前列腺癌细胞系和组织中neprilysin的表达

目的检测neprilysin（NEP）在前列腺癌细胞系和组织中的表达。方法用实时荧光定量PCR、western blot检测前列腺癌细胞系（LNCaP、PC-3）、39例前列腺癌和16例正常前列腺组织中NEP mRNA和蛋白表达。结果与正常组织相比,LNCaP及PC-3细胞中NEP mRNA表达下调,尤以LNCaP细胞更为显著;在经甲基化抑制剂作用后,PC-3细胞NEP mRNA恢复表达的程度明显高于LNCaP细胞。前列腺癌组织中NEP mRNA和蛋白表达均明显低于正常前列腺。结论 NEP表达下调可能促进前列癌发生。     

酿酒酵母 ERG6基因缺失突变株的构建

设计含有与ERG6基因两侧序列同源的长引物,以质粒pBlue-Kan为模板进行PCR扩增,构建含有Cre/lox P系统的酿酒酵母ERG6基因敲除组件.将基因敲除组件转化至酿酒酵母(Saccharomyce cerevisiae)AD1-8,通过同源重组的方式使目的基因缺失,获得为lox P-Kan-lox P序列组件所替换而产生Kanr的阳性克隆子.然后再将质粒pHis-Cre转入阳性克隆子表达Cre重组酶敲除筛选标记,成功获得酿酒酵母ERG6基因缺失的突变株,并命名为AD1-8-δ.     

Maintenance of genome stability in Saccharomyces cerevisiae

Most human cancer cells show signs of genome instability, ranging from elevated mutation rates to gross chromosomal rearrangements and alterations in chromosome number. Little is known about the molecular mechanisms that generate this instability or how it is suppressed in normal cells. Recent studies of the yeast Saccharomyces cerevisiae have begun to uncover the extensive and redundant pathways that keep the rate of genome rearrangements at very low levels. These studies, which we review here, have implicated more than 50 genes in the suppression of genome instability, including genes that function in S-phase checkpoints, recombination pathways, and telomere maintenance. Human homologs of several of these genes have well-established roles as tumor suppressors, consistent with the hypothesis that the mechanisms preserving genome stability in yeast are the same mechanisms that go awry in cancer.     

Mutational inactivation of STAG2 causes aneuploidy in human cancer

Most cancer cells are characterized by aneuploidy, an abnormal number of chromosomes. We have identified a clue to the mechanistic origins of aneuploidy through integrative genomic analyses of human tumors. A diverse range of tumor types were found to harbor deletions or inactivating mutations of STAG2, a gene encoding a subunit of the cohesin complex, which regulates the separation of sister chromatids during cell division. Because STAG2 is on the X chromosome, its inactivation requires only a single mutational event. Studying a near-diploid human cell line with a stable karyotype, we found that targeted inactivation of STAG2 led to chromatid cohesion defects and aneuploidy, whereas in two aneuploid human glioblastoma cell lines, targeted correction of the endogenous mutant alleles of STAG2 led to enhanced chromosomal stability. Thus, genetic disruption of cohesin is a cause of aneuploidy in human cancer.     

Fragile sites at 16q22 are not at the breakpoint of the chromosomal rearrangement in AMMoL

There is much speculation about fragile sites on human chromosomes predisposing to specific chromosome rearrangements seen in cancer. Acute myelomonocytic leukemia is characterized by neoplastic chromosome rearrangements involving band 16q22 in patients who carry the rare fragile site at 16q22. This specific leukemic breakpoint is within the metallothionein gene cluster, which is here shown to be proximal to the rare fragile site (FRA16B) and to a common fragile site (FRA16C) in this region. Hence neither of these fragile sites are at the breakpoint in this leukemic chromosomal rearrangement.     

Programmed gene rearrangements altering gene expression

Programmed gene rearrangements are used in nature to to alter gene copy number (gene amplification and deletion), to create diversity by reassorting gene segments (as in the formation of mammalian immunoglobulin genes), or to control the expression of a set of genes that code for the same function (such as surface antigens). Two major mechanisms for expression control are DNA inversion and DNA transposition. In DNA inversion a DNA segment flips around and is rejoined by site-specific recombination, disconnecting or connecting a gene to sequences required for its expression. In DNA transposition a gene moves into an expression site where it displaces its predecessor by gene conversion. Gene rearrangements altering gene expression have mainly been found in some unicellular organisms. They allow a fraction of the organisms to preadapt to sudden changes in environment, that is, to alter properties such as surface antigens in the absence of an inducing stimulus. The antigenic variation that helps the causative agents of African trypanosomiasis, gonorrhea, and relapsing fever to elude host defense is controlled in this way.     

Structural dynamics of eukaryotic chromosome evolution

Large-scale genome sequencing is providing a comprehensive view of the complex evolutionary forces that have shaped the structure of eukaryotic chromosomes. Comparative sequence analyses reveal patterns of apparently random rearrangement interspersed with regions of extraordinarily rapid, localized genome evolution. Numerous subtle rearrangements near centromeres, telomeres, duplications, and interspersed repeats suggest hotspots for eukaryotic chromosome evolution. This localized chromosomal instability may play a role in rapidly evolving lineage-specific gene families and in fostering large-scale changes in gene order. Computational algorithms that take into account these dynamic forces along with traditional models of chromosomal rearrangement show promise for reconstructing the natural history of eukaryotic chromosomes.     

ETV5基因敲除对小鼠肌肉基因表达谱的影响

【目的】与野生型小鼠相比较,采用CRISPR/Cas9技术制备的ETV5基因纯合敲除小鼠在表现出内源性精原干细胞消融的同时伴随着体型和体质的明显弱势,本研究的目的是探究ETV5基因敲除对小鼠肌肉表达谱的影响。【方法】采集6周龄的3只野生型公鼠和3只ETV5纯合敲除公鼠的肌肉组织并抽提RNA,进行转录组测序,并对测序结果进行生物信息学分析,对2组小鼠肌肉样品的差异表达基因进行聚类分析、GO和KEGG富集分析。【结果】2组小鼠的肌肉组织共筛选出了574个差异表达基因,其中,上调基因292个,下调基因282个。发现了多个基因影响ETV5敲除小鼠的生长发育,其中,包括影响小鼠肌肉发育的基因Amd1和影响脂肪累积的基因Chrna2。GO和KEGG分析富集到的通路大多与脂肪代谢和生长发育相关。【结论】本研究结果为ETV5敲除小鼠生长发育缓慢和延迟的分子机制提供了解释,为研究ETV5在生理和病理上的相关功能提供了参考。     

The chromosomal basis of human neoplasia

High-resolution banding techniques for the study of human chromosomes have revealed that the malignant cells of most tumors analyzed have characteristic chromosomal defects. Translocations of the same chromosome segments with precise breakpoints occur in many leukemias and lymphomas, and a specific chromosome band is deleted in several carcinomas. Trisomy, or the occurrence of a particular chromosome in triplicate, is the only abnormality observed in a few neoplasias. It is proposed that chromosomal rearrangements play a central role in human neoplasia and may exert their effects through related genomic mechanisms. Thus, a translocation could serve to place an oncogene next to an activating DNA sequence, a deletion to eliminate an oncogene repressor, and trisomy to carry extra gene dosage.     

Antibody variability. Somatic recombination between the elements of "antibody gene pairs" may explain antibody variability

I have analyzed the available amino acid sequence data from 30 myelomatosis-derived proteins. Several types of variation are apparent. I conclude that a major and genetically predetermined contribution to the variability of these proteins and of antibodies could be provided by chromosomal rearrangements resulting from somatic recombination between similar but not identical genes in antibody gene pairs. My hypothesis suggests many new types of experiment and can be tested (31).     

Identification of a chromosome 18q gene that is altered in colorectal cancers

Allelic deletions involving chromosome 18q occur in more than 70 percent of colorectal cancers. Such deletions are thought to signal the existence of a tumor suppressor gene in the affected region, but until now a candidate suppressor gene on this chromosomal arm had not been identified. A contiguous stretch of DNA comprising 370 kilobase pairs (kb) has now been cloned from a region of chromosome 18q suspected to reside near this gene. Potential exons in the 370-kb region were defined by human-rodent sequence identities, and the expression of potential exons was assessed by an "exon-connection" strategy based on the polymerase chain reaction. Expressed exons were used as probes for cDNA screening to obtain clones that encoded a portion of a gene termed DCC; this cDNA was encoded by at least eight exons within the 370-kb genomic region. The predicted amino acid sequence of the cDNA specified a protein with sequence similarity to neural cell adhesion molecules and other related cell surface glycoproteins. While the DCC gene was expressed in most normal tissues, including colonic mucosa, its expression was greatly reduced or absent in most colorectal carcinomas tested. Somatic mutations within the DCC gene observed in colorectal cancers included a homozygous deletion of the 5' end of the gene, a point mutation within one of the introns, and ten examples of DNA insertions within a 0.17-kb fragment immediately downstream of one of the exons. The DCC gene may play a role in the pathogenesis of human colorectal neoplasia, perhaps through alteration of the normal cell-cell interactions controlling growth.     

Cytoplasmic Reversion of cms-S in Maize: Association with a Transpositional Event

Spontaneous reversion to fertility in S male-sterile cytoplasm of maize is correlated with the disappearance of the mitochondrial plasmid-like DNA's, S-1 and S-2, and changes in the mitochondrial chromosomal DNA. Hybridization data indicate that one of the plasmid-like DNA's, S-2, is prominently involved in the mitochondrial DNA rearrangements.