Cerebellar Predominant Increase in mRNA Expression Levels of Sirt1 and Sirt3 Isoforms in a Transgenic Mouse Model of Huntington’s Disease

Neurochemical Research - The potential role of Sirt1 and Sirt2 subtypes of Sirtuins (class III NAD+-dependent deacetylases) in the pathogenesis of Huntington’s disease (HD) has been...     

Sulfinylated azadecalins act as functional mimics of a pollen germination stimulant in Arabidopsis pistils

Polarized cell elongation is triggered by small molecule cues during development of diverse organisms. During plant reproduction, pollen interactions with the stigma result in the polar outgrowth of a pollen tube, which delivers sperm cells to the female gametophyte to effect double fertilization. In many plants, pistils stimulate pollen germination. However, in Arabidopsis, the effect of pistils on pollen germination and the pistil factors that stimulate pollen germination remain poorly characterized. Here, we demonstrate that stigma, style, and ovules in Arabidopsis pistils stimulate pollen germination. We isolated an Arabidopsis pistil extract fraction that stimulates Arabidopsis pollen germination, and employed ultra‐high resolution electrospray ionization (ESI), Fourier‐transform ion cyclotron resonance (FT‐ICR) and MS/MS techniques to accurately determine the mass (202.126 Da) of a compound that is specifically present in this pistil extract fraction. Using the molecular formula (C₁₀H₁₉NOS) and tandem mass spectral fragmentation patterns of the m/z (mass to charge ratio) 202.126 ion, we postulated chemical structures, devised protocols, synthesized N‐methanesulfinyl 1‐ and 2‐azadecalins that are close structural mimics of the m/z 202.126 ion, and showed that they are sufficient to stimulate Arabidopsis pollen germination in vitro (30 μm stimulated approximately 50% germination) and elicit accession‐specific response. Although N‐methanesulfinyl 2‐azadecalin stimulated pollen germination in three species of Lineage I of Brassicaceae, it did not induce a germination response in Sisymbrium irio (Lineage II of Brassicaceae) and tobacco, indicating that activity of the compound is not random. Our results show that Arabidopsis pistils promote germination by producing azadecalin‐like molecules to ensure rapid fertilization by the appropriate pollen.     

Supranucleosomal organization of chromatin fibers in nuclei of Drosophila S2 cells

Earlier, the interphase chromatin structures could not be visualized due to the stickiness of the nuclear material. We have reduced stickiness by the reversal of permeabilization allowing the isolation and microscopic imaging of interphase chromatin structures. By using a high resolution of synchronization, collecting 36 elutriation fractions, we show that major intermediates of chromatin condensation include: (a) decondensed veillike chromatin at the unset of the S phase (2.0-2.2 C-value), (b) polarization of veiled chromatin (2.2-2.6 C), (c) fibrous chromatin (2.6-3.0 C), chromatin bodies (3.0-3.3 C), early precondensed chromosomes (3.3-3.6). The compaction of Drosophila chromosomes did not reach that of the mammalian cells in the final stage of condensation (3.6-4.0 C). Drosophila chromosomes consist of smaller units called rodlets. Results demonstrate that nucleosomal chromatin ("beads on string") does not form a solenoid structure; rather, the topological arrangement consists of meandering and plectonemic loops.     

ImmunoPET and biodistribution with human epidermal growth factor receptor 3 targeting antibody 89Zr-RG7116

The humanized monoclonal antibody with high affinity for the human epidermal growth factor receptor (HER) 3, RG7116, is a glycoengineered, IgG1 class antibody. By labeling RG7116 with zirconium-89 (⁸⁹Zr) we aimed to visualize in vivo HER3 expression and study the biodistribution of this antibody in human tumor-bearing mice. Biodistribution of ⁸⁹Zr-RG7116 was studied in subcutaneously xenografted FaDu tumor cells (HER3-positive). Dose-dependency of ⁸⁹Zr-RG7116 organ distribution and specific tumor uptake was assessed by administering doses ranging from 0.05 to 10 mg/kg RG7116 to SCID/Beige mice. Biodistribution was analyzed at 24 and 144 h after injection. MicroPET imaging was performed at 1, 3, and 6 days after injection of 1.0 mg/kg ⁸⁹Zr-RG7116 in the FaDu, H441, QG-56 and Calu-1 xenografts with varying HER3 expression. The excised tumors were analyzed for HER3 expression. Biodistribution analyses showed a dose- and time-dependent ⁸⁹Zr-RG7116 tumor uptake in FaDu tumors. The highest tumor uptake of ⁸⁹Zr-RG7116 was observed in the 0.05 mg/kg dose group with 27.5%ID/g at 144 h after tracer injection. MicroPET imaging revealed specific tumor uptake of ⁸⁹Zr-RG7116 in FaDu and H441 models with an increase in tumor uptake over time. Biodistribution data was consistent with the microPET findings in FaDu, H441, QG56 and Calu-1 xenografts, which correlated with HER3 expression levels. In conclusion, ⁸⁹Zr-RG7116 specifically accumulates in HER3 expressing tumors. PET imaging with this tracer provides real-time non-invasive information about RG7116 distribution, tumor targeting and tumor HER3 expression levels.     

Evolution of genes and repeats in the Nimrod superfamily

The recently identified Nimrod superfamily is characterized by the presence of a special type of EGF repeat, the NIM repeat, located right after a typical CCXGY/W amino acid motif. On the basis of structural features, nimrod genes can be divided into three types. The proteins encoded by Draper-type genes have an EMI domain at the N-terminal part and only one copy of the NIM motif, followed by a variable number of EGF-like repeats. The products of Nimrod B-type and Nimrod C-type genes (including the eater gene) have different kinds of N-terminal domains, and lack EGF-like repeats but contain a variable number of NIM repeats. Draper and Nimrod C-type (but not Nimrod B-type) proteins carry a transmembrane domain. Several members of the superfamily were claimed to function as receptors in phagocytosis and/or binding of bacteria, which indicates an important role in the cellular immunity and the elimination of apoptotic cells. In this paper, the evolution of the Nimrod superfamily is studied with various methods on the level of genes and repeats. A hypothesis is presented in which the NIM repeat, along with the EMI domain, emerged by structural reorganizations at the end of an EGF-like repeat chain, suggesting a mechanism for the formation of novel types of repeats. The analyses revealed diverse evolutionary patterns in the sequences containing multiple NIM repeats. Although in the Nimrod B and Nimrod C proteins show characteristics of independent evolution, many internal NIM repeats in Eater sequences seem to have undergone concerted evolution. An analysis of the nimrod genes has been performed using phylogenetic and other methods and an evolutionary scenario of the origin and diversification of the Nimrod superfamily is proposed. Our study presents an intriguing example how the evolution of multigene families may contribute to the complexity of the innate immune response.     

Ivy cells: a population of nitric-oxide-producing, slow-spiking GABAergic neurons and their involvement in hippocampal network activity

In the cerebral cortex, GABAergic interneurons are often regarded as fast-spiking cells. We have identified a type of slow-spiking interneuron that offers distinct contributions to network activity. "Ivy" cells, named after their dense and fine axons innervating mostly basal and oblique pyramidal cell dendrites, are more numerous than the parvalbumin-expressing basket, bistratified, or axo-axonic cells. Ivy cells express nitric oxide synthase, neuropeptide Y, and high levels of GABA(A) receptor alpha1 subunit; they discharge at a low frequency with wide spikes in vivo, yet are distinctively phase-locked to behaviorally relevant network rhythms including theta, gamma, and ripple oscillations. Paired recordings in vitro showed that Ivy cells receive depressing EPSPs from pyramidal cells, which in turn receive slowly rising and decaying inhibitory input from Ivy cells. In contrast to fast-spiking interneurons operating with millisecond precision, the highly abundant Ivy cells express presynaptically acting neuromodulators and regulate the excitability of pyramidal cell dendrites through slowly rising and decaying GABAergic inputs.