DNA Methylation and Intra-Clonal Heterogeneity: The Chronic Myeloid Leukemia Model.

Chronic Myeloid Leukemia (CML) is a model to investigate the impact of tumor intra-clonal heterogeneity in personalized medicine. Indeed, tyrosine kinase inhibitors (TKIs) target the BCR-ABL fusion protein, which is considered the major CML driver. TKI use has highlighted the existence of intra-clonal heterogeneity, as indicated by the persistence of a minority subclone for several years despite the presence of the target fusion protein in all cells. Epigenetic modifications could partly explain this heterogeneity. This review summarizes the results of DNA methylation studies in CML. Next-generation sequencing technologies allowed for moving from single-gene to genome-wide analyses showing that methylation abnormalities are much more widespread in CML cells. These data showed that global hypomethylation is associated with hypermethylation of specific sites already at diagnosis in the early phase of CML. The BCR-ABL-independence of some methylation profile alterations and the recent demonstration of the initial intra-clonal DNA methylation heterogeneity suggests that some DNA methylation alterations may be biomarkers of TKI sensitivity/resistance and of disease progression risk. These results also open perspectives for understanding the epigenetic/genetic background of CML predisposition and for developing new therapeutic strategies.

Fine monitoring of major phenolic compounds in lettuce and escarole leaves during storage.

Two varieties of lettuce (Lactuca sativa L. var. crispa and capitata) and one variety of escarole (Cichorium endivia var. latifolium) were chosen due to their different browning sensitivity during storage as minimally processed products. The changes in the compositions and contents of the primary polyphenolic compounds were investigated during the first few hours of storage and then after 1, 2, 3, and 6 days of storage at 6°C and revealed sharp variations. Browning development, activity of phenylalanine ammonia lyase, and concentration of ascorbic acid were also examined during storage. The content of chicoric acid, which was the most abundant phenolic compound, varied substantially during the first 24 hr of storage and between the different varieties. Oak leaf lettuce, which was the most sensitive variety to browning, was characterized by a higher maintained chicoric acid level with a constant decreased chlorogenic acid level during the storage period. PRACTICAL APPLICATIONS: Browning development is responsible for the short shelf life of minimally processed vegetables, such as lettuce (Lactuca sativa). Polyphenolic compounds, as substrates of enzymatic reactions, are involved in the browning susceptibility of leaves. Comparisons of the profiles and contents of these compounds in different leaves showed dramatic variations during storage. This study provides additional information to better control, optimize minimally processed produce and select more suitable leaves for the fresh-cut industry.

Alternation of light/dark period priming enhances clomazone tolerance by increasing the levels of ascorbate and phenolic compounds and ROS detoxification in tobacco (Nicotiana tabacum L.) plantlets.

The effect of the alternation of light/dark periods (AL) (16/8 min light/dark cycles and a photosynthetic photon flux density (PPFD) of 50 µmol photons m(-2) s(-1) for three days) to clarify the mechanisms involved in the clomazone tolerance of tobacco plantlets primed with AL was studied. Clomazone decreased PSII activity, the net photosynthetic rate (Pn), and the ascorbate and total polyphenol contents and increased H2O2 and starch grain accumulation and the number of the cells that underwent programmed cell death (PCD). The pretreatment with AL reduced the inhibitory effect of clomazone on the PSII activity and photosynthesis, as indicated by the decreases in the H2O2 and starch grain accumulation and the PCD levels, and increased the content of ascorbate and certain phenolic compounds, such as chlorogenic acid, neochlorogenic acid and rutin. The AL treatment could promote photorespiration via post-illumination burst (PIB) effects. This alternative photorespiratory electron pathway may reduce H2O2 generation via the consumption of photochemical energy, such as NADH+H(+). At 10 days (D10) of AL treatment, this process induced moderate stress which stimulates H2O2 detoxification systems by increasing the activity of antioxidant enzymes and the biosynthesis of antioxidant components. Therefore, the PCD levels provoked by clomazone were noticeably decreased.

Tolerance to clomazone herbicide is linked to the state of LHC, PQ-pool and ROS detoxification in tobacco (Nicotiana tabacum L.).

In this study, plantlets of two tobacco (Nicotiana tabacum L.) varieties that are clomazone-tolerant (cv. Xanthi) and clomazone-sensitive (cv. Virginie vk51) were subjected to low concentration of clomazone herbicide. The oxygen-evolving rate of isolated chloroplasts, chlorophyll a fluorescence transients, JIP-test responses, hydrogen peroxide contents, antioxidant enzyme activities, cytohistological results and photosynthetic pigment contents were recorded. The results indicated that the carotenoid content was 2-fold higher in Virginie, which had greater clomazone sensitivity than Xanthi. Virginie exhibited noticeable decreases in the LHC content (Chl a/b ratio), the maximum photochemical quantum efficiency of PSII (Fv/Fm), the performance index on the absorption basis (PIabs), and the electron flux beyond the first PSII QA evaluated as (1-VJ) with VJ=(FJ-F0)/(Fm-F0) as well as increases in the rate of photon absorption (ABS/RC) and the energy dissipation as heat (DI0/RC). These results suggest that PSII photoinhibition occurred as a consequence of more reduced PQ-pool and accumulated QA(-). The oxygen evolution measurements indicate that PSI electron transport activity was not affected by clomazone. The more significant accumulation of H2O2 in Virginie compared to Xanthi was due to the absence of ROS-scavenging enzymes, and presumably induced programmed cell death (PCD). The symptoms of PCD were observed by cytohistological analysis, which also indicated that the leaf tissues of clomazone-treated Virginie exhibited significant starch accumulation compared to Xanthi. Taken together, these results indicate that the variable tolerance to clomazone observed between Virginie and Xanthi is independent of the carotenoid content and could be related to the state of the LHC, the redox state of the PQ-pool, and the activity of detoxification enzymes.

Response of the physiological parameters of mango fruit (transpiration, water relations and antioxidant system) to its light and temperature environment.

Depending on the position of the fruit in the tree, mango fruit may be exposed to high temperature and intense light conditions that may lead to metabolic and physiological disorders and affect yield and quality. The present study aimed to determine how mango fruit adapted its functioning in terms of fruit water relations, epicarp characteristics and the antioxidant defence system in peel, to environmental conditions. The effect of contrasted temperature and light conditions was evaluated under natural solar radiation and temperature by comparing well-exposed and shaded fruit at three stages of fruit development. The sun-exposed and shaded peels of the two sides of the well-exposed fruit were also compared. Depending on fruit position within the canopy and on the side of a well-exposed fruit, the temperature gradient over a day affected fruit characteristics such as transpiration, as revealed by the water potential gradient as a function of the treatments, and led to a significant decrease in water conductance for well-exposed fruits compared to fruits within the canopy. Changes in cuticle thickness according to fruit position were consistent with those of fruit water conductance. Osmotic potential was also affected by climatic environment and harvest stage. Environmental conditions that induced water stress and greater light exposure, like on the sunny side of well-exposed fruit, increased the hydrogen peroxide, malondialdehyde and total and reduced ascorbate contents, as well as SOD, APX and MDHAR activities, regardless of the maturity stage. The lowest values were measured in the peel of the shaded fruit, that of the shaded side of well-exposed fruit being intermediate. Mango fruits exposed to water-stress-induced conditions during growth adapt their functioning by reducing their transpiration. Moreover, oxidative stress was limited as a consequence of the increase in antioxidant content and enzyme activities. This adaptive response of mango fruit to its climatic environment during growth could affect postharvest behaviour and quality.

The GENOTEND chip: a new tool to analyse gene expression in muscles of beef cattle for beef quality prediction.

BACKGROUND: Previous research programmes have described muscle biochemical traits and gene expression levels associated with beef tenderness. One of our results concerning the DNAJA1 gene (an Hsp40) was patented. This study aims to confirm the relationships previously identified between two gene families (heat shock proteins and energy metabolism) and beef quality. RESULTS: We developed an Agilent chip with specific probes for bovine muscular genes. More than 3000 genes involved in muscle biology or meat quality were selected from genetic, proteomic or transcriptomic studies, or from scientific publications. As far as possible, several probes were used for each gene (e.g. 17 probes for DNAJA1). RNA from Longissimus thoracis muscle samples was hybridised on the chips. Muscles samples were from four groups of Charolais cattle: two groups of young bulls and two groups of steers slaughtered in two different years. Principal component analysis, simple correlation of gene expression levels with tenderness scores, and then multiple regression analysis provided the means to detect the genes within two families (heat shock proteins and energy metabolism) which were the most associated with beef tenderness. For the 25 Charolais young bulls slaughtered in year 1, expression levels of DNAJA1 and other genes of the HSP family were related to the initial or overall beef tenderness. Similarly, expression levels of genes involved in fat or energy metabolism were related with the initial or overall beef tenderness but in the year 1 and year 2 groups of young bulls only. Generally, the genes individually correlated with tenderness are not consistent across genders and years indicating the strong influence of rearing conditions on muscle characteristics related to beef quality. However, a group of HSP genes, which explained about 40% of the variability in tenderness in the group of 25 young bulls slaughtered in year 1 (considered as the reference group), was validated in the groups of 30 Charolais young bulls slaughtered in year 2, and in the 21 Charolais steers slaughtered in year 1, but not in the group of 19 steers slaughtered in year 2 which differ from the reference group by two factors (gender and year). When the first three groups of animals were analysed together, this subset of genes explained a 4-fold higher proportion of the variability in tenderness than muscle biochemical traits. CONCLUSION: This study underlined the relevance of the GENOTEND chip to identify markers of beef quality, mainly by confirming previous results and by detecting other genes of the heat shock family as potential markers of beef quality. However, it was not always possible to extrapolate the relevance of these markers to all animal groups which differ by several factors (such as gender or environmental conditions of production) from the initial population of reference in which these markers were identified.

Use of gene expression profiles of peripheral blood lymphocytes to distinguish BRCA1 mutation carriers in high risk breast cancer families.

Mutations in two major genes, BRCA1 and BRCA2, account for up to 30% of families with hereditary breast cancer. Unfortunately, in most families there is little to indicate which gene should be targeted first for mutation screening, which is labor intensive, time consuming and often prohibitively expensive. As BRCA1 is a tumor suppressor gene involved in various cellular processes, heterozygous mutations could deregulate dependent pathways, such as DNA damage response, and disturb transcriptional activity of genes involved in the downstream signaling cascade. We investigated gene expression profiling in peripheral blood lymphocytes to evaluate this strategy for distinguishing BRCA1 mutation carriers from non-carriers. RNA from whole blood samples of 15 BRCA1 mutation carriers and 15 non-carriers from BRCA1 or BRCA2 families were hybridized to Agilent Technologies Whole Human Genome OligoMicroarrays (4 x 44 K multiplex format) containing 41,000 unique human genes and transcripts. Gene expression data were analyzed with Welch's t-tests and submitted to hierarchical clustering (GeneSpring GX software, Agilent Technologies). Statistical analysis revealed a slight tendency for 133 genes to be differentially expressed between BRCA1 mutation carriers and non-carriers. However, hierarchical clustering of these genes did not accurately discriminate BRCA1 mutation carriers from non-carriers. Expression variation for these genes according to BRCA1 mutation status was weak. In summary, microarray profiling of untreated whole blood does not appear to be informative in identifying breast cancer risk due to BRCA1 mutation.

Cooking behavior of rice in relation to kernel physicochemical and structural properties.

A set of 27 rice varieties were evaluated for their morphological grain characteristics (length, width, thickness, thousand kernel weight, TKW), chemical composition (amylose, protein, and ash content) and starch properties (gelatinization temperature and enthalpy, amylose-lipid complex). In addition, cell walls were characterized by the arabinoxylan and beta-glucan contents. A rapid method for determining optimum rice cooking time was developed based on the swelling ratio; a fixed value of 2.55 gave a gelatinization level of 95% assessed by differential scanning calorimetry and translucence testing. Optimum cooking time appears positively correlated with kernel thickness and TKW but also with ash content. Confocal laser and scanning electron microscope observation of uncooked rice grains revealed different structural features (cell size) and fracture behavior: for some cultivars, the fracture showed ruptured cells, whereas for others most cells were intact. These structural differences, which may be linked to pectin content, could partly explain rice kernel cooking behavior.

Metathesis of Alkanes: Evidence for Degenerate Metathesis of Ethane over a Silica-Supported Tantalum Hydride Prepared by Surface Organometallic Chemistry.

The mutual exchange of methyl groups of ethane molecules is catalyzed by a silica-supported tantalum hydride surface complex (see the schematic representation of the transition states). This process, which resembles degenerate olefin metathesis, is five times faster than the productive alkane metathesis.