Factor VIII mRNA expression from a BAC carrying the intact locus made by homologous recombination

Hemophilia A is caused by mutations in the gene encoding factor VIII (F8) and is an important target for gene therapy. The F8 gene contains 26 exons spread over approximately 186 kb and no work using the intact genomic locus has been carried out. We have constructed a 250-kb BAC carrying all 26 exons, the introns, and more than 40 kb of upstream and 20 kb of downstream DNA. This F8 BAC was further retrofitted with either the oriP/EBNA-1 elements from Epstein-Barr virus, which allow episomal maintenance in mammalian cells, or alphoid DNA, which allows human artificial chromosome formation in some human cell lines. Lipofection of the oriP/EBNA-1-containing version into mouse Hepa1-6 cells resulted in expression of F8 mRNA spanning the F8 gene. The >300-kb BAC carrying alphoid DNA was successfully delivered to 293A and HT1080 cells using bacterial delivery, resulting in greater than endogenous levels of F8 mRNA expression.     

Organization of delta-crystallin genes in the chicken.

Double-stranded DNA was synthesized from delta-crystallin mRNA prepared from lens fibers of 15-day-old chick embryos and cloned at the Pst I site of the plasmid pBR322. Using the cloned cDNA and single-stranded cDNA as hybridization probes, a number of genomic DNA fragments containing delta-crystallin gene sequences have been cloned from the partial and complete EcoRI digests of chick brain DNA. One of the clones from the partial digests contains a DNA fragment that consists of four EcoRI fragments of 7.6 kb, 4.0 kb, 2.6 kb, and 0.8 kb. The gene sequences reside in the (5')7.6 kb - 0.8 kb - 4.0 kb (3') fragments. Electron microscopy has provided evidence that the cloned DNA fragment includes the entire gene sequences complementary to delta-crystallin mRNA except for the 3' terminal poly(A) tail, and that the delta-crystallin gene is interrupted by at least 13 intervening sequences. Another clone contains a genomic fragment that consists of two EcoRI fragments of 3.0 kb and 11 kb. The DNA fragment in the latter clone represents a different delta-crystallin gene, as judged by restriction endonuclease mapping and by electron microscopy.     

Genomic Organization and 5′-Flanking DNA Sequence of the Murine Stomatin Gene (Epb72)

Stomatin is a poorly understood integral membrane protein that is absent from the erythrocyte membranes of many patients with hereditary stomatocytosis. This report describes the cloning of the murine stomatin chromosomal gene, determination of its genomic structure, and characterization of the 5′-flanking genomic DNA sequences. The stomatin gene is encoded by seven exons spread over ∼25 kb of genomic DNA. There is no concordance between the exon structure of the stomatin gene and the locations of three domains predicted on the basis of protein structure. Inspection of the 5′-flanking DNA sequences reveals features of a TATA-less housekeeping gene promoter and consensus sequences for a number of potential DNA-binding proteins.     

Genetic studies of cleavage-initiated mRNA decay and processing of ribosomal 9S RNA show that the Escherichia coli ams and rne loci are the same

We show in the present paper that the cleavages initiating decay of the ompA mRNA are suppressed both in the Escherichia coli ams(ts) strain (originally defined by a prolonged bulk mRNA half-life) and in the me(ts) strain (originally defined by aberrant 9S RNA processing). The temperature-sensitive defects of both these strains are complemented by a recombinant lambda phage containing a genomic segment that carries the putative ams locus. A 5.8 kb fragment from this genomic DNA segment was cloned into a low-copy plasmid and used to transform the ams(ts) and rne(ts) strains. This resulted in growth at the non-permissive temperature and a reoccurrence of the cleavages initiating decay of the ompA mRNA. Deletion analyses of this 5.8 kb fragment indicated that the putative ams open reading frame could complement both the Ams(ts) and the Rne(ts) phenotype with regard to the ompA cleavages. In addition we showed that the ams(ts) strain suppresses 9S RNA processing to 5S RNA to the same extent as the rne(ts) strain, and that the rne(ts0 strain has a prolonged bulk mRNA half-life, as was reported for the ams(ts) strain. Therefore we suggest that ams and rne reflect the same gene locus; one which is involved both in mRNA decay and RNA processing. We discuss how this gene locus may related to the previously characterized endoribonucleolytic activities of RNase E and RNase K.     

Delivery and long-term expression of a 135 kb LDLR genomic DNA locus in vivo by hydrodynamic tail vein injection

BACKGROUND: The delivery of a complete genomic DNA locus in vivo may prove advantageous for complementation gene therapy, especially when physiological regulation of gene expression is desirable. Hydrodynamic tail vein injection has been shown to be a highly efficient means of non-viral delivery of plasmid DNA to the liver. Here, we apply hydrodynamic tail vein injection to deliver and express large genomic DNA inserts > 100 kb in vivo. METHODS: Firstly, a size series (12-172 kb) of bacterial artificial chromosome (BAC) plasmids, carrying human genomic DNA inserts, episomal retention elements, and the enhanced green fluorescent protein (EGFP) reporter gene, was delivered to mice by hydrodynamic tail vein injection. Secondly, an episomal BAC vector carrying the whole genomic DNA locus of the human low-density lipoprotein receptor (LDLR) gene, and an expression cassette for the LacZ reporter gene, was delivered by the same method. RESULTS: We show that the efficiency of delivery is independent of vector size, when an equal number of plasmid molecules are used. We also show, by LacZ reporter gene analysis, that BAC delivery within the liver is widespread. Finally, BAC-end PCR, RT-PCR and immunohistochemistry demonstrate plasmid retention and long-term expression (4 months) of human LDLR in transfected hepatocytes. CONCLUSION: This is the first demonstration of somatic delivery and long-term expression of a genomic DNA transgene > 100 kb in vivo and shows that hydrodynamic tail vein injection can be used to deliver and express large genomic DNA transgenes in the liver.     

连续3步缺口修复构建小鼠乳清酸蛋白-人溶菌酶杂合基因座

目的:构建一个利用小鼠乳清酸蛋白(mWAP)基因座完整的上下游调控序列指导人溶菌酶(hLYZ)基因组序列在乳腺内特异性高效表达的mWAP-hLYZ杂合基因座,实现人溶菌酶的高效表达。方法:采用连续3步缺口修复的方法。首先,以pBR322载体作为骨架,插入预先合成的6个同源臂序列,构成能够连续进行3次缺口修复的基因抓捕载体。然后在大肠杆菌内利用λ噬菌体Red同源重组系统介导的同源重组方法:第一步,从含mWAP基因座的细菌人工染色体(BAC)上亚克隆8 kb的mWAP基因3’端完整侧翼序列到抓捕载体上;第二步,从含hLYZ基因的BAC上亚克隆5 kb的从起始密码子(ATG)到终止密码子(TAA)的hLYZ基因组序列;第三步,从mWAP BAC上亚克隆9kb的mWAP基因5’端完整侧翼序列,并使上述3个片段在抓捕载体上自动无痕地连接在一起。结果:构建了全长约22 kb的mWAP-hLYZ杂合基因座,经PCR扩增、限制性内切酶酶切和序列测定验证,构建的杂合基因座达到原mWAP基因座中mWAP基因组编码序列从起始密码子(ATG)到终止密码子(TAA)完全被hLYZ基因组序列精确置换的目的。结论:通过连续3步缺口修复构建杂合mWAP-hLYZ基因座乳腺表达载体,为乳腺生物反应器高效表达人溶菌酶提供了可行的思路和方法。     

Complex control of mouse apolipoprotein B gene expression revealed by targeted duplication

An elevated plasma level of apolipoprotein B-containing lipoproteins is a risk factor for atherosclerotic cardiovascular disease. Subtle genetic abnormalities in gene expression including an increased expression of the APOB gene may play an important role in determining overall risk. In an attempt to increase mouse Apob expression, we used gene targeting and duplicated approximately 65 kb of genomic DNA containing the Apob locus in its natural genomic position in mice. While we successfully generated mice carrying the Apob gene duplication, the amount of the total Apob mRNA was not increased in their liver. In the intestine, total Apob mRNA was reduced to half of the wild-type mice. Plasma lipids in the Apob duplication mice were not altered. Expression analyses showed that the proximal Apob gene in the duplicated locus was preferentially expressed in both tissues suggesting a limitation of tissue-specific enhancer function. The previously characterized distant intestinal control element was not duplicated, explaining the unequal ratio of intestinal Apob expression. While the existence of an additional liver-specific enhancer element is unknown, our findings suggest the presence of an additional enhancer outside the duplicated region, and that Apob gene expression is more complicated than previously thought.     

连续3步缺口修复构建人β肌动蛋白-人凝血因子Ⅶ杂合基因座

目的:为了获得稳定高效表达凝血因子Ⅶ的哺乳动物细胞株,构建一个利用人β肌动蛋白(hACTB)基因座完整的上下游调控序列指导人凝血因子Ⅶ(hFⅦ)基因组序列在人胚胎肾细胞特异性高效表达的hACTB-hFⅦ杂合基因座。方法:采用3步连续缺口修复的方法。首先,以pBR322载体作为骨架,插入预先合成的6个同源臂,构成能进行3次连续基因抓捕的载体。然后在大肠杆菌内利用Red同源重组系统介导的缺口修复技术:第一步,从含hACTB基因座的细菌人工染色体(BAC)上亚克隆10 kb的hACTB基因3′端完整侧翼序列;第二步,从hFⅦBAC上亚克隆13 kb的从起始密码子(ATG)到终止密码子(TAG)的hFⅦ基因组序列;第三步,从hACTB BAC上亚克隆20kb的hACTB基因5′端完整侧翼序列,并使这3个基因片段自动无痕地连接在基因抓捕载体上,形成全长约50 kb的hACTB-hFⅦ杂合基因座。结果:经过PCR扩增、限制性内切酶消化和序列测定验证,构建的杂合基因座达到了原来hACTB基因座中hACTB基因组编码序列从起始密码子到终止密码子被hFⅦ从起始密码子到终止密码子的基因组序列基因组序列精确置换的目的。结论:连续3步缺口修复构建杂合基因座细胞表达载体的技术,将为细胞高效表达大载体的制备提供一种全新的思路和方法。     

The activin receptor-like kinase 1 gene: genomic structure and mutations in hereditary hemorrhagic telangiectasia type 2.

The activin receptor-like kinase 1 gene (ALK-1) is the second locus for the autosomal dominant vascular disease hereditary hemorrhagic telangiectasia (HHT). In this paper we present the genomic structure of the ALK-1 gene, a type I serine-threonine kinase receptor expressed predominantly in endothelial cells. The coding region is contained within nine exons, spanning < 15 kb of genomic DNA. All introns follow the GT-AG rule, except for intron 6, which has a TAG/gcaag 5' splice junction. The positions of introns in the intracellular domain are almost identical to those of the mouse serine-threonine kinase receptor TSK-7L. By sequencing ALK-1 from genomic DNA, mutations were found in six of six families with HHT either shown to link to chromosome 12q13 or in which linkage of HHT to chromosome 9q33 had been excluded. Mutations were also found in three of six patients from families in which available linkage data were insufficient to allow certainty with regard to the locus involved. The high rate of detection of mutations by genomic sequencing of ALK-1 suggests that this will be a useful diagnostic test for HHT2, particularly where preliminary linkage to chromosome 12q13 can be established. In two cases in which premature termination codons were found in genomic DNA, the mutant mRNA was either not present or present at barely detectable levels. These data suggest that mutations in ALK-1 are functionally null alleles.