Meiotic Recombination Analyses in Pigs Carrying Different Balanced Structural Chromosomal Rearrangements

Correct pairing, synapsis and recombination between homologous chromosomes are essential for normal meiosis. All these events are strongly regulated, and our knowledge of the mechanisms involved in this regulation is increasing rapidly. Chromosomal rearrangements are known to disturb these processes. In the present paper, synapsis and recombination (number and distribution of MLH1 foci) were studied in three boars (Sus scrofa domestica) carrying different chromosomal rearrangements. One (T34he) was heterozygote for the t(3;4)(p1.3;q1.5) reciprocal translocation, one (T34ho) was homozygote for that translocation, while the third (T34Inv) was heterozygote for both the translocation and a pericentric inversion inv(4)(p1.4;q2.3). All three boars were normal for synapsis and sperm production. This particular situation allowed us to rigorously study the impact of rearrangements on recombination. Overall, the rearrangements induced only minor modifications of the number of MLH1 foci (per spermatocyte or per chromosome) and of the length of synaptonemal complexes for chromosomes 3 and 4. The distribution of MLH1 foci in T34he was comparable to that of the controls. Conversely, the distributions of MLH1 foci on chromosome 4 were strongly modified in boar T34Inv (lack of crossover in the heterosynaptic region of the quadrivalent, and crossover displaced to the chromosome extremities), and also in boar T34ho (two recombination peaks on the q-arms compared with one of higher magnitude in the controls). Analyses of boars T34he and T34Inv showed that the interference was propagated through the breakpoints. A different result was obtained for boar T34ho, in which the breakpoints (transition between SSC3 and SSC4 chromatin on the bivalents) seemed to alter the transmission of the interference signal. Our results suggest that the number of crossovers and crossover interference could be regulated by partially different mechanisms.     

Neutralization of radiation damping by selective feedback on a 400 MHz NMR spectrometer

Summary Radiation damping is a phenomenon well known among NMR spectroscopists of proteins as a source of undesirable features, especially in high-field and high-Q probe NMR. In this paper, we present an electronic neutralization network which dramatically reduces radiation damping. It detects the radiation field profile and feeds back into the probe an rf field with identical amplitude and opposite phase. Experimental results of a practical implementation carried out on a 400 MHz Bruker spectrometer are shown.     

Plasma and erythrocyte manganese concentrations

This study was carried out to assess manganese (Mn) status after an acute episode of myocardial infarction. Plasma and erythrocyte Mn concentrations were measured from admission to hospital to day 15 postadmission in 21 patients suffering from acute myocardial infarction and in three control groups. The determination of Mn in these biological fluids was performed by electrothermal atomic absorption spectrometry. Plasma Mn was higher (p<0.01) and erythrocyte Mn was similar in the acute myocardial infarction group compared to healthy age-matched control group. Plasma and erythrocyte Mn remained unchanged during the 2 wk after acute myocardial infarction and were not correlated to enzyme activities. A decrease of erythrocyte Mn with age, expressed in nmol/L, was noted (p<0.02). These results suggest that plasma and erythrocyte Mn do not provide an indication of myocardial damage. Nonetheless, Mn status in elderly merits further attention.     

Development of a semi-automatic system for pollen recognition

A semi-automatic system for pollen recognitionis studied for the european project ASTHMA. The goal of such a system is to provideaccurate pollen concentration measurements. This information can be used as well by thepalynologists, the clinicians or a forecastsystem to predict pollen dispersion. At first,our emphasis has been put on Cupressaceae, Olea, Poaceae and Urticaceae pollen types. The system is composed of two modules: pollengrain extraction and pollen grain recognition. In the first module, the pollen grains areobserved in light microscopy and are extractedautomatically from a pollen slide coloured withfuchsin and digitized in 3D. In the secondmodule, the pollen grain is analyzed forrecognition. To accomplish the recognition, itis necessary to work on 3D images and to usedetailed palynological knowledge. Thisknowledge describes the pollen types accordingto their main visible characteristerics and tothose which are important for recognition. Somepollen structures are identified like the porewith annulus in Poaceae, the reticulum in Oleaand similar pollen types or the cytoplasm inCupressaceae. The preliminary results show therecognition of some pollen types, likeUrticaceae or Poaceae or some groups of pollentypes, like reticulate group.     

Munc13-4 is essential for cytolytic granules fusion and is mutated in a form of familial hemophagocytic lymphohistiocytosis (FHL3)

Secretion of cytolytic granules content at the immunological synapse is a highly regulated process essential for lymphocyte cytotoxicity. This process requires the rapid transfer of perforin containing lytic granules to the target cell interface, followed by their docking and fusion with the plasma membrane. Defective cytotoxicity characterizes a genetically heterogeneous condition named familial hemophagocytic lymphohistiocytosis (FHL), which can be associated with perforin deficiency. The locus of a perforin (+) FHL subtype (FHL3), observed in 10 patients, was mapped to 17q25. This region contains hMunc13-4, a member of the Munc13 family of proteins involved in vesicle priming function. HMunc13-4 mutations were shown to cause FHL3. HMunc13-4 deficiency results in defective cytolytic granule exocytosis, despite polarization of the secretory granules and docking with the plasma membrane. Expressed tagged hMunc13-4 localizes with cytotoxic granules at the immunological synapse. HMunc13-4 is therefore essential for the priming step of cytolytic granules secretion preceding vesicle membrane fusion.     

Patterns of molecular evolution associated with two selective sweeps in the Tb1-Dwarf8 region in maize

We focused on a region encompassing a major maize domestication locus, Tb1, and a locus involved in the flowering time variation, Dwarf8 (D8), to investigate the consequences of two closely linked selective sweeps on nucleotide variation and gain some insights into maize geographical diffusion, through climate adaptation. First, we physically mapped D8 at approximately 300 kb 3' of Tb1. Second, we analyzed patterns of nucleotide variation at Tb1, D8, and seven short regions (400-700 bp) located in the Tb1-D8 region sequenced on a 40 maize inbred lines panel encompassing early-flowering temperate and late-flowering tropical lines. The pattern of polymorphism along the region is characterized by two valleys of depleted polymorphism while the region in between exhibits an appreciable amount of diversity. Our results reveal that a region approximately 100 kb upstream of the D8 gene exhibits hallmarks of divergent selection between temperate and tropical lines and is likely closer than the D8 gene to the target of selection for climate adaptation. Selection in the tropical lines appears more recent than in the temperate lines, suggesting an initial domestication of early-flowering maize. Simulation results indicate that the polymorphism pattern is consistent with two interfering selective sweeps at Tb1 and D8.     

Rotavirus Infection Reduces Sucrase-Isomaltase Expression in Human Intestinal Epithelial Cells by Perturbing Protein Targeting and Organization of Microvillar Cytoskeleton

Rotavirus infection is the most common cause of severe infantile gastroenteritis worldwide. These viruses infect mature enterocytes of the small intestine and cause structural and functional damage, including a reduction in disaccharidase activity. It was previously hypothesized that reduced disaccharidase activity resulted from the destruction of rotavirus-infected enterocytes at the villus tips. However, this pathophysiological model cannot explain situations in which low disaccharidase activity is observed when rotavirus-infected intestine exhibits few, if any, histopathologic changes. In a previous study, we demonstrated that the simian rotavirus strain RRV replicated in and was released from human enterocyte-like Caco-2 cells without cell destruction (N. Jourdan, M. Maurice, D. Delautier, A. M. Quero, A. L. Servin, and G. Trugnan, J. Virol. 71:8268–8278, 1997). In the present study, to reinvestigate disaccharidase expression during rotavirus infection, we studied sucrase-isomaltase (SI) in RRV-infected Caco-2 cells. We showed that SI activity and apical expression were specifically and selectively decreased by RRV infection without apparent cell destruction. Using pulse-chase experiments and cell surface biotinylation, we demonstrated that RRV infection did not affect SI biosynthesis, maturation, or stability but induced the blockade of SI transport to the brush border. Using confocal laser scanning microscopy, we showed that RRV infection induces important alterations of the cytoskeleton that correlate with decreased SI apical surface expression. These results lead us to propose an alternate model to explain the pathophysiology associated with rotavirus infection.     

SECIS-binding protein 2, a key player in selenoprotein synthesis,is an intrinsically disordered protein

Selenocysteine (Sec) is co-translationally incorporated into selenoproteins at a reprogrammed UGA codon. In mammals, this requires a dedicated machinery comprising a stem-loop structure in the 3′ UTR RNA (the SECIS element) and the specific SECIS Binding Protein 2. In this report, disorder-prediction methods and several biophysical techniques showed that ca. 70% of the SBP2 sequence is disordered, whereas the RNA binding domain appears to be folded and functional. These results are consistent with a recent report on the role of the Hsp90 chaperone for the folding of SBP2 and other functionally unrelated proteins bearing an RNA binding domain homologous to SBP2.     

Life on Arginine for Mycoplasma hominis: Clues from Its Minimal Genome and Comparison with Other Human Urogenital Mycoplasmas

Mycoplasma hominis is an opportunistic human mycoplasma. Two other pathogenic human species, M. genitalium and Ureaplasma parvum, reside within the same natural niche as M. hominis: the urogenital tract. These three species have overlapping, but distinct, pathogenic roles. They have minimal genomes and, thus, reduced metabolic capabilities characterized by distinct energy-generating pathways. Analysis of the M. hominis PG21 genome sequence revealed that it is the second smallest genome among self-replicating free living organisms (665,445 bp, 537 coding sequences (CDSs)). Five clusters of genes were predicted to have undergone horizontal gene transfer (HGT) between M. hominis and the phylogenetically distant U. parvum species. We reconstructed M. hominis metabolic pathways from the predicted genes, with particular emphasis on energy-generating pathways. The Embden–Meyerhoff–Parnas pathway was incomplete, with a single enzyme absent. We identified the three proteins constituting the arginine dihydrolase pathway. This pathway was found essential to promote growth in vivo. The predicted presence of dimethylarginine dimethylaminohydrolase suggested that arginine catabolism is more complex than initially described. This enzyme may have been acquired by HGT from non-mollicute bacteria. Comparison of the three minimal mollicute genomes showed that 247 CDSs were common to all three genomes, whereas 220 CDSs were specific to M. hominis, 172 CDSs were specific to M. genitalium, and 280 CDSs were specific to U. parvum. Within these species-specific genes, two major sets of genes could be identified: one including genes involved in various energy-generating pathways, depending on the energy source used (glucose, urea, or arginine) and another involved in cytadherence and virulence. Therefore, a minimal mycoplasma cell, not including cytadherence and virulence-related genes, could be envisaged containing a core genome (247 genes), plus a set of genes required for providing energy. For M. hominis, this set would include 247+9 genes, resulting in a theoretical minimal genome of 256 genes.     

An extensive analysis of the African rice genetic diversity through a global genotyping

Key message

We present here the first curated collection of wild and cultivated African rice species. For that, we designed specific SNPs and were able to structure these very low diverse species.

Abstract

Oryza glaberrima, the cultivated African rice, is endemic from Africa. This species and its direct ancestor, O. barthii, are valuable tool for improvement of Asian rice O. sativa in terms of abiotic and biotic stress resistance. However, only a few limited studies about the genetic diversity of these species were performed. In the present paper, and for the first time at such extend, we genotyped 279 O. glaberrima, selected both for their impact in current breeding and for their geographical distribution, and 101 O. barthii, chosen based on their geographic origin, using a set of 235 SNPs specifically designed for African rice diversity. Using those data, we were able to structure the individuals from our sample in three populations for O. barthii, related to geography, and two populations in O. glaberrima; these two last populations cannot be linked however to any currently phenotyped trait. Moreover, we were also able to identify misclassification in O. glaberrima as well as in O. barthii and identified new form of O. sativa from the set of African varieties.