Mutations in Radial Spoke Head Protein Genes RSPH9 and RSPH4A Cause Primary Ciliary Dyskinesia with Central-Microtubular-Pair Abnormalities

Primary ciliary dyskinesia (PCD) is a genetically heterogeneous inherited disorder arising from dysmotility of motile cilia and sperm. This is associated with a variety of ultrastructural defects of the cilia and sperm axoneme that affect movement, leading to clinical consequences on respiratory-tract mucociliary clearance and lung function, fertility, and left-right body-axis determination. We performed whole-genome SNP-based linkage analysis in seven consanguineous families with PCD and central-microtubular-pair abnormalities. This identified two loci, in two families with intermittent absence of the central-pair structure (chromosome 6p21.1, Zmax 6.7) and in five families with complete absence of the central pair (chromosome 6q22.1, Zmax 7.0). Mutations were subsequently identified in two positional candidate genes, RSPH9 on chromosome 6p21.1 and RSPH4A on chromosome 6q22.1. Haplotype analysis identified a common ancestral founder effect RSPH4A mutation present in UK-Pakistani pedigrees. Both RSPH9 and RSPH4A encode protein components of the axonemal radial spoke head. In situ hybridization of murine Rsph9 shows gene expression restricted to regions containing motile cilia. Investigation of the effect of knockdown or mutations of RSPH9 orthologs in zebrafish and Chlamydomonas indicate that radial spoke head proteins are important in maintaining normal movement in motile, “9+2”-structure cilia and flagella. This effect is rescued by reintroduction of gene expression for restoration of a normal beat pattern in zebrafish. Disturbance in function of these genes was not associated with defects in left-right axis determination in humans or zebrafish.     

Monthly day/night changes and seasonal daily rhythms of sexual steroids in Senegal sole (Solea senegalensis) under natural fluctuating or controlled environmental conditions

In this paper we attempted to investigate the existence of daily fluctuations on plasma sexual steroids (17beta-estradiol, E(2) and testosterone, T) in Senegal sole (Solea senegalensis) females. We described the monthly day/night concentrations and seasonal daily rhythms in animals reared under natural photo- and thermo-period. In addition, the influence of the natural annual fluctuation of the water temperature on the plasma concentration of these steroids was investigated, using one group of Senegal sole under a natural photoperiod, but with an attenuated thermal cycle (around 17-20 degrees C) for one year. Although no significant day/night differences were detected in monthly samplings, the existence of an annual rhythm of E(2) and T (p<0.01) with an acrophase in February was revealed by COSINOR analysis. Maximum values were reached in March for both steroids (6.1+/-1.7 ng mL(-1) at mid-dark, MD and 4.0+/-0.6 ng mL(-1) at mid-light, ML for E2 and 1.4+/-0.4 ng mL(-1) at MD and 0.8+/-0.1 ng mL(-1) at ML for T) in anticipation of the spawning season (May-June). As regards seasonal daily rhythms, the presence of daily oscillations was revealed. At the spring solstice (21st March) a daily rhythm was observed for both steroids (COSINOR, p<0.01), with an acrophase at 20:00 h (E(2)) and at 21:08 h (T). In summer, autumn and winter no daily rhythms were observed due to the low steroid levels at those seasons. When Senegal sole females were submitted to an attenuated annual thermal cycle, the steroid rhythm disappeared (there was no surge in spring, as in the control group) and these fish did not spawn, despite being subjected to natural photoperiod conditions. This result underlined the importance of the natural annual fluctuation of water temperature and photoperiod on the synchronization of the spawning season and on the onset of steroidogenesis.     

Glutamine synthetase sequence evolution in the mycobacteria and their use as molecular markers for Actinobacteria speciation

Background  

Although the gene encoding for glutamine synthetase (gln A) is essential in several organisms, multiple glnA copies have been identified in bacterial genomes such as those of the phylum Actinobacteria, notably the mycobacterial species. Intriguingly, previous reports have shown that only one copy (gln A1) is essential for growth in M. tuberculosis, while the other copies (gln A2, gln A3 and gln A4) are not.     

Bidirectional electron transfer in photosystem I: replacement of the symmetry-breaking tryptophan close to the PsaB-bound phylloquinone A1B with a glycine residue alters the redox properties of A1B and blocks forward electron transfer at cryogenic temperatures

A conserved tryptophan residue located between the A(1B) and F(X) redox centres on the PsaB side of the Photosystem I reaction centre has been mutated to a glycine in Chlamydomonas reinhardtii, thereby matching the conserved residue found in the equivalent position on the PsaA side. This mutant (PsaB:W669G) was studied using EPR spectroscopy with a view to understanding the molecular basis of the reported kinetic differences in forward electron transfer from the A(1A) and the A(1B) phyllo(semi)quinones. The kinetics of A(1)(-) reoxidation due to forward electron transfer or charge recombination were measured by electron spin echo spectroscopy at 265 K and 100 K, respectively. At 265 K, the reoxidation kinetics are considerably lengthened in the mutant in comparison to the wild-type. Under conditions in which F(X) is initially oxidised the kinetics of charge recombination at 100 K are found to be biphasic in the mutant while they are substantially monophasic in the wild-type. Pre-reduction of F(X) leads to biphasic kinetics in the wild-type, but does not alter the already biphasic kinetic properties of the PsaB:W669G mutant. Reduction of the [4Fe-4S] clusters F(A) and F(B) by illumination at 15 K is suppressed in the mutant. The results provide further support for the bi-directional model of electron transfer in Photosystem I of C. reinhardtii, and indicate that the replacement of the tryptophan residue with glycine mainly affects the redox properties of the PsaB bound phylloquinone A(1B).     

Detailed characterization of the peptide binding specificity of five common Patr class I MHC molecules

The chimpanzee (Pan troglodytes) is an important model for studying the immune response to several human pathogens, but the study of correlates of immunity has been hindered by the fact that little is known about the epitope-binding specificity of chimpanzee (Patr) class I MHC. In the present study we have characterized the peptide binding specificity of several common Patr class I molecules. Using single amino acid substitution analogs and large peptide libraries, quantitative peptide binding motifs have been derived for Patr A*0101, A*0701, A*0901, B*0101, and B*2401. Each molecule was found to bind peptides using position 2 and the C terminus as main anchor contacts. On the other hand, each Patr molecule is associated with a unique binding specificity, and the range of specificities is similar to that seen amongst HLA alleles. A high degree of cross-reactivity was noted between Patr A*0701 and Patr A*0901, suggesting the existence of a Patr-specific supertype. Consistent with previous studies suggesting that some cross-reactivity may exist between HLA and Patr alleles, Patr A*0901 was found to have an appreciable degree of cross-reactivity with molecules of the HLA A24-supertype. Finally, utilizing motif scans and peptide binding and intracellular cytokine staining assays, 77 hepatitis B virus (HBV)-derived epitopes were identified in five chimpanzees that were recently convalescent from acute HBV infection. Because the Patr alleles studied herein were found to be very common in two different chimpanzee populations, the present data should facilitate the use of chimpanzees for immunological studies.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Changes in genomic methylation patterns during the formation of triploid asexual dandelion lineages

DNA methylation is an epigenetic mechanism that has the potential to affect plant phenotypes and that is responsive to environmental and genomic stresses such as hybridization and polyploidization. We explored de novo methylation variation that arises during the formation of triploid asexual dandelions from diploid sexual mother plants using methylation‐sensitive amplified fragment length polymorphism (MS‐AFLP) analysis. In dandelions, triploid apomictic asexuals are produced from diploid sexual mothers that are fertilized by polyploid pollen donors. We asked whether the ploidy level change that accompanies the formation of new asexual lineages triggers methylation changes that contribute to heritable epigenetic variation within novel asexual lineages. Comparison of MS‐AFLP and AFLP fragment inheritance in a diploid × triploid cross revealed de novo methylation variation between triploid F₁ individuals. Genetically identical offspring of asexual F₁ plants showed modest levels of methylation variation, comparable to background levels as observed among sibs in a long‐established asexual lineage. Thus, the cross between ploidy levels triggered de novo methylation variation between asexual lineages, whereas it did not seem to contribute directly to variation within new asexual lineages. The observed background level of methylation variation suggests that considerable autonomous methylation variation could build up within asexual lineages under natural conditions.     

Reset of a critically disturbed microbial ecosystem: faecal transplant in recurrent Clostridium difficile infection

Recurrent Clostridium difficile infection (CDI) can be effectively treated by infusion of a healthy donor faeces suspension. However, it is unclear what factors determine treatment efficacy. By using a phylogenetic microarray platform, we assessed composition, diversity and dynamics of faecal microbiota before, after and during follow-up of the transplantation from a healthy donor to different patients, to elucidate the mechanism of action of faecal infusion. Global composition and network analysis of the microbiota was performed in faecal samples from nine patients with recurrent CDI. Analyses were performed before and after duodenal donor faeces infusion, and during a follow-up of 10 weeks. The microbiota data were compared with that of the healthy donors. All patients successfully recovered. Their intestinal microbiota changed from a low-diversity diseased state, dominated by Proteobacteria and Bacilli, to a more diverse ecosystem resembling that of healthy donors, dominated by Bacteroidetes and Clostridium groups, including butyrate-producing bacteria. We identified specific multi-species networks and signature microbial groups that were either depleted or restored as a result of the treatment. The changes persisted over time. Comprehensive and deep analyses of the microbiota of patients before and after treatment exposed a therapeutic reset from a diseased state towards a healthy profile. The identification of microbial groups that constitute a niche for C. difficile overgrowth, as well as those driving the reinstallation of a healthy intestinal microbiota, could contribute to the development of biomarkers predicting recurrence and treatment outcome, identifying an optimal microbiota composition that could lead to targeted treatment strategies.