Population genetics of transposable element load: A mechanistic account of observed overdispersion.

In an empirical analysis of transposable element (TE) abundance within natural populations of Mimulus guttatus and Drosophila melanogaster, we found a surprisingly high variance of TE count (e.g., variance-to-mean ratio on the order of 10 to 300). To obtain insight regarding the evolutionary genetic mechanisms that underlie the overdispersed population distributions of TE abundance, we developed a mathematical model of TE population genetics that includes the dynamics of element proliferation and purifying selection on TE load. The modeling approach begins with a master equation for a birth-death process and extends the predictions of the classical theory of TE dynamics in several ways. In particular, moment-based analyses of population distributions of TE load reveal that overdispersion is likely to arise via copy-and-paste proliferation dynamics, especially when the elementary processes of proliferation and excision are approximately balanced. Parameter studies and analytic work confirm this result and further suggest that overdispersed population distributions of TE abundance are probably not a consequence of purifying selection on total element load.

Endosperm-based incompatibilities in hybrid monkeyflowers.

Endosperm is an angiosperm innovation central to their reproduction whose development, and thus seed viability, is controlled by genomic imprinting, where expression from certain genes is parent-specific. Unsuccessful imprinting has been linked to failed inter-specific and inter-ploidy hybridization. Despite their importance in plant speciation, the underlying mechanisms behind these endosperm-based barriers remain poorly understood. Here, we describe one such barrier between diploid Mimulus guttatus and tetraploid Mimulus luteus. The two parents differ in endosperm DNA methylation, expression dynamics, and imprinted genes. Hybrid seeds suffer from underdeveloped endosperm, reducing viability, or arrested endosperm and seed abortion when M. guttatus or M. luteus is seed parent, respectively, and transgressive methylation and expression patterns emerge. The two inherited M. luteus subgenomes, genetically distinct but epigenetically similar, are expressionally dominant over the M. guttatus genome in hybrid embryos and especially their endosperm, where paternal imprints are perturbed. In aborted seeds, de novo methylation is inhibited, potentially owing to incompatible paternal instructions of imbalanced dosage from M. guttatus imprints. We suggest that diverged epigenetic/regulatory landscapes between parental genomes induce epigenetic repatterning and global shifts in expression, which, in endosperm, may uniquely facilitate incompatible interactions between divergent imprinting schemes, potentially driving rapid barriers.

Author Correction: Origin and evolution of the octoploid strawberry genome.

In the version of this article originally published, author Joshua R. Puzey was incorrectly listed as having affiliation 7 (School of Plant Sciences, University of Arizona, Tucson, AZ, USA); affiliation 6 (Department of Biology, College of William and Mary, Williamsburg, VA, USA) is the correct affiliation. The error has been corrected in the HTML and PDF versions of the article.

A likelihood ratio test for changes in homeolog expression bias.

BACKGROUND: Gene duplications are a major source of raw material for evolution and a likely contributor to the diversity of life on earth. Duplicate genes (i.e., homeologs, in the case of a whole genome duplication) may retain their ancestral function, sub- or neofunctionalize, or be lost entirely. A primary way that duplicate genes evolve new functions is by altering their expression patterns. Comparing the expression patterns of duplicate genes gives clues as to whether any of these evolutionary processes have occurred. RESULTS: We develop a likelihood ratio test for the analysis of the expression ratios of duplicate genes across two conditions (e.g., tissues). We demonstrate an application of this test by comparing homeolog expression patterns of 1448 homeologous gene pairs using RNA-seq data generated from leaves and petals of an allotetraploid monkeyflower (Mimulus luteus). We assess the sensitivity of this test to different levels of homeolog expression bias and compare the method to several alternatives. CONCLUSIONS: The likelihood ratio test derived here is a direct, transparent, and easily implemented method for detecting changes in homeolog expression bias that outperforms alternative approaches. While our method was derived with homeolog analysis in mind, this method can be used to analyze changes in the ratio of expression levels between any two genes in any two conditions.

Origin and evolution of the octoploid strawberry genome.

Cultivated strawberry emerged from the hybridization of two wild octoploid species, both descendants from the merger of four diploid progenitor species into a single nucleus more than 1 million years ago. Here we report a near-complete chromosome-scale assembly for cultivated octoploid strawberry (Fragaria × ananassa) and uncovered the origin and evolutionary processes that shaped this complex allopolyploid. We identified the extant relatives of each diploid progenitor species and provide support for the North American origin of octoploid strawberry. We examined the dynamics among the four subgenomes in octoploid strawberry and uncovered the presence of a single dominant subgenome with significantly greater gene content, gene expression abundance, and biased exchanges between homoeologous chromosomes, as compared with the other subgenomes. Pathway analysis showed that certain metabolomic and disease-resistance traits are largely controlled by the dominant subgenome. These findings and the reference genome should serve as a powerful platform for future evolutionary studies and enable molecular breeding in strawberry.

Transcriptome of neonatal preBötzinger complex neurones in Dbx1 reporter mice.

We sequenced the transcriptome of brainstem interneurons in the specialized respiratory rhythmogenic site dubbed preBötzinger Complex (preBötC) from newborn mice. To distinguish molecular characteristics of the core oscillator we compared preBötC neurons derived from Dbx1-expressing progenitors that are respiratory rhythmogenic to neighbouring non-Dbx1-derived neurons, which support other respiratory and non-respiratory functions. Results in three categories are particularly salient. First, Dbx1 preBötC neurons express κ-opioid receptors in addition to µ-opioid receptors that heretofore have been associated with opiate respiratory depression, which may have clinical applications. Second, Dbx1 preBötC neurons express the hypoxia-inducible transcription factor Hif1a at levels three-times higher than non-Dbx1 neurons, which links core rhythmogenic microcircuits to O2-related chemosensation for the first time. Third, we detected a suite of transcription factors including Hoxa4 whose expression pattern may define the rostral preBötC border, Pbx3 that may influence ipsilateral connectivity, and Pax8 that may pertain to a ventrally-derived subset of Dbx1 preBötC neurons. These data establish the transcriptomic signature of the core respiratory oscillator at a perinatal stage of development.

Hemodynamic and hormonal patterns of untreated essential hypertension in men and women.

BACKGROUND: Knowledge of hemodynamic factors accounting for the development of hypertension should help to tailor therapeutic approaches and improve blood pressure control. Few data exist regarding sex differences of hemodynamic factors contributing to hypertension progression among patients with untreated nondiabetic stage I and II prehypertension (PreHyp) as defined by the Joint National Committee-7 guidelines (JNC-7). METHODS: We utilized noninvasive impedance cardiography, applanation tonometry and plasma measures of angiotensin II, angiotensin (1-7), serum aldosterone, high-sensitivity C-reactive protein (hs-CRP) and cytokine biomarkers of inflammation to characterize the hemodynamic and hormonal profile of 100 patients with untreated hypertension (39 women). RESULTS: Despite there being no differences between women and men in terms of office blood pressure, heart rate and body mass index, men demonstrated lower values of pulse pressure, systemic vascular resistance, brachial artery pulse wave velocity and augmentation index. In each of the three hypertension categories, the increased blood pressure in men was associated with significant augmentations in stroke volume and cardiac output compared with women. Sex-related hemodynamic differences were associated in women with higher plasma levels of leptin, hs-CRP, plasma angiotensin II and serum aldosterone, and no differences in the serum concentrations of cytokinins. In women but not men, hs-CRP correlated with plasma concentrations of transforming growth factor ß1 (TGFß1) and body weight; in addition, plasma TGFß1 correlated with levels of serum vascular cell adhesion molecule 1. CONCLUSION: The impact of sex differences in the hemodynamic factors accounting for the elevation in arterial pressure in subjects with essential hypertension has been poorly characterized or this information is not available. We suggest that this gap in knowledge may adversely influence choices of drug treatment since our study shows for the first time significant differences in the hemodynamic and hormonal mechanisms accounting for the increased blood pressure in women compared to men.

Role of olmesartan in combination therapy in blood pressure control and vascular function.

Angiotensin receptor blockers have emerged as a first-line therapy in the management of hypertension and hypertension-related comorbidities. Since national and international guidelines have stressed the need to control blood pressure to <140/90 mmHg in uncomplicated hypertension and <130/80 mmHg in those with associated comorbidities such as diabetes or chronic kidney disease, these goal blood pressures can only be achieved through combination therapy. Of several drugs that can be effectively combined to attain the recommended blood pressure goals, fixed-dose combinations of angiotensin receptor blockers and the calcium channel blocker amlodipine provide additive antihypertensive effects associated with a safe profile and increased adherence to therapy. In this article, we review the evidence regarding the beneficial effects of renin-angiotensin system blockade with olmesartan medoxomil and amlodipine in terms of blood pressure control and improvement of vascular function and target organ damage.

Effects of high-dose versus low-dose losartan on clinical outcomes in patients with heart failure (HEAAL study): a randomised, double-blind trial.

BACKGROUND: Angiotensin-receptor blockers (ARBs) are effective treatments for patients with heart failure, but the relation between dose and clinical outcomes has not been explored. We compared the effects of high-dose versus low-dose losartan on clinical outcomes in patients with heart failure. METHODS: This double-blind trial was undertaken in 255 sites in 30 countries. 3846 patients with heart failure of New York Heart Association class II-IV, left-ventricular ejection fraction 40% or less, and intolerance to angiotensin-converting-enzyme (ACE) inhibitors were randomly assigned to losartan 150 mg (n=1927) or 50 mg daily (n=1919). Allocation was by block randomisation stratified by centre and presence or absence of beta-blocker therapy, and all patients and investigators were masked to assignment. The primary endpoint was death or admission for heart failure. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00090259. FINDINGS: Six patients in each group were excluded because of poor data quality. With 4.7-year median follow-up in each group (IQR 3.7-5.5 for losartan 150 mg; 3.4-5.5 for losartan 50 mg), 828 (43%) patients in the 150 mg group versus 889 (46%) in the 50 mg group died or were admitted for heart failure (hazard ratio [HR] 0.90, 95% CI 0.82-0.99; p=0.027). For the two primary endpoint components, 635 patients in the 150 mg group versus 665 in the 50 mg group died (HR 0.94, 95% CI 0.84-1.04; p=0.24), and 450 versus 503 patients were admitted for heart failure (0.87, 0.76-0.98; p=0.025). Renal impairment (n=454 vs 317), hypotension (203 vs 145), and hyperkalaemia (195 vs 131) were more common in the 150 mg group than in the 50 mg group, but these adverse events did not lead to significantly more treatment discontinuations in the 150 mg group. INTERPRETATION: Losartan 150 mg daily reduced the rate of death or admission for heart failure in patients with heart failure, reduced left-ventricular ejection fraction, and intolerance to ACE inhibitors compared with losartan 50 mg daily. These findings show the value of up-titrating ARB doses to confer clinical benefit. FUNDING: Merck (USA).

Effectiveness of open-label losartan/hydrochlorothiazide combination therapy in Asian patients with hypertension not controlled with ACE inhibitor or ARB monotherapy.

Antihypertensive efficacy and safety of losartan/hydrochlorothiazide (HCTZ) combinations have not been adequately studied in Asians. In this open-label, 12-week study in seven Asian areas, patients on monotherapy with angiotensin receptor blockers (ARBs) or angiotensin-converting enzyme inhibitors (ACEIs) but not at blood pressure (BP) goal (sitting diastolic BP (SiDBP) <90 mm Hg in non-diabetics and <80 mm Hg in diabetics) were switched to losartan 50 mg/HCTZ 12.5 mg. At 4 and 8 weeks, the therapy for patients not at goal BP was titrated to losartan 100 mg/HCTZ 12.5 mg and to losartan 100 mg/HCTZ 25 mg, respectively. Data analysis included 430 patients with mean (s.d.) age 53.0 (10.1) years and 51.9% of the female gender. After 8 weeks (primary end point; titration up to losartan 100 mg/HCTZ 12.5 mg), 73.5% (95% confidence interval (CI): 69.0-77.6) of patients reached BP goal; 63.4 and 78.1% of patients reached BP goal at 4 weeks (titration up to losartan 50 mg/HCTZ 12.5 mg) and at 12 weeks (titration up to losartan 100 mg/HCTZ 25 mg). The mean changes from baseline (95% CI) in sitting systolic BP and SiDBP at 8 weeks were -16.7 (-18.0 to -15.4) mm Hg and -12.1 (-12.9 to -11.4) mm Hg, respectively. Clinical and laboratory adverse experiences (AEs) were reported in 27.5 and 21.0% of patients, respectively. Nine patients were discontinued because of drug-related clinical AEs. Switching Asian patients currently not at BP goal with ARB or ACEI monotherapy to a losartan/HCTZ combination achieved BP goal in the majority of patients. Losartan/HCTZ combinations were generally well tolerated.

TGF-beta signal transduction in chronic kidney disease.

Transforming growth factor (TGF)-beta is a central stimulus of the events leading to chronic progressive kidney disease, having been implicated in the regulation of cell proliferation, hypertrophy, apoptosis and fibrogenesis. The fact that it mediates these varied events suggests that multiple mechanisms play a role in determining the outcome of TGF-beta signaling. Regulation begins with the availability and activation of TGF-beta and continues through receptor expression and localization, control of the TGF-beta family-specific Smad signaling proteins, and interaction of the Smads with multiple signaling pathways extending into the nucleus. Studies of these mechanisms in kidney cells and in whole-animal experimental models, reviewed here, are beginning to provide insight into the role of TGF-beta in the pathogenesis of renal dysfunction and its potential treatment.

New techniques for assessment of vascular function.

The noninvasive measurement of hemodynamic variables associated with hypertension and cardiovascular disease processes needs to be recognized as a viable adjunct to clinical practice. This review traces the history of the inception and development of noninvasive measurement of hemodynamic variable. It then identifies well established, useful, and available devices, and then notes clinical studies verifying the clinical relevance of these measurements. Given the need to intervene earlier in the course of cardiovascular disease processes, tools are needed to assist the medical team to evaluate, prognosticate, and guide their patient's therapy correctly. It is the goal of this review to heighten the awareness and enhance and encourage the implementation of these devices in our armamentarium for the betterment of our patient's health.

Reversal of vascular hypertrophy in hypertensive patients through blockade of angiotensin II receptors.

Angiotensin II (Ang II) has been linked to vascular dysfunction and target-organ damage. Blockade of the angiotensin II type 1 receptor (AT(1)) with an angiotensin receptor blocker may reverse vascular pathology independent of blood pressure (BP) lowering. Stage I hypertensive, nondiabetic patients (61% male; age 38 to 67 years) were randomized after a 4-week washout period to olmesartan medoxomil 20 to 40 mg or atenolol 50 to 100 mg plus additional agents (hydrochlorothiazide, amlodipine, or hydralazine) as needed for a goal BP <140/90 mm Hg. At baseline and after 1 year of treatment, subcutaneous gluteal resistance arteries were examined on a pressurized myograph to evaluate remodeling. Biopsies were available from 22 atenolol recipients, 27 olmesartan medoxomil recipients, and 11 normal volunteer controls. BP was reduced to a comparable degree by olmesartan medoxomil (from 149 +/- 11/92 +/- 8 mm Hg to 120 +/- 9/77 +/- 6 mm Hg; P < .05 [mean +/- standard deviation]) and atenolol (from 147 +/- 10/90 +/- 6 mm Hg to 125 +/- 12/78 +/- 7 mm Hg; P < .05 [mean +/- standard deviation]) from baseline for each arm (P = .08 for the 40-week treatment mean between arms). After one year's treatment, the wall-to-lumen ratio in arteries from patients treated with olmesartan medoxomil was significantly reduced (from 14.9% to 11.1%; P < .01), whereas no significant change was observed in arteries from atenolol-treated patients (from 16.0% to 15.5%; P = NS); the wall-to-lumen ratio in controls was 11.0%. Blockade of AT(1) receptors showed a superior corrective effect on the altered structure of resistance arteries in essential hypertension that was independent of the magnitude of BP reduction, and resulted in values similar to those in normotensive controls.

The role of noninvasive hemodynamic monitoring in the evaluation and treatment of hypertension.

Advances in the understanding of the mechanisms accounting for the elevation of arterial pressure in essential hypertension suggest that there is value in assessing the relative contribution of hemodynamic factors in tailoring specific therapies to control arterial pressure. The non-invasive method of impedance cardiography (ICG) to measure hemodynamic abnormalities in hypertensive patients has emerged as a valuable adjuvant in the decision-making process of selecting antihypertensive agents. The technique is both accurate and reproducible in delineating the hemodynamic mechanisms of hypertension, comparing age-and gender-related changes in hemodynamics, detecting the presence of left ventricular dysfunction, and demonstrating clinically significant improvement in blood pressure control using ICG-guided therapy.

The protective effects of angiotensin II blockade with olmesartan medoxomil on resistance vessel remodeling (The VIOS study): rationale and baseline characteristics.

BACKGROUND: The VIOS (Vascular Improvement with Olmesartan medoxomil Study) study is a randomized, parallel study to determine the relative effects of suppressing the renin-angiotensin system (RAS) with the angiotensin receptor antagonist olmesartan medoxomil versus suppressing sympathetic drive with the beta-adrenoceptor antagonist atenolol on remodeling of the subcutaneous small resistance vessel. Remodeling of small resistance vessels may be the earliest pathologic finding associated with hypertension. It may predate the onset of clinically apparent hypertension. METHODS: In this study, 100 patients with stage I hypertension are characterized at baseline before being treated for 1 year to obtain a goal BP of less than 140/90 mm Hg as defined by Joint National Committee (JNC)-7. Resistance vessel remodeling is determined using the gluteal fat biopsy technique in the hypertensive patients and a group of normotensive healthy volunteers. Additionally, efforts will be made to define whether noninvasive hemodynamic parameters, retinal vessel measurement changes, or biologic markers may predict and track the underlying vascular morphologic and physiologic changes induced by either regimen during the 12-month treatment period. RESULTS: The primary endpoint will be the degree of vascular remodeling as obtained from percutaneous biopsy of gluteal subcutaneous resistance vessels in each of two treatment arms compared with the normal volunteers. The design of the study and the pertinent baseline characteristics of these patients with uncomplicated essential hypertension are presented. CONCLUSION: The suppression of the RAS by the blockade of angiotensin II type 1 (AT(1)) receptors may demonstrate remodeling effects on the ubiquitous small resistance vessels similar to that seen in the myocardium and renal glomeruli, thus affording more complete end-organ protection.

Cost-effectiveness of impedance cardiography testing in uncontrolled hypertension.

To evaluate the short- and long-term cost-effectiveness of impedance cardiography (ICG) testing in uncontrolled hypertensives, we analyzed the Consideration of Noninvasive Hemodynamic Monitoring to Target Reduction of Blood Pressure Levels (CONTROL) trial results that compared the blood pressure-lowering effects of standard vs ICG care. Short-term cost-effectiveness was evaluated as the incremental cost per incremental mm Hg reduced during the trial. Long-term cost-effectiveness was evaluated as incremental cost per quality-adjusted life-year gained over 10 years. ICG care short-term cost-effectiveness was 20 US dollar per incremental mm Hg reduced for systolic blood pressure (vs standard care, 36 US dollar per mm Hg reduced) and 23 US dollar per incremental mm Hg reduced for diastolic blood pressure (vs standard care, 79 US dollar per mm Hg reduced). In the long term, ICG resulted in a 476 US dollar cost savings and 0.109 quality-adjusted life-years gained per patient (-4,371 US dollar per quality-adjusted life-year gained, sensitivity analysis -8,764 to 13,163 US dollar). The use of ICG testing to reduce blood pressure in uncontrolled hypertensive patients is cost-effective from both a short- and long-term perspective.

Value of noninvasive hemodynamics to achieve blood pressure control in hypertensive subjects.

Abnormal hemodynamics play a central role in the development and perpetuation of high blood pressure. We hypothesized that hypertension therapy guided by noninvasive hemodynamics with impedance cardiography could aid primary care physicians in reducing blood pressure more effectively. Uncontrolled hypertensive patients on 1 to 3 medications were randomized by 3:2 ratio to either a standard arm or hemodynamic arm that used impedance cardiography (BioZ, CardioDynamics). Each patient completed 5 study visits with a 2-week washout period followed by 3 months of treatment. A total of 164 patients from 11 centers completed the study, 95 in the standard arm and 69 in the hemodynamic arm. At baseline and after washout, there were no differences between arms in number of medications or demographic, blood pressure, or hemodynamic characteristics. Systolic blood pressure reductions in the hemodynamic arm were greater from baseline (19 mm Hg versus 11 mm Hg; P<0.01) and after washout (25 mm Hg versus 19 mm Hg; P<0.05). Diastolic blood pressure reductions were also greater in the hemodynamic arm from baseline (12 mm Hg versus 5 mm Hg; P<0.001) and after washout (17 mm Hg versus 10 mm Hg; P<0.001). The hemodynamic arm achieved goal blood pressure (<140/90 mm Hg) more frequently (77% versus 57%; P<0.01) and a more aggressive blood pressure level (<130/85 mm Hg) more frequently (55% versus 27%; P<0.0001). These study results indicate that antihypertensive therapy guided by impedance cardiography in uncontrolled hypertensive patients on >/=1 medications is more effective than standard care.