Protease inhibitor domain encoded by an amyloid protein precursor mRNA associated with Alzheimer's disease

Amyloid B-protein/amyloid A4 is a peptide present in the neuritic plaques, neurofibrillary tangles and cerebrovascular deposits in patients with Alzheimer's disease and Down's syndrome (trisomy 21) and may be involved in the pathogenesis of Alzheimer's disease. Recent molecular genetic studies have indicated that amyloid protein is encoded as part of a larger protein by a gene on human chromosome 21 (refs 6-9). The amyloid protein precursor (APP) gene is expressed in brain and in several peripheral tissues, but the specific biochemical events leading to deposition of amyloid are not known. We have now screened complementary DNA libraries constructed from peripheral tissues to determine whether the messenger RNA encoding APP in these tissues is identical to that expressed in brain, and we identify a second APP mRNA that encodes an additional internal domain with a sequence characteristic of a Kunitz-type serine protease inhibitor. The alternative APP mRNA is present in both brain and peripheral tissues of normal individuals and those with Alzheimer's disease, but its pattern of expression differs from that of the previously reported APP mRNA.     

The precursor of Alzheimer's disease amyloid A4 protein resembles a cell-surface receptor

Alzheimer's disease is characterized by a widespread functional disturbance of the human brain. Fibrillar amyloid proteins are deposited inside neurons as neurofibrillary tangles and extracellularly as amyloid plaque cores and in blood vessels. The major protein subunit (A4) of the amyloid fibril of tangles, plaques and blood vessel deposits is an insoluble, highly aggregating small polypeptide of relative molecular mass 4,500. The same polypeptide is also deposited in the brains of aged individuals with trisomy 21 (Down's syndrome). We have argued previously that the A4 protein is of neuronal origin and is the cleavage product of a larger precursor protein. To identify this precursor, we have now isolated and sequenced an apparently full-length complementary DNA clone coding for the A4 polypeptide. The predicted precursor consists of 695 residues and contains features characteristic of glycosylated cell-surface receptors. This sequence, together with the localization of its gene on chromosome 21, suggests that the cerebral amyloid deposited in Alzheimer's disease and aged Down's syndrome is caused by aberrant catabolism of a cell-surface receptor.     

Trisomy represses Apc(Min)-mediated tumours in mouse models of Down's syndrome

Epidemiological studies spanning more than 50 yr reach conflicting conclusions as to whether there is a lower incidence of solid tumours in people with trisomy 21 (Down's syndrome). We used mouse models of Down's syndrome and of cancer in a biological approach to investigate the relationship between trisomy and the incidence of intestinal tumours. Apc(Min)-mediated tumour number was determined in aneuploid mouse models Ts65Dn, Ts1Rhr and Ms1Rhr. Trisomy for orthologues of about half of the genes on chromosome 21 (Hsa21) in Ts65Dn mice or just 33 of these genes in Ts1Rhr mice resulted in a significant reduction in the number of intestinal tumours. In Ms1Rhr, segmental monosomy for the same 33 genes that are triplicated in Ts1Rhr resulted in an increased number of tumours. Further studies demonstrated that the Ets2 gene contributed most of the dosage-sensitive effect on intestinal tumour number. The action of Ets2 as a repressor when it is overexpressed differs from tumour suppression, which requires normal gene function to prevent cellular transformation. Upregulation of Ets2 and, potentially, other genes involved in this kind of protective effect may provide a prophylactic effect in all individuals, regardless of ploidy.     

Effect of human interferon preparations on lymphoblastogenesis in Down's syndrome

The best characterised properties of human interferon, its antiviral (AV) and cell multiplication inhibitory (CMI) activities, are controlled, in an unexplained manner, by genes on chromosomes 21 (refs 1-4; 14-16). Human and animal interferons have various immunosuppressive effects, among them the inhibition in vitro of DNA synthesis in activated lymphocytes. Using mitogen- and antigen-stimulated lymphocytes from normal subjects (disomic 21) and others with Down's syndrome (trisomic 21), we have found that DNA synthesis is inhibited to a greater degree in the latter by both fibroblastoid and leukocyte interferons. We suggest that this property is also regulated by genes on chromosome 21.     

谷胱甘肽硫转移酶在东亚飞蝗两个种群mRNA的表达研究

为研究东亚飞蝗谷胱甘肽硫转移酶基因(GSTs)表达与代谢能力的相关性,应用实时荧光定量PCR技术,对东亚飞蝗沧州和天津种群9个谷胱甘肽硫转移酶基因的mRNA表达情况进行了研究.结果表明:9个GSTs基因在东亚飞蝗不同发育阶段具有表达差异,基因LmGST1、LmGST3、LmGST5、LmGST7和LmGST8随着蝗虫的生长发育表达量增高,这些基因可能影响虫体对有毒化学物质的敏感性.沧州种群GSTs的表达水平高于天津种群,据此推测沧州种群个体对有机磷农药的代谢解毒能力强,对杀虫剂的敏感性低.     

Lambda 5, a new light-chain-related locus selectively expressed in pre-B lymphocytes

The development from stem cells to pre-B cells, B lymphocytes and, finally, plasma cells and memory cells proceeds through various stages which have been defined by the genomic context in which immunoglobulin (Ig) heavy (H) and light (L) chain gene segments are found, as well as by their state of expression. They have also been identified by surface marker analysis and susceptibility to various stimuli regulating growth and differentiation. We have searched for genes that are expressed at given stages in the B-lymphocyte development pathway and which might function to control this development at various stages. A complementary DNA sequence called pZ183 was found in a library constructed from messenger RNA of the murine pre-B lymphoma cell line 70Z/3 which is selectively expressed in pre-B cells. Here we report the nucleotide sequence of a cDNA clone (pZ183-1) containing 0.7 kilobases (kb) of the pZ183 gene. Part of this sequence shows strong homology to constant (C) and joining (J) region sequences of lambda 1 L chains. Our findings define a new immunoglobulin L-chain-related locus, which we call lambda 5, that is selectively transcribed in pre-B lymphocytes.     

专题报道Ⅰ：松材线虫病致病机理与病害防治（执行主编 叶建仁）专题编者按

松材线虫病是在我国发生最严重的毁灭性森林病害,已经在10多个省市区造成了严重的经济和生态损失。该病害原产地为北美洲,自20世纪初先后传入东亚的日本、中国和韩国等,给这些国家的松林带来了巨大的破坏。我国于1982年首次在南京发现松材线虫病,40年来病害一直在不断扩展蔓延。至2021年底,我国有19个省（自治区、直辖市）的728个县级行政区被划分为疫区,当年病死松树达到数千万株,防控形势异常严峻。本专题针对当前松材线虫病流行与防控中的一些热点和难点问题,围绕分子致病机理、疫源追溯和病害防治方法等方面开展研究,通过RNA干扰、基因重组和酵母转化实验明确松材线虫性别分化基因和热激转录因子在生长发育过程中和性别分化中具有的重要作用;以新一代测序技术、分子标记手段研究分析松材线虫在我国的种群分化情况,揭示不同线虫类群与地理区域间呈现的相关性;利用微生物培养、浸渍提取法和生理生化指标测定等方法,筛选并获得一系列对松材线虫具有明显拮抗作用的腐生线虫、松树内生细菌和植物提取物。本专题研究内容有助于深入解析松材线虫病在我国的传播蔓延规律,揭示松材线虫致病关键基因功能,提出病害防控的新方法,从而为更好地防控这一重大外来入侵物种引起的病害提供重要的理论和实践支撑。     

The ovalbumin gene region: common features in the organisation of three genes expressed in chicken oviduct under hormonal control.

Two large DNA fragments overlapping the chicken ovalbumin gene have been isolated by molecular cloning. Analysis of these fragments provided a map of a 46,000-base pair region of the chicken genome. This region contains the complete ovalbumin gene (including its mRNA leader-coding sequence) and at least two other genes of unknown function. All three genes are orientated in the same direction and their expression in chicken oviduct is under hormonal control. The three genes share some sequence homologies, suggesting that duplications have occurred in the ovalbumin gene region in the course of evolution.     

Suitable internal control genes for qRT-PCR normalization in cotton fiber development and somatic embryogenesis

The mechanisms of cotton fiber development and somatic embryogenesis have been explored sys-tematically with microarray and suppression subtractive hybridization. Real-time RT-PCR provides the simultaneous measurement of gene expression in many different samples,with which the data from microarray or others can be confirmed in detail. To achieve accurate and reliable gene expression re-sults,normalization of real-time PCR data against one or several internal control genes is required,which should not fluctuate in different tissues during various stages of development. We assessed the gene expression of 7 frequently used housekeeping genes,including 18S rRNA,Histone3,UBQ7,Actin,Cyclophilin,Gbpolyubiquitin-1 and Gbpolyubiquitin-2,in a diverse set of 21 cotton samples. For fiber developmental series the expression of all housekeeping genes had the same down tendency after 17 DPA. But the expression of the AGP gene(arabinogalactan protein) that has high expression level at the later fiber development stage was up-regulated from 15 to 27 DPA. So the relative absolute quanti-fication should be an efficient and convenient method for the fiber developmental series. The expres-sion of nonfiber tissues series varied not so much against the fiber developmental series. And three best control genes Histone3,UBQ7 and Gbpolyubiquitin-1 have to be used in a combinated way to get better normalization.     

Amyloid beta-protein deposition in tissues other than brain in Alzheimer's disease

Alzheimer's disease is the most common cause of progressive intellectual failure in aged humans. The filamentous brain lesions which define the disease occur within neurons (neurofibrillary tangles), in extracellular cerebral deposits (amyloid plaques) and in meningocerebral blood vessels (amyloid angiopathy). They are found in lesser numbers in the brains of virtually all old humans. A protein with a relative molecular mass (Mr) of approximately 4,000, designated amyloid beta-protein or amyloid A4 protein, is the subunit of the vascular and plaque amyloid filaments in individuals with Alzheimer's disease, normal ageing and trisomy 21 (Down's syndrome). The amyloid beta-protein is a small fragment of a membrane-associated glycoprotein, encoded by a gene on human chromosome 21 which is telomeric to a genetic defect that causes at least some cases of familial Alzheimer's disease. Until now, the pathological lesions of the disease have been found only in the brain, although reports of phenotypic abnormalities in non-neural tissues have suggested that Alzheimer's disease may be a widespread, systemic disorder. Here we report the detection of amyloid beta-protein deposits in non-neural tissues and blood vessels of Alzheimer's disease patients, including skin, subcutaneous tissue and intestine. The protein was also present in non-neural tissues in a proportion of aged, normal subjects. Our findings indicate that a principal feature of the disease process is expressed subclinically in tissues other than brain. The occurrence of amyloid beta-protein deposits in multiple tissues suggests that the protein may be produced locally in numerous organs or may, as in other human amyloidoses, be derived from a common circulating precursor. These observations affect the rationale for many experiments analysing the amyloid beta-protein precursor and its messenger RNAs in Alzheimer's disease brain tissue and have major implications for the pathogenesis and treatment of the disease.     

An inducible promoter fused to the period gene in Drosophila conditionally rescues adult per-mutant arrhythmicity

The period (per) gene of Drosophila melanogaster is involved in the expression of circadian rhythms of locomotor activity in adult flies. Molecular studies of per (reviewed in ref. 2) have shown that the transcribed and translated products of this gene are present primarily at the embryonic, pupal and adult stages. Here we describe experiments with arrhythmic per mutants bearing an inducible form of this gene which indicate that strongly rhythmic adult behaviour can be obtained only if per expression is induced in the adult, independent of its history of expression earlier in development. Thus per-mutant locomotor-activity phenotypes seem not to result from abnormalities in the development of neural structures or in physiological processes that may be required at pre-adult stages for the expression of this circadian rhythm. Moreover, the action of per after light:dark cycle entrainment seems to be sufficient for activity rhythms to be exhibited in constant darkness; this suggests further that the per product is required only during the time that the rhythmic behaviour is being manifested. Our strategy used a heat-shock gene promotor fused to per coding sequences to obtain conditional gene expression. Heat-shock promoter-driven genes have previously been used to study the mode of action and tissue specificity of a variety of Drosophila genes; our experiments on circadian rhythms demonstrate the use of such gene constructions for the temporal manipulation of genes whose phenotypes, behavioural and otherwise, affect whole organisms.     

Biological properties of human c-Ha-ras1 genes mutated at codon 12

Vertebrate genomes contain proto-oncogenes whose enhanced expression or alteration by mutation seems to be involved in the development of naturally occurring tumours. These activated genes, usually assayed by their ability to induce the malignant transformation of NIH 3T3 cells, are frequently related to the ras oncogene of Harvey (Ha-ras) or Kirsten (Ki-ras) murine sarcoma viruses, or a third member of this family (N-ras). Activation involves point mutation which often affect codon 12 (refs 16-26) of the encoded 21,000-molecular weight polypeptide (p21). To provide insight into structural requirements involved in p21 activation, we have now constructed 20 mutant c-Ha-ras1 genes by in vitro mutagenesis, each encoding a different amino acid at codon 12. Analysis of rat fibroblasts transfected with these altered genes demonstrates that all amino acids except glycine (which is encoded by normal cellular ras genes) and proline at position 12 activate p21, suggesting a requirement for an alpha-helical structure in this region of the polypeptide. The morphological phenotype of cells transformed by the activated genes can, however, depend on the particular amino acid at this position.     

Isolation and expression pattern analysis of novel ESTs from human fetal brain

In order to learn the mechanism of brain development and differentiation, 90 expressed sequence tags (ESTs) were isolated by differential display from the cerebrum and cerebellum of 13-week and 33-week fetal brains. After searching database, 74 of them represented novel genes, some of them were homologous to the brain development related genes. Using total cDNA probes, 79 of the ESTs and their expression differences in fetal brain were further characterized.     

黑莓果实发育过程中蔗糖磷酸合成酶基因的表达分析

【目的】蔗糖磷酸合成酶(sucrose phosphate synthase, SPS)是调控植物蔗糖代谢合成的关键酶,在植物光合产物的积累与分配方面有重要作用。本研究旨在探讨黑莓3个SPS基因的系统发育关系、编码的蛋白特性、在不同发育时期、不同组织中的时空表达特性,并分析其与黑莓发育的关系。【方法】以黑莓栽培品种‘宝森’(‘Boysenberry’)为试材,从中克隆和鉴定了3个 SPS 基因家族成员,利用生物信息学和荧光定量聚合酶链式反应(qRT-PCR)等方法对3个黑莓SPS 基因RuSPS1、RuSPS2和RuSPS3的氨基酸序列、保守作用元件、编码的蛋白特性、蛋白结构及进化关系进行分析,并对这3个基因在黑莓中的时空表达情况与酶活性进行了相关性分析。【结果】多重氨基酸序列比对显示,黑莓SPS蛋白具有植物SPS家族特有的2个保守蛋白结构域及2个相对保守的蛋白磷酸位点;系统进化分析表明,RuSPS基因分为A、B两个亚族,其中RuSPS1和RuSPS3为A亚族成员,RuSPS2为B亚族成员;保守作用元件分析表明, 除RuSPS2含基本的蛋白保守元件外, RuSPS1和RuSPS3都存在不同程度的片段缺失;序列分析和比较揭示了黑莓SPS基因与其他家族的不同特征。qRT-PCR分析显示,3个RuSPS基因在黑莓各个组织器官中均有表达,其中RuSPS1在叶片和果实中表达量较高,在花中的表达量较低;RuSPS2在发育成熟的果实中有大量的表达,在其他器官中表达量较低;RuSPS3在各器官中的表达均较高,说明 SPS基因表达具有明显的组织特异性,3个RuSPS基因都随着果实发育进程在果实和叶片中表现了表达增加的趋势。果实和叶片中SPS酶活性的变化与RuSPS基因表达水平一致。相关分析表明,叶片中SPS活性与RuSPS2显著正相关(P<0.05),果实中SPS活性与RuSPS1显著负相关(P<0.05)。【结论】3个RuSPS基因与黑莓果实发育过程中的蔗糖合成与代谢关系密切,均参与了黑莓的生长发育调控,其中叶片中SPS活性的变化一定程度上是由RuSPS2调控,果实中SPS活性的变化则是由RuSPS1调控。     

Transposition of structural genes to an expression sequence on a linear plasmid causes antigenic variation in the bacterium Borrelia hermsii

In Borrelia hermsii, a spirochaete that causes relapsing fever, the switch between expression of two frequent variable major protein (VMP) types (7 and 21) is associated with a DNA rearrangement. Both cell types 7 and 21 contain untranscribed 7 and 21 VMP genes on linear plasmids. The serotype 7 cells contain an additional copy of the 7 VMP gene fused to an expression sequence on another linear plasmid. Switching to the 21 serotype involves removal of the transcribed 7 VMP gene and fusion of a copy of the 21 VMP gene to this same expression sequence. Thus recombination between linear plasmids can activate different VMP genes.     

植物中miR160/miR167/miR390家族及其靶基因研究进展

microRNA(miRNA)是真核生物中广泛存在的一类长21～23个核苷酸的非编码RNA分子,通过与靶基因mRNA的特异结合调节基因转录后表达,在调控细胞周期、生物体发育时序等方面起重要作用。miR160、miR167和miR390 3个miRNAs家族均为靶向ARF(Auxin Response Factor)基因家族,预示着它们在行使调控功能的过程中既有相似性又有特异性。笔者详细阐述了miR160/miR167/miR390在植物发育过程中的调控作用及与其靶基因之间的相互调控关系,发现miR160/miR167/miR390均在植物生长发育过程中发挥重要的作用,但miR160则侧重于调控胚胎和根的发育,miR167侧重于调控植物花和果实的发育,而miR390则对植物横向器官的发育具有调控作用,并且,miR160/miR167/miR390与其靶基因之间存在反馈调节作用。     

mRNA差异显示技术研究低温条件下深黄被孢霉基因的表达差异

mRNA差异显示技术已经广泛应用于研究植物、动物和微生物在各种环境条件下基因的差异表达研究.研究以15℃和30℃培养的深黄被孢霉M6-22菌体为材料,利用mRNA差异显示技术研究两种培养条件下基因的表达差异.经实时荧光定量PCR验证,共获得7条差异片段,相似性搜索结果表明它们是6-磷酸葡萄糖异构酶、单糖核苷酸转运蛋白、Ras1鸟苷酸转移因子、依赖于NAD的苹果酸脱氢酶、Δ12-脂肪酸脱氢酶、CLK4关联的丝氨酸/精氨酸丰富蛋白和假定蛋白,涉及糖酵解、蛋白质修饰、信号传导、脂肪酸合成和mRNA加工等生命过程,表明深黄被孢霉M6-22低温适应性是多种途径协同调控的结果.