Diversity and Scale: Genetic Architecture of 2,068 Traits in the VA Million Veteran Program.

Genome-wide association studies (GWAS) have underrepresented individuals from non-European populations, impeding progress in characterizing the genetic architecture and consequences of health and disease traits. To address this, we present a population-stratified phenome-wide GWAS followed by a multi-population meta-analysis for 2,068 traits derived from electronic health records of 635,969 participants in the Million Veteran Program (MVP), a longitudinal cohort study of diverse U.S. Veterans genetically similar to the respective African (121,177), Admixed American (59,048), East Asian (6,702), and European (449,042) superpopulations defined by the 1000 Genomes Project. We identified 38,270 independent variants associating with one or more traits at experiment-wide P<4.6×10-11 significance; fine-mapping 6,318 signals identified from 613 traits to single-variant resolution. Among these, a third (2,069) of the associations were found only among participants genetically similar to non-European reference populations, demonstrating the importance of expanding diversity in genetic studies. Our work provides a comprehensive atlas of phenome-wide genetic associations for future studies dissecting the architecture of complex traits in diverse populations.

Effect of Ultrasonic Shot Peening and Laser Shock Peening on the Microstructure and Microhardness of IN738LC Alloys.

IN738LC is a conventional-cast Ni-based superalloy intended for power generation and aerospace applications. Typically, ultrasonic shot peening (USP) and laser shock peening (LSP) are utilized to enhance cracking, creep, and fatigue resistance. In this study, the optimal process parameters for USP and LSP were established by observing the microstructure and measuring the microhardness of the near-surface region of IN738LC alloys. The LSP impact region (modification depth) was approximately 2500 µm, which was much higher than the USP impact depth of 600 µm. The observation of the microstructural modification and resulting strengthening mechanism revealed that the build-up of dislocations upon peening with plastic deformation was crucial for alloy strengthening in both methods. In contrast, significant strengthening via γ' shearing was observed only in the USP-treated alloys.

Plain Radiographic Analysis of Laryngeal Dimensions in Young Children: Normal versus Croup.

(1) Background: Contrary to a tenet of the funnel-shaped pediatric larynx with the cricoid level being narrowest, recent studies show the glottis and subglottis as the narrowest levels. To locate the functionally narrowest level of the larynx, we reported normal laryngeal dimensions and their croup-related changes in young children. (2) Methods: We reviewed normal plain neck radiographs recorded for the evaluation of minor trauma or foreign bodies in 504 children aged ≤4 years who visited the emergency department from 2016 through 2021. Using computed tomography-based localization of the glottis, we radiographically defined the subglottis and cricoid. At these levels, we measured diameters and calculated cross-sectional areas (CSAs) on the radiographs. The values were compared to the equivalent values of a 1:1 age-matched population with croup. (3) Results: In the study population (n = 401), the narrowest diameter and CSA were observed in the glottis. In detail, the mean anteroposterior/transverse diameters were 9.8/3.4 mm at the glottis, 8.5/5.6 mm at the subglottis, and 7.4/6.8 mm at the cricoid (p < 0.001), respectively. In the same order, the mean CSAs were 26.5, 38.1, and 40.5 mm2 (p < 0.001). All dimensions were narrower in the croup population (p < 0.001). We found croup-related narrowing, namely reductions in the transverse diameter and CSA that were more severe closer to the glottis (p < 0.001), without differences per level in the anteroposterior diameter. (4) Conclusions: This study confirms the glottis as the narrowest level of the larynx in young children. In addition, level-based differences in croup-related narrowing suggest some point between the glottis and subglottis as the functionally narrowest level.

The Busan Regional CardioCerebroVascular Center Project's Experience Over a Decade in the Treatment of ST-segment Elevation Myocardial Infarction.

OBJECTIVES: The Regional CardioCerebroVascular Center (RCCVC) project was initiated to improve clinical outcomes for patients with acute myocardial infarction or stroke in non-capital areas of Korea. The purpose of this study was to evaluate the outcomes and issues identified by the Busan RCCVC project in the treatment of ST-segment elevation myocardial infarction (STEMI). METHODS: Among the patients who were registered in the Korean Registry of Acute Myocardial Infarction for the RCCVC project between 2007 and 2019, those who underwent percutaneous coronary intervention (PCI) for STEMI at the Busan RCCVC were selected, and their medical data were compared with a historical cohort. RESULTS: In total, 1161 patients were selected for the analysis. Ten years after the implementation of the Busan RCCVC project, the median door-to-balloon time was reduced from 86 (interquartile range [IQR], 64-116) to 54 (IQR, 44-61) minutes, and the median symptom-to-balloon time was reduced from 256 (IQR, 180-407) to 189 (IQR, 118-305) minutes (p<0.001). Inversely, the false-positive PCI team activation rate increased from 0.6% to 21.4% (p<0.001). However, the 1-year cardiovascular death and major adverse cardiac event rates did not change. Even after 10 years, approximately 75% of the patients had a symptom-to-balloon time over 120 minutes, and approximately 50% of the patients underwent inter-hospital transfer for primary PCI. CONCLUSIONS: A decade after the implementation of the Busan RCCVC project, although time parameters for early reperfusion therapy for STEMI improved, at the cost of an increased false-positive PCI team activation rate, survival outcomes were unchanged.

ω-3 fatty acid-enriched parenteral nutrition shortens hospital stay in acute variceal bleeding cirrhotic patients.

ABSTRACT: Acute variceal bleeding, a crucial complication of liver cirrhosis requires high energy expenditures but gastrointestinal bleeding limits enteral feeding in the acute stage. We investigated the safety and efficacy of ω-3 fatty acid-enriched parenteral nutrition in acute variceal bleeding patients.In this retrospective study, a total of 208 cirrhotic patients with acute variceal bleeding who underwent parenteral nutrition in the absence of enteral nutrition were enrolled. Among the patients, 86 patients received ω-3 fatty-acid-enriched parenteral nutrition. The primary endpoint was to evaluate the duration of hospital stay and the presence of clinical complications of liver cirrhosis.The mean age of the patients enrolled was 54.9 years-old and 185 patients (88.9%) were male. The cause of liver cirrhosis, Child-Pugh score and comorbidities were statistically not different. Patients with ω-3 enriched parenteral nutrition had a significantly lower systolic blood pressure and total bilirubin levels. The difference in the in-hospital mortality (P = .813) or rate of complications (P = .880) was not statistically significant. The duration of hospital stay was significantly shorter in the patients who underwent ω-3 fatty acid-enriched parenteral nutrition (10.7 ±â€Š7.3 vs 7.9 ±â€Š4.2 days, P = .001).In liver cirrhosis patients with acute variceal bleeding, ω-3 fatty acid-enriched parenteral nutrition significantly decreased the length of hospital stay. Further prospective studies to consolidate these findings are warranted.

NSrp70 is a lymphocyte-essential splicing factor that controls thymocyte development.

Alternative pre-mRNA splicing is a critical step to generate multiple transcripts, thereby dramatically enlarging the proteomic diversity. Thus, a common feature of most alternative splicing factor knockout models is lethality. However, little is known about lineage-specific alternative splicing regulators in a physiological setting. Here, we report that NSrp70 is selectively expressed in developing thymocytes, highest at the double-positive (DP) stage. Global splicing and transcriptional profiling revealed that NSrp70 regulates the cell cycle and survival of thymocytes by controlling the alternative processing of various RNA splicing factors, including the oncogenic splicing factor SRSF1. A conditional-knockout of Nsrp1 (NSrp70-cKO) using CD4Cre developed severe defects in T cell maturation to single-positive thymocytes, due to insufficient T cell receptor (TCR) signaling and uncontrolled cell growth and death. Mice displayed severe peripheral lymphopenia and could not optimally control tumor growth. This study establishes a model to address the function of lymphoid-lineage-specific alternative splicing factor NSrp70 in a thymic T cell developmental pathway.

Modeling Sialidosis with Neural Precursor Cells Derived from Patient-Derived Induced Pluripotent Stem Cells.

Sialidosis, caused by a genetic deficiency of the lysosomal sialidase gene (NEU1), is a systemic disease involving various tissues and organs, including the nervous system. Understanding the neurological dysfunction and pathology associated with sialidosis remains a challenge, partially due to the lack of a human model system. In this study, we have generated two types of induced pluripotent stem cells (iPSCs) with sialidosis-specific NEU1G227R and NEU1V275A/R347Q mutations (sialidosis-iPSCs), and further differentiated them into neural precursor cells (iNPCs). Characterization of NEU1G227R- and NEU1V275A/R347Q- mutated iNPCs derived from sialidosis-iPSCs (sialidosis-iNPCs) validated that sialidosis-iNPCs faithfully recapitulate key disease-specific phenotypes, including reduced NEU1 activity and impaired lysosomal and autophagic function. In particular, these cells showed defective differentiation into oligodendrocytes and astrocytes, while their neuronal differentiation was not notably affected. Importantly, we found that the phenotypic defects of sialidosis-iNPCs, such as impaired differentiation capacity, could be effectively rescued by the induction of autophagy with rapamycin. Our results demonstrate the first use of a sialidosis-iNPC model with NEU1G227R- and NEU1V275A/R347Q- mutation(s) to study the neurological defects of sialidosis, particularly those related to a defective autophagy-lysosome pathway, and may help accelerate the development of new drugs and therapeutics to combat sialidosis and other LSDs.

Prognostic effect of increased left ventricular wall thickness in severe aortic stenosis.

BACKGROUND: It is unclear whether increased left ventricular (LV) thickness is associated with worse clinical outcomes in severe aortic stenosis (AS). The aim of this study was to determine the effect of increased LV wall thickness (LVWT) on major clinical outcomes in patients with severe AS. METHODS AND RESULTS: This study included 290 severe AS patients (mean age 69.4 ± 11.0 years; 136 females) between January 2008 and December 2018. For outcome assessment, the endpoint was defined as death from all causes, cardiovascular death, and the aortic valve replacement (AVR) surgery rate. During follow-up (48.7 ± 39.0 months), 157 patients had AVR, 43 patients died, and 28 patients died from cardiovascular causes. Patients with increased LVWT underwent AVR surgery much more than those without LVWT (60.0% vs. 39.0%, p < 0.001). Furthermore, in patients with increased LVWT, the all-cause and cardiovascular death rates were significantly lower in the AVR group than in the non-AVR group (8.8% vs. 27.3%, p < 0.001, 4.8%, vs. 21.0%, p < 0.001). Multivariate analysis revealed that increased LVWT, age, dyspnea, and AVR surgery were significantly correlated with cardiovascular death. CONCLUSIONS: In patients with severe AS, increased LVWT was associated with a higher AVR surgery rate and an increased rate of cardiovascular death independent of other well-known prognostic variates. Thus, these findings suggest that increased LVWT might be used as a potential prognostic factor in severe AS patients.

HDAC Inhibitor, CG-745, Enhances the Anti-Cancer Effect of Anti-PD-1 Immune Checkpoint Inhibitor by Modulation of the Immune Microenvironment.

Histone deacetylase inhibitors (HDACis) are well-known epigenetic regulators with therapeutic potential in various diseases. Recent studies have shown that HDACis are involved in immune-mediated anti-cancer effects and may modulate the activity of immunotherapy agents. CG-745, a histone deacetylase inhibitor, has shown anti-cancer effects in pancreatic cancer, colorectal cancer, and non-small cell lung cancer. However, the exact role of CG-745 within the immune system is largely unknown. In this study, we have shown that CG-745 induces microenvironment changes promoting anti-cancer effect of anti-PD-1 antibody in syngeneic mouse models. Specifically, CG-745 induces or extends IL-2 and IFN-γ expression with or without additional stimulation, and increases proliferation of cytotoxic T cells and NK cells, while inhibiting proliferation of regulatory T cells. The analysis of immune cell distribution in the tumor microenvironment and spleen reveals that CG-745 suppresses M2 macrophage polarization and decreases the myeloid-derived suppressor cells. Recent advances in immunotherapy highlight the anti-cancer effects of immune checkpoint inhibitor despite a relatively limited clinical benefit in the subset of patients. Our results indicate that CG-745 enables the synergistic effects of the immune checkpoint inhibitor combination therapy in various cancers by suppressing tumor microenvironment.

Comparison between ticagrelor and clopidogrel on myocardial blood flow in patients with acute coronary syndrome, using 13 N-ammonia positron emission tomography.

BACKGROUND: The PLEIO (comParison of ticagreLor and clopidogrEl on mIcrocirculation in patients with acute cOronary syndrome) study showed that 6 months of ticagrelor therapy significantly improved microvascular dysfunction in acute coronary syndrome (ACS) patients with stent implantation compared to clopidogrel. Improved microvascular function may affect myocardial blood flow (MBF). We compared the effects of ticagrelor and clopidogrel on MBF over a 6-month follow-up period among patients diagnosed with ACS treated with percutaneous coronary intervention (PCI). METHODS: In the PLEIO trial, 120 participants were randomized to receive ticagrelor 90 mg twice daily or clopidogrel 75 mg once daily after at least 6 months. 13 N-ammonia positron emission tomography (PET) imaging was performed in 94 patients to measure MBF at the 6-month follow-up visit. RESULTS: On a per-patient level, MBF (1.88 ±â€¯0.52 versus 1.67 ±â€¯0.64 mL/min per gram, P = .01) was significantly higher with ticagrelor compared with clopidogrel in the hyperemic state, but not under resting state (0.75 ±â€¯0.24 versus 0.75 ±â€¯0.19 mL/min per gram, P = .84). On a culprit-vessel analysis, the resting MBF was similar (0.69 ±â€¯0.20 versus 0.70 ±â€¯0.21, P = .89) between the two groups. However, the hyperemic MBF and myocardial flow reserve in the ticagrelor group were significantly higher compared with clopidogrel (1.75 ±â€¯0.46 versus 1.52 ±â€¯0.59, P = .03 and 2.71 ±â€¯0.89 versus 2.20 ±â€¯0.81, P = .02, respectively). These differences were not observed in non-culprit vessels. CONCLUSIONS: Maintenance treatment of ticagrelor increased the hyperemic MBF and myocardial flow reserve compared with clopidogrel. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02618733.

Local Stabilization of Hypoxia-Inducible Factor-1α Controls Intestinal Inflammation via Enhanced Gut Barrier Function and Immune Regulation.

Intestinal epithelial cells are adapted in mucosal hypoxia and hypoxia-inducible factors in these cells can fortify barrier integrity to support mucosal tissue healing. Here we investigated whether hypoxia-related pathways could be proposed as potential therapeutic targets for inflammatory bowel disease. We developed a novel hypoxia-inducible factor (HIF) prolyl hydroxylase inhibitor, CG-598 which stabilized HIF-1α in the gut tissue. Treatment of CG-598 did not affect extra-intestinal organs or cause any significant adverse effects such as erythropoiesis. In the experimental murine colitis model, CG-598 ameliorated intestinal inflammation with reduction of inflammatory lesions and pro-inflammatory cytokines. CG-598 treatment fortified barrier function by increasing the expression of intestinal trefoil factor, CD73, E-cadherin and mucin. Also, IL-10 and IL-22 were induced from lamina propria CD4+ T-cells. The effectiveness of CG-598 was comparable to other immunosuppressive therapeutics such as TNF-blockers or JAK inhibitors. These results suggest that CG-598 could be a promising therapeutic candidate to treat inflammatory bowel disease.

Comparison of the Effects of Ticagrelor and Clopidogrel on Microvascular Dysfunction in Patients With Acute Coronary Syndrome Using Invasive Physiologic Indices.

BACKGROUND: Ticagrelor reduced the rate of myocardial infarction and death compared with clopidogrel in patients with acute coronary syndrome. However, little is understood about chronic treatment of ticagrelor on microvascular dysfunction. The objective of this study was to assess the impact of ticagrelor maintenance treatment on microvascular system and coronary flow in comparison with clopidogrel. METHODS: This study was a nonblinded, open-label, parallel-group, prospective, randomized controlled trial that enrolled 120 patients with acute coronary syndrome requiring stent implantation. Patients were randomized into the ticagrelor (180 mg loading dose, 90 mg twice daily thereafter) or clopidogrel (300 to 600 mg loading dose, 75 mg daily thereafter) group. The primary end point was coronary microvascular dysfunction as measured by an index of microcirculatory resistance (IMR) at 6 months after treatment. RESULTS: The baseline clinical characteristics and physiological parameters, such as fractional flow reserve, coronary flow reserve, and IMR, did not differ between the ticagrelor and clopidogrel groups. Six-month follow-up physiological data showed that the IMR value was significantly lower in the ticagrelor group than the clopidogrel group (15.57±5.65 versus 21.15±8.39, P<0.01), and coronary flow reserve was higher in the ticagrelor group than in the clopidogrel group (3.85±0.72 versus 3.37±0.76, P<0.01). However, there was no difference in fractional flow reserve (0.87±0.08 versus 0.87±0.09, P=0.94) between the 2 groups. The improvement in IMR after 6 months of treatment was higher in the ticagrelor group (P<0.01). Analyses of 223 nonculprit vessels of registered patients based on physiological results showed no differences in baseline fractional flow reserve (0.93±0.13 versus 0.92±0.09, P=0.58), coronary flow reserve (3.62±1.27 versus 3.51±1.24, P=0.16), or IMR (21.37±12.37 versus 24.19±21.08, P=0.22) or in follow-up fractional flow reserve (0.91±0.09 versus 0.91±0.08, P=0.67), coronary flow reserve (3.91±1.22 versus 3.75±1.16, P=0.36), or IMR (19.43±10.32 versus 21.52±18.90, P=0.34) between the 2 groups. CONCLUSIONS: Compared with clopidogrel, 6 months of ticagrelor therapy significantly improved microvascular dysfunction in acute coronary syndrome patients with stent implantation. CLINICAL TRIAL REGISTRATION: URL: https://www.clinicaltrials.gov. Unique identifier: NCT02618733.

Asymmetric aortic valve is related to development of eccentric aortic regurgitation in patients with tricuspid aortic valve.

BACKGROUND: It is unclear whether asymmetry itself plays a role in developing eccentric aortic regurgitation (AR) in patients with tricuspid aortic valve (TAV). The aim of this study was to determine whether an asymmetric aortic valve structure may have association with the development of eccentric AR in patients with TAV. METHODS: Of the 164 410 patients who underwent echocardiography between January 2006 and January 2018 at Dong-A University Hospital, 306 (mean age 69.9 ± 12.6 years; 62% men) eccentric AR were identified. After excluding patients with bicuspid and prolapsed AV, 104 patients who had eccentric AR with TAV were enrolled for the study. Comprehensive echocardiographic AV cusp measurements were compared to those of 104 age- and gender-matched control patients with central AR. RESULTS: In the eccentric and central AR groups, 66 (63.5%) and 48 patients (46.2%) had asymmetric AV, respectively. Mean cusp height was significantly larger in the eccentric AR group than in the central AR group (1.8 ± 0.3 cm vs 1.7 ± 0.2 cm, P = 0002). Furthermore, the mean cusp area and average asymmetry index of the cusp area were also significantly larger in the eccentric AR group than in the central AR group (2.6 ± 0.8 cm2 vs 2.3 ± 0.6 cm2 , P = 0.001, and 7.1 ± 4.5% vs 4.9 ± 2.5%, P < 0.001, respectively). CONCLUSION: AV asymmetry indices of eccentric AR were significantly larger than those of patients with central AR. These data suggest that the presence of asymmetric AV might have association with the development of eccentric AR in patients with TAV.

Left ventricular geometric patterns in patients with type A aortic dissection.

BACKGROUND: Aortic dilatation is a major risk factor for aortic dissection. The aim of the present study was to assess the relationship between left ventricular (LV) geometry and maximal ascending aorta (MAA). METHODS: We reviewed data from patients who were diagnosed with acute type A aortic dissection and who underwent surgical management from December 2002 to March 2016 at Dong-A University Hospital. Among 151 patients with non-Marfan aortic dissection in the study, 50 who had echocardiography preoperatively were investigated and MAA diameter was analyzed by LV geometric patterns. RESULTS: Patients' mean age was 59.6 ± 13.5 years and 38.0% were male. The mean MAA diameter was 52.9 ± 8.5 mm. MAA diameter was significantly correlated with LV mass index (r = 0.62, P < 0.001). On analysis by LV geometry, MAA diameter showed a significant difference between the 4 groups (P = 0.02), and the eccentric and concentric hypertrophy groups showed significantly larger MAA diameter than the other two groups. CONCLUSION: MAA diameter was associated with LV mass index and was significantly different between LV geometry types. In this study, not only concentric hypertrophy but also eccentric LV hypertrophy was related to larger MAA in type A aortic dissection patients.

A formulated red ginseng extract inhibits autophagic flux and sensitizes to doxorubicin-induced cell death.

BACKGROUND: Ginseng is believed to have antitumor activity. Autophagy is largely a prosurvival cellular process that is activated in response to cellular stressors, including cytotoxic chemotherapy; therefore, agents that inhibit autophagy can be used as chemosensitizers in cancer treatment. We examined the ability of Korean Red Ginseng extract (RGE) to prevent autophagic flux and to make hepatocellular carcinoma (HCC) cells become more sensitive to doxorubicin. METHODS: The cytotoxic effects of total RGE or its saponin fraction (RGS) on HCC cells were examined by the lactate dehydrogenase assay in a dose- or time-dependent manner. The effect of RGE or RGS on autophagy was measured by analyzing microtubule-associated protein 1A/1B-light chain (LC)3-II expression and LC3 puncta formation in HCC cells. Late-stage autophagy suppression was tested using tandem-labeled green fluorescent protein (GFP)-monomeric red fluorescent protein (mRFP)-LC3. RESULTS: RGE markedly increased the amount of LC3-II, but green and red puncta in tandem-labeled GFP-mRFP-LC3 remained colocalized over time, indicating that RGE inhibited autophagy at a late stage. Suppression of autophagy through knockdown of key ATG genes increased doxorubicin-induced cell death, suggesting that autophagy induced by doxorubicin has a protective function in HCC. Finally, RGE and RGS markedly sensitized HCC cells, (but not normal liver cells), to doxorubicin-induced cell death. CONCLUSION: Our data suggest that inhibition of late-stage autophagic flux by RGE is important for its potentiation of doxorubicin-induced cancer cell death. Therapy combining RGE with doxorubicin could serve as an effective strategy in the treatment of HCC.

Changes in mitral annular velocities after cardioversion of atrial fibrillation.

AIMS: The early diastolic mitral annular velocity (e') and mitral E/e' criteria for clinically evaluating diastolic dysfunction in patients with atrial fibrillation (AF) are almost the same as in patients with sinus rhythm. In this study, we aimed to investigate whether e' is useful to assess diastolic function in AF patients. METHODS: Thirty patients who underwent successful electric cardioversion (EC) due to persistent AF and who maintained sinus rhythm for 1 month after EC were enrolled in this study. Transthoracic echocardiography was performed on all patients before and 1 month after EC. Standard diastolic parameters, the global longitudinal strain (GLS), and left ventricular (LV) twist were measured. RESULTS: Conventional Doppler parameters measured before EC were not significantly different from 1 month after EC. However, the lateral and septal e' were significantly decreased 1 month after EC (from 12.8 ± 2.5 to 9.8 ± 2.3 cm/s and from 9.5 ± 1.9 to 7.1 ± 1.5 cm/s, respectively, P < 0.001). Likewise, the lateral and septal E/e' were also significantly increased 1 month after EC (P < 0.001). The GLS was significantly improved from -15.9 ± 2.2% to -19.4 ± 2.4% after EC (P < 0.001), as was the LV twist (from 5.8 ± 1.7° to 9.1 ± 2.4°, P < 0.001). CONCLUSION: We demonstrated that e' was significantly higher in AF compared with during sinus rhythm in the same patients. Thus, in AF patients, diastolic dysfunction should be suspected even when e' values are normal.

Interleukin-2 induces the in vitro maturation of human pluripotent stem cell-derived intestinal organoids.

Human pluripotent stem cell (hPSC)-derived intestinal organoids (hIOs) form 3D structures organized into crypt and villus domains, making them an excellent in vitro model system for studying human intestinal development and disease. However, hPSC-derived hIOs still require in vivo maturation to fully recapitulate adult intestine, with the mechanism of maturation remaining elusive. Here, we show that the co-culture with human T lymphocytes induce the in vitro maturation of hIOs, and identify STAT3-activating interleukin-2 (IL-2) as the major factor inducing maturation. hIOs exposed to IL-2 closely mimic the adult intestinal epithelium and have comparable expression levels of mature intestinal markers, as well as increased intestine-specific functional activities. Even after in vivo engraftment, in vitro-matured hIOs retain their maturation status. The results of our study demonstrate that STAT3 signaling can induce the maturation of hIOs in vitro, thereby circumventing the need for animal models and in vivo maturation.

ESRP1-Induced CD44 v3 Is Important for Controlling Pluripotency in Human Pluripotent Stem Cells.

The importance of alternative splicing (AS) events in pluripotency regulation has been highlighted by the determination of different roles and contributions of different splice isoforms of pluripotency-related genes and by the identification of distinct pluripotency-related splicing factors. In particular, epithelial splicing regulatory protein 1 (ESRP1) has been characterized as an essential splicing factor required for the regulation of human pluripotency and differentiation. Nevertheless, a detailed molecular characterization of ESRP1 (mRNA splice variants 1-6) in human pluripotency is lacking. In this study, we determined that ESRP1 splice variants are differentially expressed in undifferentiated and differentiated human pluripotent stem cells (PSCs). Undifferentiated human PSCs predominantly expressed the ESRP1 v1, v4, and v5, and their expression was downregulated upon differentiation. Ectopic expression of ESRP1 v1, v4, or v5 enhanced the pluripotent reprogramming of human fibroblasts and restored the ESRP1 knockdown-mediated reduction of reprogramming efficiency. Notably, undifferentiated human PSCs expressed the cell surface protein CD44 variant 3 (CD44 v3), and isoform switching from CD44 v3 to CD44 variant 6 (CD44 v6) occurred upon differentiation. Importantly, the human PSC-specific ESRP1 variants influenced CD44 v3 expression. CD44 knockdown or inhibition of binding of CD44 with its major ligand, hyaluronan, significantly induced the loss of human PSC pluripotency and the reduction of reprogramming efficiency. Our results demonstrate that the effect of ESRP1 and CD44 on human PSC pluripotency is isoform-dependent and that ESRP1-induced CD44 v3 is functionally associated with human PSC pluripotency control. Stem Cells 2018;36:1525-1534.