59 research outputs found
Mistranslation can promote the exploration of alternative evolutionary trajectories in enzyme evolution
Darwinian evolution preferentially follows mutational pathways whose individual steps increase fitness. Alternative pathways with mutational steps that do not increase fitness are less accessible. Here, we show that mistranslation, the erroneous incorporation of amino acids into nascent proteins, can increase the accessibility of such alternative pathways and, ultimately, of high fitness genotypes. We subject populations of the beta-lactamase TEM-1 to directed evolution in Escherichia coli under both low- and high-mistranslation rates, selecting for high activity on the antibiotic cefotaxime. Under low mistranslation rates, different evolving TEM-1 populations ascend the same high cefotaxime-resistance peak, which requires three canonical DNA mutations. In contrast, under high mistranslation rates they ascend three different high cefotaxime-resistance genotypes, which leads to higher genotypic diversity among populations. We experimentally reconstruct the adaptive DNA mutations and the potential evolutionary paths to these high cefotaxime-resistance genotypes. This reconstruction shows that some of the DNA mutations do not change fitness under low mistranslation, but cause a significant increase in fitness under high-mistranslation, which helps increase the accessibility of different high cefotaxime-resistance genotypes. In addition, these mutations form a network of pairwise epistatic interactions that leads to mutually exclusive evolutionary trajectories towards different high cefotaxime-resistance genotypes. Our observations demonstrate that protein mistranslation and the phenotypic mutations it causes can alter the evolutionary exploration of fitness landscapes and reduce the predictability of evolution
Amino acids and antibody N-glycosylation based on Raman spectroscopy in high cell density perfusion culture
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A comparison of the ECMWF forecast model with observations over the annual cycle at SHEBA
A central objective of the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment was
to provide a comprehensive observational test for single-column models of the atmosphere-sea
ice-ocean system over the Arctic Ocean. For single-column modeling, one must specify the
time-varying tendencies due to horizontal and vertical advection of air through the column. Due to
the difficulty of directly measuring these tendencies, it was decided for SHEBA to obtain them
from short-range forecasts of the European Centre for Medium-Range Weather Forecasts (ECMWF)
global forecast model, into which SHEBA rawinsonde and surface synoptic observations
were routinely assimilated. The quality of these forecasts directly affects the reliability of the derived
advective tendencies. In addition, the ECMWF-forecast thermodynamic and cloud fields,
and radiative and turbulent fluxes present an illuminating comparison of the SHEBA observations
with a state-of-the-art global numerical model.
The authors compare SHEBA soundings, cloud and boundary layer observations with the ECMWF
model output throughout the SHEBA year. They find that above the boundary layer, the
model was faithful to the SHEBA rawinsonde observations and maintained a proper long-term balance
between advective and nonadvective tendencies of heat and moisture. This lends credence to
use of the ECMWF-predicted advective tendencies for single-column modeling studies.
The model-derived cloud properties and precipitation (which were not assimilated from observations)
are compared with cloud radar, lidar, microwave radiometer, surface turbulent and radiative
measurements, and basic surface meteorology. The model s slab sea-ice model led to large
surface temperature errors and insufficient synoptic variability of temperature. The overall height
distribution of cloud was fairly well simulated (though somewhat overestimated) in all seasons, as
was precipitation. However, the model clouds typically had a much higher ratio of cloud ice to
cloud water than suggested by lidar depolarization measurements, and a smaller optical depth,
leading to monthly biases of up to 50 W m^(-2) in the monthly surface downwelling longwave and
shortwave radiation. Further biases in net radiation were due to the inaccurate model assumption
of constant surface albedo.
Observed turbulent sensible and latent heat fluxes tended to be small throughout SHEBA. During
high-wind periods during the winter, the ECMWF model predicted sustained downward heat
fluxes of up to 60 W m^(-2), much higher than observed. A detailed comparison suggests that this
error was due to both inadequate resolution of the 31-level model and a deficient parameterization
of sea-ice thermodynamics
ErbB4 regulates the timely progression of late fetal lung development
AbstractThe ErbB4 receptor has an important function in fetal lung maturation. Deletion of ErbB4 leads to alveolar hypoplasia and hyperreactive airways similar to the changes in bronchopulmonary dysplasia (BPD). BPD is a chronic pulmonary disorder affecting premature infants as a consequence of lung immaturity, lung damage, and abnormal repair. We hypothesized that proper ErbB4 function is needed for the timely progression of fetal lung development. An ErbB4 transgenic cardiac rescue mouse model was used to study the effect of ErbB4 deletion on fetal lung structure, surfactant protein (SP) expression, and synthesis, and inflammation. Morphometric analyses revealed a delayed structural development with a significant decrease in saccular size at E18 and more pronounced changes at E17, keeping these lungs in the canalicular stage. SP-B mRNA expression was significantly down regulated at E17 with a subsequent decrease in SP-B protein expression at E18. SP-D protein expression was significantly decreased at E18. Surfactant phospholipid synthesis was significantly decreased on both days, and secretion was down regulated at E18. We conclude that pulmonary ErbB4 deletion results in a structural and functional delay in fetal lung development, indicating a crucial regulatory role of ErbB4 in the timely progression of fetal lung development
Toolbox for efficient development of high cell density perfusion process, integrated with continuous DSP
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Non-perturbative renormalization of three-quark operators
High luminosity accelerators have greatly increased the interest in
semi-exclusive and exclusive reactions involving nucleons. The relevant
theoretical information is contained in the nucleon wavefunction and can be
parametrized by moments of the nucleon distribution amplitudes, which in turn
are linked to matrix elements of local three-quark operators. These can be
calculated from first principles in lattice QCD. Defining an RI-MOM
renormalization scheme, we renormalize three-quark operators corresponding to
low moments non-perturbatively and take special care of the operator mixing.
After performing a scheme matching and a conversion of the renormalization
scale we quote our final results in the MSbar scheme at mu=2 GeV.Comment: 49 pages, 3 figure
Characterization of 8p21.3 chromosomal deletions in B-cell lymphoma: TRAIL-R1 and TRAIL-R2 as candidate dosage-dependent tumor suppressor genes
Deletions of chromosome 8p are a recurrent event in B-cell non-Hodgkin lymphoma (B-NHL), suggesting the presence of a tumor suppressor gene. We have characterized these deletions using comparative genomic hybridization to microarrays, fluorescence in situ hybridization (FISH) mapping, DNA sequencing, and functional studies. A minimal deleted region (MDR) of 600 kb was defined in chromosome 8p21.3, with one mantle cell lymphoma cell line (Z138) exhibiting monoallelic deletion of 650 kb. The MDR extended from bacterial artificial chromosome (BAC) clones RP11-382J24 and RP11-109B10 and included the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) receptor gene loci. Sequence analysis of the individual expressed genes within the MDR and DNA sequencing of the entire MDR in Z138 did not reveal any mutation. Gene expression analysis and quantitative reverse transcriptase-polymerase chain reaction (QRT-PCR) showed down-regulation of TRAIL-R1 and TRAIL-R2 receptor genes as a consistent event in B-NHL with 8p21.3 loss. Epigenetic inactivation was excluded via promoter methylation analysis. In vitro studies showed that TRAIL-induced apoptosis was dependent on TRAIL-R1 and/or -R2 dosage in most tumors. Resistance to apoptosis of cell lines with 8p21.3 deletion was reversed by restoration of TRAIL-R1 or TRAIL-R2 expression by gene transfection. Our data suggest that TRAIL-R1 and TRAIL-R2 act as dosage-dependent tumor suppressor genes whose monoallelic deletion can impair TRAIL-induced apoptosis in B-cell lymphoma
Homozygous deletions localize novel tumor suppressor genes in B-cell lymphomas
Integrative genomic and gene-expression analyses have identified amplified oncogenes in B-cell non-Hodgkin lymphoma (B-NHL), but the capability of such technologies to localize tumor suppressor genes within homozygous deletions remains unexplored. Array-based comparative genomic hybridization (CGH) and gene-expression microarray analysis of 48 cell lines derived from patients with different B-NHLs delineated 20 homozygous deletions at 7 chromosome areas, all of which contained tumor suppressor gene targets. Further investigation revealed that only a fraction of primary biopsies presented inactivation of these genes by point mutation or intragenic deletion, but instead some of them were frequently silenced by epigenetic mechanisms. Notably, the pattern of genetic and epigenetic inactivation differed among B-NHL subtypes. Thus, the P53-inducible PIG7/LITAF was silenced by homozygous deletion in primary mediastinal B-cell lymphoma and by promoter hypermethylation in germinal center lymphoma, the proapoptotic BIM gene presented homozygous deletion in mantle cell lymphoma and promoter hypermethylation in Burkitt lymphoma, the proapoptotic BH3-only NOXA was mutated and preferentially silenced in diffuse large B-cell lymphoma, and INK4c/P18 was silenced by biallelic mutation in mantle-cell lymphoma. Our microarray strategy has identified novel candidate tumor suppressor genes inactivated by genetic and epigenetic mechanisms that substantially vary among the B-NHL subtypes
Denial of long-term issues with agriculture on tropical peatlands will have devastating consequences
Non peer reviewe
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