Activating and inhibitory Fcγ receptors in rheumatoid arthritis: from treatment to targeted therapies

Fcγ receptors (FcγRs) bind the constant Fc region of IgG molecules. IgG/antigen-containing immune complexes elicit a variety of effector functions in cells that express activating FcγRs. Because activating FcγRs are present on cells from the innate immune system, such as dendritic cells, monocytes/macrophages and granulocytes, these IgG receptors form a crucial link between the innate and the acquired immune systems. Recently, the ability to detect the inhibitory FcγRIIb on cells has indicated an imbalance between activating and inhibitory FcγRs in rheumatoid arthritis. This progress offers an opportunity to study modulation of FcγR balance and could stimulate development of FcγR-directed immunotherapy.     

Conservation of alternative splicing and genomic organization of the myosin alkali light-chain (Mlc1) gene among Drosophila species

The Mlc1 gene of Drosophila melanogaster encodes two MLC1 isoforms via developmentally regulated alternative pre-mRNA splicing. In larval muscle and tubular and abdominal muscles of adults, all of the six exons are included in the spliced mRNA, whereas, in the fibrillar indirect flight muscle of adult, exon 5 is excluded from the mRNA. We show that this tissue-specific pattern of alternative splicing of the Mlc1 pre-mRNA is conserved in D. simulans, D. pseudoobscura, and D. virilis. Isolation and sequencing of the Mlc1 genes from these three other Drosophila species have revealed that the overall organization of the genes is identical and that the genes have maintained a very high level of sequence identity within the coding region. Pairwise amino acid identities are 94%-99%, and there are no charge changes among the proteins. Total nucleotide divergence within the coding region of the four genes supports the accepted genealogy of these species, but the data indicate a significantly higher rate of amino acid replacement in the branch leading to D. pseudoobscura. A comparison of nucleotide substitutions in the coding portions of exon 5 and exon 6, which encode the alternative carboxyl termini of the two MLC1 isoforms, suggests that exon 5 is subject to greater evolutionary constraints than is exon 6. In addition to the coding sequences, there is significant sequence conservation within the 5' and 3' noncoding DNA and two of the introns, including one that flanks exon 5. These regions are candidates for cis- regulatory elements. Our results suggest that evolutionary constraints are acting on both the coding and noncoding sequences of the Mlc1 gene to maintain proper expression and function of the two MLC1 polypeptides.      

Length variation and secondary structure of introns in the Mlc1 gene in six species of Drosophila

A nearly universal feature of intron sequences is that even closely related species exhibit a large number of insertion/deletion differences. The goal of the analysis described here is to test whether the observed pattern of insertion/deletion events in the genealogy of the myosin alkali light chain (Mlc1) gene is consistent with neutrality, and if not, to determine the underlying forces of evolutionary change. Mlc1 pre-mRNA is alternatively spliced, and one constraint is that signals necessary for tissue-specificity of directed splicing must be conserved. If the total length of an intron is functionally constrained, then the distribution of indels on branches of the gene genealogy should reflect a departure from randomness. Here we perform a phylogenetic analysis, inferring ancestral states wherever possible on a phylogeny of 29 alleles of Mlc1 from six species of Drosophila. Observed patterns of indels on the genealogy were compared to those from simulated data, with the result that we cannot reject the null hypothesis of neutrality. A clear departure from a neutral prediction was seen in the excess folding free energy predicted for the introns flanking the alternatively spliced exon. Relative rate tests also suggest a retardation in the rate of Mlc1 sequence evolution in the simulans clade.      

Phylogenetic relationships between isolated populations of the limestone‐dwelling microsnail Gyliotrachela hungerfordiana (Gastropoda: Vertiginidae)

The vertiginid species Gyliotrachela hungerfordiana, an obligate limestone‐dwelling microsnail, is relatively widespread and is found on a large number of isolated limestone hills in Peninsular Malaysia. To elucidate the pattern of colonization of these hills, we conducted a molecular phylogenetic analysis on G. hungerfordiana subpopulations from 15 separate limestone outcrops. As outgroups, we also included five related Peninsular Malaysian Vertiginidae (Gyliotrachela frequens, Gyliotrachela transitans, Gyliotrachela salpinx, Gyliotrachela depressispira and Paraboysidia tarutao), one population each. A combined analysis of nuclear (internal transcribed spacer 1) and mitochondrial (cytochrome c oxidase 1) sequences showed that (1) G. hungerfordiana is monophyletic; (2) there is a clear geographical pattern in the phylogenetic relationships between G. hungerfordiana populations, with genetic distances increasing with geographic distance; (3) this pattern is disturbed by a few long‐distance (north‐west to south‐east and north to south) colonizations.     

Aging of Dry Desiccation-Tolerant Pollen Does Not Affect Protein Secondary Structure

Protein secondary structure and membrane phase behavior in aging Typha latifolia pollen were studied by means of Fourier transform infrared microspectroscopy (FTIR). Membranes isolated from fresh pollen occurred mainly in the liquid crystalline phase at room temperature, whereas the membrane fluidity of aged pollen was drastically decreased. This decrease did not result in large-scale irreversible protein aggregation, as was concluded from in situ FTIR assessment of the amide-1 bands. Curve-fitting on the infrared absorbance spectra enabled estimation of the proportion of different classes of protein secondary structure. Membrane proteins had a relatively large amount of [alpha]-helical structure (48%; band at 1658 cm-1), and turn-like structures (at 1637 and 1680 cm-1) were also detected. The secondary protein structure of isolated cytoplasmic proteins resembled that of proteins in whole pollen and was conserved upon drying in the absence of sucrose. The isolated cytoplasmic proteins had a large amount of [alpha]-helical structure (43%), and also [beta]-sheet (at 1637 and 1692 cm-1) and turn structures were detected. Heat-denaturing experiments with intact hydrated pollen showed low (1627 cm-1) and high (1692 cm-1) wave number bands indicating irreversible protein aggregates. The results presented in this paper show that FTIR is an extremely suitable technique to study protein secondary structure in intact plant cells of different hydration levels and developmental stages.     

ST-segment elevation associated with allergic reaction to echocardiographic contrast agent administration

We report a case of an allergic reaction after the administration of an echocardiographic contrast agent which resulted in ST-segment elevation. Hypersensitivity and allergic reactions are known causes of acute cardiovascular events. However, only limited reports are available which suggest the exact mechanism of the occurrence of angina or myocardial infarction during severe allergic reactions. In our case, through invasive imaging (coronary angiography and IVUS) we have shown for the first time a transient coronary spasm in the absence of intra-coronary thrombus and only minimal neointimal hyperplasia.     

The draft genome of a socially polymorphic halictid bee,Lasioglossum albipes

Background

Taxa that harbor natural phenotypic variation are ideal for ecological genomic approaches aimed at understanding how the interplay between genetic and environmental factors can lead to the evolution of complex traits. Lasioglossum albipes is a polymorphic halictid bee that expresses variation in social behavior among populations, and common-garden experiments have suggested that this variation is likely to have a genetic component.

Results

We present the L. albipes genome assembly to characterize the genetic and ecological factors associated with the evolution of social behavior. The de novo assembly is comparable to other published social insect genomes, with an N50 scaffold length of 602 kb. Gene families unique to L. albipes are associated with integrin-mediated signaling and DNA-binding domains, and several appear to be expanded in this species, including the glutathione-s-transferases and the inositol monophosphatases. L. albipes has an intact DNA methylation system, and in silico analyses suggest that methylation occurs primarily in exons. Comparisons to other insect genomes indicate that genes associated with metabolism and nucleotide binding undergo accelerated evolution in the halictid lineage. Whole-genome resequencing data from one solitary and one social L. albipes female identify six genes that appear to be rapidly diverging between social forms, including a putative odorant receptor and a cuticular protein.

Conclusions

L. albipes represents a novel genetic model system for understanding the evolution of social behavior. It represents the first published genome sequence of a primitively social insect, thereby facilitating comparative genomic studies across the Hymenoptera as a whole.     

Phospholipid species act as modulators in p97/p47-mediated fusion of Golgi membranes

The ATPase p97 in complex with p47 participates in Golgi cisternae rebuilding after mitosis. In a Golgi-liposome assay, the complex triggered a phosphatidylethanolamine (PE)-promoted fusion. Here we show for the first time that fusion between mitotic Golgi membranes induced by adding cytosol or purified p97/p47 is modulated by PE present in Golgi membranes. Using model membranes, we demonstrate a PE-dependent recruitment of p97/p47 to membranes, causing dramatic conformational rearrangements and favoring protein-lipid interactions. Previously buried hydrophobic sites become exposed in a controlled manner, which leads to the penetration of (a) domain(s) of the complex into lipid bilayers, facilitated by a PE-dependent increase in headgroup spacing. In contrast, when facing phosphatidylcholine (PC) the complex clusters extensively. This implies that in the presence of PC protein-protein interactions rather than fusion-promoting protein-lipid interactions occur. Importantly, PE-mediated changes in secondary and tertiary structures are exclusively observed when p97 is complexed with p47, which is a prerequisite for membrane fusion. We therefore propose that at physiological conditions PE-induced conformational changes in p97/p47 are relevant in triggering this activity.     

A member of a novel family of yeast 'zn-finger' proteins mediates the transition from stationary phase to cell proliferation.

The cloning and molecular characterization of the GCS1 gene from the budding yeast Saccharomyces cerevisiae show that stationary phase is in fact a unique developmental state, with requirements to resume cell proliferation that can be distinct from those for maintenance of proliferation. Deletion of the GCS1 gene products a novel phenotype: stationary-phase mutant cells do not resume proliferation at a restrictive temperature of 15 degrees C, but mutant cells lacking Gcs1p that are proliferating at the permissive temperature of 29 degrees C continue to proliferate after transfer to 15 degrees C as long as nutrients are available. The GCS1 gene sequence predicts a 39 kDa polypeptide with a novel 'Zn-finger' motif. A point mutation within the finger motif produces a phenotype that mimics that of deletion of the GCS1 gene, showing that the finger motif is essential for full Gcs1p activity. Gcs1p and the products of two newly identified genes, SPS18 and GLO3, constitute a family of novel Zn-finger proteins.