Analysis of the genetic variation for adaptation to a short thermal stress on young « Bos taurus » cattle

In the present work, an attempt was made to determine the adaptation to heat of some cattle breeds, especially French ones. A total of 582 young male and female cattle, about 14 months old and coming from 41 elementary genetic combinations analyzed in 5 different non bioclimatological experiments, were subjected to a heat stress for 8 hours during which the room temperature was increased from 18°C to 38 °C. The usual reaction were observed i.e. increase in the rectal temperature during the stress (+ 0,54 °C), increase in the respiratory rate ( X 3), increase in the sweating rate, heart rate and skin temperature. The statistical analyses were made at three stages of stress (beginning, middle, end). In all cases, a very strong environmental effect was noticed, ie effect of the year and of experimental errors in the management of the theoretical schedule involving temperature and relative hygrometry. The data adjusted for environmental effects rather clearly show the genetic variability. However, a more accurate analysis shows that it is mainly proceeded from a between group variability when defining the groups according to « animal husbandry » parameters (dairy purpose, beef purpose, and local breed group). As a matter of fact, in most cases, there was no significant variability between the reactions of the genotypes belonging to the same group, whereas this variability existed between the groups..The satisfactory performance of the local breed group clearly appeared in comparison with the group including the improved dairy or beef breeds exhibiting only minor differences in the parameters analyzed. In the discussion, emphasis in laid ov the possible influence of thermogenesis on the results. Although our findings could have been afrected by disturbing events such as emotional stress, they agree rather well with data obtained is practice on the behaviour of the local French breeds in some hot countries.Le but de ce travail est d’essayer de caractériser l’adaptation à la chaleur d’un certain nombre de races bovines, notamment françaises. Pour cela, 582 jeunes bovins, mâles et femelles, d’environ 14 mois et issus de 41 combinaisons génétiques élémentaires analysées dans 5 expérimentations différentes, à objectif non bioclimatologique, sont soumis en chambre chaude, à un stress thermique de 8 heures pendant lequel la température externe a été portée de 11) De 18°C à 38 °C. Les réactions classiques sont observées : augmentation de la température rectale au cours du stress (+ 0,54°C), augmentation du rythme respiratoire ( X 3), augmentation du taux de sudation, du rythme cardiaque, de la température de la peau. Les analyses statistiques sont effectuées à trois stades du stress (début, milieu, fin). Dans tous les cas, on note de très forts effets dûs au milieu : effet de l’année et des erreurs expérimentales dans la conduite du protocole théorique, concernant la température et l’hygrométrie relative. Sur les données ajustées pour les effets de milieu, la variabilité génétique apparaît assez clairement. Cependant une analyse plus fine montre qu’elle provient essentiellement d’une variabilité inter groupe en définissant le groupe d’après des critères « zootechniques » ou «fonctionnels » (groupe à vocation laitière, groupe à vocation bouchère, groupe des races locales). En effet, dans la grande majorité des cas, il n’apparaît pas de variabilité significative entre les réactions des génotypes rangés dans le même groupe, alors qu’elle existe entre les groupes. La bonne performance du groupe des races locales apparaît en comparaison des groupes mettant en oeuvre les races améliorées, laitières ou bouchères, qui diffèrent peu entre eux pour les critères analysés. Dans la discussion, l’accent est mis sur l’incidence probable sur les résultats des phénomènes de thermogénèse. Si nos résultats ont pu être affectés par des phénomènes parasites, notamment ceux de stress émotionnel, il n’en reste pas moins qu’ils concordent assez bien avec l’expérience pratique acquise sur le comportement des races locales françaises dans certains pays chauds

Paramètres génétiques des races Blonde d'Aquitaine, Charolaise et Limousine utilisées en croisement pour la production de veaux de boucherie

International audienc

Possibilités d'amélioration des conditions de vêlage par sélection. II. – Aptitude au vêlage de trois races a viande françaises

International audienc

Evaluation des aptitudes laitières des brebis de race pure ou croisées Romanov

International audienc

Comparaison des races bovines Charolaise, Limousine et Maine-Anjou en race pure et en intercroisement 2. Performances d'engraissement des taurillons purs et F1

Cette étude concerne les performances d’engraissement de 231 taurillons issus d’un schéma de croisement diallèle entre les races Charolaise, Limousine et Maine-Anjou ainsi que de 26 taurillons de race Hereford. Des contrôles de consommation et de croissance sont réalisés entre l’âge de 9 mois et l’abattage à 15 ou 18 mois. Les animaux reçoivent ad libitum un régime composé de luzerne déshydratée (70 %) et de pulpe de betterave (30 %). Entre 9 et 15 mois, les taurillons Charolais ont une croissance supérieure de 155 g/jour à celle des Limousins et inférieure de 108 g/jour à celle des Maine-Anjou. Entre 15 et 18 mois, les écarts de croissance entre races pures sont pratiquement nuls. Les différences de quantités d’aliments ingérés sont plus importantes (13 % entre les races Limousine et Charolaise, 15 % entre la Charolaise et la Maine-Anjou entre 9 et 15 mois). Après 15 mois, la Charolaise se rapproche de la Limousine et s’écarte de la Maine-Anjou. Vis-à-vis de l’efficacité alimentaire, la Limousine est supérieure à la Charolaise, elle-même supérieure à la Maine-Anjou. Les écarts sont faibles entre 9 et 15 mois (2,9 % entre les races Limousine et Charolaise, 6,5 % entre la Charolaise et la Maine-Anjou) mais importants dans la seconde période d’engraissement. L’avantage de la race Limousine est alors de 9 % sur la Charolaise et de 30 % sur la Maine-Anjou. La race Hereford a une consommation proche de celle de la Limousine et une efficacité alimentaire proche de celle de la Maine-Anjou pour les deux périodes d’engraissement. Entre 9 et 15 mois, l’effet d’hétérosis est de 3,3 % sur la vitesse de croissance et de 1,5 % sur l’efficacité alimentaire. Il est négatif après 15 mois.A total of 231 young bulls produced by a diallel cross between Charolais, Limousin and Maine-Anjou breeds as well as 26 Hereford purebreds were fattened from 9 to 15 or 18 months. They were fed ad libitum with dehydrated alfalfa (70 %) and beet root pulp (30 %). Between 9 and 15 months, Charolais had growth rate 155 g/d higher than Limousin and 108 g/d lower than Maine-Anjou. Hereford growth rate was 52 g/d lower than Limousin. From 15 to 18 months, differences in growth rate were negligible among Limousin, Charolais and Maine-Anjou but all were 202 to 232 g/d above Hereford. Daily feed intake differences were higher (13 % between Limousin and Charolais, 15 % between Charolais and Maine-Anjou from 9 to 15 months). After 15 months, Charolais was nearer to Limousin and farther from Maine-Anjou. Limousin exhibited higher feed efficiency than Charolais, which was better than Maine-Anjou. Feed efficiency differences were small between 9 and 15 months (2.9 % between Limousin and Charolais, 6.5 % between Charolais and Maine-Anjou) but larger during the second fattening period. Then, the Limousin’s advantage was 9 % over Charolais and 30 % over Maine-Anjou. During the two fattening periods, Hereford was close to Limousin for feed intake and to Maine-Anjou for feed efficiency. Between 9 and 15 months, heterosis effect was 3.3 % for growth rate and 1.5 % for feed efficiency. Heterosis in these two traits was negative after 15 months

Preservation of large-scale chromatin structure in FISH experiments

The nuclear organization of specific endogenous chromatin regions can be investigated only by fluorescence in situ hybridization (FISH). One of the two fixation procedures is typically applied: (1) buffered formaldehyde or (2) hypotonic shock with methanol acetic acid fixation followed by dropping of nuclei on glass slides and air drying. In this study, we compared the effects of these two procedures and some variations on nuclear morphology and on FISH signals. We analyzed mouse erythroleukemia and mouse embryonic stem cells because their clusters of subcentromeric heterochromatin provide an easy means to assess preservation of chromatin. Qualitative and quantitative analyses revealed that formaldehyde fixation provided good preservation of large-scale chromatin structures, while classical methanol acetic acid fixation after hypotonic treatment severely impaired nuclear shape and led to disruption of chromosome territories, heterochromatin structures, and large transgene arrays. Our data show that such preparations do not faithfully reflect in vivo nuclear architecture. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00412-006-0084-2 and is accessible for authorized users

A Gammaherpesviral Internal Repeat Contributes to Latency Amplification

BACKGROUND: Gammaherpesviruses cause important infections of humans, in particular in immunocompromised patients. The genomes of gammaherpesviruses contain variable numbers of internal repeats whose precise role for in vivo pathogenesis is not well understood. METHODOLOGY/PRINCIPAL FINDINGS: We used infection of laboratory mice with murine gammaherpesvirus 68 (MHV-68) to explore the biological role of the 40 bp internal repeat of MHV-68. We constructed several mutant viruses partially or completely lacking this repeat. Both in vitro and in vivo, the loss of the repeat did not substantially affect lytic replication of the mutant viruses. However, the extent of splenomegaly, which is associated with the establishment of latency, and the number of ex vivo reactivating and genome positive splenocytes were reduced. Since the 40 bp repeat is part of the hypothetical open reading frame (ORF) M6, it might function as part of M6 or as an independent structure. To differentiate between these two possibilities, we constructed an N-terminal M6STOP mutant, leaving the repeat structure intact but rendering ORF M6 unfunctional. Disruption of ORF M6 did neither affect lytic nor latent infection. In contrast to the situation in lytically infected NIH3T3 cells, the expression of the latency-associated genes K3 and ORF72 was reduced in the latently infected murine B cell line Ag8 in the absence of the 40 bp repeat. CONCLUSIONS/SIGNIFICANCE: These data suggest that the 40 bp repeat contributes to latency amplification and might be involved in the regulation of viral gene expression

AID-Targeting and Hypermutation of Non-Immunoglobulin Genes Does Not Correlate with Proximity to Immunoglobulin Genes in Germinal Center B Cells

Upon activation, B cells divide, form a germinal center, and express the activation induced deaminase (AID), an enzyme that triggers somatic hypermutation of the variable regions of immunoglobulin (Ig) loci. Recent evidence indicates that at least 25% of expressed genes in germinal center B cells are mutated or deaminated by AID. One of the most deaminated genes, c-Myc, frequently appears as a translocation partner with the Ig heavy chain gene (Igh) in mouse plasmacytomas and human Burkitt's lymphomas. This indicates that the two genes or their double-strand break ends come into close proximity at a biologically relevant frequency. However, the proximity of c-Myc and Igh has never been measured in germinal center B cells, where many such translocations are thought to occur. We hypothesized that in germinal center B cells, not only is c-Myc near Igh, but other mutating non-Ig genes are deaminated by AID because they are near Ig genes, the primary targets of AID. We tested this “collateral damage” model using 3D-fluorescence in situ hybridization (3D-FISH) to measure the distance from non-Ig genes to Ig genes in germinal center B cells. We also made mice transgenic for human MYC and measured expression and mutation of the transgenes. We found that there is no correlation between proximity to Ig genes and levels of AID targeting or gene mutation, and that c-Myc was not closer to Igh than were other non-Ig genes. In addition, the human MYC transgenes did not accumulate mutations and were not deaminated by AID. We conclude that proximity to Ig loci is unlikely to be a major determinant of AID targeting or mutation of non-Ig genes, and that the MYC transgenes are either missing important regulatory elements that allow mutation or are unable to mutate because their new nuclear position is not conducive to AID deamination

Stable transmission of reversible modifications: maintenance of epigenetic information through the cell cycle

Even though every cell in a multicellular organism contains the same genes, the differing spatiotemporal expression of these genes determines the eventual phenotype of a cell. This means that each cell type contains a specific epigenetic program that needs to be replicated through cell divisions, along with the genome, in order to maintain cell identity. The stable inheritance of these programs throughout the cell cycle relies on several epigenetic mechanisms. In this review, DNA methylation and histone methylation by specific histone lysine methyltransferases (KMT) and the Polycomb/Trithorax proteins are considered as the primary mediators of epigenetic inheritance. In addition, non-coding RNAs and nuclear organization are implicated in the stable transfer of epigenetic information. Although most epigenetic modifications are reversible in nature, they can be stably maintained by self-recruitment of modifying protein complexes or maintenance of these complexes or structures through the cell cycle