Study on the characteristics of Aspergillus fumigatus-sensitized asthma and allergic bronchopulmonary aspergillosis / 中华预防医学杂志

Objective: To investigate the clinical characteristics of Aspergillus fumigatus(A.f)-sensitized asthma and allergic bronchopulmonary aspergillosis (ABPA), which provides a foundation for the diagnosis and differential diagnosis of A.f-sensitized asthma and ABPA, as well as the prevention of ABPA. Methods: This was a single-center retrospective case-control study. Collected the clinical data of patients who visited the Department of Respiratory and Critical Care Medicine, Zhongnan Hospital of Wuhan University from December 2018 to May 2022.A total of 122 patients were included, including 64 males (52.5%) and 58 females (47.5%).The age range was 3 to 89 years.The median age was 44 years.The average age was 41.8 years.The patients were divided into three groups (48 ABPA, 35 A.f-sensitized asthma and 39 HDM-sensitized asthma).Analyzed the differences and correlations among clinical indicators in the three groups, and evaluated the risk factors for the development of ABPA in A.f-sensitized asthma.For statistical analysis, metrological data was tested by t-test or Wilcoxon Mann-Whitney. Classification variables by chi-square test or Fisher's exact test. Pearson correlation analysis for normal distribution data.Spearman correlation analysis for skewed distribution data. Influencing factor analysis was performed using multivariate logistic regression analysis. The receiver operating characteristic (ROC) curve was made, the area under the ROC curve (AUC) was calculated, and the sensitivity and specificity of the model were evaluated. Results: Compared with patients with A.f-sensitized asthma, the fractional exhaled nitric oxide (FeNO) [75.00(52.00, 87.00)ppb vs. 40.00(32.00, 52.00)ppb], eosinophils% (EO%) [10.60(6.75, 13.05) vs. 4.10(1.20, 7.30)], eosinophils (EO) [1.50(1.07, 2.20)×109/L vs. 0.33(0.10, 0.54)×109/L], A.f-specific Immunoglobulin E (sIgE) [10.24(4.09, 22.88)KU/L vs. 1.13(0.53, 3.72) KU/L], and sIgE to total IgE(tIgE) ratio (sIgE/tIgE) [0.0049(0.0027, 0.0100) vs. 0.0008(0.0004, 0.0017)] were higher in ABPA patients, the differences were statistically significant (P<0.001). In all patients, tIgE was positively correlated with EO% (r=0.206, P<0.05) and EO (r=0.302, P<0.001). sIgE/tIgE was negatively correlated with one-second rate (FEV1/FVC%) (r=-0.256, P<0.01). The percentage of predicted forced vital capacity [FVC(%)] was negatively correlated with FeNO (r=-0.184, P<0.05).In the ABPA group, the percentage of predicted peak expiratory flow [PEF(%)] was negatively correlated with FeNO (r=-0.295, P<0.05). In the HDM-sensitized asthma group, FeNO was positively correlated with EO% (r=0.49, P<0.01) and EO (r=0.548, P<0.001).The results of logistic regression analysis showed that FeNO and EO were the influencing factors for the development of ABPA in A.f-sensitized asthma. ROC curve analysis results showed that A.f-sIgE (cut-off, 4.108; AUC=0.749;95%CI, 0.632-0.867), sIgE/tIgE(cut-off, 0.0026;AUC=0.749;95%CI, 0.631-0.868), FeNO(cut-off, 55.5;AUC=0.794; 95%CI, 0.687-0.900), EO% (cut-off, 8.70;AUC=0.806;95%CI, 0.709-0.903) and EO (cut-off, 0.815;AUC=0.865;95%CI, 0.779-0.950) had differential diagnostic value in A.f-sensitized asthma and ABPA.The combination of FeNO, EO and EO% had good diagnostic efficiency in differentiating A.f-sensitized asthma from ABPA, with a sensitivity of 91.4% and a specificity of 84.4%. Conclusion: Compared with patients with A.f-sensitized asthma, patients with ABPA have more severe eosinophil inflammation. The higher the FeNO and EO, the more likely A.f-sensitized asthma will develop into ABPA.sIgE/tIgE may have differential diagnostic value in A.f-sensitized asthma and ABPA.The combination of FeNO, EO and EO% has good diagnostic efficacy in differentiating A.f-sensitized asthma from ABPA.

Effects of soluble glycoprotein 130 on expression of p-STAT3 and vascular endothelial growth factor-A in retina of mice with diabetes mellitus / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To observe the effect of soluble glycoprotein 130(sgp130)on expression of p-STAT3 and vascular endothelial growth factor(VEGF)-A in retina of mice with diabetes mellitus(DM), and explore the possibility of sgp130 in interfering with inflammatory damage of diabetic retinopathy(DR).METHODS: A total of 45 mice were randomly divided into normal group, DM group and sgp130 group. DM models were made in DM group and sgp130 group with streptozotocin. No special intervention was given to normal group and DM group, but sgp130 group was given intravitreal injection of 1.5mg/mL sgp130 2μL at the 1 and 5wk. After 10wk, all the mice were sacrificed to assess the protein expression of interleukin 6(IL-6), p-STAT3 and VEGF-A in the retina.RESULTS: The expressions of IL-6, p-STAT3 and VEGF-A in retina of DM group were higher than those of normal group at 10wk(all P<0.01). The expression of p-STAT3 and VEGF-A in sgp130 group were lower than those in DM group(all P<0.01).CONCLUSION: The sgp130 can selectively antagonize the trans signal transduction pathway of IL-6, down-regulate the expression of downstream inflammatory factors VEGF-A, and it may be used in the intervention of retinal inflammatory damage related with IL-6 in DM.

Single-cell profiling reveals a potent role of quercetin in promoting hair regeneration

Hair loss affects millions of people at some time in their life, and safe and efficient treatments for hair loss are a significant unmet medical need. We report that topical delivery of quercetin (Que) stimulates resting hair follicles to grow with rapid follicular keratinocyte proliferation and replenishes perifollicular microvasculature in mice. We construct dynamic single-cell transcriptome landscape over the course of hair regrowth and find that Que treatment stimulates the differentiation trajectory in the hair follicles and induces an angiogenic signature in dermal endothelial cells by activating HIF-1α in endothelial cells. Skin administration of a HIF-1α agonist partially recapitulates the pro-angiogenesis and hair-growing effects of Que. Together, these findings provide a molecular understanding for the efficacy of Que in hair regrowth, which underscores the translational potential of targeting the hair follicle niche as a strategy for regenerative medicine, and suggest a route of pharmacological intervention that may promote hair regrowth.

Single-nucleus transcriptomics reveals a gatekeeper role for FOXP1 in primate cardiac aging

Aging poses a major risk factor for cardiovascular diseases, the leading cause of death in the aged population. However, the cell type-specific changes underlying cardiac aging are far from being clear. Here, we performed single-nucleus RNA-sequencing analysis of left ventricles from young and aged cynomolgus monkeys to define cell composition changes and transcriptomic alterations across different cell types associated with age. We found that aged cardiomyocytes underwent a dramatic loss in cell numbers and profound fluctuations in transcriptional profiles. Via transcription regulatory network analysis, we identified FOXP1, a core transcription factor in organ development, as a key downregulated factor in aged cardiomyocytes, concomitant with the dysregulation of FOXP1 target genes associated with heart function and cardiac diseases. Consistently, the deficiency of FOXP1 led to hypertrophic and senescent phenotypes in human embryonic stem cell-derived cardiomyocytes. Altogether, our findings depict the cellular and molecular landscape of ventricular aging at the single-cell resolution, and identify drivers for primate cardiac aging and potential targets for intervention against cardiac aging and associated diseases.

Single-cell transcriptomic atlas of mouse cochlear aging

Progressive functional deterioration in the cochlea is associated with age-related hearing loss (ARHL). However, the cellular and molecular basis underlying cochlear aging remains largely unknown. Here, we established a dynamic single-cell transcriptomic landscape of mouse cochlear aging, in which we characterized aging-associated transcriptomic changes in 27 different cochlear cell types across five different time points. Overall, our analysis pinpoints loss of proteostasis and elevated apoptosis as the hallmark features of cochlear aging, highlights unexpected age-related transcriptional fluctuations in intermediate cells localized in the stria vascularis (SV) and demonstrates that upregulation of endoplasmic reticulum (ER) chaperon protein HSP90AA1 mitigates ER stress-induced damages associated with aging. Our work suggests that targeting unfolded protein response pathways may help alleviate aging-related SV atrophy and hence delay the progression of ARHL.

4E-BP1 counteracts human mesenchymal stem cell senescence via maintaining mitochondrial homeostasis

Although the mTOR-4E-BP1 signaling pathway is implicated in aging and aging-related disorders, the role of 4E-BP1 in regulating human stem cell homeostasis remains largely unknown. Here, we report that the expression of 4E-BP1 decreases along with the senescence of human mesenchymal stem cells (hMSCs). Genetic inactivation of 4E-BP1 in hMSCs compromises mitochondrial respiration, increases mitochondrial reactive oxygen species (ROS) production, and accelerates cellular senescence. Mechanistically, the absence of 4E-BP1 destabilizes proteins in mitochondrial respiration complexes, especially several key subunits of complex III including UQCRC2. Ectopic expression of 4E-BP1 attenuates mitochondrial abnormalities and alleviates cellular senescence in 4E-BP1-deficient hMSCs as well as in physiologically aged hMSCs. These f indings together demonstrate that 4E-BP1 functions as a geroprotector to mitigate human stem cell senescence and maintain mitochondrial homeostasis, particularly for the mitochondrial respiration complex III, thus providing a new potential target to counteract human stem cell senescence.

Single-nucleus profiling unveils a geroprotective role of the FOXO3 in primate skeletal muscle aging

Age-dependent loss of skeletal muscle mass and function is a feature of sarcopenia, and increases the risk of many aging-related metabolic diseases. Here, we report phenotypic and single-nucleus transcriptomic analyses of non-human primate skeletal muscle aging. A higher transcriptional fluctuation was observed in myonuclei relative to other interstitial cell types, indicating a higher susceptibility of skeletal muscle fiber to aging. We found a downregulation of FOXO3 in aged primate skeletal muscle, and identified FOXO3 as a hub transcription factor maintaining skeletal muscle homeostasis. Through the establishment of a complementary experimental pipeline based on a human pluripotent stem cell-derived myotube model, we revealed that silence of FOXO3 accelerates human myotube senescence, whereas genetic activation of endogenous FOXO3 alleviates human myotube aging. Altogether, based on a combination of monkey skeletal muscle and human myotube aging research models, we unraveled the pivotal role of the FOXO3 in safeguarding primate skeletal muscle from aging, providing a comprehensive resource for the development of clinical diagnosis and targeted therapeutic interventions against human skeletal muscle aging and the onset of sarcopenia along with aging-related disorders.

Aging weakens Th17 cell pathogenicity and ameliorates experimental autoimmune uveitis in mice

Aging-induced changes in the immune system are associated with a higher incidence of infection and vaccination failure. Lymph nodes, which filter the lymph to identify and fight infections, play a central role in this process. However, careful characterization of the impact of aging on lymph nodes and associated autoimmune diseases is lacking. We combined single-cell RNA sequencing (scRNA-seq) with flow cytometry to delineate the immune cell atlas of cervical draining lymph nodes (CDLNs) of both young and old mice with or without experimental autoimmune uveitis (EAU). We found extensive and complicated changes in the cellular constituents of CDLNs during aging. When confronted with autoimmune challenges, old mice developed milder EAU compared to young mice. Within this EAU process, we highlighted that the pathogenicity of T helper 17 cells (Th17) was dampened, as shown by reduced GM-CSF secretion in old mice. The mitigated secretion of GM-CSF contributed to alleviation of IL-23 secretion by antigen-presenting cells (APCs) and may, in turn, weaken APCs' effects on facilitating the pathogenicity of Th17 cells. Meanwhile, our study further unveiled that aging downregulated GM-CSF secretion through reducing both the transcript and protein levels of IL-23R in Th17 cells from CDLNs. Overall, aging altered immune cell responses, especially through toning down Th17 cells, counteracting EAU challenge in old mice.

Single-nucleus transcriptomic landscape of primate hippocampal aging

The hippocampus plays a crucial role in learning and memory, and its progressive deterioration with age is functionally linked to a variety of human neurodegenerative diseases. Yet a systematic profiling of the aging effects on various hippocampal cell types in primates is still missing. Here, we reported a variety of new aging-associated phenotypic changes of the primate hippocampus. These include, in particular, increased DNA damage and heterochromatin erosion with time, alongside loss of proteostasis and elevated inflammation. To understand their cellular and molecular causes, we established the first single-nucleus transcriptomic atlas of primate hippocampal aging. Among the 12 identified cell types, neural transiently amplifying progenitor cell (TAPC) and microglia were most affected by aging. In-depth dissection of gene-expression dynamics revealed impaired TAPC division and compromised neuronal function along the neurogenesis trajectory; additionally elevated pro-inflammatory responses in the aged microglia and oligodendrocyte, as well as dysregulated coagulation pathways in the aged endothelial cells may contribute to a hostile microenvironment for neurogenesis. This rich resource for understanding primate hippocampal aging may provide potential diagnostic biomarkers and therapeutic interventions against age-related neurodegenerative diseases.

Establishment of three-dimensional model of rat retinal angiogenesis <i>in</i> <i>vitro</i> based on endothelial cells and pericytes / 国际眼科杂志(Guoji Yanke Zazhi)

@#AIM: To establish three-dimensional(3D)model of rat retinal angiogenesis <i>in</i> <i>vitro</i> based on retinal microvascular endothelial cells(ECs)and retinal microvascular pericytes(RMPs). <p>METHODS: The identified ECs and RMPs of third generation to seventh generation were used for research after isolated, purified and cultured. The cells were stained with cell tracer. Then, it were mixed and inoculated on Matrigel by the surface culture method for dynamic observation. The expression of VEGF-A was assessed during angiogenesis. <p>RESULTS: At 12h of co-culture, RMPs were recruited by ECs and gathered into cell masses with different sizes. At 24h, ECs/RMPs formed a complex 3D vascular spline network. At 48h, the reticular structure disintegrated obviously, and only a small amount of incomplete and simple reticular structure remained. At 72h, the vascular spline cable network disintegrated completely. In the development of 3D model, the expression of VEGF-A increased, but decreased when it degenerated. <p>CONCLUSION: This study successfully established a 3D model of rat retinal angiogenesis <i>in</i> <i>vitro</i> based on ECs and RMPs.

Generation of a Hutchinson-Gilford progeria syndrome monkey model by base editing

Many human genetic diseases, including Hutchinson-Gilford progeria syndrome (HGPS), are caused by single point mutations. HGPS is a rare disorder that causes premature aging and is usually caused by a de novo point mutation in the LMNA gene. Base editors (BEs) composed of a cytidine deaminase fused to CRISPR/Cas9 nickase are highly efficient at inducing C to T base conversions in a programmable manner and can be used to generate animal disease models with single amino-acid substitutions. Here, we generated the first HGPS monkey model by delivering a BE mRNA and guide RNA (gRNA) targeting the LMNA gene via microinjection into monkey zygotes. Five out of six newborn monkeys carried the mutation specifically at the target site. HGPS monkeys expressed the toxic form of lamin A, progerin, and recapitulated the typical HGPS phenotypes including growth retardation, bone alterations, and vascular abnormalities. Thus, this monkey model genetically and clinically mimics HGPS in humans, demonstrating that the BE system can efficiently and accurately generate patient-specific disease models in non-human primates.

SIRT7 antagonizes human stem cell aging as a heterochromatin stabilizer

SIRT7, a sirtuin family member implicated in aging and disease, is a regulator of metabolism and stress responses. It remains elusive how human somatic stem cell populations might be impacted by SIRT7. Here, we found that SIRT7 expression declines during human mesenchymal stem cell (hMSC) aging and that SIRT7 deficiency accelerates senescence. Mechanistically, SIRT7 forms a complex with nuclear lamina proteins and heterochromatin proteins, thus maintaining the repressive state of heterochromatin at nuclear periphery. Accordingly, deficiency of SIRT7 results in loss of heterochromatin, de-repression of the LINE1 retrotransposon (LINE1), and activation of innate immune signaling via the cGAS-STING pathway. These aging-associated cellular defects were reversed by overexpression of heterochromatin proteins or treatment with a LINE1 targeted reverse-transcriptase inhibitor. Together, these findings highlight how SIRT7 safeguards chromatin architecture to control innate immune regulation and ensure geroprotection during stem cell aging.

A human circulating immune cell landscape in aging and COVID-19

Age-associated changes in immune cells have been linked to an increased risk for infection. However, a global and detailed characterization of the changes that human circulating immune cells undergo with age is lacking. Here, we combined scRNA-seq, mass cytometry and scATAC-seq to compare immune cell types in peripheral blood collected from young and old subjects and patients with COVID-19. We found that the immune cell landscape was reprogrammed with age and was characterized by T cell polarization from naive and memory cells to effector, cytotoxic, exhausted and regulatory cells, along with increased late natural killer cells, age-associated B cells, inflammatory monocytes and age-associated dendritic cells. In addition, the expression of genes, which were implicated in coronavirus susceptibility, was upregulated in a cell subtype-specific manner with age. Notably, COVID-19 promoted age-induced immune cell polarization and gene expression related to inflammation and cellular senescence. Therefore, these findings suggest that a dysregulated immune system and increased gene expression associated with SARS-CoV-2 susceptibility may at least partially account for COVID-19 vulnerability in the elderly.

SIRT7 antagonizes human stem cell aging as a heterochromatin stabilizer

SIRT7, a sirtuin family member implicated in aging and disease, is a regulator of metabolism and stress responses. It remains elusive how human somatic stem cell populations might be impacted by SIRT7. Here, we found that SIRT7 expression declines during human mesenchymal stem cell (hMSC) aging and that SIRT7 deficiency accelerates senescence. Mechanistically, SIRT7 forms a complex with nuclear lamina proteins and heterochromatin proteins, thus maintaining the repressive state of heterochromatin at nuclear periphery. Accordingly, deficiency of SIRT7 results in loss of heterochromatin, de-repression of the LINE1 retrotransposon (LINE1), and activation of innate immune signaling via the cGAS-STING pathway. These aging-associated cellular defects were reversed by overexpression of heterochromatin proteins or treatment with a LINE1 targeted reverse-transcriptase inhibitor. Together, these findings highlight how SIRT7 safeguards chromatin architecture to control innate immune regulation and ensure geroprotection during stem cell aging.

A human circulating immune cell landscape in aging and COVID-19

Age-associated changes in immune cells have been linked to an increased risk for infection. However, a global and detailed characterization of the changes that human circulating immune cells undergo with age is lacking. Here, we combined scRNA-seq, mass cytometry and scATAC-seq to compare immune cell types in peripheral blood collected from young and old subjects and patients with COVID-19. We found that the immune cell landscape was reprogrammed with age and was characterized by T cell polarization from naive and memory cells to effector, cytotoxic, exhausted and regulatory cells, along with increased late natural killer cells, age-associated B cells, inflammatory monocytes and age-associated dendritic cells. In addition, the expression of genes, which were implicated in coronavirus susceptibility, was upregulated in a cell subtype-specific manner with age. Notably, COVID-19 promoted age-induced immune cell polarization and gene expression related to inflammation and cellular senescence. Therefore, these findings suggest that a dysregulated immune system and increased gene expression associated with SARS-CoV-2 susceptibility may at least partially account for COVID-19 vulnerability in the elderly.

A human circulating immune cell landscape in aging and COVID-19

Age-associated changes in immune cells have been linked to an increased risk for infection. However, a global and detailed characterization of the changes that human circulating immune cells undergo with age is lacking. Here, we combined scRNA-seq, mass cytometry and scATAC-seq to compare immune cell types in peripheral blood collected from young and old subjects and patients with COVID-19. We found that the immune cell landscape was reprogrammed with age and was characterized by T cell polarization from naive and memory cells to effector, cytotoxic, exhausted and regulatory cells, along with increased late natural killer cells, age-associated B cells, inflammatory monocytes and age-associated dendritic cells. In addition, the expression of genes, which were implicated in coronavirus susceptibility, was upregulated in a cell subtype-specific manner with age. Notably, COVID-19 promoted age-induced immune cell polarization and gene expression related to inflammation and cellular senescence. Therefore, these findings suggest that a dysregulated immune system and increased gene expression associated with SARS-CoV-2 susceptibility may at least partially account for COVID-19 vulnerability in the elderly.

A multicenter epidemiological investigation of brain injury in hospitalized preterm infants in Anhui, China / 中国当代儿科杂志

OBJECTIVE@#To investigate the risk factors for brain injury in preterm infants by a multicenter epidemiological investigation of brain injury in hospitalized preterm infants in Anhui, China.@*METHODS@#Preterm infants who were hospitalized in the department of neonatology in 9 hospitals of Anhui Neonatal Collaboration Network between January 2016 and January 2017 were enrolled as subjects. The data of maternal pregnancy and clinical data of preterm infants were collected, and the logistic regression model was used to analyze the risk factors for brain injury in preterm infants.@*RESULTS@#A total of 3 378 preterm infants were enrolled. Of the 3 378 preterm infants, 798 (23.56%) had periventricular-intraventricular hemorrhage (PVH-IVH), and 88 (2.60%) had periventricular leukomalacia (PVL). Intrauterine distress, anemia, hypoglycemia and necrotizing enterocolitis (NEC) were risk factors for PVH-IVH (OR=1.310, 1.591, 1.835, and 3.310 respectively; P<0.05), while a higher gestational age was a protective factor against PVH-IVH (OR=0.671, P<0.05). PVH-IVH, NEC and mechanical ventilation were risk factors for PVL (OR=4.017, 3.018, and 2.166 respectively; P<0.05), and female sex and use of pulmonary surfactant were protective factors against PVL (OR=0.514 and 0.418 respectively; P<0.05).@*CONCLUSIONS@#Asphyxia/anoxia, infection/inflammation, mechanical ventilation, anemia and hypoglycemia may increase the risk of brain injury in preterm infants.

Chemical screen identifies a geroprotective role of quercetin in premature aging

Aging increases the risk of various diseases. The main goal of aging research is to find therapies that attenuate aging and alleviate aging-related diseases. In this study, we screened a natural product library for geroprotective compounds using Werner syndrome (WS) human mesenchymal stem cells (hMSCs), a premature aging model that we recently established. Ten candidate compounds were identified and quercetin was investigated in detail due to its leading effects. Mechanistic studies revealed that quercetin alleviated senescence via the enhancement of cell proliferation and restoration of heterochromatin architecture in WS hMSCs. RNA-sequencing analysis revealed the transcriptional commonalities and differences in the geroprotective effects by quercetin and Vitamin C. Besides WS hMSCs, quercetin also attenuated cellular senescence in Hutchinson-Gilford progeria syndrome (HGPS) and physiological-aging hMSCs. Taken together, our study identifies quercetin as a geroprotective agent against accelerated and natural aging in hMSCs, providing a potential therapeutic intervention for treating age-associated disorders.

Modeling CADASIL vascular pathologies with patient-derived induced pluripotent stem cells

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a rare hereditary cerebrovascular disease caused by a NOTCH3 mutation. However, the underlying cellular and molecular mechanisms remain unidentified. Here, we generated non-integrative induced pluripotent stem cells (iPSCs) from fibroblasts of a CADASIL patient harboring a heterozygous NOTCH3 mutation (c.3226C>T, p.R1076C). Vascular smooth muscle cells (VSMCs) differentiated from CADASIL-specific iPSCs showed gene expression changes associated with disease phenotypes, including activation of the NOTCH and NF-κB signaling pathway, cytoskeleton disorganization, and excessive cell proliferation. In comparison, these abnormalities were not observed in vascular endothelial cells (VECs) derived from the patient's iPSCs. Importantly, the abnormal upregulation of NF-κB target genes in CADASIL VSMCs was diminished by a NOTCH pathway inhibitor, providing a potential therapeutic strategy for CADASIL. Overall, using this iPSC-based disease model, our study identified clues for studying the pathogenic mechanisms of CADASIL and developing treatment strategies for this disease.

Telomere-dependent and telomere-independent roles of RAP1 in regulating human stem cell homeostasis

RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclear. Here we generated RAP1-deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via directed differentiation. In both hMSCs and hNSCs, RAP1 not only negatively regulated telomere length but also acted as a transcriptional regulator of RELN by tuning the methylation status of its gene promoter. RAP1 deficiency enhanced self-renewal and delayed senescence in hMSCs, but not in hNSCs, suggesting complicated lineage-specific effects of RAP1 in adult stem cells. Altogether, these results demonstrate for the first time that RAP1 plays both telomeric and nontelomeric roles in regulating human stem cell homeostasis.