The Stem Cell Factor Sox2 Is a Positive Timer of Oligodendrocyte Development in the Postnatal Murine Spinal Cord

Myelination in the central nervous system takes place predominantly during the postnatal development of humans and rodents by myelinating oligodendrocytes (OLs), which are differentiated from oligodendrocyte progenitor cells (OPCs). We recently reported that Sox2 is essential for developmental myelination in the murine brain and spinal cord. It is still controversial regarding the role of Sox2 in oligodendroglial lineage progression in the postnatal murine spinal cord. Analyses of a series of cell- and stage-specific Sox2 mutants reveal that Sox2 plays a biphasic role in regulating oligodendroglial lineage progression in the postnatal murine spinal cord. Sox2 controls the number of OPCs for subsequent differentiation through regulating their proliferation. In addition, Sox2 regulates the timing of OL differentiation and modulates the rate of oligodendrogenesis. Our experimental data prove that Sox2 is an intrinsic positive timer of oligodendroglial lineage progression and suggest that interventions affecting oligodendroglial Sox2 expression may be therapeutic for overcoming OPC differentiation arrest in dysmyelinating and demyelinating disorders.     

Herpes Simplex Virus Type 1 Glycoprotein gC Mediates Immune Evasion In Vivo

Many microorganisms encode proteins that interact with molecules involved in host immunity; however, few of these molecules have been proven to promote immune evasion in vivo. Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC) binds complement component C3 and inhibits complement-mediated virus neutralization and lysis of infected cells in vitro. To investigate the importance of the interaction between gC and C3 in vivo, we studied the virulence of a gC-null strain in complement-intact and C3-deficient animals. Using a vaginal infection model in complement-intact guinea pigs, we showed that gC-null virus grows to lower titers and produces less severe vaginitis than wild-type or gC rescued virus, indicating a role for gC in virulence. To determine the importance of complement, studies were performed with C3-deficient guinea pigs; the results demonstrated significant increases in vaginal titers of gC-null virus, while wild-type and gC rescued viruses showed nonsignificant changes in titers. Similar findings were observed for mice where gC null virus produced significantly less disease than gC rescued virus at the skin inoculation site. Proof that C3 is important was provided by studies of C3 knockout mice, where disease scores of gC-null virus were significantly higher than in complement-intact mice. The results indicate that gC-null virus is approximately 100-fold (2 log₁₀) less virulent that wild-type virus in animals and that gC-C3 interactions are involved in pathogenesis.     

The Easter Egg Weevil (Pachyrhynchus) genome reveals syntenic patterns in Coleoptera across 200 million years of evolution

Patterns of genomic architecture across insects remain largely undocumented or decoupled from a broader phylogenetic context. For instance, it is unknown whether translocation rates differ between insect orders. We address broad scale patterns of genome architecture across Insecta by examining synteny in a phylogenetic framework from open-source insect genomes. To accomplish this, we add a chromosome level genome to a crucial lineage, Coleoptera. Our assembly of the Pachyrhynchus sulphureomaculatus genome is the first chromosome scale genome for the hyperdiverse Phytophaga lineage and currently the largest insect genome assembled to this scale. The genome is significantly larger than those of other weevils, and this increase in size is caused by repetitive elements. Our results also indicate that, among beetles, there are instances of long-lasting (>200 Ma) localization of genes to a particular chromosome with few translocation events. While some chromosomes have a paucity of translocations, intra-chromosomal synteny was almost absent, with gene order thoroughly shuffled along a chromosome. This large amount of reshuffling within chromosomes with few inter-chromosomal events contrasts with patterns seen in mammals in which the chromosomes tend to exchange larger blocks of material more readily. To place our findings in an evolutionary context, we compared syntenic patterns across Insecta in a phylogenetic framework. For the first time, we find that synteny decays at an exponential rate relative to phylogenetic distance. Additionally, there are significant differences in decay rates between insect orders, this pattern was not driven by Lepidoptera alone which has a substantially different rate.     

Enhanced A3 adenosine receptor selectivity of multivalent nucleoside-dendrimer conjugates

Background

An approach to use multivalent dendrimer carriers for delivery of nucleoside signaling molecules to their cell surface G protein-coupled receptors (GPCRs) was recently introduced.

Results

A known adenosine receptor (AR) agonist was conjugated to polyamidoamine (PAMAM) dendrimer carriers for delivery of the intact covalent conjugate to on the cell surface. Depending on the linking moiety, multivalent conjugates of the N ⁶-chain elongated functionalized congener ADAC (N ⁶-[4-[[[4-[[[(2-aminoethyl)amino]carbonyl]methyl]anilino]carbonyl]methyl]phenyl]-adenosine) achieved unanticipated high selectivity in binding to the cytoprotective human A₃ AR, a class A GPCR. The key to this selectivity of > 100-fold in both radioreceptor binding (K_{i app} = 2.4 nM) and functional assays (EC₅₀ = 1.6 nM in inhibition of adenylate cyclase) was maintaining a free amino group (secondary) in an amide-linked chain. Attachment of neutral amide-linked chains or thiourea-containing chains preserved the moderate affinity and efficacy at the A₁ AR subtype, but there was no selectivity for the A₃ AR. Since residual amino groups on dendrimers are associated with cytotoxicity, the unreacted terminal positions of this A₃ AR-selective G2.5 dendrimer were present as carboxylate groups, which had the further benefit of increasing water-solubility. The A₃ AR selective G2.5 dendrimer was also visualized binding the membrane of cells expressing the A₃ receptor but did not bind cells that did not express the receptor.

Conclusion

This is the first example showing that it is feasible to modulate and even enhance the pharmacological profile of a ligand of a GPCR based on conjugation to a nanocarrier and the precise structure of the linking group, which was designed to interact with distal extracellular regions of the 7 transmembrane-spanning receptor. This ligand tool can now be used in pharmacological models of tissue rescue from ischemia and to probe the existence of A₃ AR dimers.     

Proteomic profiling of nonenzymatically glycated proteins in human plasma and erythrocyte membranes

Nonenzymatic glycation of peptides and proteins by d-glucose has important implications in the pathogenesis of diabetes mellitus, particularly in the development of diabetic complications. In this work, we report the first proteomics-based characterization of nonenzymatically glycated proteins in human plasma and erythrocyte membranes from individuals with normal glucose tolerance, impaired glucose tolerance, and type 2 diabetes mellitus. Phenylboronate affinity chromatography was used to enrich glycated proteins and glycated tryptic peptides from both human plasma and erythrocyte membranes. The enriched peptides were subsequently analyzed by liquid chromatography coupled with electron transfer dissociation-tandem mass spectrometry, resulting in the confident identification of 76 and 31 proteins from human plasma and erythrocyte membranes, respectively. Although most of the glycated proteins could be identified in samples from individuals with normal glucose tolerance, slightly higher numbers of glycated proteins and more glycation sites were identified in samples from individuals with impaired glucose tolerance and type 2 diabetes mellitus.     

Caries clinical trial of a remineralising toothpaste in radiation patients

Objectives: The purpose of this study was to determine the efficacy and safety of a specially formulated remineralising toothpaste in controlling caries in a high‐risk population: head and neck radiation patients. Design: The study compared the performance of the remineralising toothpaste with a conventional fluoride dentifrice using double‐blind randomisation. Materials and methods: Test products: The products compared contained equivalent quantities of fluoride (1100 p.p.m.). The dual‐phase remineralising toothpaste, Enamelon^®, also delivered soluble calcium and phosphate ions, essential components of teeth, from separate phases. Both groups had all caries restored at baseline and used a fluoride rinse daily. Subjects: Fifty‐seven subjects who received radiation to the head and neck causing saliva hypofunction, entered the study, while 44 completed the 10–12 month visit. Measurements: Examinations included coronal and root caries using the Pitts Diagnostic Criteria, salivary flow rate, plaque and gingival indices and microbiological counts over a 1‐year period. Results: The average net increment per year for root caries per subject was 0.04 (±.052) in subjects completing the study using the remineralising toothpaste and 1.65 (±0.51) for root caries in subjects completing the study using the conventional fluoride dentifrice. The difference was statistically significant (p = 0.03), suggesting lower net root surface increment/year for the remineralising toothpaste relative to the conventional toothpaste. No significant differences were noted on coronal surfaces. Conclusion: The results indicate that the remineralising toothpaste provides a significant benefit in preventing and remineralising root caries in high‐risk patients.     

Shifts in leaf vein density through accelerated vein formation in C4 Flaveria (Asteraceae)

Background and Aims

Leaf venation in many C₄ species is characterized by high vein density, essential in facilitating rapid intercellular diffusion of C₄ photosynthetic metabolites between different tissues (mesophyll, bundle sheath). Greater vein density has been hypothesized to be an early step in C₄ photosynthesis evolution. Development of C₄ vein patterning is thought to occur from either accelerated or prolonged procambium formation, relative to ground tissue development.

Methods

Cleared and sectioned tissues of phylogenetically basal C₃ Flaveria robusta and more derived C₄ Flaveria bidentis were compared for vein pattern in mature leaves and vein pattern formation in developing leaves.

Key Results

In mature leaves, major vein density did not differ between C₃ and C₄ Flaveria species, whereas minor veins were denser in C₄ species than in C₃ species. The developmental study showed that both major and minor vein patterning in leaves of C₃ and C₄ species were initiated at comparable stages (based on leaf length). An additional vein order in the C₄ species was observed during initiation of the higher order minor veins compared with the C₃ species. In the two species, expansion of bundle sheath and mesophyll cells occurred after vein pattern was complete and xylem differentiation was continuous in minor veins. In addition, mesophyll cells ceased dividing sooner and enlarged less in C₄ species than in C₃ species.

Conclusions

Leaf vein pattern characteristic to C₄ Flaveria was achieved primarily through accelerated and earlier offset of higher order vein formation, rather than other modifications in the timing of vein pattern formation, as compared with C₃ species. Earlier cessation of mesophyll cell division and reduced expansion also contributed to greater vein density in the C₄ species. The relatively late expansion of bundle sheath and mesophyll cells shows that vein patterning precedes ground tissue development in C₄ species.Key words: Bundle sheath, C₄ photosynthesis evolution, Flaveria, heterochrony, leaf development, mesophyll, vein density, vein pattern formation