Epithelial Stem Cell Proliferation Research Articles

EVI and MDS/EVI are required for adult intestinal stem cell formation during postembryonic vertebrate development.

The gene ectopic viral integration site 1 (EVI) and its variant myelodysplastic syndrome 1 (MDS)/EVI encode zinc-finger proteins that have been recognized as important oncogenes in various types of cancer. In contrast to the established role of EVI and MDS/EVI in cancer development, their potential function during vertebrate postembryonic development, especially in organ-specific adult stem cells, is unclear. Amphibian metamorphosis is strikingly similar to postembryonic development around birth in mammals, with both processes taking place when plasma thyroid hormone (T3) levels are high. Using the T3-dependent metamorphosis in Xenopus tropicalis as a model, we show here that high levels of EVI and MDS/EVI are expressed in the intestine at the climax of metamorphosis and are induced by T3. By using the transcription activator-like effector nuclease gene editing technology, we have knocked out both EVI and MDS/EVI and have shown that EVI and MDS/EVI are not essential for embryogenesis and premetamorphosis in X. tropicalis On the other hand, knocking out EVI and MDS/EVI causes severe retardation in the growth and development of the tadpoles during metamorphosis and leads to tadpole lethality at the climax of metamorphosis. Furthermore, the homozygous-knockout animals have reduced adult intestinal epithelial stem cell proliferation at the end of metamorphosis (for the few that survive through metamorphosis) or during T3-induced metamorphosis. These findings reveal a novel role of EVI and/or MDS/EVI in regulating the formation and/or proliferation of adult intestinal adult stem cells during postembryonic development in vertebrates.-Okada, M., Shi, Y.-B. EVI and MDS/EVI are required for adult intestinal stem cell formation during postembryonic vertebrate development.

LKB1-AMPK modulates nutrient-induced changes in the mode of division of intestinal epithelial crypt cells in mice.

Nutrient availability influences intestinal epithelial stem cell proliferation and tissue growth. Increases in food result in a greater number of epithelial cells, villi height and crypt depth. We investigated whether this nutrient-driven expansion of the tissue is the result of a change in the mode of intestinal epithelial stem cell division and if LKB1-AMPK signaling plays a role. We utilized invivo and invitro experiments to test this hypothesis. C57BL/6J mice were separated into four groups and fed varying amounts of chow for 18 h: (1) ad libitum, (2) 50% of their average daily intake (3) fasted or (4) fasted for 12 h and refed. Mice were sacrificed, intestinal sections excised and immunohistochemically processed to determine the mitotic spindle orientation. Epithelial organoids invitro were treated with no (0 mM), low (5 mM) or high (20 mM) amounts of glucose with or without an activator (Metformin) or inhibitor (Compound C) of LKB1-AMPK signaling. Cells were then processed to determine the mode of stem cell division. Fasted mice show a greater % of asymmetrically dividing cells compared with the other feeding groups. Organoids incubated with 0 mM glucose resulted in a greater % of asymmetrically dividing cells compared with the low or high-glucose conditions. In addition, LKB1-AMPK activation attenuated the % of symmetric division normally seen in high-glucose conditions. In contrast, LKB1-AMPK inhibition attenuated the % of asymmetric division normally seen in no glucose conditions. These data suggest that nutrient availability dictates the mode of division and that LKB1-AMPK mediates this nutrient-driven effect on intestinal epithelial stem cell proliferation. Impact statement The underlying cell biology of changes in the polarity of mitotic spindles and its relevance to tissue growth is a new concept and, thus, these data provide novel findings to begin to explain how this process contributes to the regeneration and growth of tissues. We find that short-term changes in food intake invivo or glucose availability invitro dictate the mode of division of crypt cells. In addition, we find that LKB1-AMPK signaling modulates the glucose-induced changes in the mode of division invitro. Identifying mechanisms involved in the mode of division may provide new targets to control tissue growth.

Conditional cell reprogramming involves non-canonical β-catenin activation and mTOR-mediated inactivation of Akt.

The combination of irradiated fibroblast feeder cells and Rho kinase inhibitor, Y-267362, converts primary epithelial cells growing in vitro into an undifferentiated adult stem cell-like state that is characterized by long-term proliferation. This cell culture method also maintains the proliferation of adult epithelial stem cells from various tissues. Both primary and adult stem cells retain their tissue-specific differentiation potential upon removal of the culture conditions. Due to the ability to modulate the proliferation and differentiation of the cells, this method is referred to as conditional reprogramming and it is increasingly being used in studies of tumor heterogeneity, personalized medicine and regenerative medicine. However, little is known about the biology of these conditionally reprogrammed (CR) cells. Previously we showed that β-catenin activation, a hallmark of stem cells in vivo, occurs in CR human ectocervical cells (HECs). Here we show that β-catenin-dependent transcription is necessary for the induction of epithelial stem cell markers, and that β-catenin is activated via a non-canonical pathway that is independent of Wnt and Akt/GSK-3. Active Akt actually decreases due to increased mTOR signaling, with a consequent increase in dephosphorylated, active GSK-3. Despite the increase in active GSK-3, β-catenin associates with protein phosphatase 2A (PP2A) and is activated. Inhibition of PP2A catalytic activity reduces both the level of active β-catenin and the acute induction of stem cell markers, suggesting an important role for PP2A in the activation of β-catenin. Moreover, we demonstrate similar results using human prostate and breast cells, indicating that these changes are not restricted to ectocervical epithelial cells and may represent a more fundamental property of conditional reprogramming.

Recruited Monocytes and Type 2 Immunity Promote Lung Regeneration following Pneumonectomy

To investigate the role of immune cells in lung regeneration, we used a unilateral pneumonectomy model that promotes the formation of new alveoli in the remaining lobes. Immunofluorescence and single-cell RNA sequencing found CD115+ and CCR2+ monocytes and M2-like macrophages accumulating in the lung during the peak of type 2 alveolar epithelial stem cell (AEC2) proliferation. Genetic loss of function in mice and adoptive transfer studies revealed that bone marrow-derived macrophages (BMDMs) traffic to the lung through a CCL2-CCR2 chemokine axis and are required for optimal lung regeneration, along with Il4ra-expressing leukocytes. Our data suggest that these cells modulate AEC2 proliferation and differentiation. Finally, we provide evidence that group 2 innate lymphoid cells are a source of IL-13, which promotes lung regeneration. Together, our data highlight the potential for immunomodulatory therapies to stimulate alveologenesis in adults.

Obesity, Independent of the Type of Diet, Drives Lasting Effects on Intestinal Epithelial Stem Cell Proliferation

The intestinal epithelium plays an essential role in nutrient absorption, satiety hormone release and immune barrier function. Maintenance of the epithelium is driven by continuous cell renewal by intestinal epithelial stem cells (IESCs) located in the intestinal crypts. Obesity affects this process and results in changes in the size and cellular make‐up of the tissue. In addition, isolated IESCs from obese mice have a reduced growth potential to develop into organoids in culture compared with IESCs from lean mice, indicating that obesity may produce long‐lasting effects on IESC proliferation and differentiation. Because the amount and type of diet contribute to obesity, we wanted to determine whether the amount (in kilocalories) or type of diet differentially alters IESC proliferation. C57BL/6J mice were fed two different diet combinations, a high‐fat diet or a Westernized high‐fat/high‐sugar diet. The high‐fat and control groups were as follows: 1) 60% high‐fat fed, 2) 10% low‐fat fed, and 3) 60% high‐fat pair fed (fed a high‐fat diet, but in equal kcal as that eaten by the low‐fat fed animals to keep them lean). The Westernized high‐fat/high‐sugar and control groups were as follows: 1) 31.8% high‐fat, 25% sugar fed, 2) 10.6% low‐fat, 25% sugar fed, and 3) 31.8% high‐fat, 25% sugar pair fed group (fed a high‐fat high‐sugar diet, but in equal kcal as that eaten by the low‐fat high‐sugar fed animals to keep them lean). After 3 months, IESCs were isolated from each mouse using antibody‐based fluorescent cell sorting and grown in media containing inhibitors of differentiation. Crypt development was tracked for 14 days post‐plating and glucose‐induced crypt cell proliferation was measured on day 14. We found that crypts developed from IESCs isolated from high‐fat fed, obese mice formed a reduced number and size of budding structures compared with low‐fat fed, lean mice and high‐fat pair fed, lean mice, while the number of crypts developed per area measured were the same between the groups. Furthermore, glucose increased the proliferation of crypts developed from IESCs isolated from both low‐fat fed, lean mice and high‐fat pair fed, lean mice, but had no effect on the proliferation of crypts developed from IESCs isolated from high‐fat fed, obese mice. In contrast, the mice in the Westernized diet groups ate equal kcal amounts of each diet, were equal in body weight, and there were no significant differences in crypt cell proliferation between the groups. These results suggest that factors related to obesity and not the type of diet (high‐fat or high‐fat/high‐sugar) are driving lasting effects on IESC proliferation.Support or Funding InformationUSDA Hatch ILLU‐538‐926

Nephronectin plays critical roles in Sox2 expression and proliferation in dental epithelial stem cells via EGF-like repeat domains

Tooth development is initiated by epithelial-mesenchymal interactions via basement membrane (BM) and growth factors. In the present study, we found that nephronectin (Npnt), a component of the BM, is highly expressed in the developing tooth. Npnt localizes in the BM on the buccal side of the tooth germ and shows an expression pattern opposite that of the dental epithelial stem cell marker Sox2. To identify the roles of Npnt during tooth development, we performed knockdown and overexpression experiments using ex vivo organ and dental epithelial cell cultures. Our findings showed that loss of Npnt induced ectopic Sox2-positive cells and reduced tooth germ size. Over expression of Npnt showed increased proliferation, whereas the number of Sox2-positive cells was decreased in dental epithelial cells. Npnt contains 5 EGF-like repeat domains, as well as an RGD sequence and MAM domain. We found that the EGF-like repeats are critical for Sox2 expression and cell proliferation. Furthermore, Npnt activated the EGF receptor (EGFR) via the EGF-like repeat domains and induced the PI3K-Akt signaling pathway. Our results indicate that Npnt plays a critical scaffold role in dental epithelial stem cell differentiation and proliferation, and regulates Sox2 expression during tooth development.

Functional Transcriptomics in Diverse Intestinal Epithelial Cell Types Reveals Robust MicroRNA Sensitivity in Intestinal Stem Cells to Microbial Status

Gut microbiota play an important role in regulating the development of the host immune system, metabolic rate, and at times, disease pathogenesis. The factors and mechanisms that mediate interactions between microbiota and the intestinal epithelium are not fully understood. We provide novel evidence that microbiota may control intestinal epithelial stem cell (IESC) proliferation in part through microRNAs (miRNAs). We demonstrate that miRNA profiles differ dramatically across functionally distinct cell types of the mouse jejunal intestinal epithelium and that miRNAs respond to microbiota in a highly cell type-specific manner. Importantly, we also show that miRNAs in IESCs are more prominently regulated by microbiota compared with miRNAs in any other intestinal epithelial cell subtype. We identify miR-375 as one miRNA that is significantly suppressed by the presence of microbiota in IESCs. Using a novel method to knockdown gene and miRNA expression ex vivo enteroids, we demonstrate that we can knock down gene expression in Lgr5+ IESCs. Furthermore, when we knock down miR-375 in IESCs, we observe significantly increased proliferative capacity. Understanding the mechanisms by which microbiota regulate miRNA expression in IESCs and other intestinal epithelial cell subtypes will elucidate a critical molecular network that controls intestinal homeostasis and, given the heightened interest in miRNA-based therapies, may offer novel therapeutic strategies in the treatment of gastrointestinal diseases associated with altered IESC function.

Long-term maintenance and proliferation of murine skin epithelial stem cells by Wnt-3a in vitro

Long-term maintenance and proliferation of murine skin epithelial stem cells by Wnt-3a in vitro

Snail controls proliferation of Drosophila ovarian epithelial follicle stem cells, independently of E-cadherin

Epithelial stem cells undergo constant self-renewal and differentiation to maintain the homeostasis of epithelial tissues that undergo rapid turnover. Recent studies have shown that the epithelial-mesenchymal transition (EMT), which is primarily mediated by Snail via the suppression of E-cadherin, is able to generate cells with stem cell properties. However, the role of Snail in epithelial stem cells remains unclear. Here, we report that Snail directly controls proliferation of follicle stem cells (FSCs) in Drosophila females. Disruption of Snail expression in FSCs compromises their proliferation, but not their maintenance. Conversely, FSCs with excessive Snail expression display increased proliferation and lifespan, which is accompanied by a moderate decrease in the expression of E-cadherin (required for adhesion of FSCs to their niche) at the junction between their adjacent cells, indicating a conserved role of Snail in E-cadherin inhibition, which promote epithelial cell proliferation. Interestingly, a decrease in E-cadherin in snail-knock down FSCs does not restore the decreased proliferation of snail-knock down FSCs, suggesting that adhesion strength of FSCs to their niche is dispensable for Snail-mediated FSC division. Our results demonstrate that Snail controls epithelial stem cell division independently of its known role in the EMT, which contributes to induction of cancer stem cells.

Inactivation of a Gα(s)-PKA tumour suppressor pathway in skin stem cells initiates basal-cell carcinogenesis.

Genomic alterations in GNAS, the gene coding for the Gαs heterotrimeric G-protein, are associated with a large number human of diseases. Here, we explored the role of Gαs on stem cell fate decisions by using the mouse epidermis as a model system. Conditional epidermal deletion of Gnas or repression of PKA signaling caused a remarkable expansion of the stem cell compartment, resulting in rapid basal cell carcinoma formation. In contrast, inducible expression of active Gαs in the epidermis caused hair follicle stem cell exhaustion and hair loss. Mechanistically, we found that Gαs-PKA disruption promotes the cell autonomous Sonic Hedgehog pathway stimulation and Hippo signaling inhibition, resulting in the non-canonical activation of GLI and YAP1. Our study highlights an important tumor suppressive function of Gαs-PKA, limiting the proliferation of epithelial stem cells and maintaining proper hair follicle homeostasis. These findings can have broad implications in multiple pathophysiological conditions, including cancer.

Roles of limbal microvascular net and limbal stroma in regulating maintenance of limbal epithelial stem cells.

Knowledge of the microenvironment (niche) of stem cells is helpful for stem-cell-based regenerative medicine. In the eye, limbal epithelial stem cells (corneal epithelial stem cells) provide the self-renewal capacity of the corneal epithelium and are essential for maintaining corneal transparency and vision. Limbal epithelial stem cell deficiency results in significant visual deterioration. Successful treatment of this type of blinding disease requires studies of the limbal epithelial stem cells and their microenvironment. We investigate the function of the limbal microvascular net and the limbal stroma in the maintenace of the limbal epithelial stem cell niche in vivo and examine the regulation of limbal epithelial stem cell survival, proliferation and differentiation in vivo. We assess the temporal and spatial changes in the expression patterns of the following markers during a six-month follow-up of various rabbit limbal autograft transplantation models: vascular endothelial cell marker CD31, corneal epithelium differentiation marker K3, limbal epithelial stem-cell-associated markers P63 and ABCG2 and proliferating cell nuclear marker Ki67. Our results suggest that limbal epithelial stem cells cannot maintain their stemness or proliferation without the support of the limbal microvascular net microenvironment. Thus, both the limbal microvascular net and the limbal stroma play important roles as components of the limbal epithelial stem cell niche maintaining limbal epithelial stem cell survival and proliferation and the avoidance of differentiation. The limbal stroma constitutes the structural basis of the limbal epithelial stem cell niche and the limbal microvascular net is a requirement for this niche. These new insights should aid the eventual construction of tissue-engineered cornea for corneal blind patients in the future.

Krüppel-like factor 5 is essential for proliferation and survival of mouse intestinal epithelial stem cells

Krüppel-like factor 5 (KLF5) is a pro-proliferative transcription factor that is expressed in dividing epithelial cells of the intestinal crypt. Leucine-rich repeat-containing G-protein coupled receptor 5 (Lgr5) has been identified as a stem cell marker in both small intestinal and colonic epithelial cells. To determine whether KLF5 regulates proliferation of intestinal stem cells, we investigated the effects of Klf5 deletion specifically from the intestinal stem cells in adult mice. Mice with inducible intestinal stem cell-specific deletion of Klf5 (Lgr5-Klf5fl/fl) were injected with tamoxifen for 5 consecutive days to induce Lgr5-driven Cre expression. Intestinal and colonic tissues were examined by immunohistochemistry at various time points up to 112days following start of tamoxifen treatment. Klf5 is co-localized in the crypt-based columnar (CBC) cells that express Lgr5. By 11days following the start of tamoxifen treatment, Lgr5-positive crypts from which Klf5 was deleted exhibited a loss of proliferation that was accompanied by an increase in apoptosis. Beginning at 14days following the start of tamoxifen treatment, both Klf5 expression and proliferation were re-established in the transit-amplifying epithelial cells but not in the Lgr5-positive CBC cells. By 112days post-treatment, up to 90% of the Lgr5-positive cells from which Klf5 was deleted were lost from the intestinal crypts. These results indicate a critical role for KLF5 in the survival and maintenance of intestinal stem cells.

Spatial Distribution of Niche and Stem Cells in Ex Vivo Human Limbal Cultures

Stem cells at the limbus mediate corneal epithelial regeneration and regulate normal tissue homeostasis. Ex vivo cultured limbal epithelial transplantations are being widely practiced in the treatment of limbal stem cell deficiency. In this report, we examined whether the limbal niche cells that nurture and regulate epithelial stem cells coexist in ex vivo limbal cultures. We also compared the inherent differences between explant and suspension culture systems in terms of spatial distribution of niche cells and their effect on epithelial stem cell proliferation, migration, and differentiation in vitro. We report that the stem cell content of both culture systems was similar, explaining the comparable clinical outcomes reported using these two methods. We also showed that the niche cells get expanded in culture and the nestin-positive cells migrate at the leading edges to direct epithelial cell migration in suspension cultures, whereas they are limited to the intact niche in explant cultures. We provide evidence that C/EBPδ-positive, p15-positive, and quiescent, label-retaining, early activated stem cells migrate at the leading edges to regulate epithelial cell proliferation in explant cultures, and this position effect is lost in early suspension cultures. However, in confluent suspension cultures, the stem cells and niche cells interact with each another, migrate in spiraling patterns, and self-organize to form three-dimensional niche-like compartments resembling the limbal crypts and thereby reestablish the position effect. These 3D-sphere clusters are enriched with nestin-, vimentin-, S100-, and p27-positive niche cells and p15-, p21-, p63α-, C/EBPδ-, ABCG2-, and Pax6-positive quiescent epithelial stem cells.

Differential nuclear expression of Yap in basal epithelial cells across the cornea and substrates of differing stiffness

Corneal epithelium is maintained throughout life by well-orchestrated proliferation of limbal epithelial stem cells, followed by migration and maturation centripetally across the ocular surface. The present study sets out to explore the role tissue stiffness (compliance) may have in directing both differentiation and centripetal migration of limbal epithelial stem cells during homeostasis. For that, we analysed the localization of the Yes-associated protein (Yap), a transcriptional co-activator previously shown to mediate cellular response and mechanical stimuli. Using both models of ocular surface compliance and normal bovine corneas we evaluated the nuclear/cytoplasmic expression ratio of Yap. Expression levels within corneal epithelial cells were compared in situ between the limbus and central cornea, and in vitro between limbal epithelial stem cells expanded upon biomimetic collagen gels of increasing stiffness. Nuclear expression of Yap was shown to increase within the expanded cells upon substrates of increasing stiffness. Subsequently, Yap was used as a novel molecular probe to investigate the mechanical microenvironment within a normal ocular surface. The in situ localization of Yap was predominantly cytoplasmic within basal limbal epithelial cells and nuclear within basal central corneal epithelial cells. Furthermore, nuclear p63 expression was not co-localized with Yap in basal limbal epithelial cells. In conclusion, the current investigation provides new insights into the relationship between Yap and distinct cell populations across the ocular surface indicating that cells experience a different mechanical environment between the limbus and central cornea. A new hypothesis is put forward, in which centripetal differences in substrate stiffness drives the migration and differentiation of limbal epithelial stem cells, thus controlling corneal epithelium homeostasis.

A Novel Role of Autophagy in Intestinal Epithelial Stem Cell Proliferation and Renewal

A Novel Role of Autophagy in Intestinal Epithelial Stem Cell Proliferation and Renewal

Overnutrition Stimulates Intestinal Epithelium Proliferation Through β-Catenin Signaling in Obese Mice

Obesity is a major risk factor for type 2 diabetes and cardiovascular diseases. And overnutrition is a leading cause of obesity. After most nutrients are ingested, they are absorbed in the small intestine. Signals from β-catenin are essential to maintain development of the small intestine and homeostasis. In this study, we used a hyperphagia db/db obese mouse model and a high-fat diet (HFD)-induced obesity mouse model to investigate the effects of overnutrition on intestinal function and β-catenin signaling. The β-catenin protein was upregulated along with inactivation of glycogen synthase kinase (GSK)-3β in the intestines of both db/db and HFD mice. Proliferation of intestinal epithelial stem cells, villi length, nutrient absorption, and body weight also increased in both models. These changes were reversed by caloric restriction in db/db mice and by β-catenin inhibitor JW55 (a small molecule that increases β-catenin degradation) in HFD mice. Parallel, in vitro experiments showed that β-catenin accumulation and cell proliferation stimulated by glucose were blocked by the β-catenin inhibitor FH535. And the GSK-3 inhibitor CHIR98014 in an intestinal epithelial cell line increased β-catenin accumulation and cyclin D1 expression. These results suggested that, besides contribution to intestinal development and homeostasis, GSK-3β/β-catenin signaling plays a central role in intestinal morphological and functional changes in response to overnutrition. Manipulating the GSK-3β/β-catenin signaling pathway in intestinal epithelium might become a therapeutic intervention for obesity induced by overnutrition.

Effect of Nanoporous Fibers on Growth and Proliferation of Cells on Electrospun Poly (ϵ-caprolactone) Scaffolds

Scaffold design has a critical role in tissue engineering as scaffold features affect cell attachment and proliferation. Size scale similarities of electrospun nano-/microfibrous scaffolds with a native extracellular matrix have been appealing for tissue engineering applications and numerous studies have investigated the effect of different aspects of nano-/microfibrous scaffolds such as fiber diameter, thickness of nano-/microfibrous scaffolds on cell behavior. In this study, electrospun poly (ϵ-caprolactone) (PCL) microfibrous scaffolds were fabricated with nanosized pores on the surfaces of fibers created by the electrospinning of PCL solution with a highly volatile solvent in a humid ambient and the effects of nanopores on the attachment and proliferation of epithelial kidney cells (Vero) and mesenchymal stem cells (MSCs) were investigated. Morphology and hydrophilicity of the scaffolds were analyzed by scanning electron microscopy (SEM) and the video contact angle system and evaluation of cells proliferation and morphology of them on scaffolds were performed by MTS assay and SEM. Our results showed that relative humidity (RH) and electrospinning parameters affect the creation of pores on the surface of scaffolds. Furthermore, MTS assay and SEM results showed that nanopores on the surface of microfibers enhance initial attachment and proliferations of Vero and MSCs cells, which may be related to an increase in surface area of the porous fibrous scaffold compared to the nonporous fibrous scaffold.

The incidental pore: CaV1.2 and stem cell activation in quiescent hair follicles

The hair follicle undergoes a lifelong developmental cycle that depends on the integration between activating and inhibitory signals acting to regulate and guide the proliferation and differentiation of pluripotent epithelial stem cells. The effectors and mechanisms responsible for re-entry of quiescent telogen hair follicles into the hair-producing anagen stage in mature skin remain incompletely understood. In the June 1, 2013, issue of Genes & Development, Yucel and colleagues (pp. 1217-1222) reported the unexpected finding that CaV1.2, the pore-forming subunit in a well-characterized voltage-gated, L-type calcium channel, is expressed in hair follicle stem cells and contributes to anagen re-entry but does so in a calcium flux-independent fashion.

Transcriptional Dissection of Human Limbal Niche Compartments by Massive Parallel Sequencing

Corneal epithelium is maintained throughout life by well-orchestrated proliferation of limbal epithelial stem cells (LESCs), followed by migration and maturation centripetally towards the ocular surface. Disturbance of LESCs can potentially lead to a blinding condition, which can be reversed by reconstitution of a functional LESC pool. The current clinical procedures are effective to some degree, however, deeper knowledge of the molecular interplay within the limbal niche is necessary to achieve a fully satisfactory patient outcome. The present study was thus undertaken to carry out a comprehensive transcriptome analysis of four distinct human limbal compartments, including basal limbal crypts (BLCs), superficial limbal crypts (SLCs), cornea, and the supporting stroma, with the aid of laser capture microdissection and deep RNA sequencing. The tissue harvest pipeline was rigorously optimized so that the exposure to cold ischemia would be less than five minutes. The global gene ontology analysis confirmed existence of primitive cells in BLCs, migratory and activated cells in SLCs, and differentiated cells in cornea. Interestingly, many significantly upregulated genes in SLCs mapped to processes involved in regulation of vasculature, such as sFLT1. In contrast, BLCs exhibited many genes mapping to neurogenic processes and processes related to cell development. The primitive nature of BLCs was, furthermore, confirmed by the KEGG pathway analysis, and some potential regulators of LESCs were revealed, such as Lrig1 and SOX9. The analysis also yielded comprehensive lists of uniquely expressed genes in both BLCs and cornea, which may be useful to identify possible biomarkers. In conclusion, the current investigation provides new insight into the relationship between distinct cell populations within the limbal niche, identifies candidates to be verified for novel biological functions, and yields a wealth of information for prospective data mining.

Diet controls Drosophila follicle stem cell proliferation via Hedgehog sequestration and release

A healthy diet improves adult stem cell function and delays diseases such as cancer, heart disease, and neurodegeneration. Defining molecular mechanisms by which nutrients dictate stem cell behavior is a key step toward understanding the role of diet in tissue homeostasis. In this paper, we elucidate the mechanism by which dietary cholesterol controls epithelial follicle stem cell (FSC) proliferation in the fly ovary. In nutrient-restricted flies, the transmembrane protein Boi sequesters Hedgehog (Hh) ligand at the surface of Hh-producing cells within the ovary, limiting FSC proliferation. Upon feeding, dietary cholesterol stimulates S6 kinase-mediated phosphorylation of the Boi cytoplasmic domain, triggering Hh release and FSC proliferation. This mechanism enables a rapid, tissue-specific response to nutritional changes, tailoring stem cell divisions and egg production to environmental conditions sufficient for progeny survival. If conserved in other systems, this mechanism will likely have important implications for studies on molecular control of stem cell function, in which the benefits of low calorie and low cholesterol diets are beginning to emerge.