Recurrent Tissue-Specific mtDNA Mutations Are Common in Humans

Mitochondrial DNA (mtDNA) variation can affect phenotypic variation; therefore, knowing its distribution within and among individuals is of importance to understanding many human diseases. Intra-individual mtDNA variation (heteroplasmy) has been generally assumed to be random. We used massively parallel sequencing to assess heteroplasmy across ten tissues and demonstrate that in unrelated individuals there are tissue-specific, recurrent mutations. Certain tissues, notably kidney, liver and skeletal muscle, displayed the identical recurrent mutations that were undetectable in other tissues in the same individuals. Using RFLP analyses we validated one of the tissue-specific mutations in the two sequenced individuals and replicated the patterns in two additional individuals. These recurrent mutations all occur within or in very close proximity to sites that regulate mtDNA replication, strongly implying that these variations alter the replication dynamics of the mutated mtDNA genome. These recurrent variants are all independent of each other and do not occur in the mtDNA coding regions. The most parsimonious explanation of the data is that these frequently repeated mutations experience tissue-specific positive selection, probably through replication advantage.     

The Smc5/Smc6/MAGE Complex Confers Resistance to Caffeine and Genotoxic Stress in Drosophila melanogaster

The SMC5/6 protein complex consists of the Smc5, Smc6 and Non-Smc-Element (Nse) proteins and is important for genome stability in many species. To identify novel components in the DNA repair pathway, we carried out a genetic screen to identify mutations that confer reduced resistance to the genotoxic effects of caffeine, which inhibits the ATM and ATR DNA damage response proteins. This approach identified inactivating mutations in CG5524 and MAGE, homologs of genes encoding Smc6 and Nse3 in yeasts. The fact that Smc5 mutants are also caffeine-sensitive and that Mage physically interacts with Drosophila homologs of Nse proteins suggests that the structure of the Smc5/6 complex is conserved in Drosophila. Although Smc5/6 proteins are required for viability in S. cerevisiae, they are not essential under normal circumstances in Drosophila. However, flies carrying mutations in Smc5, Smc6 and MAGE are hypersensitive to genotoxic agents such as ionizing radiation, camptothecin, hydroxyurea and MMS, consistent with the Smc5/6 complex serving a conserved role in genome stability. We also show that mutant flies are not compromised for pre-mitotic cell cycle checkpoint responses. Rather, caffeine-induced apoptosis in these mutants is exacerbated by inhibition of ATM or ATR checkpoint kinases but suppressed by Rad51 depletion, suggesting a functional interaction involving homologous DNA repair pathways that deserves further scrutiny. Our insights into the SMC5/6 complex provide new challenges for understanding the role of this enigmatic chromatin factor in multi-cellular organisms.     

三株芽胞杆菌菌株对松材线虫低温存活与繁殖的影响

为明确细菌在松材线虫生态适应性中的作用,本研究选择与致病相关的松材线虫伴生细菌GD1、马尾松内生细菌GD2以及具有杀松材线虫活性的湿地松内生细菌NJSZ-13为试验对象,测定经这3株芽胞杆菌菌株3个浓度低温驯化10、15和20 d后,在冷冻条件下松材线虫强毒虫株AMA3、中毒虫株AA3和弱毒虫株YW4的存活率和繁殖量。结果表明：低温驯化15 d和20 d后3株菌株对不同毒力线虫的活力影响较驯化10 d后的更显著。在低温驯化15 d、-20℃冷冻处理1 h后,5×10⁶ CFU/mL浓度菌株GD1处理下,虫株AMA3、AA3和YW4的存活率分别为77.22%、83.68%和84.26%,与对照差异显著;5×10⁵ CFU/mL浓度菌株GD1处理下,虫株AMA3、AA3和YW4的存活率分别为75.76%、80.67%和81.50%,与对照差异显著。5×10⁶ CFU/mL和5×10⁵ CFU/mL浓度菌株GD2处理下,与GD1处理组结果相似,菌株NJSZ-13处理组则与菌株GD1和GD2的结果相反。低温驯化15 d、-20℃冷冻处理1 h后,5×10⁶ CFU/mL浓度菌株GD1处理下,虫株AMA3、AA3和YW4的繁殖量分别为7 530、9 317和12 793条/皿,与对照（3 192、3 840和5 823条/皿）差异显著;5×10⁵ CFU/mL浓度菌株GD1处理时,3个虫株的繁殖量均与对照差异显著。而菌株GD2和NJSZ-13处理后,3个虫株的繁殖量均无显著变化。表明不同芽胞杆菌对松材线虫的低温适应性影响存在差异,松材线虫伴生细菌GD1和马尾松内生细菌GD2能增强其低温适应性,而湿地松内生细菌NJSZ-13菌株则相反。     

Molecular cloning and expression of five glutathione S-transferase (GST) genes from Banana (Musa acuminata L. AAA group, cv. Cavendish)

Key message

Three tau class MaGSTs responded to abiotic stress, MaGSTF1 and MaGSTL1 responded to signaling molecules, they may play an important role in the growth of banana plantlet.

Abstract

Glutathione S-transferases (GST) are multifunctional detoxification enzymes that participate in a variety of cellular processes, including stress responses. In this study, we report the molecular characteristics of five GST genes (MaGSTU1, MaGSTU2, MaGSTU3, MaGSTF1 and MaGSTL1) cloned from banana (Musa acuminate L. AAA group, cv. Cavendish) using a RACE-PCR-based strategy. The predicted molecular masses of these GSTs range from 23.4 to 27.7 kDa and their pIs are acidic. At the amino acid level, they share high sequence similarity with GSTs in the banana DH-Pahang (AA group) genome. Phylogenetic analysis showed that the deduced amino acid sequences of MaGSTs also have high similarity to GSTs of other plant species. Expression analysis by semi-quantitative RT-PCR revealed that these genes are differentially expressed in various tissues. In addition, their expression is regulated by various stress conditions, including exposure to signaling molecules, cold, salinity, drought and Fusarium oxysporum f specialis(f. Sp) cubense Tropical Race 4 (Foc TR4) infection. The expression of the tau class MaGSTs (MaGSTU1, MaGSTU2 and MaGSTU3) mainly responded to cold, salinity and drought while MaGSTF1 and MaGSTL1 expressions were upregulated by signaling molecules. Our findings suggest that MaGSTs play a key role in both development and abiotic stress responses.     

Speciation, Distribution, and Bioavailability of Soil Selenium in the Tibetan Plateau Kashin–Beck Disease Area—A Case Study in Songpan County, Sichuan Province, China

To clarify the relationship between the soil selenium distribution and its bioavailability with the distribution of Kashin–Beck disease (KBD) endemic areas on the eastern edge of the Tibetan Plateau, samples of natural soil (0–20 cm), cultivated topsoil, and main crops of the region (highland barley) were collected at different altitudes according to topographical and geomorphological features in both KBD and non-KBD areas of Songpan County. These samples were used for determination and analysis of total selenium content in soil and highland barley and available selenium that can be absorbed and utilized by plants. The results showed that the average total selenium content of natural and cultivated topsoil in KBD areas was lower than that in non-KBD areas (natural soil, P?=?0.061; cultivated soil, P?=?0.002), which is in agreement with the geographical distributions of selenium in other KBD-affected areas. However, the total soil selenium content exhibits certain micro-spatial distribution features, namely, the total selenium content in some endemic areas was significantly higher than that of non-KBD areas. This result was contrary to the general distribution that total selenium content in a KBD-affected area is lower than that in a non-KBD area. We further studied the extraction rate and content of soil selenium in six different fractions. The results indicated that the content and extraction rate of available selenium in KBD-affected areas were significantly lower than those in non-KBD areas. There is a distinct positive correlation between plant-available selenium and highland barley selenium (r?=?0.875, P?=?0.001) and a distinct negative correlation with altitude (r?=??0.801, P?=?0.010). Therefore, in KBD endemic areas, the selenium content in crops decreases as the available selenium content in soil decreases and is closely related to the geographical environment features (such as altitude and precipitation). These results suggest that the soil available selenium and ecological features are important factors that restrict the dietary selenium flux for residents in KBD endemic areas of the Tibetan Plateau, providing a theoretical and experimental basis for implementing agricultural measures to regulate the ecological cycle of the selenium flux in the KBD endemic area.     

Cortical GluK1 kainate receptors modulate scratching in adult mice

Recent investigations into the mechanisms mediating itch transmission have focused on spinal mechanisms, whereas few studies have investigated the role of the cerebral cortex in itch‐related behaviors. Human imaging studies show that several cortical regions are active in correspondence with itch, including the anterior cingulate cortex (ACC). We present here evidence of cortical modulation of pruritogen‐induced scratching behavior. We combine pharmacological, genetic, and electrophysiological approaches to show that cortical GluK1‐containing kainate (KA) receptors are involved in scratching induced by histamine and non‐histamine‐dependent itching stimuli. We further show that scratching corresponds with enhanced excitatory transmission in the ACC through KA receptor modulation of inhibitory circuitry. In addition, we found that inhibiting GluK1‐containing KA receptors in the ACC also reduced behavioral nociceptive responses induced by formalin. Our results reveal a new role of the cortex in pruritogen‐induced scratching.

     

Identification of Mamu-DPA1, Mamu-DQA1, and Mamu-DRA alleles in a cohort of Chinese rhesus macaques

Rhesus macaques have long been used as animal models for various human diseases; the susceptibility and/or resistance to some of these diseases are related to the major histocompatibility complex (MHC). To gain insight into the MHC background and to facilitate the experimental use of Chinese rhesus macaques, Mamu-DPA1, Mamu-DQA1, and Mamu-DRA alleles were investigated in 30 Chinese rhesus macaques by gene cloning and sequencing. A total of 14 Mamu-DPA1, 17 Mamu-DQA1, and 9 Mamu-DRA alleles were identified in this study. Of these alleles, 22 novel sequences have not been documented in earlier studies, including nine Mamu-DPA1, ten Mamu-DQA1, and three Mamu-DRA alleles. Interestingly, like Mafa-DQA1 and Mafa-DPA1, more than two Mamu-DQA1 and Mamu-DPA1 alleles were detected in one animal in this study, which suggested that they might represent gene duplication. If our findings can be validated by other studies, it will further increase the number of known Mamu-DPA1 and Mamu-DQA1 polymorphisms. Our data also indicated significant differences in MHC class II allele distribution among the Chinese rhesus macaques, Vietnamese cynomolgus macaques, and the previously reported rhesus macaques, which were mostly of Indian origin. This information will not only promote the understanding of Chinese rhesus macaque MHC diversity and polymorphism but will also facilitate the use of Chinese rhesus macaques in studies of human disease.     

Structure-based design of HSPA5 inhibitors: From peptide to small molecule inhibitors

We identified nine small-molecule hit compounds of Heat shock 70 kDa protein 5 (HSPA5) from cascade in silico screening based on the binding modes of the tetrapeptides derived from the peptide substrate or inhibitors of Escherichia coli HSP70. Two compounds exhibit promising inhibition activities from cancer cell viability and tumor inhibition assays. The binding modes of the hit compounds provide a platform for development of selective small molecule inhibitors of HSPA5.     

Affinity chromatographic purification of human immunoglobulin a from chinese hamster ovary cell culture supernatant

Hexamer peptide ligand HWRGWV, initially screened from a solid phase combinatorial peptide library for immunoglobulins G (IgG) purification, is shown to also have potential for immunoglobulin A (IgA) purification. The determined dissociation constants for hIgA on HWRGWV resins at three different peptide densities from 0.11 to 0.55 meq/g fall in the range of 10^?6–10^?7 M, which are somewhat lower than those for hIgG. Although relatively low dynamic binding capacity (DBC) in the range of 9.2–16.8 mg IgA/mL resin at linear flow rates from 173 to 35 cm/h were obtained for IgA compared to IgG, the DBC value of HWRGWV for IgA is much greater than current commercially available affinity ligands. Although relatively lower binding affinity to secretory IgA compared to monomeric IgA was observed, the peptide ligand resins exhibit great potential for large‐scale purification of both human IgA and secretory IgA. Recoveries of 96.0% and 94.3%, and purities of 90.3% and 91.7% were achieved for human IgA and secretory IgA purification, respectively, from spiked Chinese hamster ovary cell culture supernatants without an extra afterwash step. Over 95% in purities were achieved for IgA and secretory IgA with an extra afterwash step; however, the recoveries would decrease at least 15% and 40% for IgA and secretory IgA, respectively. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2013     

CD106 Identifies a Subpopulation of Mesenchymal Stem Cells with Unique Immunomodulatory Properties

Mesenchymal stem cells (MSCs) reside in almost all of the body tissues, where they undergo self-renewal and multi-lineage differentiation. MSCs derived from different tissues share many similarities but also show some differences in term of biological properties. We aim to search for significant differences among various sources of MSCs and to explore their implications in physiopathology and clinical translation. We compared the phenotype and biological properties among different MSCs isolated from human term placental chorionic villi (CV), umbilical cord (UC), adult bone marrow (BM) and adipose (AD). We found that CD106 (VCAM-1) was expressed highest on the CV-MSCs, moderately on BM-MSCs, lightly on UC-MSCs and absent on AD-MSCs. CV-MSCs also showed unique immune-associated gene expression and immunomodulation. We thus separated CD106⁺cells and CD106⁻cells from CV-MSCs and compared their biological activities. Both two subpopulations were capable of osteogenic and adipogenic differentiation while CD106⁺CV-MSCs were more effective to modulate T helper subsets but possessed decreased colony formation capacity. In addition, CD106⁺CV-MSCs expressed more cytokines than CD106⁻CV-MSCs. These data demonstrate that CD106 identifies a subpopulation of CV-MSCs with unique immunoregulatory activity and reveal a previously unrecognized mechanism underlying immunomodulation of MSCs.