattoli ◽

Elaine M. Dunleavy

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Cell Fate ◽

Germ Line ◽

Asymmetric Distribution ◽

Germline Stem Cells ◽

Daughter Cells ◽

Sister Chromatids ◽

Asymmetric Divisions ◽

Centromere Assembly

Germline stem cells divide asymmetrically to produce one new daughter stem cell and one daughter cell that will subsequently undergo meiosis and differentiate to generate the mature gamete. The silent sister hypothesis proposes that in asymmetric divisions, the selective inheritance of sister chromatids carrying specific epigenetic marks between stem and daughter cells impacts cell fate. To facilitate this selective inheritance, the hypothesis specifically proposes that the centromeric region of each sister chromatid is distinct. In Drosophila germ line stem cells (GSCs), it has recently been shown that the centromeric histone CENP-A (called CID in flies)—the epigenetic determinant of centromere identity—is asymmetrically distributed between sister chromatids. In these cells, CID deposition occurs in G2 phase such that sister chromatids destined to end up in the stem cell harbour more CENP-A, assemble more kinetochore proteins and capture more spindle microtubules. These results suggest a potential mechanism of ‘mitotic drive’ that might bias chromosome segregation. Here we report that the inner kinetochore protein CENP-C, is required for the assembly of CID in G2 phase in GSCs. Moreover, CENP-C is required to maintain a normal asymmetric distribution of CID between stem and daughter cells. In addition, we find that CID is lost from centromeres in aged GSCs and that a reduction in CENP-C accelerates this loss. Finally, we show that CENP-C depletion in GSCs disrupts the balance of stem and daughter cells in the ovary, shifting GSCs toward a self-renewal tendency. Ultimately, we provide evidence that centromere assembly and maintenance via CENP-C is required to sustain asymmetric divisions in female Drosophila GSCs.

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