New implications on genomic adaptation derived from the Helicobacter pylori genome comparison

Background

Helicobacter pylori has a reduced genome and lives in a tough environment for long-term persistence. It evolved with its particular characteristics for biological adaptation. Because several H. pylori genome sequences are available, comparative analysis could help to better understand genomic adaptation of this particular bacterium.

Principal Findings

We analyzed nine H. pylori genomes with emphasis on microevolution from a different perspective. Inversion was an important factor to shape the genome structure. Illegitimate recombination not only led to genomic inversion but also inverted fragment duplication, both of which contributed to the creation of new genes and gene family, and further, homological recombination contributed to events of inversion. Based on the information of genomic rearrangement, the first genome scaffold structure of H. pylori last common ancestor was produced. The core genome consists of 1186 genes, of which 22 genes could particularly adapt to human stomach niche. H. pylori contains high proportion of pseudogenes whose genesis was principally caused by homopolynucleotide (HPN) mutations. Such mutations are reversible and facilitate the control of gene expression through the change of DNA structure. The reversible mutations and a quasi-panmictic feature could allow such genes or gene fragments frequently transferred within or between populations. Hence, pseudogenes could be a reservoir of adaptation materials and the HPN mutations could be favorable to H. pylori adaptation, leading to HPN accumulation on the genomes, which corresponds to a special feature of Helicobacter species: extremely high HPN composition of genome.

Conclusion

Our research demonstrated that both genome content and structure of H. pylori have been highly adapted to its particular life style.     

Phosphatidylinositol 3-phosphate indirectly activates KCa3.1 via 14 amino acids in the carboxy terminus of KCa3.1

KCa3.1 is an intermediate conductance Ca2+-activated K+ channel that is expressed predominantly in hematopoietic cells, smooth muscle cells, and epithelia where it functions to regulate membrane potential, Ca2+ influx, cell volume, and chloride secretion. We recently found that the KCa3.1 channel also specifically requires phosphatidylinositol-3 phosphate [PI(3)P] for channel activity and is inhibited by myotubularin-related protein 6 (MTMR6), a PI(3)P phosphatase. We now show that PI(3)P indirectly activates KCa3.1. Unlike KCa3.1 channels, the related KCa2.1, KCa2.2, or KCa2.3 channels do not require PI(3)P for activity, suggesting that the KCa3.1 channel has evolved a unique means of regulation that is critical for its biological function. By making chimeric channels between KCa3.1 and KCa2.3, we identified a stretch of 14 amino acids in the carboxy-terminal calmodulin binding domain of KCa3.1 that is sufficient to confer regulation of KCa2.3 by PI(3)P. However, mutation of a single potential phosphorylation site in these 14 amino acids did not affect channel activity. These data together suggest that PI(3)P and these 14 amino acids regulate KCa3.1 channel activity by recruiting an as yet to be defined regulatory subunit that is required for Ca2+ gating of KCa3.1.     

7TD1细胞及其克隆对IL-6的反应性和依赖性

比较了基础所和北医大提供的两株7TD1细胞。选择北医大细胞株进行克隆,筛选出对IL-6增殖反应性和依赖性较强的3株细胞(7TD1 MC1、7TD1 MC4、7TD1MC5)。其中,7TD1 MC5细胞的反应曲线呈典型的“倒S”形,对IL-6有很好的反应性和依赖性。MTT比色法显示了与~3H-TdR掺入法一致的结果,采用7TD1 MC5细胞及MTT比色法测定IL-6生物活性,可减少仪器测试的费用和避免放射性污染。确定了培养基中IL-6的最适浓度(2ng/ml)。细胞传代培养和冻存6个月,7TD1 MC5细胞对IL-6的反应性和依赖性均无明显变化。     

柯萨奇B3病毒对心肌细胞离子通道电流的影响

目的 :探讨柯萨奇B3病毒 (coxsackievirusB3,CVB3)对大鼠心肌细胞离子通道的影响 ,以了解病毒感染导致细胞电生理活动异常的机理。方法 :酶消化法获得单个心肌细胞后利用膜片钳全细胞电流记录技术观察CVB3对L型钙通道电流、钠通道电流、外向钾电流和内向整流性钾电流的影响。结果 :CVB3感染使L型钙通道电流、外向钾电流增加 ,内向整流性钾电流减小 ,对钠通道电流无明显影响。结论 :CVB3对L型钙通道电流、外向钾电流和内向整流性钾电流的影响可能是病毒感染后细胞损伤和产生异常电活动的原因。     

云南水稻品种冬糯的白叶枯病抗性基因定位研究——Ⅰ.抗病基因的初级三体分析定位

本文研究了云南稻品种冬糯对我国水稻白叶枯病(Xanthomonas campestris pv. oryxac)菌系“江陵691”的抗性遗传和抗病基因与初级三体额外染色体的关系。冬糯对白叶枯病菌系“江陵691"的抗性受一对隐性基因控制(xa-k);该抗病基因分别与Xa-a、xa-c、Xa-(?)、Xa-f和Xa-i不等位,并呈独立遗传;与Xa-g不等位,呈连锁遗传,重组值为28.7%。冬糯抗病基因与Triplo-7的额外染色体即第7染色体有关,推定冬糯所带的抗病基因位于第7染色体上。以IR36为遗传背景的初级三体系带有一对显性抗白叶枯病基因,该抗病基因位于第11染色体上。     

Spatially Discordant Alternans and Arrhythmias in Tachypacing-Induced Cardiac Myopathy in Transgenic LQT1 Rabbits: The Importance of IKs and Ca2+ Cycling

BackgroundRemodeling of cardiac repolarizing currents, such as the downregulation of slowly activating K⁺ channels (I_Ks), could underlie ventricular fibrillation (VF) in heart failure (HF). We evaluated the role of I_ks remodeling in VF susceptibility using a tachypacing HF model of transgenic rabbits with Long QT Type 1 (LQT1) syndrome.ConclusionsCompared with LMC-TICM, LQT1-TICM rabbits exhibit steepened APD restitution and complex DA modulated by Ca²⁺. Our results strongly support the contention that the downregulation of I_Ks in HF increases Ca²⁺ dependent alternans and thereby the risk of VF.     

幽门螺杆菌对胃粘膜损伤机制的实验研究

实验采用ＨＰ 活菌悬液,制成大鼠ＨＰ 损伤性胃炎模型,以便观察ＨＰ 对胃粘膜的损伤机制。结果表明：实验组与对照组比较,胃粘膜损伤指数增高（Ｐ＜ ０．０５） ,胃壁结合粘液量明显降低（Ｐ＜ ０．０１） ,胃粘膜ＰＧＥ２ 和ＳＳ 的含量降低（Ｐ＜ ０．０１） 。说明幽门螺杆菌对胃粘膜防御系统有明显的损伤作用。     

大鼠,豚鼠心肌细胞的简单,快速分离

本文介绍了一种简单、快速分离成年大鼠、豚鼠心肌细胞的方法。所分得的细胞形态结构完整,具有良好的钙耐受性,膜片钳上易于形成高阻抗接封,因而适于作各种电生理记录。     

MutPrimerDesign:用于人类基因编码区域突变位点的引物设计程序

位于基因编码区的DNA突变与基因的功能密切相关。在已知人类基因编码区的突变位点时,如何在基因组上设计引物验证该突变是一个重要的问题。本文利用Python语言开发了引物设计程序MutPrimerDesign。MutPrimerDesign通过解析人类基因组序列数据库以及基因注释信息,转换基因编码区坐标为基因组坐标,并调用Primer3的python程序包接口,可批量自动化完成基因突变位点的引物及探针序列设计。MutPrimerDesign使用简便,可识别多种数据库的基因名称,并能够修改引物常规参数,实现引物的快速调整。