Role for rodent Smc6 in pericentromeric heterochromatin domains during spermatogonial differentiation and meiosis

Chromatin structure and function are for a large part determined by the six members of the structural maintenance of chromosomes (SMC) protein family, which form three heterodimeric complexes: Smc1/3 (cohesin), Smc2/4 (condensin) and Smc5/6. Each complex has distinct and important roles in chromatin dynamics, gene expression and differentiation. In yeast and Drosophila, Smc6 is involved in recombinational repair, restarting collapsed replication forks and prevention of recombination in repetitive sequences such as rDNA and pericentromeric heterochromatin. Although such DNA damage control mechanisms, as well as highly dynamic changes in chromatin composition and function, are essential for gametogenesis, knowledge on Smc6 function in mammalian systems is limited. We therefore have investigated the role of Smc6 during mammalian spermatogonial differentiation, meiosis and subsequent spermiogenesis. We found that, during mouse spermatogenesis, Smc6 functions as part of meiotic pericentromeric heterochromatin domains that are initiated when differentiating spermatogonia become irreversibly committed toward meiosis. To our knowledge, we are the first to provide insight into how commitment toward meiosis alters chromatin structure and dynamics, thereby setting apart differentiating spermatogonia from the undifferentiated spermatogonia, including the spermatogonial stem cells. Interestingly, Smc6 is not essential for spermatogonial mitosis, whereas Smc6-negative meiotic cells appear unable to finish their first meiotic division. Importantly, during meiosis, we find that DNA repair or recombination sites, marked by γH2AX or Rad51 respectively, do not co-localize with the pericentromeric heterochromatin domains where Smc6 is located. Considering the repetitive nature of these domains and that Smc6 has been previously shown to prevent recombination in repetitive sequences, we hypothesize that Smc6 has a role in the prevention of aberrant recombination events between pericentromeric regions during the first meiotic prophase that would otherwise cause chromosomal aberrations leading to apoptosis, meiotic arrest or aneuploidies.     

Adiponectin receptor agonist AdipoRon attenuates calcification of osteoarthritis chondrocytes by promoting autophagy

Cartilage calcification contributes to the development and progression of osteoarthritis (OA). It has been well-investigated adiponectin regulates vascular calcification. The purpose of this study is to investigate the therapeutic value and the molecular mechanism of AdipoRon, an adiponectin receptor agonist, on the chondrocytes calcification. Primary chondrocytes were isolated and cultured from normal cartilage and OA cartilage. The calcification in tissues was evaluated by inductively coupled plasma/atomic emission spectroscopy and alizarin red S staining. The calcification in chondrocytes was determined using the alkaline phosphatase (ALP) staining and an ALP assay kit. The cellular effects of AdipoRon were assessed by immunofluorescence staining and Western blot analysis. We found that calcification was significantly increased in OA cartilage tissues and cells. Importantly, the degree of calcification and ALP activity of the OA chondrocytes was decreased upon the treatment with AdipoRon. The AdipoRon-induced cellular effects, including the reduction of the calcification of chondrocytes and improvement of autophagy, were blocked by dorsomorphin, an 5′-adenosine monophosphate-activated protein kinase (AMPK) inhibitor. Moreover, autophagy activation by AdipoRon was mediated by the AMPK-mammalian target of rapamycin (mTOR) signaling pathway. Our results suggest that AdipoRon significantly alleviates the calcification of OA chondrocytes via activating AMPK-mTOR signaling to promote autophagy. Therefore, AdipoRon could be a potential therapeutic agent for the prevention and treatment of OA.     

An Inherited Small Microdeletion at 15q13.3 in a Patient with Early- Onset Obsessive-Compulsive Disorder

Copy number variations (CNVs) have been previously associated with several different neurodevelopmental psychiatric disorders, such as autism, schizophrenia, and attention deficit hyperactivity disorder (ADHD). The present study consisted of a pilot genome-wide screen for CNVs in a cohort of 16 patients with early-onset obsessive-compulsive disorder (OCD) and 12 mentally healthy individuals, using array-based comparative genomic hybridization (aCGH) on 44K arrays. A small rare paternal inherited microdeletion (∼64 kb) was identified in chromosome 15q13.3 of one male patient with very early onset OCD. The father did not have OCD. The deletion encompassed part of the FMN1 gene, which is involved with the glutamatergic system. This finding supports the hypothesis of a complex network of several genes expressed in the brain contributing for the genetic risk of OCD, and also supports the glutamatergic involvement in OCD, which has been previously reported in the literature.     

Imbalance of antioxidant defense in mice lacking cellular prion protein

Prion diseases are fatal neurodegenerative disorders resulting from conformational changes in the prion protein from its normal cellular isoform, PrPC, to the infectious scrapie isoform, PrP(Sc). In spite of many studies, the physiological function of PrPC remains unknown. Recent work shows that PrPC binds Cu2+, internalizing it into the cytoplasm. Since many antioxidant enzymes depend on Cu2+ (e.g., Cu/ZnSOD), their function could be affected in prion diseases. Here we investigate a possible relationship between PrP(C) and the cellular antioxidant systems in different structures isolated from PrPC knockout and wild-type mice by determining oxidative damage in protein and lipids and activity of antioxidant enzymes (CAT, SOD) and stress-adaptive enzymes (ODC). Our results show that, in the absence of PrPC, there is an increased oxidation of lipid and protein in all structures investigated. Decreased SOD activity and changes in CAT/ODC activities were also observed. Taking into account these results, we suggest that the physiological function of PrP(C) is related to cellular antioxidant defenses. Therefore, during development of prion diseases, the whole organism becomes more sensitive to ROS injury, leading to a progressive oxidative disruption of tissues and vital organs, especially the central nervous system.     

Higher number of <Emphasis Type="Italic">Helicobacter pylori</Emphasis> CagA EPIYA C phosphorylation sites increases the risk of gastric cancer,but not duodenal ulcer

Background  

Helicobacter pylori infection is one of the most common infections worldwide and is associated with gastric cancer and peptic ulcer. Bacterial virulence factors such as CagA have been shown to increase the risk of both diseases. Studies have suggested a causal role for CagA EPIYA polymorphisms in gastric carcinogenesis, and it has been shown to be geographically diverse. We studied associations between H. pylori CagA EPIYA patterns and gastric cancer and duodenal ulcer, in an ethnically admixed Western population from Brazil. CagA EPIYA was determined by PCR and confirmed by sequencing. A total of 436 patients were included, being 188 with gastric cancer, 112 with duodenal ulcer and 136 with gastritis.     

A whole genome screen for HIV restriction factors

Background

Human T-cell leukemia virus type 1 (HTLV-1) causes adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in a small percentage of infected individuals. ATL is often associated with general immune suppression and an impaired HTLV-1-specific T-cell response, an important host defense system. We previously found that a small fraction of asymptomatic HTLV-1-carriers (AC) already showed impaired T-cell responses against the major target antigen, Tax. However, it is unclear whether the impaired HTLV-1 Tax-specific T-cell response in these individuals is an HTLV-1-specific phenomenon, or merely reflects general immune suppression. In this study, in order to characterize the impaired HTLV-1-specific T-cell response, we investigated the function of Tax-specific CD8⁺ T-cells in various clinical status of HTLV-1 infection.

Results

By using tetramers consisting of HLA-A*0201, -A*2402, or -A*1101, and corresponding Tax epitope peptides, we detected Tax-specific CD8⁺ T-cells in the peripheral blood from 87.0% of ACs (n = 20/23) and 100% of HAM/TSP patients (n = 18/18) tested. We also detected Tax-specific CD8⁺ T-cells in 38.1% of chronic type ATL (cATL) patients (n = 8/21), although its frequencies in peripheral blood CD8⁺ T cells were significantly lower than those of ACs or HAM/TSP patients. Tax-specific CD8⁺ T-cells detected in HAM/TSP patients proliferated well in culture and produced IFN-γ when stimulated with Tax peptides. However, such functions were severely impaired in the Tax-specific CD8⁺ T-cells detected in cATL patients. In ACs, the responses of Tax-specific CD8⁺ T-cells were retained in most cases. However, we found one AC sample whose Tax-specific CD8⁺ T-cells hardly produced IFN-γ, and failed to proliferate and express activation (CD69) and degranulation (CD107a) markers in response to Tax peptide. Importantly, the same AC sample contained cytomegalovirus (CMV) pp65-specific CD8⁺ T-cells that possessed functions upon CMV pp65 peptide stimulation. We further examined additional samples of two smoldering type ATL patients and found that they also showed dysfunctions of Tax-specific but not CMV-specific CD8⁺ T-cells.

Conclusions

These findings indicated that Tax-specific CD8⁺ T-cells were scarce and dysfunctional not only in ATL patients but also in a limited AC population, and that the dysfunction was selective for HTLV-1-specifc CD8⁺ T-cells in early stages.     

Effect of Biotic Factors on the Spatial Distribution of Stingless Bees (Hymenoptera: Apidae, Meliponini) in Fragmented Neotropical Habitats

We recorded stingless bee colony abundance and nesting habits in three sites with different anthropogenic activities in the Soconusco region of Chiapas, Mexico: (1) agroforestry (7 hacacao crop), (2) grassland (12?ha), and (3) urban area (3?ha). A total of 67 nests were found, representing five stingless bee species, Tetragonisca angustula angustula (Lepeletier), Trigona fulviventris (Guérin), Scaptotrigona mexicana (Guérin), Scaptotrigona pectoralis (Dalla Torre), and Oxytrigona mediorufa (Cockerell). The most abundant stingless bee in each site was T. angustula angustula (>50%). The primary tree species used by the bees were Ficus spp. (Moraceae, 37.8%) and Cordia alliodora (Boraginaceae, 13.5%). The nest entrance height of T. angustula angustula (96?±?19?cm) was different than the other species, and this bee was the only one that used all different nesting sites. Volatiles analyzed by gas chromatography from pollen collected by the stingless bees differed between bee species, but were highly similar in respect to the fragrances of the pollen collected by the same species at any site. Our data indicate that T. angustula angustula experienced low heterospecific and high intraspecific foraging overlap especially in the urban site. We observed cluster spatial distribution in grassland and in agroforestry sites. In the urban site, T. angustula angustula presented random distribution tended to disperse. Trigona fulviventris was the only overdispersed and solitary species.