Developmental constraints and convergent evolution in Drosophila sex comb formation

SUMMARY The most complex and diverse secondary sexual character in Drosophila is the sex comb (SC), an arrangement of modified bristles on the forelegs of a subclade of male fruit flies. We examined SC formation in six representative nonmodel fruit fly species, in an effort to understand how the variation in comb patterning arises. We first compared SC development in two species with relatively small combs, Drosophila takahashii , where the SCs remain approximately transverse, and Drosophila biarmipes , where two rows of SC teeth rotate and move in an anterior direction relative to other bristle landmarks. We then analyzed comb ontogeny in species with prominent extended SCs parallel to the proximodistal axis, including Drosophila ficusphila and species of the montium subgroup. Our study allowed us to identify two general methods of generating longitudinal combs on the tarsus, and we showed that a montium subgroup species ( Drosophila nikananu ) with a comb convergently similar in size, orientation and position to the model organism Drosophila melanogaster , forms its SC through a different developmental mechanism. We also found that the protein product of the leg patterning gene, dachshund (dac) , is strongly reduced in the SC in all species, but not in other bristles. Our results suggest that an apparent constraint on SC position in the adult may be attributable to at least two different lineage-specific developmental processes, although external forces could also play a role.     

Cell dynamics and developmental bias in the ontogeny of a complex sexually dimorphic trait in Drosophila melanogaster

SUMMARY The Drosophila sex comb (SC) has been hailed as a powerful tool for integrative studies in development, evolution, and behavior, but its ontogeny is poorly understood, even in the model organism Drosophila melanogaster . Using 4D live imaging and other techniques, we carried out a detailed analysis of the cellular events that take place during the development of the SC. We showed that the comb and other contiguous bristle formations assemble from noncontiguous precursor cells, which join together through intercalation. Most of the rotation of the SC (which has a longitudinal orientation in D. melanogaster but is initially transverse) occurs after this stage, when the structure is a single unit. We have provided evidence that male-specific convergent extension through cell rearrangement is responsible for both this rotation and another sexually dimorphic bristle trait. Contiguous bristle formations act as barriers to cell movement within the epithelium, and we demonstrated that a particularly rapid rotation of the proximal region of the comb is associated with the presence of a constricted area between a portion of the SC and a transverse row of contiguous bristle precursors. Our results suggest that the cell dynamics in the neighborhood of the SC may have biased its evolution.     

Microfabricated Microbial Fuel Cell Arrays Reveal Electrochemically Active Microbes

Microbial fuel cells (MFCs) are remarkable “green energy” devices that exploit microbes to generate electricity from organic compounds. MFC devices currently being used and studied do not generate sufficient power to support widespread and cost-effective applications. Hence, research has focused on strategies to enhance the power output of the MFC devices, including exploring more electrochemically active microbes to expand the few already known electricigen families. However, most of the MFC devices are not compatible with high throughput screening for finding microbes with higher electricity generation capabilities. Here, we describe the development of a microfabricated MFC array, a compact and user-friendly platform for the identification and characterization of electrochemically active microbes. The MFC array consists of 24 integrated anode and cathode chambers, which function as 24 independent miniature MFCs and support direct and parallel comparisons of microbial electrochemical activities. The electricity generation profiles of spatially distinct MFC chambers on the array loaded with Shewanella oneidensis MR-1 differed by less than 8%. A screen of environmental microbes using the array identified an isolate that was related to Shewanella putrefaciens IR-1 and Shewanella sp. MR-7, and displayed 2.3-fold higher power output than the S. oneidensis MR-1 reference strain. Therefore, the utility of the MFC array was demonstrated.     

VEGF-B: A survival,or an angiogenic factor?

Despite its early discovery and high sequence homology to the other VEGF family members, the biological function of VEGF-B remained debatable for a long time, and VEGF-B has received little attention from the field thus far. Recently, we and others have found that (1) VEGF-B is a potent survival factor for different types of cells by inhibiting apoptosis via suppressing the expression of BH3-only protein and other apoptotic/cell death-related genes. (2) VEGF-B has a negligible role in inducing blood vessel growth in most organs. Instead, it is critically required for blood vessel survival. VEGF-B targeting inhibited pathological angiogenesis by abolishing blood vessel survival in different animal models. (3) Using different types of neuro-injury and neurodegenerative disease models, VEGF-B treatment protected endangered neurons from apoptosis without inducing undesired blood vessel growth or permeability. Thus, VEGF-B is the first member of the VEGF family that has a potent survival/anti-apoptotic effect, while lacking a general angiogenic activity. Our work thus advocates that the major function of VEGF-B is to act as a “survival,” rather than an “angiogenic” factor and implicates a therapeutic potential of VEGF-B in treating different types of vascular and neurodegenerative diseases.Key words: VEGF-B, survival factor, angiogenesis, apoptosis, vascular biology     

17β-Estradiol Enhances the Response of Plasmacytoid Dendritic Cell to CpG

Gender differences in immune capabilities suggest that sex hormones such as estrogens were involved in the regulation of the immunocompetence. Numerous studies also suggest that plasmacytoid dendritic cells (PDCs) play a pathogenic role in SLE. However, it is unclear whether estrogen can modulate the function of PDCs to influence the development of SLE. In the present study, PDCs from murine spleens were treated with 17β-estradiol (E2) and CpG respectively or both in vitro, then cell viability, costimulatory molecule expression, cytokine secretion of PDCs, as well as stimulatory capacity of PDCs to B cells were analyzed. Results showed that E2 and CpG increased the cell viability and costimulatory molecule expression on PDCs synergistically. Moreover, the intracellular and extracellular secretion of IFN-α was increased by E2 or E2 plus CpG. In addition, E2 and CpG also increased the stimulatory capacity of PDCs to B cells, and the viability of B cells was decreased after neutralizing IFN-α significantly. In the experiments in vivo, mice received daily s.c. injections of E2 and CpG respectively or both, then we found that the plasma concentration of IgM were elevated by E2 and CpG synergistically and the expression of IFN-α/β in spleens were noticeably increased by CpG plus E2 compared with the treatment of E2 or CpG only. This study indicates that E2 could exacerbate PDCs'' activation with CpG, which further activates B cells to upregulate susceptibility to autoantigens. IFN-α plays an important role in the stimulatory effect of PDCs on B cells. E2 stimulation of IFN-α production may result in female prevalence in autoimmune diseases such as SLE through activation of PDCs. This study provides novel evidence of relationship between estrogen and SLE and also sheds light on gender biases among SLE patients.     

Fine mapping and interaction analysis of a linear rabies virus neutralizing epitope

A novel human antibody AR16, targeting the G5 linear epitope of rabies virus glycoprotein (RVG) was shown to have promising antivirus potency. Using AR16, the minimal binding region within G5 was identified as HDFR (residues 261–264), with key residues HDF (residues 261–263) identified by alanine replacement scanning. The key HDF was highly conserved within phylogroup I Lyssaviruses but not those in phylogroup II. Using computer-aided docking and interaction models, not only the key residues (Asp30, Asp31, Tyr32, Trp53, Asn54, Glu99, Ile101, and Trp166) of AR16 that participated in the interaction with G5 were identified, the van der Waals forces that mediated the epitope–antibody interaction were also revealed. Seven out of eight presumed key residues (Asp30, Asp31, Tyr32, Trp53, Asn54, Glu99, and Ile101) were located at the variable regions of AR16 heavy chains. A novel mAb cocktail containing AR16 and CR57, has the potential to recognize non-overlapping, non-competing epitopes, and neutralize a broad range of rabies virus.     

A new neutralizing antibody against botulinum neurotoxin B recognizes the protein receptor binding sites for synaptotagmins II

Botulinum neurotoxins (BoNts) pose a biological hazard to humans and a serious potential bioweapon threat. Given the safety concern regarding the currently used equine antitoxin therapy for botulism, it is imperative to develop agents that are effective binding inhibitors. The aim of this study was to identify a novel neutralizing antibody against botulinum neurotoxin B (BoNtb) that recognizes the protein receptor binding sites for synaptotagmins II. This antibody showed significant dose-dependent protection against lethal toxin challenge in vivo at an intraperitoneal (i.p.) dose 10 times the half lethal dose (LD50). We proved that the efficacy of SC12 was based on its counteraction on the recognition and binding of BoNtb to target cells, resulting from the combination of antibody with the high affinity (KD: 1.34 nM) to protein receptor binding sites of BoNt by targeting a 25-mer dominant antigenic site on Hcc region (residues 1253–1277). The structure of the site targeted by this antibody overlaps the pocket-like protein receptor binding sites located at the distal tip of toxin molecule. Information gained from this study will facilitate the development of potent inhibitors that prevent the binding of BoNts with its receptors.     

Comparison of Beta-value and M-value methods for quantifying methylation levels by microarray analysis

Background  

High-throughput profiling of DNA methylation status of CpG islands is crucial to understand the epigenetic regulation of genes. The microarray-based Infinium methylation assay by Illumina is one platform for low-cost high-throughput methylation profiling. Both Beta-value and M-value statistics have been used as metrics to measure methylation levels. However, there are no detailed studies of their relations and their strengths and limitations.