Polycomb Repressive Complex 2 Regulates Lineage Fidelity during Embryonic Stem Cell Differentiation

Polycomb Repressive Complex 2 (PRC2) catalyzes histone H3 lysine 27 tri-methylation (H3K27me3), an epigenetic modification associated with gene repression. H3K27me3 is enriched at the promoters of a large cohort of developmental genes in embryonic stem cells (ESCs). Loss of H3K27me3 leads to a failure of ESCs to properly differentiate, making it difficult to determine the precise roles of PRC2 during lineage commitment. Moreover, while studies suggest that PRC2 prevents DNA methylation, how these two epigenetic regulators coordinate to regulate lineage programs is poorly understood. Using several PRC2 mutant ESC lines that maintain varying levels of H3K27me3, we found that partial maintenance of H3K27me3 allowed for proper temporal activation of lineage genes during directed differentiation of ESCs to spinal motor neurons (SMNs). In contrast, genes that function to specify other lineages failed to be repressed in these cells, suggesting that PRC2 is also necessary for lineage fidelity. We also found that loss of H3K27me3 leads to a modest gain in DNA methylation at PRC2 target regions in both ESCs and in SMNs. Our study demonstrates a critical role for PRC2 in safeguarding lineage decisions and in protecting genes against inappropriate DNA methylation.National Cancer Institute (U.S.) (Cancer Center Support (Core) Grant P30-CA14051)National Institutes of Health (U.S.) (Training Grant T 32 GM007287)Smith Family Foundation (Contract LTR DATED 11/6/09

Fine structure, microstructure, and vertical mixing processes in the upper ocean in the western Weddell Sea

The upward flux of heat from the subsurface core of Warm Deep Water (WDW) to the perennially ice-covered sea surface over the continental slope in the western Weddell Sea is estimated using data obtained during February-June 1992 from a drifting ice station. Through the permanent pycnocline the diapycnal heat flux is estimated to be about 3 W m⁻², predominantly because of double-diffusive convection. There is no evidence that shear-driven mixing is important in the pycnocline. The estimated mean rate of heat transfer from the mixed layer to the ice is 1.7 W m⁻², although peak heat fluxes of up to 15 W m⁻² are found during storms. It is hypothesized that isopycnal mixing along sloping intrusions also contributes to the loss of heat from the WDW in this region; however, we are unable to quantify the fluxes associated with this process. Intrusions occur intermittently throughout this experiment but are most commonly found near the boundary of the warm-core current and the shelf-modified water to the east. These heat fluxes are significantly lower than the basin-averaged value of 19 W m⁻² (Fahrbach et al., 1994) that is required to balance the heat budget of the Weddell Gyre. Other studies suggest that shelf processes to the west of the ice station drift track and more energetic double-diffusive convection in the midgyre to the east could account for the difference between our flux estimates for this region and those based on the basin-scale heat budget

Some Sex Hormone Profiles are Consistent over Time in Normal Menstruating Women: Implications for Sports Injury Epidemiology

Purpose-It is unclear whether sex hormone profiles obtained in two consecutive months are consistent within women. Month-to-month consistency in daily, nadir, peak and mean hormone concentrations during the early follicular and luteal phases in recreationally active, young eumenorrheic women was prospectively examined. Methods-60 healthy, non-smoking women who reported normal and consistent menstrual cycles lasting 26–32 days for the past 6 months were followed prospectively to obtain serum samples for the first 6 days of menses and for 8 days after a positive ovulation test over two consecutive months. Month-to-month consistency of daily concentrations of oestradiol (pg/ml), progesterone (ng/ml), testosterone (ng/dl), sex hormone-binding globulin (nmol/l) and free androgen index were determined using linear mixed models. Month-to-month consistency in nadir, peak and mean concentrations were then assessed using intraclass correlation coefficients and SEM to more precisely examine intraindividual consistency. Results-Linear mixed models revealed stable hormone concentrations across cycles and cycles by day. Reliability estimates for nadir, peak, mean menses and mean postovulatory concentrations range from 0.56 to 0.86 for oestradiol, 0.44 to 0.91 for progesterone, 0.60 to 0.86 for testosterone, 0.88 to 0.97 for sex hormone-binding globulin and 0.78 to 0.91 for free androgen index. Conclusions-Hormone profiles were reproducible over two consecutive months. To reduce month-to-month intraindividual variations and improve measurement consistency, it is recommended that multiple samples be taken over consecutive days as opposed to a single sample

A Correction to the Baroclinic Pressure Gradient Term in the Princeton Ocean Model

An error in the calculation of the baroclinic pressure gradient term in the Princeton Ocean Model (POM) was identified while modeling the M₂ tidal current near its critical latitude in the southern Weddell Sea. The error arises from the present calculation of density, which involves the subtraction of a background density profile from the density field calculated at each internal time step. The small displacement of sigma surface depths relative to the surface, as surface elevation changes, causes a slight error in the calculation of the vertical and horizontal gradients of potential density. The error is largest at the seabed over rapidly changing bathymetry such as the continental slope. The baroclinic pressure gradient error is typically much smaller than the Coriolis term in the momentum equations and, therefore, usually unimportant. Close to the critical latitude, however, near-resonance between the error and Coriolis terms can cause an energetic and spatially complex spurious inertial mode to develop. The error is significant when modeling tides near their critical latitudes, and will contribute to the error in the baroclinic pressure gradient in other simulations. Two methods were suggested for fixing this problem. The preferred method was tested by applying the new form of POM to the southern Weddell Sea. The new results are consistent with both current meter data and predictions of linear internal wave theory

Internal waves and tides in the western Weddell Sea: Observations from Ice Station Weddell

The upper ocean current and temperature fields in the western Weddell Sea were measured from the drifting pack ice at Ice Station Weddell 1 (ISW) and nearby sites using a vertical profiler and an array of moored sensors in January–June 1992. These data document the structure and variability of the internal gravity wave field and tidal currents in this remote region. The variance of the internal wave continuum (ƒ < frequency < N) at ISW was 0.2–0.6 of the Garrett‐Munk (GM) universal level for the first 60 days, increasing to near GM levels during the final 10 days of the deployment. In contrast, the energy density at site C, 50 km west of ISW and farther up the continental slope, was always near GM levels. Variations may be due to a combination of spatial and temporal gradients of the internal wave field. At ISW, coherence between vertically separated sensors was used to estimate vertical wave number bandwidth. Energy and bandwidth estimates are compared with previous studies in both ice‐covered and temperate oceans. Using our measurements of the internal wave field and existing parameterizations of mixing, we estimate the vertical heat flux from the Warm Deep Water toward the surface. At ISW the upward heat flux due to mixing associated with the internal waves was about 1 W m⁻², much less than the 20 W m⁻² average flux required to balance the heat budget for the Weddell Gyre. Tidal currents contributed significantly to the total measured horizontal velocity variance. The tides were primarily barotropic and increased toward the west in both the semidiurnal and diurnal frequency bands. It is suggested that the stronger tidal currents to the west, over the shallower water of the upper continental slope, are indirectly responsible for the higher internal wave energy at site C relative to ISW

Hydrography and microstructure of an Arctic cyclonic eddy

Hydrographic and velocity profiles were made through a small baroclinic cyclonic eddy during the Arctic Internal Wave Experiment in the Canada Basin in April 1985. The maximum measured azimuthal velocity was 0.38 m s⁻¹ at a depth of 115 m, with velocities decaying to near zero at 30 and 270 m. Maximum isopycnal displacements at the closest approach to the eddy's axis were about 40 m. The deduced radius of maximum velocity is r₀ = 7 ± 2 km, and the total radius is about 13 km. Kinetic energy dissipation rate, ε, was enhanced within 70 m of the surface throughout the transect, and for radius r < r₀ near 60 m and 180 m. The subsurface maxima in ε do not correspond to regions of low Richardson number, but are colocated with locally reduced shear, consistent with the observed dissipation rates being merely the remnants of recent, more energetic mixing events. The time scale for the decay of the eddy, based on its total energy and the measured dissipation rates, is O(10) years. Given this large dissipation time scale, critical layer absorption of vertically propagating internal wave momentum may be dynamically significant to the eddy's evolution

Forum: Parental education and child mortality

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Comparability of neuraminidase inhibition antibody titers measured by enzyme-linked lectin assay (ELLA) for the analysis of influenza vaccine immunogenicity

AbstractNeuraminidase-inhibition (NI) antibody titers can be used to evaluate the immunogenicity of inactivated influenza vaccines and have provided evidence of serologic cross-reactivity between seasonal and pandemic H1N1 viruses. The traditional thiobarbituric acid assay is impractical for large serologic analyses, and therefore many laboratories use an enzyme-linked lectin assay (ELLA) to determine serum NI antibody titers. The comparability of ELLA NI antibody titers when measured in different laboratories was unknown. Here we report a study conducted through the Consortium for the Standardisation of Influenza SeroEpidemiology (CONSISE) to evaluate the variability of the ELLA. NI antibody titers of a set of 12 samples were measured against both N1 and N2 neuraminidase antigens in 3 independent assays by each of 23 laboratories. For a sample repeated in the same assay, ≥96% of N1 and N2 assays had less than a 4-fold difference in titer. Comparison of the titers measured in assays conducted on 3 different days in the same laboratory showed that a four-fold difference in titer was uncommon. Titers of the same sera measured in different laboratories spanned 3 to 6 two-fold dilutions (i.e., 8–64 fold difference in titer), with an average percent geometric coefficient of variation (%GCV) of 112 and 82% against N1 and N2 antigens, respectively. The difference in titer as indicated by fold range and %GCV was improved by normalizing the NI titers to a standard that was included in each assay. This study identified background signal and the amount of antigen in the assay as critical factors that influence titer, providing important information toward development of a consensus ELLA protocol

Major Contribution of Somatostatin-Expressing Interneurons and Cannabinoid Receptors to Increased GABA Synaptic Activity in the Striatum of Huntington’s Disease Mice

Huntington’s disease (HD) is a heritable neurological disorder that affects cognitive and motor performance in patients carrying the mutated huntingtin (HTT) gene. In mouse models of HD, previous reports showed a significant increase in spontaneous GABAA receptor-mediated synaptic activity in striatal spiny projection neurons (SPNs). In this study, using optogenetics and slice electrophysiology, we examined the contribution of γ-aminobutyric acid (GABA)-ergic parvalbumin (PV)- and somatostatin (SOM)-expressing interneurons to the increase in GABA neurotransmission using the Q175 (heterozygote) mouse model of HD. Patch clamp recordings in voltage-clamp mode were performed on SPNs from brain slices of presymptomatic (2 months) and symptomatic (8 and 12 months) Q175 mice and wildtype (WT) littermates. While inhibitory postsynaptic currents (IPSCs) evoked in SPNs following optical activation of PV- and SOM-expressing interneurons differed in amplitude, no genotype-dependent differences were observed at all ages from both interneuron types; however, responses evoked by either type were found to have faster kinetics in symptomatic mice. Since SOM-expressing interneurons are constitutively active in striatal brain slices, we then examined the effects of acutely silencing these neurons in symptomatic mice with enhanced Natronomonas pharaonis halorhodopsin (eNpHR). Optically silencing SOM-expressing interneurons resulted in a greater decrease in the frequency of spontaneous IPSCs (sIPSCs) in a subset of SPNs from Q175 mice compared to WTs, suggesting that SOM-expressing interneurons are the main contributors to the overall increased GABA synaptic activity in HD SPNs. Additionally, the effects of activating GABAB and cannabinoid (CB1) receptors were investigated to determine whether these receptors were involved in modulating interneuron-specific GABA synaptic transmission and if this modulation differed in HD mice. When selectively activating PV- and SOM-expressing interneurons in the presence of the CB1 receptor agonist WIN-55,212, the magnitudes of the evoked IPSCs in SPNs decreased for both interneuron types although this change was less prominent in symptomatic Q175 SPNs during SOM-expressing interneuron activation. Overall, these findings show that dysfunction of SOM-expressing interneurons contributes to the increased GABA synaptic activity found in HD mouse models and that dysregulation of the endocannabinoid system may contribute to this effect

A cross-sectional study of depressive symptoms and diabetes self-care in African Americans and Hispanics/Latinos with diabetes: the role of self-efficacy

Purpose The purpose of this study is to examine the relationship between depressive symptoms and diabetes self-care in African American and Hispanic/Latino patients with type 2 diabetes and whether the association, if any, is mediated by diabetes-related self-efficacy. Methods The sample included self-report baseline data of African American and Hispanic/Latino patients with type 2 diabetes who were aged ≥18 years and enrolled in a diabetes self-management intervention study. Depressive symptoms were assessed with the 9-item Patient Health Questionnaire. The Summary of Diabetes Self-care Activities measured engagement in healthy eating, physical activity, blood glucose checking, foot care, and smoking. The Diabetes Empowerment Scale–Short Form assessed diabetes-related psychosocial self-efficacy. Indirect effects were examined with the Baron and Kenny regression technique and Sobel testing. Results Sample characteristics (n = 250) were as follows: mean age of 53 years, 68% women, 54% African American, and 74% with income <$20 000. Depressive symptoms showed a significant inverse association with the self-care domains of general diet, specific diet, physical activity, and glucose monitoring in the African American group. In Hispanics/Latinos, depression was inversely associated with specific diet. Self-efficacy served a significant mediational role in the relation between depression and foot care among African Americans. Conclusions Self-efficacy mediated the relationship between depression and foot care in the African American group but was not found to be a mediator of any self-care areas within the Hispanic/Latino group. In clinical practice, alleviation of depressive symptoms may improve self-care behavior adherence. Diabetes education may consider inclusion of components to build self-efficacy related to diabetes self-care, especially among African American patients