Enhancing the efficiency of transgene expression

Exogenous aralar/slc25a12 can replace citrin/slc25a13 as malate aspartate shuttle component in liver

The deficiency of CITRIN, the liver mitochondrial aspartate-glutamate carrier (AGC), is the cause of four human clinical phenotypes, neonatal intrahepatic cholestasis caused by CITRIN deficiency (NICCD), silent period, failure to thrive and dyslipidemia caused by CITRIN deficiency (FTTDCD), and citrullinemia type II (CTLN2). Clinical symptoms can be traced back to disruption of the malate-aspartate shuttle due to the lack of citrin. A potential therapy for this condition is the expression of aralar, the AGC present in brain, to replace citrin. To explore this possibility we have first verified that the NADH/NAD⁺ ratio increases in hepatocytes from citrin(-/-) mice, and then found that exogenous aralar expression reversed the increase in NADH/NAD⁺ observed in these cells. Liver mitochondria from citrin (-/-) mice expressing liver specific transgenic aralar had a small (~ 4-6 nmoles x mg prot^-1 x min^-1) but consistent increase in malate aspartate shuttle (MAS) activity over that of citrin(-/-) mice. These results support the functional replacement between AGCs in the liver. To explore the significance of AGC replacement in human therapy we studied the relative levels of citrin and aralar in mouse and human liver through absolute quantification proteomics. We report that mouse liver has relatively high aralar levels (citrin/aralar molar ratio of 7.8), whereas human liver is virtually devoid of aralar (CITRIN/ARALAR ratio of 397). This large difference in endogenous aralar levels partly explains the high residual MAS activity in liver of citrin(-/-) mice and why they fail to recapitulate the human disease, but supports the benefit of increasing aralar expression to improve the redox balance capacity of human liver, as an effective therapy for CITRIN deficiency.

Genome-Scale Computational Identification and Characterization of UTR Introns in Atalantia buxifolia

Accumulated evidence has shown that CDS introns (CIs) play important roles in regulating gene expression. However, research on UTR introns (UIs) is limited. In this study, UIs (including 5′UTR and 3′UTR introns (5UIs and 3UIs)) were identified from the Atalantia buxifolia genome. The length and nucleotide distribution characteristics of both 5UIs and 3UIs and the distributions of cis-acting elements and transcription factor binding sites (TFBSs) in 5UIs were investigated. Moreover, PageMan enrichment analysis was applied to show the possible roles of transcripts containing UIs (UI-Ts). In total, 1077 5UIs and 866 3UIs were identified from 897 5UI-Ts and 670 3UI-Ts, respectively. Among them, 765 (85.28%) 5UI-Ts and 527 (78.66%) 3UI-Ts contained only one UI, and 94 (6.38%) UI-Ts contained both 5UI and 3UI. The UI density was lower than that of CDS introns, but their mean and median intron sizes were ~2 times those of the CDS introns. The A. buxifolia 5UIs were rich in gene-expression-enhancement-related elements and contained many TFBSs for BBR-BPC, MIKC_MADS, AP2 and Dof TFs, indicating that 5UIs play a role in regulating or enhancing the expression of downstream genes. Enrichment analysis revealed that UI-Ts involved in ‘not assigned’ and ‘RNA’ pathways were significantly enriched. Noteworthily, 119 (85.61%) of the 3UI-Ts were genes encoding pentatricopeptide (PPR) repeat-containing proteins. These results will be helpful for the future study of the regulatory roles of UIs in A. buxifolia.

Expanded inverted repeat region with large scale inversion in the first complete plastid genome sequence of Plantago ovata

Plantago ovata (Plantaginaceae) is an economically and medicinally important species, however, least is known about its genomics and evolution. Here, we report the first complete plastome genome of P. ovata and comparison with previously published genomes of related species from Plantaginaceae. The results revealed that P. ovata plastome size was 162,116 bp and that it had typical quadripartite structure containing a large single copy region of 82,084 bp and small single copy region of 5,272 bp. The genome has a markedly higher inverted repeat (IR) size of 37.4 kb, suggesting large-scale inversion of 13.8 kb within the expanded IR regions. In addition, the P. ovata plastome contains 149 different genes, including 43 tRNA, 8 rRNA, and 98 protein-coding genes. The analysis revealed 139 microsatellites, of which 71 were in the non-coding regions. Approximately 32 forward, 34 tandem, and 17 palindromic repeats were detected. The complete genome sequences, 72 shared genes, matK gene, and rbcL gene from related species generated the same phylogenetic signals, and phylogenetic analysis revealed that P. ovata formed a single clade with P. maritima and P. media. The divergence time estimation as employed in BEAST revealed that P. ovata diverged from P. maritima and P. media about 11.0 million years ago (Mya; 95% highest posterior density, 10.06-12.25 Mya). In conclusion, P. ovata had significant variation in the IR region, suggesting a more stable P. ovata plastome genome than that of other Plantaginaceae species.

RNAa and Vector-Mediated Overexpression of DIRAS1 Suppresses Tumor Growth and Migration in Renal Cell Carcinoma

The downregulation of DIRAS1 has been suggested to potentially contribute to tumor development and progression in several human cancers. However, the role of DIRAS1 in renal cell carcinoma (RCC) remains elusive. In this study, we examined the DIRAS1 expression level in RCC cell lines and tissues. Both RNA activation (RNAa) and vector transfection methods were used to upregulate the expression of DIRAS1 in RCC cells. Expression analysis revealed that DIRAS1 was significantly downregulated in RCC cell lines and tissues compared with nontumorigenic renal cells and adjacent nontumor tissues individually. Promoter methylation analysis indicated that the reduced DIRAS1 expression might be partly mediated by epigenetic modulation. The RNAa-mediated overexpression of DIRAS1 inhibited cell proliferation and tumorigenicity in vitro and in vivo. The re-activation of DIRAS1 also promoted apoptosis and suppressed migration and invasion in RCC cells. The ectopic expression of DIRAS1 via an expression vector recapitulated the RNAa results. These results reveal that DIRAS1, functioning as a putative tumor suppressor in RCC cells, could potentially be a therapeutic target and RNAa could be a therapeutic strategy for RCC.

Introns: The Functional Benefits of Introns in Genomes

The intron has been a big biological mystery since it was first discovered in several aspects. First, all of the completely sequenced eukaryotes harbor introns in the genomic structure, whereas no prokaryotes identified so far carry introns. Second, the amount of total introns varies in different species. Third, the length and number of introns vary in different genes, even within the same species genome. Fourth, all introns are copied into RNAs by transcription and DNAs by replication processes, but intron sequences do not participate in protein-coding sequences. The existence of introns in the genome should be a burden to some cells, because cells have to consume a great deal of energy to copy and excise them exactly at the correct positions with the help of complicated spliceosomal machineries. The existence throughout the long evolutionary history is explained, only if selective advantages of carrying introns are assumed to be given to cells to overcome the negative effect of introns. In that regard, we summarize previous research about the functional roles or benefits of introns. Additionally, several other studies strongly suggesting that introns should not be junk will be introduced.

Association and interaction of PPARα, δ, and γ gene polymorphisms with low-density lipoprotein-cholesterol in a Chinese Han population

AIMS

Elevated low-density lipoprotein-cholesterol (LDL-C) is regarded as one of major risks of cardiovascular diseases and atherosclerotic events. It has been previously reported that peroxisome proliferator-activated receptors (PPARs) play an important role in the regulation of lipid metabolism. In this study, we aimed to investigate the influence of PPARα/δ/γ gene polymorphisms on LDL-C level. Eight hundred twenty unrelated participants were recruited. Ten single-nucleotide polymorphisms (SNPs) were genotyped to analyze the gene-gene interactions among these polymorphisms using the generalized multifactor dimensionality reduction (GMDR) method.

RESULTS

The results of single-locus analyses indicated that the genotypes with minor allele variants at the rs1800206, rs9794, rs1805192, rs709158, and rs3856806 loci are associated with higher LDL-C levels (p<0.05) after adjusting for covariates. In contrast, individuals that were homozygous for the major allele (CC) of rs10865710 had significantly higher LDL-C than those with either one or more minor type alleles (CG+GG, mean difference: -0.21 mM; 95% confidence interval [CI]: -0.37 to -0.04 mM; p=0.013). Significant gene-gene interactions among PPAR gene polymorphisms on LDL-C were identified by a generalized multifactor dimensionality reduction (GMDR) approach in 2- to 8-locus models (p<0.05).

CONCLUSION

Our results provide evidence that multiple PPARα/δ/γ gene polymorphisms are individually associated with increased LDL-C, and that interactions, among these alleles result in additional increased risk suggesting that PPAR genes may contribute substantially to the risk of cardiovascular diseases and atherosclerosis.

Inducing gene expression by targeting promoter sequences using small activating RNAs

Vector-based systems comprised of exogenous nucleic acid sequences remain the standard for ectopic expression of a particular gene. Such systems offer robust overexpression, but have inherent drawbacks such as the tedious process of construction, excluding sequences (e.g. introns and untranslated regions) important for gene function and potential insertional mutagenesis of host genome associated with the use of viral vectors. We and others have recently reported that short double-stranded RNAs (dsRNAs) can induce endogenous gene expression by targeting promoter sequences in a phenomenon referred to as RNA activation (RNAa) and such dsRNAs are termed small activating RNAs (saRNAs). To date, RNAa has been successfully utilized to induce the expression of different genes such as tumor suppressor genes. Here, we describe a detailed protocol for target selection and dsRNA design with associated experiments to facilitate RNAa in cultured cells. This technique may be applied to selectively activate endogenous gene expression for studying gene function, interrogating molecular pathways and reprogramming cell fate.

Epigenetic alterations of Krüppel-like factor 4 and its tumor suppressor function in renal cell carcinoma

Krüppel-like factor 4 (KLF4) is a transcription factor that can have divergent functions in different malignancies. The expression and role of KLF4 in renal cell cancer remain unclear. The purpose of this study is to determine epigenetic alterations and possible roles of KLF4 in renal cell carcinoma. The KLF4 expression in primary renal cell cancer tissues and case-matched normal renal tissues was determined by protein and messenger RNA analyses. The epigenetic alterations were detected by methylation-specific PCR and Sequenom MassARRAY. Kaplan-Meier curves and the log-rank test were used for the survival analysis. The effects of KLF4 on cell growth and epithelial-to-mesenchymal transition (EMT) were determined in renal cancer cell lines after viral-based and RNA activation-mediated overexpression of KLF4. In vivo antitumor activity of KLF4 was evaluated by using stably KLF4-transfected renal cancer cells. KLF4 expression was dramatically decreased in various pathological types of renal cancer and associated with poor survival after nephrectomy. Hypermethylation of KLF4 promoter mainly contributed to its expression suppression. In vitro assays indicated that KLF4 overexpression inhibited renal cancer cell growth and survival. KLF4 overexpression also suppressed renal cancer cell migration and invasion by altering the EMT-related factors. In vivo assay showed that ectopic expression of KLF4 also inhibited tumorigenicity and metastasis of renal cancer. Our results suggest that KLF4 is a putative tumor suppressor gene epigenetically silenced in renal cell cancers by promoter CpG methylation and that it has prognostic value for renal cell progression.

Expression of nitrous oxide reductase from Pseudomonas stutzeri in transgenic tobacco roots using the root-specific rolD promoter from Agrobacterium rhizogenes

The nitrous oxide (N₂O) reduction pathway from a soil bacterium, Pseudomonas stutzeri, was engineered in plants to reduce N₂O emissions. As a proof of principle, transgenic plants expressing nitrous oxide reductase (N₂OR) from P. stutzeri, encoded by the nosZ gene, and other transgenic plants expressing N₂OR along with the more complete operon from P. stutzeri, encoded by nosFLZDY, were generated. Gene constructs were engineered under the control of a root-specific promoter and with a secretion signal peptide. Expression and rhizosecretion of the transgene protein were achieved, and N₂OR from transgenic Nicotiana tabacum proved functional using the methyl viologen assay. Transgenic plant line 1.10 showed the highest specific activity of 16.7 µmol N₂O reduced min⁻¹ g⁻¹ root protein. Another event, plant line 1.9, also demonstrated high specific activity of N₂OR, 13.2 µmol N₂O reduced min⁻¹ g⁻¹ root protein. The availability now of these transgenic seed stocks may enable canopy studies in field test plots to monitor whole rhizosphere N flux. By incorporating one bacterial gene into genetically modified organism (GMO) crops (e.g., cotton, corn, and soybean) in this way, it may be possible to reduce the atmospheric concentration of N₂O that has continued to increase linearly (about 0.26% year⁻¹) over the past half-century.

The function of introns

The intron–exon architecture of many eukaryotic genes raises the intriguing question of whether this unique organization serves any function, or is it simply a result of the spread of functionless introns in eukaryotic genomes. In this review, we show that introns in contemporary species fulfill a broad spectrum of functions, and are involved in virtually every step of mRNA processing. We propose that this great diversity of intronic functions supports the notion that introns were indeed selfish elements in early eukaryotes, but then independently gained numerous functions in different eukaryotic lineages. We suggest a novel criterion of evolutionary conservation, dubbed intron positional conservation, which can identify functional introns.

RNAa-mediated overexpression of WT1 induces apoptosis in HepG2 cells

Aim

Recent studies have reported that double-stranded RNA (dsRNA) can activate gene expression by targeting promoter sequence in a process termed RNA activation. The present study was conducted to evaluate the potential of WT1 induction by small activating RNA targeting the WT1 promoter (dsWT1) in the treatment of hepatocellular carcinoma.

Methods

The human hepatocellular carcinoma cell line HepG2 was transfected with dsRNA by liposomes. The expression of mRNA and protein in cells were investigated using real-time reverse real-time quantitative PCR and Western blot, respectively. Cell viability and clonogenicity were determined by MTT assay and clonogenicity assay, respectively. Cell apoptosis was evaluated by flow-cytometric analysis.

Results

Expressions of WT1 mRNA and protein in dsWT1 treated HepG2 cells were significantly elevated. Inhibition of cell viability by dsWT1 was dose-dependent and time-dependent. Reduction of the number and size of colonies formed were found in dsWT1 treated cells. dsWT1 induced significant apoptosis in HepG2 cells. The decreased anti-apoptotic protein Bcl-2 and elevated pro-apoptotic protein Bak expression were detected in dsWT1 treated cells. The level of pro-caspase-3 remarkably decreased and cleaved caspase-3 and PARP fragment were also detected in dsWT1 treated cells.

Conclusion

These data show that RNAa-mediated overexpression of WT1 may have therapeutic potential in the treatment of hepatocellular carcinoma.

Small RNA and transcriptional upregulation

Small RNA molecules, such as microRNA and small interfering RNA, have emerged as master regulators of gene expression through their ability to suppress target genes in a phenomenon collectively called RNA interference (RNAi). There is growing evidence that small RNAs can also serve as activators of gene expression by targeting gene regulatory sequences. This novel mechanism, known as RNA activation (RNAa), appears to be conserved in at least mammalian cells and triggered by both endogenous and artificially designed small RNAs. RNAa depends on Argonaute proteins, but possesses kinetics distinct from that of RNAi. Epigenetic changes are associated with RNAa and may contribute to transcriptional activation of target genes, but the underlying mechanism remains elusive. Given the potential of RNAa as a molecular tool for studying gene function and as a therapeutic for disease, further research is needed to completely elucidate its molecular mechanism in order to refine the rules for target selection and improve strategies for exploiting it therapeutically. WIREs RNA 2011 2 748-760 DOI: 10.1002/wrna.90 For further resources related to this article, please visit the WIREs website.

Prognostic value and function of KLF4 in prostate cancer: RNAa and vector-mediated overexpression identify KLF4 as an inhibitor of tumor cell growth and migration

KLF4/GLKF4 is a transcription factor that can have divergent functions in different malignancies. The role of KLF4 in prostate cancer etiology remains unclear. We have recently reported that small double-stranded RNA can induce gene expression by targeting promoter sequence in a phenomenon referred to as RNA activation (RNAa). In this study, we examine KLF4 levels in prostate cancer tissue and utilize RNAa as a tool for gene overexpression to investigate its function. Expression analysis indicated that KLF4 is significantly downregulated in prostate cancer cell lines compared with nontumorigenic prostate cells. Meta-analysis of existing cDNA microarray data also revealed that KLF4 is frequently depleted in prostate cancer tissue with more pronounced reduction in metastases. In support, tissue microarray analysis of tumors and patient-matched controls indicated downregulation of KLF4 in metastatic tumor samples. Logistic regression analysis found that tumors with a KLF4 staining score less than 5 had a 15-fold higher risk for developing metastatic prostate cancer (P = 0.001; 95% confidence interval, 3.0-79.0). In vitro analysis indicated that RNAa-mediated overexpression of KLF4 inhibited prostate cancer cell proliferation and survival and altered the expression of several downstream cell-cycle-related genes. Ectopic expression of KLF4 via viral transduction recapitulated the RNAa results, validating its inhibitory effects on cancer growth. Reactivation of KLF4 also suppressed migration and invasion of prostate cancer cells. These results suggest that KLF4 functions as an inhibitor of tumor cell growth and migration in prostate cancer and decreased expression has prognostic value for predicting prostate cancer metastasis.

Isolation of Tanichthys albonubes beta actin gene and production of transgenic Tanichthys albonubes

A beta actin cDNA of Tanichthys albonubes was isolated through the RT-PCR and RACE approach. The cDNA was 1,787-bp in length, including a 1,128-bp CDS, a 95-bp 5'UTR and a 564-bp 3'UTR. Genomic DNA containing the transcription region and 5'-flanking region was cloned based on the beta actin cDNA by Genome walker. A 3,000-bp beta actin gene promoter was then produced by PCR according to the sequences of the 5'-flanking region and the first intron. This promoter consisted of a 1,800-bp 5'-flanking region, and a 1,200-bp 5'-UTR. 3 transcription elements, CAAT box, CArG motif and TATA box were found in the 5'-flanking region. This promoter was inserted into the vector pDsRed2-1 and microinjected into fertilized eggs of Tanichthys albonubes to prove its transcription activity. The beta actin promoter and GH CDS of Tanichthys albonubes were then fused to construct an expression vector pTLA-GH. GH-transgenic Tanichthys albonubes was obtained by microinjection of the pTLA-GH into the fertilized eggs. Fast-growth individuals were observed in the transgenic group and the body weight of the largest individual was 2.1-fold that of the maximum in its non-transgenic siblings in 100 dph. In addition, a co-injection strategy was employed with pTLA-DsRed and pTLA-GH vector and proven to enhance the efficiency of GH-transgenic fish detection.

An insulator with barrier-element activity promotes alpha-spectrin gene expression in erythroid cells

Understanding mechanisms controlling expression of the alpha-spectrin gene is important for understanding erythropoiesis, membrane biogenesis, and spectrin-linked hemolytic anemia. We showed previously that a minimal alpha-spectrin promoter directed low levels of expression only in early erythroid development, indicating elements outside the promoter are required for expression in adult erythrocytes. Addition of noncoding exon 1' and intron 1' conferred a 10-fold increase in activity in reporter gene assays. In this report, we used a transgenic mouse model to show that addition of exon 1' and intron 1' to the alpha-spectrin promoter conferred tissue-specific expression of a linked (A)gamma-globin gene in erythroid cells at all developmental stages. Expression was nearly position-independent, as 21 of 23 lines expressed the transgene, and gamma-globin protein was present in 100% of erythrocytes, indicating uniform expression. Additional in vivo studies revealed that exon 1' functions as an insulator with barrier-element activity. Chromatin immunoprecipitation assays demonstrated that this region was occupied by the upstream stimulatory factors 1/2 (USF1/USF2), similar to the well-characterized chicken HS4 insulator. These data identify the first barrier element described in an erythrocyte membrane protein gene and indicate that exon 1' and intron 1' are excellent candidate regions for mutations in patients with spectrin-linked hemolytic anemia.

Cloning and characterization of 5'-untranslated region of porcine beta casein gene (CSN2)

beta-Casein (CSN2) is a major milk protein in most mammals. The CSN2 gene is generally induced by lactogenic hormones bound to its promoter. The expression of this gene can be enhanced by signal transducers and activators of transcription (STAT) and glucocorticoid receptor (GR). Here, we analyzed the promoter and intron 1 regions of the porcine CSN2 gene. The porcine CSN2 promoter and intron 1 regions (-3098bp to +2446bp) were cloned into the pGL3-Basic vector containing the luciferase reporter gene (pCSN2-PEI). Lactogenic signals induced the transcription of porcine CSN2. By using AG490, a Janus kinase (JAK) inhibitor, we demonstrated that STAT5 positively regulates the transcription of porcine CSN2. Further, seven STAT mutants were generated by site-directed mutagenesis. By performing electrophoretic mobility shift assays (EMSAs), we located a critical element for pCSN2-PEI transcription bound to STAT5 in the -102bp to -84bp region. The construct containing only the promoter region (pCSN2-P), however, did not exert any promotive effects on transcription in two cell types-a mouse mammary epithelial cell line (HC11) and porcine mammary gland epithelial cells (PMECs). Thus, the construct containing intron 1 of porcine CSN2 exerts an elevating effect on transcription. We suggest that the transcription of porcine CSN2 is regulated by lactogenic signals via the STAT5 site (-102bp to -84bp) and intron 1.

Analysis of lactation defects in transgenic mice

Although lactation is the only physiological function of the mammary gland, little is known about the molecular events required for secretory activation and milk production. Genetically altered mice have been used extensively to study mammary gland development during puberty and pregnancy, as well as mammary tumorigenesis. A number of approaches have been used to produce genetic modifications in mammary glands of mice, including transgenic mice utilizing mammary specific promoters, traditional knockout mice, mammary-specific gene deletion, and conditionally-regulated transgenes. The same technologies can be used to study secretory activation and lactation; however only a comparatively small number of studies to date have used these approaches to study these events. In this paper we review the technologies available to make genetically modified mice for the study of secretory activation and lactation as well as specific analytical procedures that can be used to characterize mice with lactation defects.

Insertion of natural intron 6a-6b into a human cDNA-derived gene therapy vector for cystic fibrosis improves plasmid stability and permits facile RNA/DNA discrimination

BACKGROUND

The gene therapy vector pCMV-CFTR containing human CFTR cDNA shows high segregational instability during growth in Escherichia coli.

METHODS

By host strain screening and optimization of fermentation, satisfactory levels of pCMV-CFTR production were achieved. However, the vector was also vulnerable to structural instability manifested by the appearance during fermentation of a more stable mutant form in which the bacterial insertion sequence IS1 had transposed into exon 7 of plasmidborne CFTR. The instability of pCMV-CFTR is attributable to transcription from an upstream cryptic promoter leading to the production of CFTR peptide fragments known to be toxic when expressed in E. coli. To address this, we inserted the 1.1 kb natural human 6a-6b intron into pCMV-CFTR.

RESULTS

The new vector pCMV-CFTR-int6ab is more stable in E. coli than either pCMV-CFTR or the IS1 mutant, grows to high cell density giving higher DNA yields and expresses CFTR appropriately in transfected cells. Thus, the intron has a stabilizing effect comparable to the IS1 insertion yet retains full functionality for gene therapy. We describe a PCR assay using primers directed to sequences flanking the intron that allows differentiation between DNA and mature mRNA. The T936C mutation present only in vector DNA has also been exploited to allow transgene CFTR to be distinguished and its dose-dependent expression to be detected in human cellular backgrounds.

CONCLUSIONS

Instability of a plasmid vector for gene therapy has been minimized by rational modification. The introduction of an intron for this purpose offers the additional advantage of providing a discriminatory RT-PCR assay.

Transgenic animal bioreactors in biotechnology and production of blood proteins

The regulatory elements of genes used to target the tissue-specific expression of heterologous human proteins have been studied in vitro and in transgenic mice. Hybrid genes exhibiting the desired performance have been introduced into large animals. Complex proteins like protein C, factor IX, factor VIII, fibrinogen and hemoglobin, in addition to simpler proteins like alpha 1-antitrypsin, antithrombin III, albumin and tissue plasminogen activator have been produced in transgenic livestock. The amount of functional protein secreted when the transgene is expressed at high levels may be limited by the required posttranslational modifications in host tissues. This can be overcome by engineering the transgenic bioreactor to express the appropriate modifying enzymes. Genetically engineered livestock are thus rapidly becoming a choice for the production of recombinant human blood proteins.

Lactogenic immunity in transgenic mice producing recombinant antibodies neutralizing coronavirus

Protection against coronavirus infections can be provided by the oral administration of virus neutralizing antibodies. To provide lactogenic immunity, eighteen lines of transgenic mice secreting a recombinant IgG1 monoclonal antibody (rIgG1) and ten lines of transgenic mice secreting recombinant IgA monoclonal antibodies (rIgA) neutralizing transmissible gastroenteritis coronavirus (TGEV) into the milk were generated. Genes encoding the light and heavy chains of monoclonal antibody (MAb) 6A.C3 were expressed under the control of regulatory sequences derived from the mouse genomic DNA encoding the whey acidic protein (WAP) and beta-lactoglobulin (BLG), which are highly abundant milk proteins. The MAb 6A.C3 binds to a highly conserved epitope present in coronaviruses of several species. This MAb does not allow the selection of neutralization escaping virus mutants. The antibody was expressed in the milk of transgenic mice with titers of one million as determined by RIA, and neutralized TGEV infectivity by one million fold corresponding to immunoglobulin concentrations of 5 to 6 mg per ml. Matrix attachment regions (MAR) sequences were not essential for rIgG1 transgene expression, but co-microinjection of MAR and antibody genes led to a twenty to ten thousand-fold increase in the antibody titer in 50% of the rIgG1 transgenic animals generated. Co-microinjection of the genomic BLG gene with rIgA light and heavy chain genes led to the generation of transgenic mice carrying the three transgenes. The highest antibody titers were produced by transgenic mice that had integrated the antibody and BLG genes, although the number of transgenic animals generated does not allow a definitive conclusion on the enhancing effect of BLG co-integration. Antibody expression levels were transgene copy number independent and integration site dependent. The generation of transgenic animals producing virus neutralizing antibodies in the milk could be a general approach to provide protection against neonatal infections of the enteric tract.

Transgenic mice secreting coronavirus neutralizing antibodies into the milk

Ten lines of transgenic mice secreting transmissible gastroenteritis coronavirus (TGEV) neutralizing recombinant monoclonal antibodies (rMAbs) into the milk were generated. The rMAb light- and heavy-chain genes were assembled by fusing the genes encoding the variable modules of the murine MAb 6A.C3, which binds an interspecies conserved coronavirus epitope essential for virus infectivity, and a constant module from a porcine myeloma with the immunoglobulin A (IgA) isotype. The chimeric antibody led to dimer formation in the presence of J chain. The neutralization specific activity of the recombinant antibody produced in transiently or stably transformed cells was 50-fold higher than that of a monomeric rMAb with the IgG1 isotype and an identical binding site. This rMAb had titers of up to 10(4) by radioimmunoassay (RIA) and neutralized virus infectivity up to 10(4)-fold. Of 23 transgenic mice, 17 integrated both light and heavy chains, and at least 10 of them transmitted both genes to the progeny, leading to 100% of animals secreting functional TGEV neutralizing antibody during lactation. Selected mice produced milk with TGEV-specific antibody titers higher than 10(6) as determined by RIA, neutralized virus infectivity by 10(6)-fold, and produced up to 6 mg of antibody per ml. Antibody expression levels were transgene copy number independent and integration site dependent. Comicroinjection of the genomic beta-lactoglobulin gene with rMAb light- and heavy-chain genes led to the generation of transgenic mice carrying the three transgenes. The highest antibody titers were produced by transgenic mice that had integrated the antibody and beta-lactoglobulin genes, although the number of transgenic animals generated does not allow a definitive conclusion on the enhancing effect of beta-lactoglobulin cointegration. This approach may lead to the generation of transgenic animals providing lactogenic immunity to their progeny against enteric pathogens.

Regulation and expression of transgenes in fish -- a review

Transgenic fish, owing to a number of advantages which they offer over other species, are proving to be valuable model systems for the study of gene regulation and development genetics in addition to being useful targets for the genetic manipulation of commercially important traits. Despite having begun only a decade ago, the production of transgenic fish has become commonplace in a number of laboratories world-wide and considerable progress has been made. In this review, we initially consider the various regulatory elements and coding genes which have been used in fish, and subsequently discuss and compare both the transient and long-term fate and expression patterns of injected DNA sequences in the context of the different factors which are likely to have an effect on the expression of transgenes.

Production of active anti-CD6 mouse/human chimeric antibodies in the milk of transgenic mice

The expression of chimeric genes in the mammary gland of transgenic farm animals has become an alternative for the large-scale production of recombinant proteins and for the modification of milk composition. In this paper, we show that a mouse/human chimeric antibody against the human CD6 leukocyte antigen can be assembled and correctly folded by the mammary gland, and secreted to milk, where it maintains its specificity. The base sequences encoding for the heavy and light chain variable regions of the anti-CD6 mouse monoclonal antibody IOR-T1 were cloned by the polymerase chain reaction from hybridoma cDNA, coupled to human heavy and light chain constant region genes, and inserted in a vector containing the 5' regulatory region of the rabbit whey acidic protein gene. Transgenic mice were produced by conventional pronuclei microinjection techniques. Integration and transgene copy number were determined by Southern blot. Assembled human immunoglobulin was detected in milk using a sandwich ELISA. Expression levels of chimeric antibodies in milk were determined to be around 400 micrograms/ml by Western blot, using CHO-derived chimeric IOR-T1 antibodies as reference. The chimeric antibodies produced in milk recognized human peripheral blood T lymphocytes by indirect immunofluorescence, with the classical patch-like pattern of IOR-T1.