MeCP2-chromatin interactions include the formation of chromatosome-like structures and are altered in mutations causing Rett syndrome

hMeCP2 (human methylated DNA-binding protein 2), mutations of which cause most cases of Rett syndrome (RTT), is involved in the transmission of repressive epigenetic signals encoded by DNA methylation. The present work focuses on the modifications of chromatin architecture induced by MeCP2 and the effects of RTT-causing mutants. hMeCP2 binds to nucleosomes close to the linker DNA entry-exit site and protects approximately 11 bp of linker DNA from micrococcal nuclease. MeCP2 mutants differ in this property; the R106W mutant gives very little extra protection beyond the approximately 146-bp nucleosome core, whereas the large C-terminal truncation R294X reveals wild type behavior. Gel mobility assays show that linker DNA is essential for proper MeCP2 binding to nucleosomes, and electron microscopy visualization shows that the protein induces distinct conformational changes in the linker DNA. When bound to nucleosomes, MeCP2 is in close proximity to histone H3, which exits the nucleosome core close to the proposed MeCP2-binding site. These findings firmly establish nucleosomal linker DNA as a crucial binding partner of MeCP2 and show that different RTT-causing mutations of MeCP2 are correspondingly defective in different aspects of the interactions that alter chromatin architecture.     

西藏飞蝗九个地理种群群居型形态特征的数量分析

为探讨群居型西藏飞蝗Locusta migratoria tibetensis Chen地理种群数量性状关系,从青藏高原9个地区采集到不同地理种群,以数值分析对形态指标及其比值进行了分析。结果表明,前翅长度(E)、后足股节长度(F)、头宽(C)形态指标和E/F、F/C两个比值可以作为分析种群关系的参数。聚类分析和主成分分析结果相似,能够较好地说明青藏高原9个种群的地理变异和种群相互关系,9个地理种群可以分三个类群,即第Ⅰ类群包括百巴(BB)与八美(BM)种群;第Ⅱ类群包括普兰(PL)、扎囊(ZN)、洛须(LX)种群;第Ⅲ类群包括噶尔(GE)、香孜(XZ)、日土(RT)、那嘎(NG)种群。     

石蜡油对离子注入动物细胞真空环境的保护效应初探

利用石蜡油的高效护水功能进行动物细胞(HeLa细胞)的真空及注入保护,研究了不同的预处理时间对细胞活性的影响,并将石蜡油浸泡细胞2 m in~6 m in选为最佳保护时间。当细胞经过2 m in~6 m in的预处理后再进行真空、注入,结果显示成活率大幅度提高。     

Water cytotoxicity and dioxins bioaccumulation in an Egyptian delta wetland ecosystem

Manzala Lake, as one of the main Egyptian wetland ecosystems, is facing risks of pollution. An in vitro cytotoxicity test using a mammalian cell line was employed to determine the toxicity of multiple pollutants in the water and Tilapia zillii fish sampled from the lake. The concentrations of seven polychlorinated dibenzo-p-dioxins and ten polychlorinated dibenzofurans were investigated in water and muscle of the fish in 2014. Cytotoxicity testing showed that the percentage inhibition of cell viability in the studied sites ranged between 56.16% and 83.22%. Dioxin analysis indicated that the average concentrations of 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin, 1,2,3,4,7,8-hexachlorodibenzofuran, 1,2,3,4,6,7,8-heptachlorodibenzofuran and 1,2,3,4,6,7,8,9-octachlorodibenzofuran were higher than the toxic equivalence quotients (TEQs) set by the World Health Organization (WHO) in all water and fish muscle samples; however, the average concentration of 2,3,7,8-tetrachlorodibenzofuran was higher only in fish muscle samples. The bioaccumulation factor (BAF) ranged dramatically between 2 and 58.5 for the detected dioxins. Adverse human health effects through the consumption of fish are not expected, because dioxin levels in fish muscle are deemed safe for human consumption. Implementation of a strategic multidisciplinary action plan is strongly recommended to sustain this delta wetland ecosystem.