Association of Altered Collagen Content and Lysyl Oxidase Expression in Degenerative Mitral Valve Disease

Background—Collagen cross-linking is mediated by lysyl oxidase (LOX) enzyme in the extracellular matrix (ECM) of mitral valve leaflets. Alterations in collagen content and LOX protein expression in the ECM of degenerative mitral valve may enhance leaflet expansion and disease severity. Methods—Twenty posterior degenerative mitral valve leaflets from patients with severe mitral regurgitation were obtained at surgery. Five normal posterior mitral valve leaflets procured during autopsy served as controls. Valvular interstitial cells (VICs) density was quantified by immunohistochemistry, collagen types I and III by picro-sirius red staining and immunohistochemistry, and proteoglycans by alcian blue staining. Protein expression of LOX and its mediator TGFβ1 were quantified by immunofluorescence and gene expression by PCR. Results—VICs density was increased, structural type I collagen density was reduced, while reparative type III collagen and proteoglycan densities were increased (p \u3c 0.0001) with an increase in spongiosa layer thickness in myxomatous valves. These changes were associated with a reduction in LOX (p \u3c 0.0001) and increase in TGFβ1 protein expression (p \u3c 0.0001). However, no significant change was seen in gene expression. Linear regression analysis identified a correlation between type I collagen density and LOX grade (R2 = 0.855; p \u3c 0.0001). Conclusions—Reduced type I collagen density with a simultaneous increase in type III collagen and proteoglycan densities possibly contributes to spongiosa layer expansion resulting in incompetent mitral valve leaflets. Observed changes in type I and III collagen densities in DMVD may be secondary to alterations in LOX protein expression, contributing to disorganization of ECM and disease severity

Muscle-directed gene therapy corrects Pompe disease and uncovers species-specific GAA immunogenicity

Pompe disease is a severe disorder caused by loss of acid α-glucosidase (GAA), leading to glycogen accumulation in tissues and neuromuscular and cardiac dysfunction. Enzyme replacement therapy is the only available treatment. AT845 is an adeno-associated viral vector designed to express human GAA specifically in skeletal muscle and heart. Systemic administration of AT845 in Gaa−/− mice led to a dose-dependent increase in GAA activity, glycogen clearance in muscles and heart, and functional improvement. AT845 was tolerated in cynomolgus macaques at low doses, while high doses caused anti-GAA immune response, inflammation, and cardiac abnormalities resulting in unscheduled euthanasia of two animals. Conversely, a vector expressing the macaque GAA caused no detectable pathology, indicating that the toxicity observed with AT845 was an anti-GAA xenogeneic immune response. Western blot analysis showed abnormal processing of human GAA in cynomolgus muscle, adding to the species-specific effects of enzyme expression. Overall, these studies show that AAV-mediated GAA delivery to muscle is efficacious in Gaa−/− mice and highlight limitations in predicting the toxicity of AAV vectors encoding human proteins in non-human species

Unscrambling confounded effects of sowing date trials to screen for crop adaptation to high temperature

Against the backdrop of climate change, genotypes with improved adaptation to elevated temperature are required; reliable screening methods are therefore important. Sowing date experiments are a practical and in expensive approach for comparison of large collections of lines. Late-sown crops usually experience hotter conditions and phenotypes thus partially capture this environmental influence. Two sets of confounded factors, however, limit the value of sowing date trials. First, daily mean temperature correlates with both minimum and maximum temperature, photoperiod, radiation and vapour pressure deficit, and it may also correlate with rainfall. Second, temperature alters the genotype-dependent phen-ology of crops, effectively shifting the timing and duration of critical periods against the background of temperature and other environmental variables.Here we advance a crop-level framework to unscramble the confounded effects of sowing date experiments; it is based on four physiological concepts: (1) annual crops accommodate environmen-tal variation through seed number rather than seed size; (2) seed number is most responsive to the environment in species-specific critical windows; (3) non-stressful thermal effects affecting seed set through development and canopy size can be integrated in a photothermal quotient relating intercepted photosynthetically active radiation (PAR) and mean temperature during the critical window; (4) stressful temperature reduces yield by disrupting reproduction.The framework was tested in a factorial experiment combining four chickpea varieties with puta-tively contrasting adaptation to thermal stress and five environments resulting from the combination of seasons and sowing dates. Yield ranged from 13 to 577 g m−2. Shifts in phenology led to contrasting photothermal conditions in the critical window between flowering and 400◦C d after flowering that were specific for each variety–environment combination. The photothermal quotient ranged from 2.72to 6.85 MJ m−2 ◦C−1; it explained 50% of the variation in yield and maximum temperature explained 32% of the remaining variation. Thus, half of the variation in yield was associated with developmental,non-stressful thermal effect and (at most) 16% of the variation was attributable to thermal stress. Thephotothermal quotient corrected by vapour pressure deficit accounted for by 75% of the variation in yieldand provided further insight on photosynthesis-mediated responses to temperature.Crop adaptation to non-stressful, developmental thermal effects and stressful temperatures disrupting reproduction involve different physiological processes and requires partially different agronomic and breeding solutions. Our analytical approach partially separates these effects, adds value to sowing datetrials, and is likely to return more robust rankings of varietie

Genotypic variation in soil water use and root distribution and their implications for drought tolerance in chickpea

Chickpeas are often grown under receding soil moisture and suffer ~50% yield losses due to drought stress. The timing of soil water use is considered critical for the efficient use of water under drought and to reduce yield losses. Therefore the root growth and the soil water uptake of 12 chickpea genotypes known for contrasts in drought and rooting response were monitored throughout the growth period both under drought and optimal irrigation. Root distribution reduced in the surface and increased in the deep soil layers below 30 cm in response to drought. Soil water uptake was the maximum at 45–60 cm soil depth under drought whereas it was the maximum at shallower (15–30 and 30–45 cm) soil depths when irrigated. The total water uptake under drought was 1-fold less than optimal irrigation. The amount of water left unused remained the same across watering regimes. All the drought sensitive chickpea genotypes were inferior in root distribution and soil water uptake but the timing of water uptake varied among drought tolerant genotypes. Superiority in water uptake in most stages and the total water use determined the best adaptation. The water use at 15–30 cm soil depth ensured greater uptake from lower depths and the soil water use from 90–120 cm soil was critical for best drought adaptation. Root length density and the soil water uptake across soil depths were closely associated except at the surface or the ultimate soil depths of root presence

Root traits confer grain yield advantages under terminal drought in chickpea (Cicer arietinum L.)

Chickpea, the second most important legume crop, suffers major yield losses by terminal drought stress (DS). Stronger root system is known to enhance drought yields but this understanding remains controversial. To understand precisely the root traits contribution towards yield, 12 chickpea genotypes with well-known drought response were field evaluated under drought and optimal irrigation. Root traits, such as root length density (RLD), total root dry weight (RDW), deep root dry weight (deep RDW) and root:shoot ratio (RSR), were measured periodically by soil coring up to 1.2 m soil depth across drought treatments. Large variations were observed for RLD, RDW, deep RDW and RSR in both the drought treatments. DS increased RLD below 30 cm soil depth, deep RDW, RSR but decreased the root diameter. DS increased the genetic variation in RDW more at the penultimate soil depths. Genetic variation under drought was the widest for RLD ∼50 DAS, for deep RDW ∼50–75 DAS and for RSR at 35 DAS. Genotypes ICC 4958, ICC 8261, Annigeri, ICC 14799, ICC 283 and ICC 867 at vegetative stage and genotypes ICC 14778, ICCV 10, ICC 3325, ICC 14799 and ICC 1882 at the reproductive phase produced greater RLD. Path- and correlation coefficients revealed strong positive contributions of RLD after 45 DAS, deep RDW at vicinity of maturity and RSR at early podfill stages to yield under drought. Breeding for the best combination of profuse RLD at surface soil depths, and RDW at deeper soil layers, was proposed to be the best selection strategy, for an efficient water use and an enhanced terminal drought tolerance in chickpea