Arabidopsis TCH4, regulated by hormones and the environment, encodes a xyloglucan endotransglycosylase.

Adaptation of plants to environmental conditions requires that sensing of external stimuli be linked to mechanisms of morphogenesis. The Arabidopsis TCH (for touch) genes are rapidly upregulated in expression in response to environmental stimuli, but a connection between this molecular response and developmental alterations has not been established. We identified TCH4 as a xyloglucan endotransglycosylase by sequence similarity and enzyme activity. Xyloglucan endotransglycosylases most likely modify cell walls, a fundamental determinant of plant form. We determined that TCH4 expression is regulated by auxin and brassinosteroids, by environmental stimuli, and during development, by a 1-kb region. Expression was restricted to expanding tissues and organs that undergo cell wall modification. Regulation of genes encoding cell wall-modifying enzymes, such as TCH4, may underlie plant morphogenetic responses to the environment.     

Immunohistochemistry in the evaluation of neovascularization in tumor xenografts

Angiogenesis, or neovascularization, is known to play an important role in the neoplastic progression leading to metastasis. CD31 or Factor VIII-related antigen (F VIII RAg) immunohistochemistry is widely used in experimental studies for quantifying tumor neovascularization in immunocompromised animal models implanted with transformed human cell lines. Quantification, however, can be affected by variations in the methodology used to measure vascularization including antibody selection, antigen retrieval (AR) pretreatment, and evaluation techniques. To examine this further, we investigated the microvessel density (MVD) and the intensity of microvascular staining among five different human tumor xenografts and a mouse syngeneic tumor using anti-CD31 and F VIII RAg immunohistochemical staining. Different AR methods also were evaluated. Maximal retrieval of CD31 was achieved using 0.5 M Tris (pH 10) buffer, while maximum retrieval of F VIII RAg was achieved using 0.05% pepsin treatment of tissue sections. For each optimized retrieval condition, anti-CD31 highlighted small vessels better than F VIII RAg. Furthermore, the MVD of CD31 was significantly greater than that of F VIII RAg decorated vessels (p<0.001). The choice of antibody and AR method has a significant affect on immunohistochemical findings when studying angiogenesis. One also must use caution when comparing studies in the literature that use different techniques and reagents.     

Repolarization reserve determines drug responses in human pluripotent stem cell derived cardiomyocytes

Unexpected induction of arrhythmias in the heart is still one of the major risks of new drugs despite recent improvements in cardiac safety assays. Here we address this in a novel emerging assay system. Eleven reference compounds were administrated to spontaneously beating clusters of cardiomyocytes from human pluripotent stem cells (hPSC-CM) and the responses determined using multi-electrode arrays. Nine showed clear dose-dependence effects on field potential (FP) duration. Of these, the Ca^2 + channel blockers caused profound shortening of action potentials, whereas the classical hERG blockers, like dofetilide and d,l-sotalol, induced prolongation, as expected.Unexpectedly, two potent blockers of the slow component of the delayed rectifier potassium current (I_Ks), HMR1556 and JNJ303, had only minor effects on the extracellular FP of wild-type hPSC-CM despite evidence of functional I_Ks channels. These compounds were therefore re-evaluated under conditions that mimicked reduced “repolarization reserve,” a parameter reflecting the capacity of cardiomyocytes to repolarize and a strong risk factor for the development of ventricular arrhythmias. Strikingly, in both pharmacological and genetic models of diminished repolarization reserve, HMR1556 and JNJ03 strongly increased the FP duration. These profound effects indicate that I_Ks plays an important role in limiting action potential prolongation when repolarization reserve is attenuated. The findings have important clinical implications and indicate that enhanced sensitization to repolarization-prolonging compounds through pharmacotherapy or genetic predisposition should be taken into account when assessing drug safety.     

Intestinal Epithelial Cell-Intrinsic Deletion of Setd7 Identifies Role for Developmental Pathways in Immunity to Helminth Infection

The intestine is a common site for a variety of pathogenic infections. Helminth infections continue to be major causes of disease worldwide, and are a significant burden on health care systems. Lysine methyltransferases are part of a family of novel attractive targets for drug discovery. SETD7 is a member of the Suppressor of variegation 3-9-Enhancer of zeste-Trithorax (SET) domain-containing family of lysine methyltransferases, and has been shown to methylate and alter the function of a wide variety of proteins in vitro. A few of these putative methylation targets have been shown to be important in resistance against pathogens. We therefore sought to study the role of SETD7 during parasitic infections. We find that Setd7 ^-/- mice display increased resistance to infection with the helminth Trichuris muris but not Heligmosomoides polygyrus bakeri. Resistance to T. muris relies on an appropriate type 2 immune response that in turn prompts intestinal epithelial cells (IECs) to alter differentiation and proliferation kinetics. Here we show that SETD7 does not affect immune cell responses during infection. Instead, we found that IEC-specific deletion of Setd7 renders mice resistant to T. muris by controlling IEC turnover, an important aspect of anti-helminth immune responses. We further show that SETD7 controls IEC turnover by modulating developmental signaling pathways such as Hippo/YAP and Wnt/β-Catenin. We show that the Hippo pathway specifically is relevant during T. muris infection as verteporfin (a YAP inhibitor) treated mice became susceptible to T. muris. We conclude that SETD7 plays an important role in IEC biology during infection.     

Dietary input of microbes and host genetic variation shape among-population differences in stickleback gut microbiota

To explain differences in gut microbial communities we must determine how processes regulating microbial community assembly (colonization, persistence) differ among hosts and affect microbiota composition. We surveyed the gut microbiota of threespine stickleback (Gasterosteus aculeatus) from 10 geographically clustered populations and sequenced environmental samples to track potential colonizing microbes and quantify the effects of host environment and genotype. Gut microbiota composition and diversity varied among populations. These among-population differences were associated with multiple covarying ecological variables: habitat type (lake, stream, estuary), lake geomorphology and food- (but not water-) associated microbiota. Fish genotype also covaried with gut microbiota composition; more genetically divergent populations exhibited more divergent gut microbiota. Our results suggest that population level differences in stickleback gut microbiota may depend more on internal sorting processes (host genotype) than on colonization processes (transient environmental effects).     

Relation between Red Cell Distribution Width and Fibroblast Growth Factor 23 Cleaving in Patients with Chronic Kidney Disease and Heart Failure

Objective

In chronic kidney disease (CKD), both anemia and deregulated phosphate metabolism are common and predictive of adverse outcome. Previous studies suggest that iron status influences phosphate metabolism by modulating proteolytic cleavage of FGF23 into C-terminal fragments. Red cell distribution width (RDW) was recently identified as a strong prognostic determinant for cardiovascular morbidity and mortality, independently of iron status. We assessed whether RDW is associated with FGF23 cleaving in CKD patients with heart failure.

Materials and Methods

The associations between RDW and either intact FGF23 (iFGF23), C-terminal FGF23 (cFGF23, reflecting iFGF23 and C-terminal fragments together) and the iFGF23/cFGF23 ratio were analyzed in 52 patients with CKD (eGFR 34,9 ± 13.9 ml/min/1.73m²) and chronic heart failure (CHF). Associations between RDW and FGF23 forms were studied by linear regression analysis adjusted for parameters of renal function, iron metabolism, phosphate metabolism and inflammation.

Results

Median cFGF23 levels were 197.5 [110–408.5] RU/ml, median iFGF23 levels were 107.3 [65.1–162.2] pg/ml and median FGF23 ratio was 0.80 [0.37–0.86]. Mean RDW was 14.1 ± 1.2%. cFGF23 and RDW were associated (β = 1.63x10^-3, P <0.001), whereas iFGF23 and RDW were not (β = -1.38x10^-3, P = 0.336). The iFGF23/cFGF23 ratio was inversely associated with RDW. The difference between cFGF23 and iFGF23 (cFGF23- iFGF23) was positively associated with RDW (β = 1.74x10^-3, P< 0.001). The association between cFGF23 and RDW persisted upon multivariable linear regression analysis, adjusted for parameters of renal function, phosphate metabolism, iron metabolism and inflammation (β = 0.97x10^-3, P = 0.047).

Conclusion

RDW is associated with cFGF23 but not with iFGF23 levels in patients with CKD and CHF. This suggests a connection between RDW and FGF23 catabolism, independent of iron status and inflammation. Future studies are needed to unravel underlying mechanisms and whether these pertain to the link between RDW and outcome.     

Rupture of right coronary sinus of Valsalva aneurysm into right ventricle

A sinus of Valsalva aneurysm is a rare cardiac anomaly that may be congenital or acquired; a coexisting cardiac lesion might be present. If the aneurysm ruptures, it causes acute symptoms of dyspnoea. Echocardiography and cardiac magnetic resonance imaging are useful for diagnosis. The treatment of choice is surgery. We present a case of a patient with acute onset of symptoms due to a ruptured sinus of Valsalva aneurysm. (Neth Heart J 2010;18:209-11)     

Aortic aneurysm formation following coarctation repair by Dacron patch aortoplasty

We describe the finding of an aortic aneurysm in an asymptomatic 43-year-old male, who was managed by Dacron patch aortoplasty for native coarctation of the aorta 25 years before. The role of magnetic resonance angiography as standard imaging technique in lifelong postoperative surveillance is discussed subsequently. (Neth Heart J 2010;18:376-7.)