Intergeneric complementation by Agrobacterium tumefaciens chromosomal genes and its potential use for linkage mapping

The IncP1 type plasmids pULB113 (RP4:: mini-Mu) and pJB3JI were used for chromosome mobilization and R prime formation in Agrobacterium tumefaciens. With pULB113, R primes were selected for complementation of an auxotrophic marker in an Alcaligenes eutrophus recipient strain. With pJB3JI, R primes containing the Agrobacterium chromosomal virulence region chv, inactivated by a Tn5 insertion, were constructed. Selection was for kanamycin resistance in E. coli strain GV1000. Complementation tests were performed in auxotrophic A. tumefaciens, A. eutrophus and Pseudomonas fluorescens strains. This allowed us to map 9 loci, including the chv loci, in a region accounting for about 10% of the Agrobacterium chromosome.     

Dynamic study of the transition from hyaluronan- to integrin-mediated adhesion in chondrocytes

Membrane-bound hyaluronan mediates the initial adhesive interactions between many cell types and external surfaces. In RCJ-P chondrocytes, such early contacts are mediated through a thick hyaluronidase-sensitive coat. The early adhesion is followed by integrin-mediated interactions and the formation of stable focal adhesions. During this process, the distance between the cell membrane and the surface is reduced from micrometers to few tens of nanometers. The transition from hyaluronan- to integrin-mediated adhesion was studied on glass surfaces by total internal reflection fluorescence microscopy. Hyaluronan-mediated adhesion precedes focal adhesions formation by 2-10 min. After these initial interactions, the pericellular hyaluronan remains sequestered into discrete pockets between the cell and the surface, which are a few hundreds nanometers thick and a few micrometers wide, and are flanked by focal adhesions. The hyaluronan coat facilitates the nucleation of small paxillin-rich contacts, which later mature into focal adhesions. These dynamic studies demonstrate that pericellular hyaluronan mediates initial cell-surface adhesion, and regulates the formation of focal adhesions.     

Evolution of the visual sensory system in cichlid fishes from crater lake Barombi Mbo in Cameroon

In deep‐water animals, the visual sensory system is often challenged by the dim‐light environment. Here, we focus on the molecular mechanisms involved in rapid deep‐water adaptations. We examined visual system evolution in a small‐scale yet phenotypically and ecologically diverse adaptive radiation, the species flock of cichlid fishes in deep crater lake Barombi Mbo in Cameroon, West Africa. We show that rapid adaptations of the visual system to the novel deep‐water habitat primarily occurred at the level of gene expression changes rather than through nucleotide mutations, which is compatible with the young age of the radiation. Based on retinal bulk RNA sequencing of all eleven species, we found that the opsin gene expression pattern was substantially different for the deep‐water species. The nine shallow‐water species feature an opsin palette dominated by the red‐sensitive (LWS) opsin, whereas the two unrelated deep‐water species lack expression of LWS and the violet‐sensitive (SWS2B) opsin, thereby shifting the cone sensitivity to the centre of the light spectrum. Deep‐water species further predominantly express the green‐sensitive RH2Aα over RH2Aβ. We identified one amino acid substitution in the RH2Aα opsin specific to the deep‐water species. We finally performed a comparative gene expression analysis in retinal tissue of deep‐ vs. shallow‐water species. We thus identified 46 differentially expressed genes, many of which are associated with functions in vision, hypoxia management or circadian clock regulation, with some of them being associated with human eye diseases.     

L’échographie-Doppler obstétricale dans la lutte contre les complications materno-fœtales de l’accouchement en salle de travail

ObjectiveTo demonstrate the role of obstetric Doppler ultrasound in reducing the rate of maternal-fetal complications in childbirth.Patients and methodsCase-control study lasting 12 months carried out at the regional hospital center in Yamoussoukro (Ivory Coast). It involved 204 parturients who had a “complicated delivery”. We have divided them into two groups with one group of cases, consisting of 151 parturients who did not have obstetric ultrasound and a group of controls, consisting of 53 parturients who had an obstetric ultrasound during labor. We studied the occurrence of maternal and neonatal complications in the two groups.ResultsDuring the study period, 1182 vaginal deliveries were made. Of these, 204 were complicated (17.3%). Three maternal deaths and 12 cases of uterine rupture were observed in the case group against none maternal complication in the control group. Thirty-eight cases of stillbirth against zero in controls, 69 cases of neonatal brain injury cases against three among controls were evidenced. The causes of complications were dominated by the obstruction (21 cases) followed by abruptio placentae (eight cases) in the mother. Fetal distress (69 cases) followed by the circular of umbilical cord (48 cases) was the dominant causes in fetus.ConclusionComplicated deliveries represent over a quarter of births in Ivory Coast. Most complications can be avoided by an ultrasound exploration of all new mothers in the labor ward.     

Notch, epidermal growth factor receptor, and beta1-integrin pathways are coordinated in neural stem cells

Notch1 and beta1-integrins are cell surface receptors involved in the recognition of the niche that surrounds stem cells through cell-cell and cell-extracellular matrix interactions, respectively. Notch1 is also involved in the control of cell fate choices in the developing central nervous system (Lewis, J. (1998) Semin. Cell Dev. Biol. 9, 583-589). Here we report that Notch and beta1-integrins are co-expressed and that these proteins cooperate with the epidermal growth factor receptor in neural progenitors. We describe data that suggests that beta1-integrins may affect Notch signaling through 1) physical interaction (sequestration) of the Notch intracellular domain fragment by the cytoplasmic tail of the beta1-integrin and 2) affecting trafficking of the Notch intracellular domain via caveolin-mediated mechanisms. Our findings suggest that caveolin 1-containing lipid rafts play a role in the coordination and coupling of beta1-integrin, Notch1, and tyrosine kinase receptor signaling pathways. We speculate that this will require the presence of the adequate beta1-activating extracellular matrix or growth factors in restricted regions of the central nervous system and namely in neurogenic niches.