Improvement of Dietary Habits among German Medical Students by Attending a Nationwide Online Lecture Series on Nutrition and Planetary Health ("Eat This!").

Nutrition is a major influential factor in optimizing human health and environmental sustainability. Medical students often do not follow national dietary guideline recommendations. Raising awareness of a healthy lifestyle is important as physicians with healthy lifestyle behaviors are more likely to counsel on nutrition. Our study aims to evaluate a Germany-wide online lecture series on nutritional medicine, "Eat This!". Before and after the course, 520 medical students who participated and 64 who did not participate in the course (comparison group) filled out an online survey. To assess the students' dietary habits, a validated FFQ was used. According to this questionnaire, only 31% of the lecture participants consumed enough fruits and 24% consumed enough vegetables, while almost half of the students exceeded the recommended maximum amount of crisps and sweets. After attending the lecture series, guideline adherence with respect to fruits and vegetables showed a significant increase, as did awareness of healthy nutrition and percentage of students with low-risk lifestyle habits. Our results show that low-threshold approaches, such as "Eat This!", can positively influence the dietary behaviors and lifestyle habits of medical students. This can help future doctors fulfill their role in the fight against the global burden of non-communicable diseases.

CXCR7 prevents excessive CXCL12-mediated downregulation of CXCR4 in migrating cortical interneurons.

The CXCL12/CXCR4 signaling pathway is involved in the development of numerous neuronal and non-neuronal structures. Recent work established that the atypical second CXCL12 receptor, CXCR7, is essential for the proper migration of interneuron precursors in the developing cerebral cortex. Two CXCR7-mediated functions were proposed in this process: direct modulation of ß-arrestin-mediated signaling cascades and CXCL12 scavenging to regulate local chemokine availability and ensure responsiveness of the CXCL12/CXCR4 pathway in interneurons. Neither of these functions has been proven in the embryonic brain. Here, we demonstrate that migrating interneurons efficiently sequester CXCL12 through CXCR7. CXCR7 ablation causes excessive phosphorylation and downregulation of CXCR4 throughout the cortex in mice expressing CXCL12, but not in CXCL12-deficient animals. Cxcl12(-/-) mice lack activated CXCR4 in embryonic brain lysates and display a similar interneuron positioning defect as Cxcr4(-/-), Cxcr7(-/-) and Cxcl12(-/-);Cxcr7(-/-) animals. Thus, CXCL12 is the only CXCR4-activating ligand in the embryonic brain and deletion of one of the CXCL12 receptors is sufficient to generate a migration phenotype that corresponds to the CXCL12-deficient pathway. Our findings imply that interfering with the CXCL12-scavenging activity of CXCR7 causes loss of CXCR4 function as a consequence of excessive CXCL12-mediated CXCR4 activation and degradation.

CXCR4 prevents dispersion of granule neuron precursors in the adult dentate gyrus.

Neurogenesis in the adult dentate gyrus (DG) generates new granule neurons that differentiate in the inner one-third of the granule cell layer (GCL). The migrating precursors of these neurons arise from neural stem cells (NSCs) in the subgranular zone (SGZ). Although it is established that pathological conditions, including epilepsy and stroke, cause dispersion of granule neuron precursors, little is known about the factors that regulate their normal placement. Based on the high expression of the chemokine CXCL12 in the adult GCL and its role in guiding neuronal migration in development, we addressed the function of the CXCL12 receptor CXCR4 in adult neurogenesis. Using transgenic reporter mice, we detected Cxcr4-GFP expression in NSCs, neuronal-committed progenitors, and immature neurons of adult and aged mice. Analyses of hippocampal NSC cultures and hippocampal tissue by immunoblot and immunohistochemistry provided evidence for CXCL12-promoted phosphorylation/activation of CXCR4 receptors in NSCs in vivo and in vitro. Cxcr4 deletion in NSCs of the postnatal or mature DG using Cre technology reduced neurogenesis. Fifty days after Cxcr4 ablation in the mature DG, the SGZ showed a severe reduction of Sox2-positive neural stem/early progenitor cells, NeuroD-positive neuronal-committed progenitors, and DCX-positive immature neurons. Many immature neurons were ectopically placed in the hilus and inner molecular layer, and some developed an aberrant dendritic morphology. Only few misplaced cells survived permanently as ectopic neurons. Thus, CXCR4 signaling maintains the NSC pool in the DG and specifies the inner one-third of the GCL as differentiation area for immature granule neurons.

Hierarchical organization of multi-site phosphorylation at the CXCR4 C terminus.

The chemokine receptor CXCR4 regulates cell migration during ontogenesis and disease states including cancer and inflammation. Upon stimulation by the endogenous ligand CXCL12, CXCR4 becomes phosphorylated at multiple sites in its C-terminal domain. Mutations in the CXCR4 gene affecting C-terminal phosphorylation sites are a hallmark of WHIM syndrome, a genetic disorder characterized by a gain-of-CXCR4-function. To better understand how multi-site phosphorylation of CXCR4 is organized and how perturbed phosphorylation might affect CXCR4 function, we developed novel phosphosite-specific CXCR4 antibodies and studied the differential regulation and interaction of three C-terminal phosphorylation sites in human embryonic kidney cells (HEK293). CXCL12 promoted a robust phosphorylation at S346/347 which preceded phosphorylation at S324/325 and S338/339. After CXCL12 washout, the phosphosites S338/339 and S324/325 were rapidly dephosphorylated whereas phosphorylation at S346/347 was long-lasting. CXCL12-induced phosphorylation at S346/347 was staurosporine-insensitive and mediated by GRK2/3. WHIM syndrome-associated CXCR4 truncation mutants lacking the S346/347 phosphosite and the recently identified E343K WHIM mutant displayed strongly impaired phosphorylation at S324/325 and S338/339 as well as reduced CXCL12-induced receptor internalization. Relevance of the S346-S348 site was confirmed by a S346-348A mutant showing strongly impaired CXCL12-promoted phosphorylation at S324/325 and S338/339, defective internalization, gain of calcium mobilization, and reduced desensitization. Thus, the triple serine motif S346-S348 contains a major initial CXCR4 phosphorylation site and is required for efficient subsequent multi-site phosphorylation and receptor regulation. Hierarchical organization of CXCR4 phosphorylation explains why small deletions at the extreme CXCR4 C terminus typically associated with WHIM syndrome severely alter CXCR4 function.

CXC chemokine receptor 7 (CXCR7) regulates CXCR4 protein expression and capillary tuft development in mouse kidney.

BACKGROUND: The CXCL12/CXCR4 axis is involved in kidney development by regulating formation of the glomerular tuft. Recently, a second CXCL12 receptor was identified and designated CXCR7. Although it is established that CXCR7 regulates heart and brain development in conjunction with CXCL12 and CXCR4, little is known about the influence of CXCR7 on CXCL12 dependent kidney development. METHODOLOGY/PRINCIPAL FINDINGS: We provided analysis of CXCR7 expression and function in the developing mouse kidney. Using in situ hybridization, we identified CXCR7 mRNA in epithelial cells including podocytes at all nephron stages up to the mature glomerulus. CXCL12 mRNA showed a striking overlap with CXCR7 mRNA in epithelial structures. In addition, CXCL12 was detected in stromal cells and the glomerular tuft. Expression of CXCR4 was complementary to that of CXCR7 as it occurred in mesenchymal cells, outgrowing ureteric buds and glomerular endothelial cells but not in podocytes. Kidney examination in CXCR7 null mice revealed ballooning of glomerular capillaries as described earlier for CXCR4 null mice. Moreover, we detected a severe reduction of CXCR4 protein but not CXCR4 mRNA within the glomerular tuft and in the condensed mesenchyme. Malformation of the glomerular tuft in CXCR7 null mice was associated with mesangial cell clumping. CONCLUSIONS/SIGNIFICANCE: We established that there is a similar glomerular pathology in CXCR7 and CXCR4 null embryos. Based on the phenotype and the anatomical organization of the CXCL12/CXCR4/CXCR7 system in the forming glomerulus, we propose that CXCR7 fine-tunes CXCL12/CXCR4 mediated signalling between podocytes and glomerular capillaries.

Cxcr7 controls neuronal migration by regulating chemokine responsiveness.

The chemokine Cxcl12 binds Cxcr4 and Cxcr7 receptors to control cell migration in multiple biological contexts, including brain development, leukocyte trafficking, and tumorigenesis. Both receptors are expressed in the CNS, but how they cooperate during migration has not been elucidated. Here, we used the migration of cortical interneurons as a model to study this process. We found that Cxcr4 and Cxcr7 are coexpressed in migrating interneurons, and that Cxcr7 is essential for chemokine signaling. Intriguingly, this process does not exclusively involve Cxcr7, but most critically the modulation of Cxcr4 function. Thus, Cxcr7 is necessary to regulate Cxcr4 protein levels, thereby adapting chemokine responsiveness in migrating cells. This demonstrates that a chemokine receptor modulates the function of another chemokine receptor by controlling the amount of protein that is made available for signaling at the cell surface.

A chemically defined production process for highly attenuated poxviruses.

Highly attenuated poxviruses are promising vectors for protective and therapeutic vaccines. These vectors do not replicate in human cells and can therefore be safely given even to immunocompromised recipients. They can accommodate very large inserts and provide strong stimulation of the immune system against the vectored antigen. Disadvantages include that very high numbers of infectious units are required per dose for full efficacy. Because they are difficult to produce, improved cellular substrates and processes are urgently needed to facilitate programs intended to reach a large number of vaccinees. We have developed a fully scalable and very efficient chemically-defined production process for modified vaccinia Ankara (MVA), canarypox (CNPV, strain ALVAC) and fowlpox viruses (FPV) based on a continuous cell line.