GATA6 Cooperates with EOMES/SMAD2/3 to Deploy the Gene Regulatory Network Governing Human Definitive Endoderm and Pancreas Formation

Heterozygous de novo mutations in GATA6 are the most frequent cause of pancreatic agenesis in humans. In mice, however, a similar phenotype requires the biallelic loss of Gata6 and its paralog Gata4. To elaborate the human-specific requirements for GATA6, we chose to model GATA6 loss in vitro by combining both gene-edited and patient-derived pluripotent stem cells (hPSCs) and directed differentiation toward β-like cells. We find that GATA6 heterozygous hPSCs show a modest reduction in definitive endoderm (DE) formation, while GATA6-null hPSCs fail to enter the DE lineage. Consistent with these results, genome-wide studies show that GATA6 binds and cooperates with EOMES/SMAD2/3 to regulate the expression of cardinal endoderm genes. The early deficit in DE is accompanied by a significant reduction in PDX1⁺ pancreatic progenitors and C-PEPTIDE⁺ β-like cells. Taken together, our data position GATA6 as a gatekeeper to early human, but not murine, pancreatic ontogeny.

Tiled array-based sequencing identifies enrichment of loss-of-function variants in the highly homologous filaggrin gene in African-American children with severe atopic dermatitis

Filaggrin (FLG) loss-of-function (LOF) variants are a major risk factor for the common inflammatory skin disease, atopic dermatitis (AD) and are often population-specific. African-American (AA) children are disproportionately affected with AD, often later developing asthma and/or allergic rhinitis and comprise an atopy health disparity group for which the role of FLG LOF is not well known. Discovery of FLG LOF using exome sequencing is challenging given the known difficulties for accurate short-read alignment to FLG's high homology repeat variation. Here, we employed an array-based sequencing approach to tile across each FLG repeat and discover FLG LOF in a well-characterized cohort of AA children with moderate-to-severe AD. Five FLG LOF were identified in 23% of our cohort. Two novel FLG LOF singletons, c.488delG and p.S3101*, were discovered as well as p.R501*, p.R826* and p.S3316* previously reported for AD. p.S3316* (rs149484917) is likely an African ancestral FLG LOF, reported in African individuals in ExAC (Exome Aggregation Consortium), Exome Variant Server (ESP), and 4 African 1000G population databases (ESN, MSL, ASW, and ACB). The proportion of FLG LOF (11.5%) among the total FLG alleles in our cohort was significantly higher in comparisons with FLG LOF reported for African individuals in ExAC (2.5%; P = 4.3 × 10^-4 ) and ESP (1.7%; P = 3.5 × 10^-5 ) suggesting a disease-enrichment effect for FLG LOF. Our results demonstrate the utility of array-based sequencing in discovering FLG LOF, including novel and population-specific, which are of higher prevalence in our AA severe AD group than previously reported.

Long-Term Culture of Self-renewing Pancreatic Progenitors Derived from Human Pluripotent Stem Cells

Pluripotent stem cells have been proposed as an unlimited source of pancreatic β cells for studying and treating diabetes. However, the long, multi-step differentiation protocols used to generate functional β cells inevitably exhibit considerable variability, particularly when applied to pluripotent cells from diverse genetic backgrounds. We have developed culture conditions that support long-term self-renewal of human multipotent pancreatic progenitors, which are developmentally more proximal to the specialized cells of the adult pancreas. These cultured pancreatic progenitor (cPP) cells express key pancreatic transcription factors, including PDX1 and SOX9, and exhibit transcriptomes closely related to their in vivo counterparts. Upon exposure to differentiation cues, cPP cells give rise to pancreatic endocrine, acinar, and ductal lineages, indicating multilineage potency. Furthermore, cPP cells generate insulin+ β-like cells in vitro and in vivo, suggesting that they offer a convenient alternative to pluripotent cells as a source of adult cell types for modeling pancreatic development and diabetes.

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Culture on 3T3 cells enables long-term self-renewal of human pancreatic progenitors

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Proliferation requires EGF, FGF10, retinoic acid, and inhibition of Notch and TGF-β

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Cultured progenitors upregulate genes required for mitosis and telomere maintenance

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Pancreatic duct and β-like cells are generated in vitro and in vivo

Lgr5-expressing chief cells drive epithelial regeneration and cancer in the oxyntic stomach

The daily renewal of the corpus epithelium is fuelled by adult stem cells residing within tubular glands, but the identity of these stem cells remains controversial. Lgr5 marks homeostatic stem cells and 'reserve' stem cells in multiple tissues. Here, we report Lgr5 expression in a subpopulation of chief cells in mouse and human corpus glands. Using a non-variegated Lgr5-2A-CreERT2 mouse model, we show by lineage tracing that Lgr5-expressing chief cells do not behave as corpus stem cells during homeostasis, but are recruited to function as stem cells to effect epithelial renewal following injury by activating Wnt signalling. Ablation of Lgr5⁺ cells severely impairs epithelial homeostasis in the corpus, indicating an essential role for these Lgr5⁺ cells in maintaining the homeostatic stem cell pool. We additionally define Lgr5⁺ chief cells as a major cell-of-origin of gastric cancer. These findings reveal clinically relevant insights into homeostasis, repair and cancer in the corpus.

On cross-sectional associations of leukocyte telomere length with cardiac systolic, diastolic and vascular function: the Asklepios study

BACKGROUND

Systemic telomere length has been associated with measures of diastolic function, vascular stiffness and left ventricular mass mainly in smaller, patient-specific settings and not in a general population. In this study we describe the applicability of these findings in a large, representative population.

METHODS AND RESULTS

Peripheral blood leukocyte telomere length (PBL TL) was measured using telomere restriction fragment analysis in the young to middle-aged (>2500 volunteers, ∼35 to 55 years old) Asklepios study population, free from overt cardiovascular disease. Subjects underwent extensive echocardiographic, hemodynamic and biochemical phenotyping. After adjusting for relevant confounders (age, sex, systolic blood pressure, heart rate, body mass index and use of antihypertensive drugs) we found no associations between PBL TL and left ventricular mass index (P = 0.943), ejection fraction (P = 0.933), peak systolic septal annular motion (P = 0.238), pulse wave velocity (P = 0.971) or pulse pressure (P = 0.999). In contrast, our data showed positive associations between PBL TL and parameters of LV filling: the transmitral flow early (E) to late (A) velocity ratio (E/A-ratio; P<0.001), the ratio of early (e') to late (a') mitral annular velocities (e'/a'-ratio; P = 0.012) and isovolumic relaxation time (P = 0.015). Interestingly, these associations were stronger in women than in men and were driven by associations between PBL TL and the late diastolic components (A and a').

CONCLUSIONS

In a generally healthy, young to middle-aged population, PBL TL is not related to LV mass or systolic function, but might be associated with an altered LV filling pattern, especially in women.

Addition of a novel, protective family history category allows better profiling of cardiovascular risk and atherosclerotic burden in the general population. The Asklepios Study

Objectives

Whereas the importance of family history (FH) is widely recognized in cardiovascular risk assessment, its full potential could be underutilized, when applied with its current simple guidelines-based definition (cFH): presence of premature cardiovascular disease (CVD) in a first-degree relative. We tested the added value of a new, extended family history definition (eFH), also taking into account later onset of disease, second-degree relatives and number of affected relatives, on profiling cardiovascular risk and atherosclerotic burden in the general population.

Design

longitudinal population study.

Setting

random, representative population sample from Erpe-Mere and Nieuwerkerken (Belgium, primary care).

Subjects

2524 male/female volunteers, aged 35–55 years, free from overt CVD.

Main outcome measures

Subjects were extensively phenotyped including presence of atherosclerosis (ultrasound) and a newly developed FH questionnaire (4 generations).

Results

Compared to cFH, eFH was superior in predicting an adverse risk profile (glycemic state, elevated blood pressure, lipid abnormalities, presence of metabolic syndrome components) and presence of atherosclerosis (all age & sex-adjusted p<0.05). Unlike cFH, eFH remained a significant predictor of subclinical atherosclerosis after adjusting for confounders. Most relations with eFH were not graded but showed clear informational breakpoints, with absence of CVD (including late onset) in any first-degree relative being a negative predictor of atherosclerosis, and a particularly interesting phenotype for further study.

Conclusions

A novel, extended FH definition is superior to the conventional definition in profiling cardiovascular risk and atherosclerotic burden in the general population. There remain clear opportunities to refine and increase the performance and informational content of this simple, readily-available inexpensive tool.