Visualizing monolayers with a water-soluble fluorophore to quantify adsorption, desorption, and the double layer
Ian C. Shieh and Joseph A. Zasadzinski
Visualizing phase separation in monolayers at the air–water interface with fluorescence microscopy has, up to now, relied on image contrast provided by fluorescently tagged lipids. However, the tagged lipids are insoluble and cannot leave the interface, ultimately reaching high concentrations as the phase distribution changes. This can lead to alterations in phase behavior, domain shape, and fluorescence quenching. Here (pp. E826–E835) we show that a water-soluble dye in the subphase preferentially adsorbs into less-ordered monolayer domains and can provide quantifiable contrast in confocal microscopy images. The dye distribution in the double layer adjacent to charged monolayers can also be imaged quantitatively and used to rapidly assess the surface potential and the fractional dissociation of the monolayer lipids.
C-terminal sequence of amyloid-resistant type F apolipoprotein A-II inhibits amyloid fibril formation of apolipoprotein A-II in mice
Jinko Sawashita, Beiru Zhang, Kazuhiro Hasegawa, Masayuki Mori, Hironobu Naiki, Fuyuki Kametani, and Keiichi Higuchi (樋口京一)
Apolipoprotein (apo) A-II is the most important protein associated with senile amyloidosis. Because some variants of apoA-II protein have been found among inbred strains of mice, we hypothesized that investigating amyloidogenesis of the variants would improve our understanding of the molecular and biological mechanisms of senile amyloidosis. Here, we demonstrate that mice with type F apoA-II (APOA2F) protein were absolutely resistant to senile amyloidosis. Moreover, a selective C-terminal APOA2F peptide inhibited fibril formation of amyloidogenic apoA-II in vitro and prevented senile amyloidosis in mice. We propose (pp. E836–E845) an inhibitory model in which the C-terminal APOA2F peptide prevents further fibril extension by blocking the active ends of seeds. This approach could provide a novel therapeutic option for the treatment of senile amyloidosis.
Convergence of ion channel genome content in early animal evolution
Benjamin J. Liebeskind, David M. Hillis, and Harold H. Zakon
The early evolution of animal nervous systems is poorly understood, but comparative genomics provides a new window into the past. One important controversy is about whether nervous systems evolved just once or independently in different animal lineages. In this work (pp. E846–E851), we explore the history of the gene families most central to nervous system function: ion channels. We track when these gene families expanded in animal evolution and find that these gene families radiated on several occasions and, in some cases, underwent periods of contraction. The multiple origins of these gene families may signify large-scale convergent evolution of nervous system complexity.
Constraints on the evolution of a doublesex target gene arising from doublesex’s pleiotropic deployment
Shengzhan D. Luo and Bruce S. Baker
Most sexually dimorphic features of Drosophila melanogaster are specified by the action of sex-specific transcription factors encoded by the doublesex (dsx) gene. Evolutionary changes in such sexually dimorphic features are often a result of changes in the cis-regulatory sequences of the DSX target genes. When a particular target gene is directly regulated by DSX in multiple tissues, evolutionarily conflicting constraints may be generated. The research we present here (pp. E852–E861) reveals that such conflict can be solved by deploying different cis-regulatory modules (sharing the DSX-binding site) for different tissues. This mechanism could also apply to other transcription factors.
Automated analysis of high-throughput B-cell sequencing data reveals a high frequency of novel immunoglobulin V gene segment alleles
Daniel Gadala-Maria, Gur Yaari, Mohamed Uduman, and Steven H. Kleinstein
High-throughput sequencing of B-cell immunoglobulin receptors is providing unprecedented insight into adaptive immunity. A key step in analyzing these data involves assignment of the germline variable (V), diversity (D), and joining (J) gene-segment alleles that comprise each immunoglobulin sequence by matching them against a database of known V(D)J alleles. However, this process will fail for sequences that use previously undetected alleles, whose frequency in the population is unclear. Here (pp. E862–E870) we describe TIgGER, a computational method that significantly improves V(D)J allele assignments by first determining the complete set of gene segments carried by a subject, including novel alleles. The application of TIgGER identifies a surprisingly high frequency of novel alleles, highlighting the critical need for this approach.
Dysregulation of Escherichia coli α-hemolysin expression alters the course of acute and persistent urinary tract infection
Kanna Nagamatsu, Thomas J. Hannan, Randi L. Guest, Maria Kostakioti, Maria Hadjifrangiskou, Jana Binkley, Karen Dodson, Tracy L. Raivio, and Scott J. Hultgren
The majority of urinary tract infections (UTIs) are caused by uropathogenic Escherichia coli (UPEC). Upon UPEC infection, exfoliation of host bladder epithelial (urothelial) cells leads to sloughing of bacteria-laden cells into the urine for expulsion. However, it can also facilitate bacterial dissemination into deeper tissues. Thus, the balance and timing of exfoliation are important in determining disease outcomes (pp. E871–E880). Here, we investigate host–pathogen dynamics in human urothelial cells in vitro and in murine model of acute cystitis. We discovered that the CpxR response regulator-CpxA sensor kinase two-component system regulates the expression of the pore-forming toxin α-hemolysin (HlyA) in response to environmental conditions. HlyA, in turn, is critical for fine-tuning the dynamics of host cell exfoliation and enhancing UPEC fitness during acute UTI.
Contribution of reactive oxygen species to cerebral amyloid angiopathy, vasomotor dysfunction, and microhemorrhage in aged Tg2576 mice
Byung Hee Han, Meng-liang Zhou, Andrew W. Johnson, Itender Singh, Fan Liao, Ananth K. Vellimana, James W. Nelson, Eric Milner, John R. Cirrito, Jacob Basak, Min Yoo, Hans H. Dietrich, David M. Holtzman, and Gregory Joseph Zipfel
One of the hallmarks of Alzheimer’s disease (AD) is cerebral amyloid angiopathy (CAA), which is a strong and independent risk factor for cerebral hemorrhage, ischemic stroke, and dementia. However, the mechanisms by which CAA contributes to these conditions are poorly understood. Results from the present study (pp. E881–E890) provide strong evidence that vascular oxidative stress plays a causal role in CAA-induced cerebrovascular dysfunction, CAA-induced cerebral hemorrhage, and CAA formation, itself. They also suggest that NADPH oxidase is the source of this oxidative stress and that strategies to inhibit NADPH oxidase may have therapeutic potential in patients with AD and CAA.
MmTX1 and MmTX2 from coral snake venom potently modulate GABAA receptor activity
Jean-Pierre Rosso, Jürgen R. Schwarz, Marcelo Diaz-Bustamante, Brigitte Céard, José M. Gutiérrez, Matthias Kneussel, Olaf Pongs, Frank Bosmans, and Pierre E. Bougis
In this study (pp. E891–E900), we report the identification of the first potent GABAA receptor-targeting toxins, to our knowledge, in snake venom, which provides a conceptual example for discovering novel ligands to study this receptor family, both functionally and structurally. Moreover, successful synthetic and recombinant production of these toxins [micrurotoxin1 (MmTX1) and MmTX2] will be valuable to further enhance their subtype selectivity or potency. In a broader context, both toxins may provide tools to evoke seizures in assays geared toward testing antiepileptic drugs or as lead molecules for designing therapeutics that modulate GABAA receptor activity.
FT-like proteins induce transposon silencing in the shoot apex during floral induction in rice
Shojiro Tamaki, Hiroyuki Tsuji, Ayana Matsumoto, Akiko Fujita, Zenpei Shimatani, Rie Terada, Tomoaki Sakamoto, Tetsuya Kurata, and Ko Shimamoto
FLOWERING LOCUS T (FT) acts as a mobile floral activator that is synthesized in leaf and transported to shoot apex. A Rice FT-like protein, Heading date 3a (Hd3a), requires interaction with 14-3-3 proteins and transcription factor FD to induce flowering. We confirm that Hd3a and its interactors, as well as their transcriptional target, coexist in the shoot apex at the appropriate time during floral transition. RNA-sequencing analysis of shoot apices from wild-type and RNA-interference plants for FT-like genes showed that 58% of classified transposable elements are transcribed, and >200 are down-regulated in response to FT-like. Our results (pp. E901–E910) indicate a link between reproductive development and transposon behavior in the shoot apical meristem, supporting and extending recent evidence for such a link during gametophyte development.
Structure, variation, and assembly of the root-associated microbiomes of rice
Joseph Edwards, Cameron Johnson, Christian Santos-Medellín, Eugene Lurie, Natraj Kumar Podishetty, Srijak Bhatnagar, Jonathan A. Eisen, and Venkatesan Sundaresan
Land plants continuously contact beneficial, commensal, and pathogenic microbes in soil via their roots. There is limited knowledge as to how the totality of root-associated microbes (i.e., the microbiome) is shaped by various factors or its pattern of acquisition in the root. Using rice as a model (pp. E911–E920), we show that there exist three different root niches hosting different microbial communities of eubacteria and methanogenic archaea. These microbial communities are affected by geographical location, soil source, host genotype, and cultivation practice. Dynamics of the colonization pattern for the root-associated microbiome across the three root niches provide evidence for rapid acquisition of root-associated microbiomes from soil, and support a multistep model wherein each root niche plays a selective role in microbiome assembly.