Pairing centers recruit a Polo-like kinase to orchestrate meiotic chromosome dynamics in C. elegans

Faithful segregation of homologous chromosomes during meiosis requires pairing, synapsis, and crossing-over. In C.?elegans, homolog pairing and synapsis depend on pairing centers (PCs), special regions near one end of each chromosome that interact with the nuclear envelope (NE) and cytoplasmic microtubules. Here, we report that PCs are required for nuclear reorganization at the onset of meiosis. We demonstrate that PCs recruit the Polo-like kinase PLK-2 to induce NE remodeling, chromosome pairing, and synapsis. Recruitment of PLK-2 is also required to mediate a cell cycle delay and selective apoptosis of nuclei containing unsynapsed chromosomes, establishing a molecular link between these two quality control mechanisms. This work reveals unexpected functions for the conserved family of Polo-like kinases, and advances our understanding of how meiotic processes are properly coordinated to ensure transmission of genetic information from parents to progeny.     

Influenza vaccination for immunocompromised patients: systematic review and meta-analysis from a public health policy perspective

Background

Immunocompromised patients are vulnerable to severe or complicated influenza infection. Vaccination is widely recommended for this group. This systematic review and meta-analysis assesses influenza vaccination for immunocompromised patients in terms of preventing influenza-like illness and laboratory confirmed influenza, serological response and adverse events.

Methodology/Principal Findings

Electronic databases and grey literature were searched and records were screened against eligibility criteria. Data extraction and risk of bias assessments were performed in duplicate. Results were synthesised narratively and meta-analyses were conducted where feasible. Heterogeneity was assessed using I² and publication bias was assessed using Begg''s funnel plot and Egger''s regression test. Many of the 209 eligible studies included an unclear or high risk of bias. Meta-analyses showed a significant effect of preventing influenza-like illness (odds ratio [OR] = 0.23; 95% confidence interval [CI] = 0.16–0.34; p<0.001) and laboratory confirmed influenza infection (OR = 0.15; 95% CI = 0.03–0.63; p = 0.01) through vaccinating immunocompromised patie nts compared to placebo or unvaccinated controls. We found no difference in the odds of influenza-like illness compared to vaccinated immunocompetent controls. The pooled odds of seroconversion were lower in vaccinated patients compared to immunocompetent controls for seasonal influenza A(H1N1), A(H3N2) and B. A similar trend was identified for seroprotection. Meta-analyses of seroconversion showed higher odds in vaccinated patients compared to placebo or unvaccinated controls, although this reached significance for influenza B only. Publication bias was not detected and narrative synthesis supported our findings. No consistent evidence of safety concerns was identified.

Conclusions/Significance

Infection prevention and control strategies should recommend vaccinating immunocompromised patients. Potential for bias and confounding and the presence of heterogeneity mean the evidence reviewed is generally weak, although the directions of effects are consistent. Areas for further research are identified.     

PRGmatic: an efficient pipeline for collating genome-enriched second-generation sequencing data using a 'provisional-reference genome'

Second-generation sequencing is increasingly being used in combination with genome-enrichment techniques to amplify a large number of loci in many individuals for the purpose of population genetic and phylogeographic analysis. Compiling all the necessary tools to analyse these data is complex and time-consuming. Here, we assemble a set of programs and pipe them together with Perl, enabling research laboratories without a dedicated bioinformatician to utilize second-generation sequencing. User input is a folder of the second-generation sequencing reads sorted by individual (in FASTA format) and pipeline output is a folder of multi-FASTA files that correspond to loci (with 2 alleles called per individual). Additional output includes a summary file of the number of individuals per locus, observed and expected heterozygosity for each locus, distribution of multiple hits and summary statistics (θ, Tajima's D, etc.). This user-friendly, open source pipeline, which requires no a priori reference genome because it constructs its own, allows the user to set various parameters (e.g. minimum coverage) in the dependent programs (CAP3, BWA, SAMtools and VarScan) and facilitates evaluation of the nature and quality of data collected prior to analysis in software packages.     

A family of zinc-finger proteins is required for chromosome-specific pairing and synapsis during meiosis in C. elegans

Homologous chromosome pairing and synapsis are prerequisite for accurate chromosome segregation during meiosis. Here, we show that a family of four related C2H2 zinc-finger proteins plays a central role in these events in C. elegans. These proteins are encoded within a tandem gene cluster. In addition to the X-specific HIM-8 protein, three additional paralogs collectively mediate the behavior of the five autosomes. Each chromosome relies on a specific member of the family to pair and synapse with its homolog. These "ZIM" proteins concentrate at special regions called meiotic pairing centers on the corresponding chromosomes. These sites are dispersed along the nuclear envelope during early meiotic prophase, suggesting a role analogous to the telomere-mediated meiotic bouquet in other organisms. To gain insight into the evolution of these components, we characterized homologs in C. briggsae and C. remanei, which revealed changes in copy number of this gene family within the nematode lineage.     

GPRC6A mediates the non-genomic effects of steroids

The identity of the putative G-protein coupled receptor (GPCR) that mediates the non-genomic effects of androgens is unknown. We present in vitro and in vivo evidence that the orphan GPRC6A receptor, a widely expressed calcium and amino acid sensing GPCR, transduces the non-genomic effects of testosterone and other steroids. Overexpression of GPRC6A imparts the ability of extracellular testosterone to illicit a rapid, non-genomic signaling response in HEK-293 cells lacking the androgen receptor. Conversely, testosterone-stimulated rapid signaling and phosphorylation of ERK is attenuated in bone marrow stromal cells derived from GPRC6A(-/-) mice and in 22Rv1 prostate cancer cells after siRNA-mediated knockdown of GPRC6A. Compared with wild-type controls, GPRC6A(-/-) null mice exhibit significantly less ERK activation and Egr-1 expression in both bone marrow and testis in response to pharmacological doses of testosterone in vivo. In addition, testosterone administration results in suppression of luteinizing hormone in wild-type male mice, but paradoxically stimulates serum luteinizing hormone levels in GPRC6A(-/-) null mice. These results suggest that GPRC6A is functionally important in regulating non-genomic effects of androgens in multiple tissues.     

Multiple cholesterol recognition/interaction amino acid consensus (CRAC) motifs in cytosolic C tail of Slo1 subunit determine cholesterol sensitivity of Ca2+- and voltage-gated K+ (BK) channels

Large conductance, Ca(2+)- and voltage-gated K(+) (BK) channel proteins are ubiquitously expressed in cell membranes and control a wide variety of biological processes. Membrane cholesterol regulates the activity of membrane-associated proteins, including BK channels. Cholesterol modulation of BK channels alters action potential firing, colonic ion transport, smooth muscle contractility, endothelial function, and the channel alcohol response. The structural bases underlying cholesterol-BK channel interaction are unknown. Such interaction is determined by strict chemical requirements for the sterol molecule, suggesting cholesterol recognition by a protein surface. Here, we demonstrate that cholesterol action on BK channel-forming Cbv1 proteins is mediated by their cytosolic C tail domain, where we identified seven cholesterol recognition/interaction amino acid consensus motifs (CRAC4 to 10), a distinct feature of BK proteins. Cholesterol sensitivity is provided by the membrane-adjacent CRAC4, where Val-444, Tyr-450, and Lys-453 are required for cholesterol sensing, with hydrogen bonding and hydrophobic interactions participating in cholesterol location and recognition. However, cumulative truncations or Tyr-to-Phe substitutions in CRAC5 to 10 progressively blunt cholesterol sensitivity, documenting involvement of multiple CRACs in cholesterol-BK channel interaction. In conclusion, our study provides for the first time the structural bases of BK channel cholesterol sensitivity; the presence of membrane-adjacent CRAC4 and the long cytosolic C tail domain with several other CRAC motifs, which are not found in other members of the TM6 superfamily of ion channels, very likely explains the unique cholesterol sensitivity of BK channels.     

Identification of I137M and other mutations that modulate incubation periods for two human prion strains

We report here the transmission of human prions to 18 new transgenic (Tg) mouse lines expressing 8 unique chimeric human/mouse prion proteins (PrP). Extracts from brains of two patients, who died of sporadic Creutzfeldt-Jakob disease (sCJD), contained either sCJD(MM1) or sCJD(VV2) prion strains and were used for inocula. Mice expressing chimeric PrP showed a direct correlation between expression level and incubation period for sCJD(MM1) prions irrespective of whether the transgene encoded methionine (M) or valine (V) at polymorphic residue 129. Tg mice expressing chimeric transgenes encoding V129 were unexpectedly resistant to infection with sCJD(VV2) prions, and when transmission did occur, it was accompanied by a change in strain type. The transmission of sCJD(MM1) prions was modulated by single amino acid reversions of each human PrP residue in the chimeric sequence. Reverting human residue 137 in the chimeric transgene from I to M prolonged the incubation time for sCJD(MM1) prions by more than 100 days; structural analyses suggest a profound change in the orientation of amino acid side chains with the I→M mutation. These findings argue that changing the surface charge in this region of PrP greatly altered the interaction between PrP isoforms during prion replication. Our studies contend that strain-specified replication of prions is modulated by PrP sequence-specific interactions between the prion precursor PrP(C) and the infectious product PrP(Sc).