Allelic Variation in Malawi Cichlid Opsins: A Tale of Two Genera

The role of sequence variation in the spectral tuning of color vision is well established in many systems. This includes the cichlids of Lake Victoria where sequence variation has been linked to environmental light gradients and speciation. The cichlids of Lake Malawi are a similar model for visual evolution, but the role of gene sequence variation in visual tuning between closely related species is unknown. This work describes such variation in multiple species of two rock-dwelling genera: Metriaclima and Labidochromis. Genomic DNA for seven cone opsin genes was sequenced and the structure of the opsin proteins was inferred. Retinal binding pocket polymorphisms were identified and compared to available data regarding spectral absorbance shifts. Sequence variation with known or potential effects on absorbance spectra were found in four genes: SWS1 (UV sensitive), SWS2B (violet sensitive), RH2Aβ (green sensitive), and LWS (red sensitive). Functional variation was distributed such that each genus had both a variable short-wavelength and long-wavelength sensitive opsin. This suggests spectral tuning is important at the margins of the cichlid visual spectrum. Further, there are two SWS1 opsin alleles that differ in sensitivity by 10 nm and are >2 MY divergent. One of these occurs in a haplotype block >1 kb. Potential haplotype blocks were found around the RH2 opsin loci. These data suggest that molecular diversification has resulted in functionally unique alleles and changes to the visual system. These data also suggest that opsin sequence variation tunes spectral sensitivities between closely related species and that the specific regions of spectral tuning are genus-specific.     

Pathogenic bacteria as vaccine vectors: teaching old bugs new tricks

As our scientific knowledge of bacteria grows, so does our ability to manipulate these bacteria to protect rather than infect mammalian hosts from a diverse group of diseases. The old axiom that the best way to protect from a disease is to get infected in the first place is not feasible in the face of the diverse group of pathogens that infect humans. Therefore, reprogramming bacteria to protect against diverse bacterial, viral, and parasitic diseases as well as cancer is a new reality in the field of vaccines.     

Clinical and economic consequences of a reimbursement restriction of nebulised respiratory therapy in adults: direct comparison of randomised and observational evaluations

Objective To compare the results of a randomised and an observational evaluation of the same policy that restricted reimbursement for nebulised respiratory medications in adult patients in a community setting.Designs Cluster randomised controlled trial and observational time series with historical controls.Setting Pharmacare, the government funded drug benefits plan for elderly people and patients receiving social assistance in British Columbia, Canada.Participants In the randomised controlled trial 104 clusters of medical practices, pair matched by geography and approximately by practice size, were randomised to the intervention group (449 patients affected by the policy on 1 March 1999), and the control group (offered a six month exemption, affecting 386 patients). The observational analysis included all Pharmacare beneficiaries (excluding the 386 exempt patients) who had used any nebulised drugs six months before the policy (4624 patients).Intervention Pharmacare restricted reimbursement for nebulised bronchodilators, steroids, and cromoglycate to patients whose doctors applied for an individual patient''s exemption, giving an appropriate clinical reason.Main outcome measures Number of contacts with doctors and services, emergency admissions to hospital, and utilisation of and expenditure for respiratory drugs in databases of British Columbia''s Ministry of Health.Results Contacts with doctors or emergency admissions to hospital did not increase in association with the restriction, regardless of the analytical approach. In the observational analysis, we found a reduction of $C24 per patient month in all nebulised drug use (95% confidence interval 19 to 29) and an increase of $C3 per patient month in all expenditure for inhalers (1.4 to 4.5). The randomised evaluation found savings of $C8 per patient month for nebulisers (P = 0.24) and no increase in spending on inhalers (P = 0.79). Correcting for 60% non-compliance by exempt doctors in a sensitivity analysis yielded similar results as the observational evaluation.Conclusions Observational as well as randomised analyses found moderate net savings and no increase in unintended healthcare outcomes after restricting reimbursement for nebulised respiratory drugs. Randomised policy trials are feasible and, if carefully implemented, likely to be concordant with observational evaluations.     

Dynamic ensemble odor coding in the mammalian olfactory bulb: sensory information at different timescales

Neural firing discharges are often temporally patterned, but it is often ambiguous as to whether the temporal features of these patterns constitute a useful code. Here we show in the mouse olfactory bulb that ensembles of projection neurons respond with complex odor- and concentration-specific dynamic activity sequences developing below and above sniffing frequency. Based on this activity, almost optimal discrimination of presented odors was possible during single sniffs, consistent with reported behavioral data. Within a sniff cycle, slower features of the dynamics alone (>100 ms resolution, including mean firing rate) were sufficient for maximal discrimination. A smaller amount of information was also observed in faster features down to 20-40 ms resolution. Therefore, mitral cell ensemble activity contains information at different timescales that could be separately or complementarily exploited by downstream brain centers to make odor discriminations. Our results also support suggestive analogies in the dynamics of odor representations between insects and mammals.     

Upregulated miR-146a expression in peripheral blood mononuclear cells from rheumatoid arthritis patients

Introduction

MicroRNAs are small noncoding RNA molecules that negatively regulate gene expression via degradation or translational repression of their targeted mRNAs. It is known that aberrant microRNA expression can play important roles in cancer, but the role of microRNAs in autoimmune diseases is only beginning to emerge. In this study, the expression of selected microRNAs is examined in rheumatoid arthritis.

Methods

Total RNA was isolated from peripheral blood mononuclear cells obtained from patients with rheumatoid arthritis, and healthy and disease control individuals, and the expression of miR-146a, miR-155, miR-132, miR-16, and microRNA let-7a was analyzed using quantitative real-time PCR.

Results

Rheumatoid arthritis peripheral blood mononuclear cells exhibited between 1.8-fold and 2.6-fold increases in miR-146a, miR-155, miR-132, and miR-16 expression, whereas let-7a expression was not significantly different compared with healthy control individuals. In addition, two targets of miR-146a, namely tumor necrosis factor receptor-associated factor 6 (TRAF6) and IL-1 receptor-associated kinase 1 (IRAK-1), were similarly expressed between rheumatoid arthritis patients and control individuals, despite increased expression of miR-146a in patients with rheumatoid arthritis. Repression of TRAF6 and/or IRAK-1 in THP-1 cells resulted in up to an 86% reduction in tumor necrosis factor-α production, implicating that normal miR-146a function is critical for the regulation of tumor necrosis factor-α production.

Conclusions

Recent studies have shown that synovial tissue and synovial fibroblasts from patients with rheumatoid arthritis exhibit increased expression of certain microRNAs. Our data thus demonstrate that microRNA expression in rheumatoid arthritis peripheral blood mononuclear cells mimics that of synovial tissue/fibroblasts. The increased microRNA expression in rheumatoid arthritis patients is potentially useful as a marker for disease diagnosis, progression, or treatment efficacy, but this will require confirmation using a large and well defined cohort. Our data also suggest a possible mechanism contributing to rheumatoid arthritis pathogenesis, whereby miR-146a expression is increased but unable to properly function, leading to prolonged tumor necrosis factor-α production in patients with rheumatoid arthritis.     

Giantin is the major Golgi autoantigen in human anti-Golgi complex sera

Anti-Golgi complex antibodies (AGAs) are primarily associated with systemic lupus erythematosus and Sjögren's syndrome. Here we report on the immunoreactivity of AGAs against five Golgi autoantigens (giantin, golgin-245, golgin-160, golgin-95/GM130, and golgin-97) and provide data from epitope mapping on the most common Golgi autoantigen, namely giantin. A total of 80 human sera containing AGAs, as defined by indirect immunofluorescence on HEp-2 cells, were analyzed by ELISA using recombinant autoantigens and immunoprecipitation. The proportion of AGA sera that reacted with the five Golgi autoantigens was correlated with the molecular mass of the Golgi antigens. Autoantibodies to giantin, the largest Golgi autoantigen, were the predominant AGAs, being found in 50% of the AGA sera. Epitope mapping of giantin was performed using six recombinant fragments spanning the entire protein. Antigiantin-positive sera with low titer autoantibodies recognized epitopes in the carboxyl-terminal fragments that are proximal to the Golgi membrane, whereas higher titer sera exhibited strong reactivity to amino-terminal and central domains that are likely to extend from the Golgi membrane into the cytoplasm. Our working hypothesis is that aberrantly expressed Golgi complex autoantigens may be released into the immune system when cells undergo lysis. By virtue of a carboxyl-terminal transmembrane domain, giantin is likely to be more stably associated with the cytoplasmic face of the Golgi complex than are other golgins, which are peripheral proteins. The stable association of giantin with the putative released Golgi complex may contribute to its preferential autoantigenicity.     

Mitochondrial DNA heteroplasmy in laboratory mice experimentally enclosed in the radioactive Chernobyl environment

Mitochondrial DNA heteroplasmy using the protein-coding cytochrome b (Mtcyb) gene was assessed in laboratory mice (C57BL/6 and BALB/c) exposed to the Chernobyl environment. Subacute to subchronic (30-40 days) exposure resulted in a cumulative radiation dose of 1.2-1.6 Gy ( approximately 0.04 Gy/day). Mice were sampled prior to introduction into the enclosures and again after removal from the enclosures. Nucleotide variation (site heteroplasmy) in 306 pre-exposure Mtcyb gene copies (122400 base pairs) was compared to variation in 354 postexposure gene copies (141600 base pairs). Five mutant copies, each characterized by a single nucleotide substitution, were observed (four in the pre-exposure samples, one in a postexposure sample). The frequencies of mutant gene copies and nucleotide substitutions in pre-exposure and postexposure samples were not significantly different. This suggests that this type of exposure (i.e. low dose rate) does not pose a significant mutation risk to the Mtcyb gene in digit tissue. Furthermore, no significant radiation risk to analogous human tissues may exist when occupational exposures involve low dose rates such as these. Finally, linear, cumulative models of genetic risk currently used to estimate radiation-induced effects are likely to be inappropriate for low-dose-rate exposures and need to be re-evaluated critically.     

Colour vision and speciation in Lake Victoria cichlids of the genus Pundamilia

Lake Victoria cichlids are one of the most speciose groups of vertebrates. Selection on coloration is likely playing an important role in their rapid speciation. To test the hypothesis that sensory biases could explain species differences in mating preferences and nuptial coloration, we studied seven populations of four closely related species of the genus Pundamilia that differ in visual environment and male nuptial colour. Microspectrophotometry determined that the wavelength of maximum absorption (lambdamax) of the rod pigment and three cone pigments were similar in all four species. Only the long wavelength sensitive (LWS) pigment varied among species, with 3-4 nm shifts in lambdamax that correlated with differences in the LWS opsin sequence. These subtle shifts in lambdamax coincided with large shifts in male body colour, with red species having longer LWS pigments than blue species. Furthermore, we observed within and between species a correlation between water transparency and the proportion of red/red vs. red/green double cones. Individuals from turbid water had more red/red double cones than individuals from clear water. The variation in LWS lambdamax and in the proportion of red/red double cones could lead to differences in perceived brightness that may explain the evolution of variation in male coloration. However, other factors, such as chromophore shifts and higher order neural processing, should also be investigated to fully understand the physiological basis of differential responses to male mating hues in cichlid fish.     

Sonic hedgehog controls stem cell behavior in the postnatal and adult brain

Sonic hedgehog (Shh) signaling controls many aspects of ontogeny, orchestrating congruent growth and patterning. During brain development, Shh regulates early ventral patterning while later on it is critical for the regulation of precursor proliferation in the dorsal brain, namely in the neocortex, tectum and cerebellum. We have recently shown that Shh also controls the behavior of cells with stem cell properties in the mouse embryonic neocortex, and additional studies have implicated it in the control of cell proliferation in the adult ventral forebrain and in the hippocampus. However, it remains unclear whether it regulates adult stem cell lineages in an equivalent manner. Similarly, it is not known which cells respond to Shh signaling in stem cell niches. Here we demonstrate that Shh is required for cell proliferation in the mouse forebrain's subventricular zone (SVZ) stem cell niche and for the production of new olfactory interneurons in vivo. We identify two populations of Gli1+ Shh signaling responding cells: GFAP+ SVZ stem cells and GFAP- precursors. Consistently, we show that Shh regulates the self-renewal of neurosphere-forming stem cells and that it modulates proliferation of SVZ lineages by acting as a mitogen in cooperation with epidermal growth factor (EGF). Together, our data demonstrate a critical and conserved role of Shh signaling in the regulation of stem cell lineages in the adult mammalian brain, highlight the subventricular stem cell astrocytes and their more abundant derived precursors as in vivo targets of Shh signaling, and demonstrate the requirement for Shh signaling in postnatal and adult neurogenesis.