RAG-1 and ATM coordinate monoallelic recombination and nuclear positioning of immunoglobulin loci.

Coordinated recombination of homologous antigen receptor loci is thought to be important for allelic exclusion. Here we show that homologous immunoglobulin alleles pair in a stage-specific way that mirrors the recombination patterns of these loci. The frequency of homologous immunoglobulin pairing was much lower in the absence of the RAG-1-RAG-2 recombinase and was restored in Rag1-/- developing B cells with a transgene expressing a RAG-1 active-site mutant that supported DNA binding but not cleavage. The introduction of DNA breaks on one immunoglobulin allele induced ATM-dependent repositioning of the other allele to pericentromeric heterochromatin. ATM activated by the cleaved allele acts in trans on the uncleaved allele to prevent biallelic recombination and chromosome breaks or translocations.

Association between the Igk and Igh immunoglobulin loci mediated by the 3' Igk enhancer induces 'decontraction' of the Igh locus in pre-B cells.

Variable-(diversity)-joining (V(D)J) recombination at loci encoding the immunoglobulin heavy chain (Igh) and immunoglobulin light chain (Igk) takes place sequentially during successive stages in B cell development. Using three-dimensional DNA fluorescence in situ hybridization, here we identify a lineage-specific and stage-specific interchromosomal association between these two loci that marks the transition between Igh and Igk recombination. Colocalization occurred between pericentromerically located alleles in pre-B cells and was mediated by the 3' Igk enhancer. Deletion of this regulatory element prevented association of the Igh and Igk loci, inhibited pericentromeric recruitment and locus 'decontraction' of an Igh allele, and resulted in greater distal rearrangement of the gene encoding the variable heavy-chain region. Our data indicate involvement of the Igk locus and its 3' enhancer in directing the Igh locus to a repressive nuclear subcompartment and inducing the Igh locus to decontract.

The relationship between pre-pregnancy BMI, gestational weight gain and neonatal birth weight: a retrospective cohort study.

OBJECTIVES: Maternal pre-pregnancy body mass index (BMI) and gestational weight gain (GWG) have a meaningful impact on pregnancy and perinatal outcomes. The first aim of the study was to analyze the association between pre-pregnancy BMI and the prevalence of small for gestational age (SGA) and large for gestational age (LGA) outcomes. The second aim was to assess the relation- ship between pre-pregnancy BMI combined with gestational weight gain (GWG) and the prevalence of SGA and LGA measurements. MATERIAL AND METHODS: The retrospective cohort study was conducted at Jagiellonian University Hospital in Cracow, Po- land from 2016 to 2017. During this time there were 2,123 deliveries. Patients with chronic diseases, multiple pregnancies, fetal defects and incomplete data were excluded. Finally, 474 cases were enrolled. Patients were divided into BMI groups (underweight, normal, overweight and obese) and into GWG groups (inadequate, adequate, excessive). Relationships between maternal BMI, GWG and newborn weight were examined. RESULTS: There was no statistically significant association between maternal pre-pregnancy BMI and prevalence of SGA measurements. However, underweight women with inadequate GWG showed a higher risk to bear SGA babies (OR 5.2, 95% CI 1.57-17.18). Obese women with adequate GWG had higher risk of bearing LGA newborns (OR 5.48, 95% CI 1.15-26.13). High BMI correlated with excessive GWG (overweight: OR 3.0, 95% CI 1.84-3.87; obese OR 2.45, 95% CI 1.1-5.48). CONCLUSIONS: There is a considerable risk of giving birth to a SGA newborn for underweight women with inadequate GWG. There is a statistically significant association between maternal obesity and LGA outcomes. Our study shows that redefining the risks of abnormal neonatal weight considering both pre-pregnancy BMI and gestational weight gain can be useful in providing effective prevention during pregnancy.

Neuroimmunomodulatory effect of Nitric Oxide on chronic wound healing after photodynamic therapy.

Neuroimmunomodulation is the capacity of the nervous system to regulate immune processes. The existence of neurotransmitter receptors in immune cells enables this phenomenon to take place. Neuronal mediators possess the capacity to direct and control several occurrences during the wound healing process. Nitric oxide (NO) functions as a neuromodulator, playing a crucial role in the regulation of vascular tone and blood pressure with antimicrobial properties. Photodynamic therapy has been shown to augment the function of immune cells involved in the healing process of venous leg ulcers. Nitric oxide can be secreted into the extracellular environment by these cells. In lesions treated with PDT, the synthesis of iNOs (the enzyme that releases NO) increased, as demonstrated by the experimental results. Therefore the significance of PDT in enhancing the clinical condition of the lesion is thus highlighted.

Rab46 integrates Ca2+ and histamine signaling to regulate selective cargo release from Weibel-Palade bodies.

Endothelial cells selectively release cargo stored in Weibel-Palade bodies (WPBs) to regulate vascular function, but the underlying mechanisms are poorly understood. Here we show that histamine evokes the release of the proinflammatory ligand, P-selectin, while diverting WPBs carrying non-inflammatory cargo away from the plasma membrane to the microtubule organizing center. This differential trafficking is dependent on Rab46 (CRACR2A), a newly identified Ca2+-sensing GTPase, which localizes to a subset of P-selectin-negative WPBs. After acute stimulation of the H1 receptor, GTP-bound Rab46 evokes dynein-dependent retrograde transport of a subset of WPBs along microtubules. Upon continued histamine stimulation, Rab46 senses localized elevations of intracellular calcium and evokes dispersal of microtubule organizing center-clustered WPBs. These data demonstrate for the first time that a Rab GTPase, Rab46, integrates G protein and Ca2+ signals to couple on-demand histamine signals to selective WPB trafficking.

Homotypic endothelial nanotubes induced by wheat germ agglutinin and thrombin.

Endothelial barrier formation is maintained by intercellular communication through junctional proteins. The mechanisms involved in maintaining endothelial communication subsequent to barrier disruption remain unclear. It is known that low numbers of endothelial cells can be interconnected by homotypic actin-driven tunneling nanotubes (TNTs) which could be important for intercellular transfer of information in vascular physiology. Here we sought insight into the triggers for TNT formation. Wheat germ agglutinin, a C-type lectin and known label for TNTs, unexpectedly caused striking induction of TNTs. A succinylated derivative was by contrast inactive, suggesting mediation by a sialylated protein. Through siRNA-mediated knockdown we identified that this protein was likely to be CD31, an important sialylated membrane protein normally at endothelial cell junctions. We subsequently considered thrombin as a physiological inducer of endothelial TNTs because it reduces junctional contact. Thrombin reduced junctional contact, redistributed CD31 and induced TNTs, but its effect on TNTs was CD31-independent. Thrombin-induced TNTs nevertheless required PKCα, a known mediator of thrombin-dependent junctional remodelling, suggesting a necessity for junctional proteins in TNT formation. Indeed, TNT-inducing effects of wheat germ agglutinin and thrombin were both correlated with cortical actin rearrangement and similarly Ca2+-dependent, suggesting common underlying mechanisms. Once formed, Ca2+ signalling along TNTs was observed.

Piezo1 channels sense whole body physical activity to reset cardiovascular homeostasis and enhance performance.

Mammalian biology adapts to physical activity but the molecular mechanisms sensing the activity remain enigmatic. Recent studies have revealed how Piezo1 protein senses mechanical force to enable vascular development. Here, we address Piezo1 in adult endothelium, the major control site in physical activity. Mice without endothelial Piezo1 lack obvious phenotype but close inspection reveals a specific effect on endothelium-dependent relaxation in mesenteric resistance artery. Strikingly, the Piezo1 is required for elevated blood pressure during whole body physical activity but not blood pressure during inactivity. Piezo1 is responsible for flow-sensitive non-inactivating non-selective cationic channels which depolarize the membrane potential. As fluid flow increases, depolarization increases to activate voltage-gated Ca2+ channels in the adjacent vascular smooth muscle cells, causing vasoconstriction. Physical performance is compromised in mice which lack endothelial Piezo1 and there is weight loss after sustained activity. The data suggest that Piezo1 channels sense physical activity to advantageously reset vascular control.The mechanisms that regulate the body's response to exercise are poorly understood. Here, Rode et al. show that the mechanically activated cation channel Piezo1 is a molecular sensor of physical exercise in the endothelium that triggers endothelial communication to mesenteric vessel muscle cells, leading to vasoconstriction.