Revisiting the significance of keratin expression in complex epithelia.

A large group of keratin genes (n=54 in the human genome) code for intermediate filament (IF)-forming proteins and show differential regulation in epithelial cells and tissues. Keratin expression can be highly informative about the type of epithelial tissue, differentiation status of constituent cells and biological context (e.g. normal versus diseased settings). The foundational principles underlying the use of keratin expression to gain insight about epithelial cells and tissues primarily originated in pioneering studies conducted in the 1980s. The recent emergence of single cell transcriptomics provides an opportunity to revisit these principles and gain new insight into epithelial biology. Re-analysis of single-cell RNAseq data collected from human and mouse skin has confirmed long-held views regarding the quantitative importance and pairwise regulation of specific keratin genes in keratinocytes of surface epithelia. Furthermore, such analyses confirm and extend the notion that changes in keratin gene expression occur gradually as progenitor keratinocytes commit to and undergo differentiation, and challenge the prevailing assumption that specific keratin combinations reflect a mitotic versus a post-mitotic differentiating state. Our findings provide a blueprint for similar analyses in other tissues, and warrant a more nuanced approach in the use of keratin genes as biomarkers in epithelia.

A role for keratin 17 during DNA damage response and tumor initiation.

High levels of the intermediate filament protein keratin 17 (K17) are associated with poor prognoses for several human carcinomas. Studies in mouse models have shown that K17 expression is positively associated with growth, survival, and inflammation in skin and that lack of K17 delays onset of tumorigenesis. K17 occurs in the nucleus of human and mouse tumor keratinocytes where it impacts chromatin architecture, gene expression, and cell proliferation. We report here that K17 is induced following DNA damage and promotes keratinocyte survival. The presence of nuclear K17 is required at an early stage of the double-stranded break (DSB) arm of the DNA damage and repair (DDR) cascade, consistent with its ability to associate with key DDR effectors, including γ-H2A.X, 53BP1, and DNA-PKcs. Mice lacking K17 or with attenuated K17 nuclear import showed curtailed initiation in a two-step skin carcinogenesis paradigm. The impact of nuclear-localized K17 on DDR and cell survival provides a basis for the link between K17 induction and poor clinical outcomes for several human carcinomas.

Abnormalities of Kidney Function in Acute Malarial and non-Malarial Infections.

INTRODUCTION: The tropical environment is endemic with malaria and non-malarial infections which are responsible for the high morbidity and mortality in these low- and middle-income countries. In particular, acute malarial infection can cause significant multi-organ dysfunction, including kidney involvement. Early detection of kidney dysfunction will help to improve the quality of care and reduce associated morbidity and mortality. This study aimed at identifying the spectrum of kidney dysfunction in patients with acute malaria and non-malarial infections. METHODS: This was a prospective observational study in which participants with acute malarial infection, acute non-malarial infection, and apparently healthy individuals were enrolled. For acute malarial infection, participants with thick blood smear parasite density of ≥1000 parasite/µl and falciparum species on thin smear were enrolled. Demographic, clinical, and laboratory parameters were measured. The renal abnormalities examined were urea, creatinine and eGFR, albuminuria, electrolytes, and presence of acute kidney injury (AKI). RESULTS: The following electrolyte abnormalities were observed in participants with acute falciparum infection: hyponatraemia (10.7%), hypernatraemia (4.0%), hypokalaemia (8.0%), and hyperkalaemia (13.3%). The mean serum urea in participants with acute malaria was 33.8±8.8mmol/l while participants with non-malarial febrile illnesses and healthy controls had 34.7±9.0mmol/l and 26.8±7.6mmol/l, respectively. The mean serum creatinine among participants with acute falciparum infection was 1.0±0.3mg/dl compared to those of participants with non-malarial infections and healthy controls which were 1.1±0.4mg/dl and 0.8±0.3mg/dl, respectively. The difference in the observed mean serum creatinine among the 3 groups was statistically significant (p=0.023). The mean urinary sodium among participants with non-malarial infection was highest at 23.03mmol/l. There was transient albuminuria in 6.7% of participants with acute malarial infection which resolved after recovery from the infection. CONCLUSION: A relatively high frequency of serum electrolyte abnormalities, albuminuria and urine microscopic abnormalities were observed among subjects with acute malaria compared to those without malaria infection.

INTRODUCTION: L'environnement tropical est endémique d'infections paludéennes et non paludéennes qui sont responsables d'une morbidité et d'une mortalité élevées dans ces pays à revenu faible et moyen. En particulier, l'infection palustre aiguë peut provoquer un dysfonctionnement significatif de plusieurs organes, y compris une atteinte rénale. La détection précoce du dysfonctionnement rénal permettra d'améliorer la qualité des soins et de réduire la morbidité et la mortalité associées. Cette étude visait à identifier le spectre du dysfonctionnement rénal chez les patients atteints d'une infection palustre aiguë ou d'une infection non palustre. MÉTHODES: Il s'agit d'une étude prospective d'observation à laquelle ont participé des personnes souffrant d'une infection palustre aiguë, d'une infection non palustre aiguë et des personnes apparemment en bonne santé. Pour l'infection palustre aiguë, les participants présentant une densité de parasites sur frottis sanguin épais de ≥1000 parasites/µl et des espèces de falciparum sur frottis mince ont été enrôlés. Les paramètres démographiques, cliniques et de laboratoire ont été mesurés. Les anomalies rénales examinées étaient l'urée, la créatinine et le DFGe, l'albuminurie, les électrolytes et la présence de lésions rénales aiguës (IRA). RÉSULTATS: Les anomalies électrolytiques suivantes ont été observées chez les participants atteints d'une infection aiguë à falciparum : hyponatrémie (10,7 %), hypernatrémie (4,0 %), hypokaliémie (8,0 %) et hyperkaliémie (13,3 %). L'urée sérique moyenne chez les participants atteints de paludisme aigu était de 33,8±8,8mmol/l alors que les participants atteints de maladies fébriles non palustres et les témoins sains avaient 34,7±9,0mmol/l et 26,8±7,6mmol/l, respectivement. La créatinine sérique moyenne chez les participants atteints d'une infection aiguë à falciparum était de 1,0±0,3mg/dl par rapport à celle des participants atteints d'infections non palustres et des témoins sains qui étaient de 1,1±0,4mg/dl et 0,8±0,3mg/dl, respectivement. La différence dans la créatinine sérique moyenne observée entre les 3 groupes était statistiquement significative (p=0.023). Le sodium urinaire moyen parmi les participants atteints d'une infection non palustre était le plus élevé à 23,03 mmol/l. Une albuminurie transitoire a été observée chez 6,7 % des participants atteints d'une infection palustre aiguë, qui s'est résorbée après la guérison de l'infection. CONCLUSION: Une fréquence relativement élevée d'anomalies des électrolytes sériques, d'albuminurie et d'anomalies microscopiques de l'urine a été observée chez les sujets atteints de paludisme aigu par rapport à ceux qui n'étaient pas infectés par le paludisme. Mots-clés: Anomalies de la fonction rénale, infection aiguë par le paludisme à falciparum, infections non palustres.

Keratin 17 regulates nuclear morphology and chromatin organization.

Keratin 17 (KRT17; K17), a non-lamin intermediate filament protein, was recently found to occur in the nucleus. We report here on K17-dependent differences in nuclear morphology, chromatin organization, and cell proliferation. Human tumor keratinocyte cell lines lacking K17 exhibit flatter nuclei relative to normal. Re-expression of wild-type K17, but not a mutant form lacking an intact nuclear localization signal (NLS), rescues nuclear morphology in KRT17-null cells. Analyses of primary cultures of skin keratinocytes from a mouse strain expressing K17 with a mutated NLS corroborated these findings. Proteomics screens identified K17-interacting nuclear proteins with known roles in gene expression, chromatin organization and RNA processing. Key histone modifications and LAP2ß (an isoform encoded by TMPO) localization within the nucleus are altered in the absence of K17, correlating with decreased cell proliferation and suppression of GLI1 target genes. Nuclear K17 thus impacts nuclear morphology with an associated impact on chromatin organization, gene expression, and proliferation in epithelial cells.This article has an associated First Person interview with the first author of the paper.

Alteration of media enables efficient in vitro cloning of mature Elaeocarpus serratus L. (Ceylon olive): a commercially important fruit tree.

Elaeocarpus serratus is a fruit tree able to propagate through conventional vegetative means to a limited extent restricts its wide cultivation by the farmers. In the present report, we have developed an efficient in vitro propagation protocol using mature nodal explants from a 17-year-old tree for the first time with 6.6 shoots/culture. Explants cultured on agar (0.8%) gelled standard Murashige and Skoog (MS) medium, ½ MS, ¾ MS, White's, Gamborg's B5 or woody plant medium (WPM) supplemented with 2.5 µM benzyl adenine (BA) and 0.1 µM α-naphthalene acetic acid (NAA) showed the superiority of ½ MS medium in terms of explant response and number shoots (6.6). Further optimization of ½ MS medium by altering nutrient elements (macros, micros, vitamins and Fe EDTA) were undertaken, and MS medium composed of half-strength major salts, original strength of minor salts and vitamins were supplemented with BA (2.5 µM) and NAA (0.1 µM), produced enhanced axillary bud proliferation (8.88/explant) and shoot elongation (3.83 cm). Reculturing of original explant on this medium after IV passages produced more than 16 healthy shoots per culture which attained a length of 4.13 cm. Microshoots raised through this way were rooted (86.11%) ex vitro by pulse treatment with 2 mM indole-3-butyric acid (IBA) for 5 min followed by planting in nursery pots containing a 1:1:1 (v/v/v) mix of sand, soil, and farmyard manure. The hardened plants were successfully planted in the fruit tree garden of the Department. Genetic fidelity of micropropagated and mother plants were tested using random amplified polymorphic DNA (RAPD) and inter simple sequence repeat (ISSR) markers which showed a high degree of monomorphism thus supported morphological uniformity of micropropagated plants.

Association of Proteinuria and Hematuria with Acute Kidney Injury and Mortality in Hospitalized Patients with COVID-19.

INTRODUCTION: Acute kidney injury (AKI) is strongly associated with poor outcomes in hospitalized patients with coronavirus disease 2019 (COVID-19), but data on the association of proteinuria and hematuria are limited to non-US populations. In addition, admission and in-hospital measures for kidney abnormalities have not been studied separately. METHODS: This retrospective cohort study aimed to analyze these associations in 321 patients sequentially admitted between March 7, 2020 and April 1, 2020 at Stony Brook University Medical Center, New York. We investigated the association of proteinuria, hematuria, and AKI with outcomes of inflammation, intensive care unit (ICU) admission, invasive mechanical ventilation (IMV), and in-hospital death. We used ANOVA, t test, χ2 test, and Fisher's exact test for bivariate analyses and logistic regression for multivariable analysis. RESULTS: Three hundred patients met the inclusion criteria for the study cohort. Multivariable analysis demonstrated that admission proteinuria was significantly associated with risk of in-hospital AKI (OR 4.71, 95% CI 1.28-17.38), while admission hematuria was associated with ICU admission (OR 4.56, 95% CI 1.12-18.64), IMV (OR 8.79, 95% CI 2.08-37.00), and death (OR 18.03, 95% CI 2.84-114.57). During hospitalization, de novo proteinuria was significantly associated with increased risk of death (OR 8.94, 95% CI 1.19-114.4, p = 0.04). In-hospital AKI increased (OR 27.14, 95% CI 4.44-240.17) while recovery from in-hospital AKI decreased the risk of death (OR 0.001, 95% CI 0.001-0.06). CONCLUSION: Proteinuria and hematuria both at the time of admission and during hospitalization are associated with adverse clinical outcomes in hospitalized patients with COVID-19.

ATM-ROS-iNOS axis regulates nitric oxide mediated cellular senescence.

Cellular senescence is an outcome of the accumulation of DNA damage which induces the growth arrest in cells. Physiologically, it is presumed to be mediated by accumulation of reactive oxygen species (ROS). Here, we show that another free radical, nitric oxide (NO) produced during inflammation or present as an environmental pollutant can also induce cellular senescence. In primary cells and various immortalized cell lines, exposure to chronic NO, through external addition or internally generated by iNOS expression, leads to the activation of DNA damage response and causes cellular senescence. The phenotype generated by NO includes robust growth arrest, increase in the levels of the DNA damage foci, ROS, SAß-gal staining, and inflammatory cytokines like IL-6 and IL-8, all hallmarks of cellular senescence similar to replicative senescence. Mechanistically, inhibitor and knockdown analysis revealed that NO mediates senescence through ATM kinase activation and the viability of cells is dependent on both ROS and ATM kinase involving the ATM-ROS-iNOS axis. Overall, we demonstrate that nitric oxide mediates cellular senescence through a novel free radical dependent genotoxic stress pathway.

Temporally distinct roles of ATM and ROS in genotoxic-stress-dependent induction and maintenance of cellular senescence.

Cells exposed to genotoxic stress induce cellular senescence through a DNA damage response (DDR) pathway regulated by ATM kinase and reactive oxygen species (ROS). Here, we show that the regulatory roles for ATM kinase and ROS differ during induction and maintenance of cellular senescence. Cells treated with different genotoxic agents were analyzed using specific pathway markers and inhibitors to determine that ATM kinase activation is directly proportional to the dose of the genotoxic stress and that senescence initiation is not dependent on ROS or the p53 status of cells. Cells in which ROS was quenched still activated ATM and initiated the DDR when insulted, and progressed normally to senescence. By contrast, maintenance of a viable senescent state required the presence of ROS as well as activated ATM. Inhibition or removal of either of the components caused cell death in senescent cells, through a deregulated ATM-ROS axis. Overall, our work demonstrates existence of an intricate temporal hierarchy between genotoxic stress, DDR and ROS in cellular senescence. Our model reports the existence of different stages of cellular senescence with distinct regulatory networks.

IL-17 Control of Cutaneous Immune Homeostasis.

IL-17 is widely recognized for its roles in host defense and inflammatory disorders. However, it has become clear that IL-17 is also an essential regulator of barrier tissue physiology. Steady-state microbe sensing at the skin surface induces low-level IL-17 expression that enhances epithelial integrity and resists pathogens without causing overt inflammation. Recent reports describe novel protective roles for IL-17 in wound healing and counteracting physiologic stress; however, chronic amplification of these beneficial responses contributes to skin pathologies as diverse as fibrosis, cancer, and autoinflammation. In this paper, we discuss the context-specific roles of IL-17 in skin health and disease and therapeutic opportunities.

Nuclear roles for non-lamin intermediate filament proteins.

The nuclear-localized lamins have long been thought to be the only intermediate filaments (IFs) with an impact on the architecture, properties, and functions of the nucleus. Recent studies, however, uncovered significant roles for IFs other than lamins (here referred to as "non-lamin IFs") in regulating key properties of the nucleus in various cell types and biological settings. In the cytoplasm, IFs often occur in the perinuclear space where they contribute to local stiffness and impact the shape and/or the integrity of the nucleus, particularly in cells under stress. In addition, selective non-lamin IF proteins can occur inside the nucleus where they partake in fundamental processes including nuclear architecture and chromatin organization, regulation of gene expression, cell cycle progression, and the repair of DNA damage. This text reviews the evidence supporting a role for non-lamin IF proteins in regulating various properties of the nucleus and highlights opportunities for further study.

Hydrogel crosslinking modulates macrophages, fibroblasts, and their communication, during wound healing.

Biomaterial wound dressings, such as hydrogels, interact with host cells to regulate tissue repair. This study investigates how crosslinking of gelatin-based hydrogels influences immune and stromal cell behavior and wound healing in female mice. We observe that softer, lightly crosslinked hydrogels promote greater cellular infiltration and result in smaller scars compared to stiffer, heavily crosslinked hydrogels. Using single-cell RNA sequencing, we further show that heavily crosslinked hydrogels increase inflammation and lead to the formation of a distinct macrophage subpopulation exhibiting signs of oxidative activity and cell fusion. Conversely, lightly crosslinked hydrogels are more readily taken up by macrophages and integrated within the tissue. The physical properties differentially affect macrophage and fibroblast interactions, with heavily crosslinked hydrogels promoting pro-fibrotic fibroblast activity that drives macrophage fusion through RANKL signaling. These findings suggest that tuning the physical properties of hydrogels can guide cellular responses and improve healing, offering insights for designing better biomaterials for wound treatment.

Short- and Long-Term Recovery after Moderate/Severe AKI in Patients with and without COVID-19.

Background: Severe AKI is strongly associated with poor outcomes in coronavirus disease 2019 (COVID-19), but data on renal recovery are lacking. Methods: We retrospectively analyzed these associations in 3299 hospitalized patients (1338 with COVID-19 and 1961 with acute respiratory illness but who tested negative for COVID-19). Uni- and multivariable analyses were used to study mortality and recovery after Kidney Disease Improving Global Outcomes Stages 2 and 3 AKI (AKI-2/3), and Machine Learning was used to predict AKI and recovery using admission data. Long-term renal function and other outcomes were studied in a subgroup of AKI-2/3 survivors. Results: Among the 172 COVID-19-negative patients with AKI-2/3, 74% had partial and 44% complete renal recovery, whereas 12% died. Among 255 COVID-19 positive patients with AKI-2/3, lower recovery and higher mortality were noted (51% partial renal recovery, 25% complete renal recovery, 24% died). On multivariable analysis, intensive care unit admission and acute respiratory distress syndrome were associated with nonrecovery, and recovery was significantly associated with survival in COVID-19-positive patients. With Machine Learning, we were able to predict recovery from COVID-19-associated AKI-2/3 with an average precision of 0.62, and the strongest predictors of recovery were initial arterial partial pressure of oxygen and carbon dioxide, serum creatinine, potassium, lymphocyte count, and creatine phosphokinase. At 12-month follow-up, among 52 survivors with AKI-2/3, 26% COVID-19-positive and 24% COVID-19-negative patients had incident or progressive CKD. Conclusions: Recovery from COVID-19-associated moderate/severe AKI can be predicted using admission data and is associated with severity of respiratory disease and in-hospital death. The risk of CKD might be similar between COVID-19-positive and -negative patients.

Ocular status of commercial drivers in Osun State, Nigeria.

AIMS/OBJECTIVES: To determine the ocular status of commercial vehicle drivers in Osun State, Western Nigeria and highlight the effect on safety on the road. DESIGN: A cross-sectional-survey utilizing a multistage-random-sampling-technique done between May and June 2004. PARTICIPANTS: 99 consenting commercial vehicle drivers, registered with NURTW, Osogbo. Motorcyclists and non-registered NURTW drivers were excluded. METHODS: Clearance from LAUTECH Teaching Hospital's (LTH) ethical committee and informed consent obtained. Structured questionnaire and complete eye examination with vision test was done in the clinic. Driving test and ability to read number plates from a distance of 20.5m before and after dilatation were done in the hospital premises. RESULTS: Mean age of the subjects was 45.9 years (SD 7.7). Prevalence of visual impairment was 6.1%.and of failed driving test was 6.1%, while, uniocular blindness was 5.1%. Pupillary dilatation significantly reduced both ability to drive and to read number plate p < 0.05. Road traffic accident was associated with visual impairement, field loss, protan colour deficiency, cup:disc ratio > 0.5, and intraocular pressure > 21 mmHg. RTA was less likely among those who could read number plates (OR = 0.51). Prevalence of cataract was 24.3%, pterygia 20.7%, cornea opacity 6.6% and uncorrected-refractive errors 31.3%, with hypermetropia being most prevalent (19.7%). None had corrective lenses as at time of examination. CONCLUSION: Eye diseases causing uniocular blindness, visual impairment and uncorrected refractive errors were seen to be common among the commercial vehicle drivers. Mandatory, specific-periodic ophthalmological examination for correcting and preventing these are necessary before first issuance and revalidation of driver's license. Health education about eye care is therefore necessary to enhance safety on our roads.

Mechanically activated ion channel Piezo1 modulates macrophage polarization and stiffness sensing.

Macrophages perform diverse functions within tissues during immune responses to pathogens and injury, but molecular mechanisms by which physical properties of the tissue regulate macrophage behavior are less well understood. Here, we examine the role of the mechanically activated cation channel Piezo1 in macrophage polarization and sensing of microenvironmental stiffness. We show that macrophages lacking Piezo1 exhibit reduced inflammation and enhanced wound healing responses. Additionally, macrophages expressing the transgenic Ca2+ reporter, Salsa6f, reveal that Ca2+ influx is dependent on Piezo1, modulated by soluble signals, and enhanced on stiff substrates. Furthermore, stiffness-dependent changes in macrophage function, both in vitro and in response to subcutaneous implantation of biomaterials in vivo, require Piezo1. Finally, we show that positive feedback between Piezo1 and actin drives macrophage activation. Together, our studies reveal that Piezo1 is a mechanosensor of stiffness in macrophages, and that its activity modulates polarization responses.

YAP-mediated mechanotransduction tunes the macrophage inflammatory response.

Macrophages are innate immune cells that adhere to the extracellular matrix within tissues. However, how matrix properties regulate their function remains poorly understood. Here, we report that the adhesive microenvironment tunes the macrophage inflammatory response through the transcriptional coactivator YAP. We find that adhesion to soft hydrogels reduces inflammation when compared to adhesion on stiff materials and is associated with reduced YAP expression and nuclear localization. Substrate stiffness and cytoskeletal polymerization, but not adhesive confinement nor contractility, regulate YAP localization. Furthermore, depletion of YAP inhibits macrophage inflammation, whereas overexpression of active YAP increases inflammation. Last, we show in vivo that soft materials reduce expression of inflammatory markers and YAP in surrounding macrophages when compared to stiff materials. Together, our studies identify YAP as a key molecule for controlling inflammation and sensing stiffness in macrophages and may have broad implications in the regulation of macrophages in health and disease.

Plasmonic photocatalytic activity of ZnO:Au nanostructures: Tailoring the plasmon absorption and interfacial charge transfer mechanism.

ZnO:Au nanostructures with tunable surface Plasmon band were synthesizedvia co-precipitation method. X-ray diffraction analysis, high resolution transmission electron microscopy and Raman spectra confirmed the hexagonal wurtzite phase for these ZnO:Au nanostructures with preferential growth along the (101) plane. The selective enhancement in the intensity of Raman band due to the excited free electrons of Au nanoparticles confirmed the incorporation of Au in ZnO matrix. Scanning electron microscopic images showed the transformation of morphology of these nanostructures from rod geometry to rose flower and then to marigold flower-like structures with increase in the Au content. Detailed investigations were carried out to understand the role of plasmons present in the ZnO:Au nanostructures on the photocatalytic degradation of sulforhodamine B under sunlight. It is found that ZnO:Au nanostructures with plasmon band in the close approximation of solar maximum ˜550 nm as catalysts exhibit ultra-fast degradation of the dye. This highly efficient photocatalytic activity of these nanostructures is attributed to the electron scavenging action of Au due to its high electronegativity, enhanced absorption of sunlight due to plasmons, the enhanced surface area of ZnO:Au nanostructures and the formation of Schottky barrier between the Au and ZnO interface. The reusability and photostability of these catalysts were tested through repetitive cycles and demonstrated that these nanostructures can form excellent reusable photocatalysts for the degradation of toxic organic waste in water.

Extracellular Matrix-Based Strategies for Immunomodulatory Biomaterials Engineering.

The extracellular matrix (ECM) is a complex and dynamic structural scaffold for cells within tissues and plays an important role in regulating cell function. Recently it has become appreciated that the ECM contains bioactive motifs that can directly modulate immune responses. This review describes strategies for engineering immunomodulatory biomaterials that utilize natural ECM-derived molecules and have the potential to harness the immune system for applications ranging from tissue regeneration to drug delivery. A top-down approach utilizes full-length ECM proteins, including collagen, fibrin, or hyaluronic acid-based materials, as well as matrices derived from decellularized tissue. These materials have the benefit of maintaining natural conformation and structure but are often heterogeneous and encumber precise control. By contrast, a bottom-up approach leverages immunomodulatory domains, such as Arg-Gly-Asp (RGD), matrix metalloproteinase (MMP)-sensitive peptides, or leukocyte-associated immunoglobulin-like receptor-1(LAIR-1) ligands, by incorporating them into synthetic materials. These materials have tunable control over immune cell functions and allow for combinatorial approaches. However, the synthetic approach lacks the full natural context of the original ECM protein. These two approaches provide a broad range of engineering techniques for immunomodulation through material interactions and hold the potential for the development of future therapeutic applications.

Niche-Specific Factors Dynamically Regulate Sebaceous Gland Stem Cells in the Skin.

Oil-secreting sebaceous glands (SGs) are critical for proper skin function; however, it remains unclear how different factors act together to modulate SG stem cells. Here, we provide functional evidence that each SG lobe is serviced by its own dedicated stem cell population. Upon ablating Notch signaling in different skin subcompartments, we find that this pathway exerts dual counteracting effects on SGs. Suppressing Notch in SG progenitors traps them in a hybrid state where stem and differentiation features become intermingled. In contrast, ablating Notch outside of the SG stem cell compartment indirectly drives SG expansion. Finally, we report that a K14:K5→K14:K79 keratin shift occurs during SG differentiation. Deleting K79 destabilizes K14 in sebocytes, and attenuates SGs and eyelid meibomian glands, leading to corneal ulceration. Altogether, our findings demonstrate that SGs integrate diverse signals from different niches and suggest that mutations incurred within one stem cell compartment can indirectly influence another.

Clampdown of inflammation in aging and anticancer therapies by limiting upregulation and activation of GPCR, CXCR4.

One of the major pathological outcomes of DNA damage during aging or anticancer therapy is enhanced inflammation. However, the underlying signaling mechanism that drives this is not well understood. Here, we show that in response to DNA damage, ubiquitously expressed GPCR, CXCR4 is upregulated through the ATM kinase-HIF1α dependent DNA damage response (DDR) signaling, and enhances inflammatory response when activated by its ligand, chemokine CXCL12. A pharmacologically active compound screen revealed that this increased inflammation is dependent on reduction in cAMP levels achieved through activation of Gαi through CXCR4 receptor and PDE4A. Through in vivo analysis in mice where DNA damage was induced by irradiation, we validated that CXCR4 is induced systemically after DNA damage and inhibition of its activity or its induction blocked inflammation as well as tissue injury. We thus report a unique DNA damage-linked inflammatory cascade, which is mediated by expression level changes in a GPCR and can be targeted to counteract inflammation during anticancer therapies as well as aging.