Hybrid Transcripts Research Articles

Local Gene Transfer and Expression Following Intramuscular Administration of FGF-1 Plasmid DNA in Patients With Critical Limb Ischemia

NV1FGF is an expression plasmid encoding sp.FGF-1(21-154) currently under investigation for therapeutic angiogenesis in clinical trials. NV1FGF plasmid distribution and transgene expression following intramuscular (IM) injection in patients is unknown. The study involved six patients with chronic critical limb ischemia (CLI) planned to undergo amputation. A total dose of 0.5, 2, or 4 mg NV1FGF was administered as eight IM injections (0.006, 0.25, or 0.5 mg per injection) 3-5 days before amputation. Injected sites (30 cm(3)) were divided into equally sized smaller pieces to assess spatial distribution of NV1FGF sequences (PCR), NV1FGF mRNA (reverse transcriptase-PCR), and fibroblast growth factor-1 (FGF-1)-expressing cells (immunohistochemistry). Data indicated gene expression at all doses. The distribution area was within 5-12 cm for NV1FGF sequences containing the expression cassette, up to 5 cm for NV1FGF mRNA, and up to 3 cm for FGF-1-expressing myofibers. All FGF receptors were detected indicating robust potential for bioactivity after NV1FGF gene transfer. Circulating levels of NV1FGF sequences were shown to decrease within days after injection. Data support demonstration of plasmid-mediated gene transfer and expression in muscles from patients with CLI. FGF-1 expression was shown to be limited to injection sites, which supports the concept of multiple-site injection for therapeutic use.

Molecular and chromosomal mutations among children with B-lineage lymphoblastic leukemia in Brazil’s Federal District

Acute lymphoblastic leukemia (ALL) accounts for approximately 80% of all acute leukemias during childhood. Chromosomal anomalies resulting from gene fusion, which are frequent in leukemias, create hybrid transcripts, the great majority of which encode transcription factors. We analyzed 88 pediatric patients (median age 7.3 years) who had B-lineage acute lymphoblastic leukemia (B-ALL), using reverse transcriptase-polymerase chain reaction, to look for gene fusion transcripts of TEL/AML1, E2A/PBX1, BCR/ABL p190, and MLL/AF4. The frequencies of these transcripts were 21.21, 9.68, 3.03, and 0%, respectively. All positive cases had a common B-ALL immunophenotype. The low frequency of the TEL/AML1 transcript that is found in developing countries, such as Brazil, may be due to the low incidence of leukemia; this would support Greaves' hypothesis.

An unusual presentation of eosinophilic variant of chronic myeloid leukemia (eoCML)

Dear Editor, Eosinophilia, a common sign of chronic myeloid leukemia (CML) and often used as one of the criteria for accelerated phase, but there is paucity of literature with eosinophilia as the only presentation of CML. Whether these patients clinically resemble with other hypereosinophilic syndromes (HESs) is not known. High eosinophil count can cause heart, lung, and central nervous system damage in both the eosiniphilic variant of CML (eoCML) and HES. Superficial venous thrombophlebitis (SVT) is usually a benign disorder but can be the first manifestation of hypercoagulable states. Secondary causes of SVT must be sought, particularly when SVT is recurrent or multifocal or has spontaneous onset. Among the various risk factors of SVT, vasculitis, malignant blood disorders, and solid tumors are the commonest. Association of eosinophilia with SVT is a rare situation that can reveal neoplasia, but it has never been described in eoCML, which prompted present communication. A 55-year-old man presented with a history of recurrent subcutaneous swelling of the right upper limb and anterior chest wall for 3 months. Each time, the swelling used to last from a few days to few weeks. There was history of itching and sometimes pain over the swollen area. There was no response to therapy with antihistaminics or analgesics. On examination, there was ill-defined erythematous swelling, with local rise of temperature over the right forearm extending to anterior chest wall. There were palpable, hardened, and painful erythematous veins over the right forearm. Vital signs were stable. Chest and neck examination was remarkable. Therewas no lymphadenopathy or hepatosplenomegaly. Hemogram showed white blood cell count of 12,300/mm with 10% neutrophils, 5% lymphocytes, and 85% eosinophils. The absolute eosinophil count was 10,455/mm. His peripheral blood picture revealed only eosinophilic leukocytosis with normocytic normochromic red blood cells and adequate platelets. Ultrasound color Doppler showed multiple foci of superficial vein thrombosis in the swollen areas without any evidence of deep-vein thrombosis. Magnetic resonance imaging of the right upper limb showed extensive subcutaneous and intramuscular edema with superficial thrombophlebitis. He was further investigated for causes of eosinophilia and recurrent superficial thrombophlebitis. Stool culture for ova and parasites were negative. Chest X-ray and contrast-enhanced computed tomography of the chest and abdomen were normal. Serum carcinoembryonic antigen and prostate-specific antigen levels were also normal. His lipid profile, antinuclear antibodies, anticardiolipin antibodies, lupus anticoagulant, protein S, protein C, and homocysteine levels were also found to be within normal limits. Echocardiography revealed early features of endomyocardial fibrosis, and pulmonary function test was normal. Bone marrow aspirate and biopsy showed a hypercellular marrow with myeloid hyperplasia and increased number of eosinophilic precursors. His peripheral blood and bone marrow aspirate was sent for reverse transcriptase polymerase chain reaction for FIP1L1-PDGFRα and bcr–abl, for detection of any clonal abnormality. The hybrid transcript for FIP1L1-PDGFRα was absent. At presentation, the patient’s BCR–ABL/ABL ratio was 10%. Fluorescent in situ hybridization was performed for BCR/ABL gene fusion, which showed that 60% of cells were positive for this gene rearrangement. On the basis of clonal evidence, a diagnosis of eoCML was made. The patient was started with imatinib mesylate 400 mg/day, and within 4 weeks of therapy, his Ann Hematol (2009) 88:89–90 DOI 10.1007/s00277-008-0545-1

Transposon-based mutagenesis identifies short RIP1 asan activator of NFκB

We used a vector based on the Sleeping Beauty transposon to search for constitutive activators of NF-κB in cultured cells. Dominant mutations were produced by random insertion of a tetracycline-regulated promoter, which provided robust and exceptionally well-regulatedexpression of downstream genes. The ability to regulate the mutant phenotype was used to attribute the latter to the insertional event. In one such mutant, the promoter was inserted in the middle of the gene encoding receptor-interacting protein kinase 1 (RIP1). The protein encoded by the hybrid transcript lacks the putative kinase domain of RIP1, but potently stimulates NF-κB, AP-1 and Ets-1 activity. Similarly to TNFα treatment, expression of the short RIP1 was toxic to cells that failed to up-regulate NF-κB. The effects of short RIP1 did not require endogenous RIP1 or cytokine treatment and coincided with reduced responsiveness to TNFα. Additional evidenceindicates that a similar short RIP1 could be produced naturally from the ripk1 locus. Interestingly, elevated expression of short RIP1 resulted in the loss of full length RIP1 from cells, pointing to a novel mechanism through which the abundance of RIP1 and the status of the related signaling cascades may be regulated.

Mifepristone-inducible LexPR system to drive and control gene expression in transgenic zebrafish

Effective transgenesis methods have been successfully employed in many organisms including zebrafish. However, accurate spatiotemporal control of transgene expression is still difficult to achieve. Here we describe a system for chemical-inducible gene expression and demonstrate its feasibility for generating transgenic driver lines in zebrafish. The key element of this system is a hybrid transcription factor engineered by fusion of the DNA-binding domain of the bacterial LexA repressor, a truncated ligand-binding domain of the human progesterone receptor, and the activation domain of the human NF-κB/p65 protein. This hybrid transcription factor (LexPR transactivator) binds to the synthetic steroid, mifepristone (RU-486), and functions in a ligand-dependent manner to induce expression of the gene(s) placed under the control of a synthetic operator-promoter sequence that harbors LexA binding sites. Transgene expression is strictly controlled and can be induced at any stage of the life cycle through administration of mifepristone in the water. To demonstrate the utility of this system, we generated stable transgenic lines which allow inducible tissue-specific expression of activated K-ras(V12). Combined with the Ac/ Ds-mediated transgenesis, the LexPR expression system has many potential applications in the fields of genetics and biotechnology.

New strategy for increasing the specific and efficient expression of transgene in plastids

Plastid gene engineering has become a new way for plant genetic improvements, particularly showing a unique application value in the use of plants as reactors to produce biopharmaceuticals and other important organic compounds. However, plastids only have a semi-autonomous transcription and translation machinery. The transcription of endogenous plastid genes is largely dependent on nuclear-encoded transcription factors. Regulation of foreign gene expression in plastids is influenced by various factors. Several technique strategies for regulation of transgene expression in plastids were reported recently, such as hybrid transcription factor-mediated system, phage T7-based transcription system and bacterial lac suppressor-based system. The application and improvement of these systems will greatly enhance the specific and effective expression of the transgenes, and achieve high-level accumulations of foreign proteins in plastids.

The impact of multiple splice sites in human L1 elements

LINE-1 elements represent a significant proportion of mammalian genomes. The impact of their activity on the structure and function of the host genomes has been recognized from the time of their discovery as an endogenous source of insertional mutagenesis. L1 elements contain numerous functional internal polyadenylation signals and splice sites that generate a variety of processed L1 transcripts. These sites are also reported to contribute to the generation of hybrid transcripts between L1 elements and host genes. Using northern blot analysis we demonstrate that L1 splicing, but not L1 polyadenylation, is delayed during the course of L1 expression. L1 splicing can also be negatively regulated by EBV SM protein known to alter this process. These results suggest a potential for L1 mRNA processing to be regulated in a tissue- and/or development-specific manner. The delay in L1 splicing may also serve to protect host genes from the excessive burden of L1 interference with their normal expression via aberrant splicing.

Detection of TMPRSS2-ERG Translocations in Human Prostate Cancer by Expression Profiling Using GeneChip Human Exon 1.0 ST Arrays

Translocation of TMPRSS2 to the ERG gene, found in a high proportion of human prostate cancer, results in overexpression of the 3'-ERG sequences joined to the 5'-TMPRSS2 promoter. The studies presented here were designed to test the ability of expression analysis on GeneChip Human Exon 1.0 ST arrays to detect 5'-TMPRSS2-ERG-3' hybrid transcripts encoded by this translocation. Monitoring the relative expression of each ERG exon revealed altered transcription of the ERG gene in 15 of a series of 27 prostate cancer samples. In all cases, exons 4 to 11 exhibited enhanced expression compared with exons 2 and 3. This pattern of expression indicated that the most abundant hybrid transcripts involve fusions to ERG exon 4, and RT-PCR analyses confirmed the joining of TMPRSS2 exon 1 to ERG exon 4 in all 15 cases. The exon expression patterns also indicated that TMPRSS2-ERG fusion transcripts commonly contain deletion of ERG exon 8. Analysis of gene-level data from the arrays allowed the identification of genes whose expression levels significantly correlated with the presence of the translocation. These studies demonstrate that expression analyses using exon arrays represent a valuable approach for detecting ETS gene translocation in prostate cancer, in parallel with analyses of gene expression profiles.

Fusion of the COL1A1 and USP6 genes in a benign bone tumor

Aneurysmal bone cyst (ABC) is a benign intraskeletal cyst that often expands rapidly and shows a strong tendency to recur. Rearrangement of chromosome band 17p13 is a characteristic genetic feature of ABC, with t(16;17)(q22;p13) the most frequent chromosomal aberration. This translocation generates a CDH11–USP6 fusion gene in which the strong promoter of osteoblast cadherin 11 gene at 16q22 is fused to the entire ubiquitin-specific protease 6 coding sequence at 17p13. As a result, USP6 (alias Tre2) is transcriptionally upregulated. Fusion genes of several variant translocations have been reported in ABC, including a case with t(17;17) and COL1A1–USP6 fusion. In each translocation, the entire USP6 coding sequence is fused downstream to the promoter region of the partner gene. Here we report a second case of a bone tumor carrying a t(17;17) resulting in a COL1A1–USP6 chimeric gene. As in the previous case, exon 1 of COL1A1 was fused to exon 2 of USP6 in the chimeric transcript. A translation process of the hybrid transcript using the starting ATG codon of the COL1A1 gene results in a truncated, 38 amino acid residues variant of the COL1A1 peptide. Although a pathogenic effect of the small COL1A1 peptide cannot be ruled out, overexpression of USP6 through fusion with the COL1A1 promoter is a more reasonable hypothesis.

Clofibrate and gemfibrozil induce an embryonic malabsorption syndrome in zebrafish

Nutrient availability is one of the major non-genetic factors determining embryonic growth and larval or fetal size. Due to the high human consumption of blood lipid regulators, fibrates have recently been reported as pollutants in rivers. Our study investigated the developmental toxicity of fibrates in zebrafish. Treatment with micromolar concentrations of clofibrate or gemfibrozil induced an embryonic malabsorption syndrome (EMS) with very little yolk consumption, resulting in small-sized larvae. This effect was reversible on removing the drug from the water. Clofibrate delayed hatching time and decreased the amount of oil red O lipid staining in the vasculature. It also induced higher density, round-shaped neuromuscular junctions associated with disorganization and less striation of muscular fibers, and pericardial edema, as well as impairing thyroid gland morphogenesis. acox1, apoa1 and mtp hybridization transcript signals were not affected in the yolk syncytial layer (YSL) after clofibrate exposure. Di-(2-ethylhexyl)-phthalate did not slow down yolk resorption, whereas brefeldin A induced EMS. These findings suggest that the inhibition of yolk sac resorption on exposure to fibrate is not at a pre-translational level or peroxisome proliferator-activated receptor alpha dependent and may be due to an inhibition of the YSL constitutive cell secretion. The effects of fibrates and the potential bioconcentration in eggs as well as the additive action of structurally related toxicants warrant an evaluation of the developmental impact of these compounds after long-term exposure at environmentally relevant concentrations. Fibrate-induced EMS in zebrafish seems useful for studying the morphogenetic consequences of impaired nutrient availability during the early stages of vertebrate development.

Aural and written music traditions: a drumming ensemble case study

This essay focuses on a transcription of a recording of ‘Creative from Guinea’, a piece composed and taught to me orally by Atsu Dagadu of Ghana. The transcription is innovative, combining West African drum language mnemonics and the Time Unit Box System in a hybrid transcription system which I devised. I drew on my experience as a student of drumming as well as a single recording in prioritising transcription decisions. The transcription draws attention to the structure and arrangement of ‘Creative’, and provides an accurate score for educational use to correct memory errors. I discuss transcription as facilitating internalisation and understanding, fitting together with transmission, memory and preservation of music.

Microfluidic Chips for Detecting the t(4;14) Translocation and Monitoring Disease during Treatment Using Reverse Transcriptase-Polymerase Chain Reaction Analysis of IgH-MMSET Hybrid Transcripts

Diagnosis platforms incorporating low-cost microfluidic chips enable sensitive, rapid, and accurate genetic analysis that could facilitate customized therapies tailored to match the vulnerabilities of any types of cancer. Using ex vivo cancer cells, we have detected the unique molecular signature and a chromosomal translocation in multiple myeloma. Multiple myeloma is characterized by IgH rearrangements and translocations that enable unequivocal identification of malignant cells, detected here with integrated microfluidic chips incorporating genetic amplification via reverse transcriptase-polymerase chain reaction and capillary electrophoresis. On microfluidic chips, we demonstrated accurate and versatile detection of molecular signatures in individual cancer cells, with value for monitoring response to therapy, detecting residual cancer cells that mediate relapse, and evaluating prognosis. Thus, testing for two clinically important molecular biomarkers, the IgH VDJ signature and hybrid transcripts signaling the t(4;14) chro-mosomal translocation, with predictive value in diagnosis, treatment decisions, and monitoring has been efficiently implemented on a miniaturized microfluidic system.

Treatment of Newly Diagnosed Multiple Myeloma Based on Mayo Stratification of Myeloma and Risk-Adapted Therapy (mSMART): Consensus Statement

Treatment of Newly Diagnosed Multiple Myeloma Based on Mayo Stratification of Myeloma and Risk-Adapted Therapy (mSMART): Consensus Statement

Genome-Wide Reprogramming in Hybrids of Somatic Cells and Embryonic Stem Cells

Recent experiments demonstrate that somatic nuclei can be reprogrammed to a pluripotent state when fused to ESCs. The resulting hybrids are pluripotent as judged by developmental assays, but detailed analyses of the underlying molecular-genetic control of reprogrammed transcription in such hybrids are required to better understand fusion-mediated reprogramming. We produced hybrids of mouse ESCs and fibroblasts that, although nearly tetraploid, exhibit characteristics of normal ESCs, including apparent immortality in culture, ESC-like colony morphology, and pluripotency. Comprehensive analysis of the mouse embryonic fibroblast/ESC hybrid transcriptome revealed global patterns of gene expression reminiscent of ESCs. However, combined analysis of variance and hierarchical clustering analyses revealed at least seven distinct classes of differentially regulated genes in comparisons of hybrids, ESCs, and somatic cells. The largest class includes somatic genes that are silenced in hybrids and ESCs, but a smaller class includes genes that are expressed at nearly equivalent levels in hybrids and ESCs that contain many genes implicated in pluripotency and chromatin function. Reprogrammed genes are distributed throughout the genome. Reprogramming events include both transcriptional silencing and activation of genes residing on chromosomes of somatic origin. Somatic/ESC hybrid cell lines resemble their pre-fusion ESC partners in terms of behavior in culture and pluripotency. However, they contain unique expression profiles that are similar but not identical to normal ESCs. ESC fusion-mediated reprogramming provides a tractable system for the investigation of mechanisms of reprogramming. Disclosure of potential conflicts of interest is found at the end of this article.

Transactivation from Gal4-VP16 transgenic insertions for tissue-specific cell labeling and ablation in zebrafish

Prior studies with transgenic zebrafish confirmed the functionality of the transcription factor Gal4 to drive expression of other genes under the regulation of upstream activator sequences (UAS). However, widespread application of this powerful binary system has been limited, in part, by relatively inefficient techniques for establishing transgenic zebrafish and by the inadequacy of Gal4 to effect high levels of expression from UAS-regulated genes. We have used the Tol2 transposition system to distribute a self-reporting gene/enhancer trap vector efficiently throughout the zebrafish genome. The vector uses the potent, hybrid transcription factor Gal4-VP16 to activate expression from a UAS:eGFP reporter cassette. In a pilot screen, stable transgenic lines were established that express eGFP in reproducible patterns encompassing a wide variety of tissues, including the brain, spinal cord, retina, notochord, cranial skeleton and muscle, and can transactivate other UAS-regulated genes. We demonstrate the utility of this approach to track Gal4-VP16 expressing migratory cells in UAS:Kaede transgenic fish, and to induce tissue-specific cell death using a bacterial nitroreductase gene under UAS control. The Tol2-mediated gene/enhancer trapping system together with UAS transgenic lines provides valuable tools for regulated gene expression and for targeted labeling and ablation of specific cell types and tissues during early zebrafish development.

Characterization of Gene Rearrangements Leading to Activation of MDR-1

Expression of the MDR-1/P-glycoprotein gene confers drug resistance both in vitro and in vivo. We previously reported that gene rearrangements resulting in a hybrid MDR-1 transcript represent a common mechanism for acquired activation of MDR-1/P-glycoprotein. We have identified hybrid MDR-1 transcripts in nine MDR-1-overexpressing cell lines and two patients with relapsed ALL. We characterize these rearrangements as follows. 1) Non-MDR-1 sequences in the hybrid MDR-1 transcripts are expressed in unselected cell lines, showing that these sequences are constitutively expressed. 2) The rearrangements occur randomly and involve partner genes (sequences) on chromosome 7 and on chromosomes other than 7. Breakpoints have been characterized in six cell lines. In one, the rearrangement occurred within intron 2 of MDR-1; in the other five, the rearrangement occurred 24 to >96 kb 5' of the normal start of transcription of MDR-1. In one cell line, homologous recombination involving an Alu repeat was observed. However, in the remaining five cell lines, nonhomologous recombination was observed. 3) The rearrangements arise during drug selection. The acquired rearrangements are not detected in parental cells. 4) Five of the six active promoters that captured MDR-1 controlled MDR-1 from a distance of 29 to more than 110 kb 5' to MDR-1. Transcription was initiated in an antegrade or retrograde direction. We conclude that drug selection with natural products targeting DNA or microtubules leads to DNA damage, nonhomologous recombination, and acquired drug resistance, wherein MDR-1 expression is driven by a random but constitutively active promoter.

Bone Involvement in Multiple Myeloma Patients Carrying the T (4;14) Chromosomal Translocation.

Chromosomal translocations involving the immunoglobulin heavy chain switch region (IgH) are quite common in multiple myeloma (MM), and some of them can reliably predict disease outcome. In particular, t(4;14) chromosomal abnormality is one of the most adverse prognostic factors for response duration and survival after high dose therapy and autologous stem cell transplantation. Despite the dismal prognosis, however, in this subset of patients, bone involvement, as evaluated by spine MRI, is relatively infrequent, at variance to what has been observed in other MM subtypes according to TC classification. In the present study we aimed at further testing this hypothesis by analyzing the extent of whole bone involvement in patients showing t(4;14) chromosomal translocation as compared to negative patients. For this purpose, 50 newly diagnosed MM patients (32M, 18F, median age = 54 yrs) underwent evaluation of total skeletal X-ray, whole spine MRI and, at the same time, quantification of markers of bone resorption (urinary NTX, PYR and DPYR and serum crosslaps) and bone formation (bone alkaline phosphatase-BAP and osteocalcin) was performed. Using a real-time PCR assay to detect the presence of IgH/MMSET fusion gene as a surrogate marker for t(4;14), we found 15 patients carrying this chromosomal abnormality, 7 of whom (46%) were also positive for the deletion of chromosome 13, this abnormality was detected in 11/35 (31%) patients who proved negative for IgH/MMSET hybrid transcript. The two groups of patients did not differ significantly in terms of median age, distribution of M protein isotype and light chain, beta-2 microglobulin, bone marrow plasma cell infiltration and disease stage. Spinal MRI was negative in 3/15 (20%) t(4;14) positive patients as compared to 12% t(4;14) negative patients; skeletal involvement, however, was more pronounced in t(4;14) positive patients (median skeletal score = 6.24, as compared to 3.58 in t(4;14) negative cases, p= 0.00). These data were confirmed by the evaluation of bone resorption markers; specifically, serum crosslaps were significantly increased in patients with t(4;14) abnormality compared to negative individuals (7984 pmol/L±1682SE vs 5123pmol/L±783SE p=0.04). Conversely, no difference in bone formation markers was found in the two groups of patients. Our results indicate that, despite a spinal involvement at MRI that is comparable to what is observed in negative patients, individuals who are t(4;14) positive show a more pronounced bone resorption pattern, this in contrast to what has been reported so far, but in line with the aggressive features of the disease in these patients.

Diversity of TMPRSS2-ERG fusion transcripts in the human prostate

TMPRSS2-ERG gene fusions have recently been reported to be present in a high proportion of human prostate cancers. In the current study, we show that great diversity exists in the precise structure of TMPRSS2-ERG hybrid transcripts found in human prostates. Fourteen distinct hybrid transcripts are characterized, each containing different combinations of sequences from the TMPRSS2 and ERG genes. The transcripts include two that are predicted to encode a normal full-length ERG protein, six that encode N-terminal truncated ERG proteins and one that encodes a TMPRSS2-ERG fusion protein. Interestingly, distinct patterns of hybrid transcripts were found in samples taken from separate regions of individual cancer-containing prostates, suggesting that TMPRSS2-ERG gene fusions may be arising independently in different regions of a single prostate.

Outliers in RhD membrane integration are explained by variant RH haplotypes

Variations in a multipass transmembrane protein may affect its membrane integration. To study this effect, the systematic molecular characterization of variant D antigen density is a suitable model. Unlike most other membrane proteins, the expression of the D antigen is often determined by a single allele, because it occurs frequently in hemizygous form. The D antigen density distribution of 530 CcDee, 475 ccDEe, and 514 ccDee random samples was established by flow cytometry. The molecular bases of samples with D antigen densities outside a bell-shaped peak was investigated. The antigen densities of 499 CcDee, 437 ccDEe, and 480 ccDee samples formed bell-shaped peaks. Three, 10, and 12 samples, respectively, had decreased antigen densities and carried variant RHD alleles. Weak D type 19, RHD(I204T); weak D type 20, RHD(F417S); and the partial D DYU (also known as DQC), RHD(R234W) were new RHD alleles. Twenty-eight CcDee, 28 ccDEe, and 22 ccDee samples had increased antigen densities; 53 of them lacked a hybrid Rhesus box and were thus predicted to be RHD homozygous. Eight ccDee samples were predicted to be heterozygous despite a large relative dose of RHD to RHCE alleles in quantitative polymerase chain reaction. One of these samples was further investigated and carried an RHD-CE hybrid transcript characteristic for a -D- haplotype. Unusual little and large RhD protein integration into the membrane could be traced to a host of distinct protein variants. Weak expression of D antigen was invariably associated with variant RHD alleles. Larger than normal D antigen density may often be caused by the presence of two D encoding alleles, which may be located in cis, and confounding zygosity testing that is solely based on gene copy number.

Hybrid transcription system for controlled plastid transgene expression

Plastid transformation technologies have developed rapidly over the last few years, reflecting their value in the study of the principal mechanisms of plastid gene expression and commercial interest in using plastids as bioreactors. Application of this technology is still limited by the difficulty of obtaining regulated, selective expression of plastid transgenes. The plastid genome is transcribed by two different types of RNA polymerase. One of them is of the eubacterial type of polymerase, and its subunits are encoded in the plastid genome [plastid-encoded RNA polymerase (PEP)]. The other one is of the phage type and nucleus-encoded [nucleus-encoded RNA polymerase (NEP)]. To obtain selective transgene expression, we have made use of the similarities and differences between the eubacterial and the plastid eubacterial type transcription systems. We created a hybrid transcription system in which the transgene is placed under the control of a eubacterial promoter which does not exist in the plastid genome and which is not recognized by the plastid endogenous transcriptional machinery. Selective transcription of the transgene is achieved by the supply of a chimeric transcription factor that interacts with PEP and directs it specifically to the foreign eubacterial-type transgene promoter. This hybrid transcription system could be used for biotechnological and fundamental research applications as well as in the characterization of the evolutionary differences between the eubacterial and the plastid eubacterial-type transcription systems.