Efficient in vitro and in vivo gene regulation of a retrovirally delivered pro-apoptotic factor under the control of the Drosophila HSP70 promoter

The somatotropic axis during the physiological estrus cycle in dairy heifers--Effect on hepatic expression of GHR and SOCS2

Pituitary growth hormone (GH) release and hepatic insulin-like growth factor-I (IGF-I) production increase after an injection of 17β-estradiol (E2) in ovariectomized dairy cattle. However, whether endogenous sexual steroid hormones also influence the hepatic GH receptor (GHR) signaling pathway during a physiological estrus cycle remains unclear. The aim of this study was to analyze the hepatic GHR signaling pathway during the luteal phase and after a period of increased E2 concentrations (after ovulation) as well as in 7 heifers before ovulation. Ovarian ultrasounds were performed daily during repeated physiological cycles (n = 56) of 30 Holstein Friesian heifers to determine ovulation [before ovulation (n = 7, bOv) and after ovulation 24-60 h after the appearance of estrus signs (n = 49, aOv)] and luteal phase (CLP; d 12 ± 1 after ovulation). Blood samples and liver biopsies were obtained, and blood concentrations of E2, P4, insulin-like growth factor (IGF)-I, IGF-II, and GH were measured. In the liver biopsies, we determined mRNA expression of the estrogen receptor α (ERα), GHR, Janus kinase 2 (JAK2), signal transducer and activator of transcription 5B (STAT5B), suppressor of cytokine signaling (SOCS)2 and 3, IGF-I, and IGF-II by quantitative reverse transcription-PCR. The concentration of E2 was higher bOv than aOv and CLP, as expected. The concentrations of IGF-I and GH were higher bOv and aOv compared with CLP. In contrast, concentrations of IGF-II were lower aOv compared with bOv and CLP. The mRNA expression of GHR was higher in liver biopsies obtained bOv compared with aOv and CLP. Notably, the expression of SOCS2 was higher bOv than aOv and in the CLP. Increased hepatic expression of SOCS2 during estrus was detectable when IGF-I concentrations were high; this result might indicate that SOCS2 expression attenuates the GHR signal transduction pathway during the phase of increased pituitary GH release. In conclusion, hepatic GHR and SOCS2 mRNA expression appeared to be promptly and sensitively regulated by increased E2 levels before ovulation of dairy heifers.

Current advances in retroviral gene therapy

There have been major changes since the incidents of leukemia development in X-SCID patients after the treatments using retroviral gene therapy. Due to the risk of oncogenesis caused by retroviral insertional activation of host genes, most of the efforts focused on the lentiviral therapies. However, a relative clonal dominance was detected in a patient with β-thalassemia Major, two years after the subject received genetically modified hematopoietic stem cells using lentiviral vectors. This disappointing result of the recent clinical trial using lentiviral vector tells us that the current and most advanced vector systems does not have enough safety. In this review, various safety features that have been tried for the retroviral gene therapy are introduced and the possible new ways of improvements are discussed. Additional feature of chromatin insulators, co-transduction of a suicidal gene under the control of an inducible promoter, conditional expression of the transgene only in appropriate target cells, targeted transduction, cell type-specific expression, targeted local administration, splitting of the viral genome, and site specific insertion of retroviral vector are discussed here.

Mitostatin is down-regulated in human prostate cancer and suppresses the invasive phenotype of prostate cancer cells

MITOSTATIN, a novel putative tumor suppressor gene induced by decorin overexpression, is expressed in most normal human tissues but is markedly down-regulated in advanced stages of mammary and bladder carcinomas. Mitostatin negatively affects cell growth, induces cell death and regulates the expression and activation levels of Hsp27. In this study, we demonstrated that ectopic expression of Mitostatin in PC3, DU145, and LNCaP prostate cancer cells not only induced a significant reduction in cell growth, but also inhibited migration and invasion. Moreover, Mitostatin inhibited colony formation in soft-agar of PC3 and LNCaP cells as well as tumorigenicity of LNCaP cells in nude mice. Conversely, targeting endogenous Mitostatin by siRNA and anti-sense strategies in PC3 and DU145 prostate cancer cells enhanced the malignant phenotype in both cell lines. In agreement of these anti-oncogenic roles, we discovered that Mitostatin was absent in ∼35% (n = 124) of prostate tumor samples and its overall reduction was associated with advanced cancer stages. Collectively, our findings indicate that MITOSTATIN may acts as a tumor suppressor gene in prostate cancer and provide a novel cellular and molecular mechanism to be further exploited and deciphered in our understanding of prostate cancer progression.

A laser pointer driven microheater for precise local heating and conditional gene regulation in vivo. Microheater driven gene regulation in zebrafish

Background

Tissue heating has been employed to study a variety of biological processes, including the study of genes that control embryonic development. Conditional regulation of gene expression is a particularly powerful approach for understanding gene function. One popular method for mis-expressing a gene of interest employs heat-inducible heat shock protein (hsp) promoters. Global heat shock of hsp-promoter-containing transgenic animals induces gene expression throughout all tissues, but does not allow for spatial control. Local heating allows for spatial control of hsp-promoter-driven transgenes, but methods for local heating are cumbersome and variably effective.

Results

We describe a simple, highly controllable, and versatile apparatus for heating biological tissue and other materials on the micron-scale. This microheater employs micron-scale fiber optics and uses an inexpensive laser-pointer as a power source. Optical fibers can be pulled on a standard electrode puller to produce tips of varying sizes that can then be used to reliably heat 20-100 μm targets. We demonstrate precise spatiotemporal control of hsp70l:GFP transgene expression in a variety of tissue types in zebrafish embryos and larvae. We also show how this system can be employed as part of a new method for lineage tracing that would greatly facilitate the study of organogenesis and tissue regulation at any time in the life cycle.

Conclusion

This versatile and simple local heater has broad utility for the study of gene function and for lineage tracing. This system could be used to control hsp-driven gene expression in any organism simply by bringing the fiber optic tip in contact with the tissue of interest. Beyond these uses for the study of gene function, this device has wide-ranging utility in materials science and could easily be adapted for therapeutic purposes in humans.

Interaction between serine phosphorylated IRS-1 and beta1-integrin affects the stability of neuronal processes

Tumor necrosis factor-alpha (TNFalpha) released in the brain by HIV-activated macrophages/microglia is suspected to compromise neuronal survival. Previously, we have demonstrated that activated receptor for insulin-like growth factor I (IGF-IR) protects neurons from TNFalpha-induced neuronal damage (Wang et al. [ 2006] J. Neurosci. Res. 83:7-18). Because TNFalpha triggers phosphorylation of insulin receptor substrate 1 (IRS-1) on serine residues (pS-IRS-1; Rui et al. [ 2001] J. Clin. Invest. 107:181-189), and pS-IRS-1 binds integrins (Reiss et al. [ 2001] Oncogene 20:490-500), we asked how these events affect neuronal processes. We show that beta1-integrin and pS-IRS-1 colocalize in PC12 cells and in primary cortical neurons. TNFalpha treatment elevated membrane-associated pS-IRS-1, enhanced pS-IRS-1 interaction with beta1-integrin, and attenuated cell attachment to collagen IV. In contrast, IGF-I inhibited pS-IRS-1-beta1-integrin complexes and improved cell attachment. The domain of IRS-1 involved in beta1-integrin binding mapped between amino acids 426 and 740, and the expression of 426-740/IRS-1 mutant attenuated neuronal outgrowth. Our results indicate that TNFalpha facilitates the interaction of pS-IRS-1 and beta1-integrin and destabilizes neuronal processes. IGF-I counteracts TNFalpha-mediated accumulation of pS-IRS-1-beta1-integrin complexes supporting the stability of neuronal processes.

Interplasmid transposition demonstrates piggyBac mobility in vertebrate species

The piggyBac transposon is an extremely versatile helper-dependent vector for gene transfer and germ line transformation in a wide range of invertebrate species. Analyses of genome sequencing databases have identified piggyBac homologues among several sequenced animal genomes, including the human genome. In this report we demonstrate that this insect transposon is capable of transposition in primate cells and embryos of the zebrafish, Danio rerio. piggyBac mobility was demonstrated using an interplasmid transposition assay that has consistently predicted the germ line transformation capabilities of this mobile element in several other species. Both transfected COS-7 primate cells and injected zebrafish embryos supported the helper-dependent movement of tagged piggyBac element between plasmids in the characteristic cut-and-paste, TTAA target-site specific manner. These results validate piggyBac as a valuable tool for genetic analysis of vertebrates.

Involvement of alpha1beta1 integrin in insulin-like growth factor-1-mediated protection of PC12 neuronal processes from tumor necrosis factor-alpha-induced injury

Insulin-like growth factor 1 receptor (IGF-1R) supports neuronal survival against a wide variety of insults. This includes tumor necrosis factor-alpha (TNFalpha)-mediated neuronal damage, which represents one of the factors suspected to play a role in HIV-associated dementia (HAD). PC12 neurons engineered to express human IGF-1R (PC12/IGF-1R) maintain neuronal processes on collagen IV for several weeks. However, prolonged treatment with TNFalpha caused degeneration of neuronal processes, with no apparent signs of apoptosis. In this process, TNFalpha did not affect IGF-1-mediated phosphorylation of IRS-1, IRS-2, Akt, or Erks. In addition, PC12/IGF-1R cells were found to express predominantly alpha1beta1 integrin, which has high affinity to collagen IV. The treatment of PC12/IGF-1R neurons with a specific alpha1beta1 integrin inhibitor, obtustatin, also caused loss of neuronal processes, accompanied by a quick cell detachment and extensive apoptosis. In the presence of IGF-1, both TNFalpha-induced and obtustatin-induced degeneration of neuronal processes were effectively inhibited. Furthermore, TNFalpha-mediated neuronal degeneration correlated with decreased attachment of PC12/IGF-1R cells to collagen IV and with a reduced level of alpha1beta1 integrin, consistent with a role for this surface protein in the maintenance of neuronal processes. Thus the neuroprotective effects of IGF-1 are not restricted to its antiapoptotic properties but also involve an additional neuroprotective mechanism, by which IGF-1 counteracts the negative effect of TNFalpha on alpha1beta1 integrin-mediated attachment to collagen IV.

The CCT promoter directs high-level transgene expression in distal lung epithelial cell lines

Gene therapy requires the presence of a robust and yet small promoter to drive high-level expression of desired proteins. In comparative analysis, we investigated the promoter strength of the CTP:phosphocholine cytidylyltransferase promoter (CCT alpha) with other commonly used promoters, which were all cloned into a similar background vector (PGL3 basic). Transient promoter-reporter assays in murine lung epithelial (MLE-12) cells revealed that the core CCT alpha promoter (240 bp) was observed to exhibit a 40-fold, 8-fold, and 3-fold higher level of activity compared with the simian virus 40, human cytomegalovirus, and Rous sarcoma virus promoters, respectively. The CCT alpha promoter was significantly more active than the Clara cell 10, thymidine kinase, and phosphoglycerate kinase promoters. This pattern of high-level expression for CCT alpha was detected primarily in cell lines of distal lung epithelial origin (MLE-12, RLE, H441) and was reduced in other cell lines (A549, CHO, HepG 2). CCT alpha promoter-reporter activity, CCT alpha transcript levels, and immunoreactive protein levels increased significantly in the presence of all-trans retinoic acid. The CCT alpha promoter, in a retinoic acid-inducible manner, efficiently directed expression of murine erythropoietin in MLE-12 cells. Collectively, these observations suggest that the CCT alpha construct might be useful to drive high-level, regulatable expression of heterologous proteins in alveolar epithelia.

Signaling differences from the A and B isoforms of the insulin receptor (IR) in 32D cells in the presence or absence of IR substrate-1

The A isoform of the insulin receptor (IR) is frequently overexpressed in cancer cells and is activated by IGF-II as well as by insulin, whereas the B isoform is predominant in differentiated tissues and responds poorly to IGF-II. The IR substrate-1 (IRS-1), a docking protein for the IR, is known to send a mitogenic signal and to be a powerful inhibitor of cell differentiation. We have investigated the biological effects of the two IR isoforms in parental 32D hemopoietic cells, which do not express IRS-1, and in 32D-derived cells in which IRS-1 is ectopically expressed. The effects of the two isoforms on cell survival, differentiation markers and nuclear translocation of IRS-1 were compared. The results confirm that the A isoform responds to IGF-II and preferentially sends mitogenic, antiapoptotic signals, whereas the B form, poorly responsive to IGF-II, tends to send differentiation signals.

Spatial and temporal control of transgene expression in vivo using a heat-sensitive promoter and MRI-guided focused ultrasound

BACKGROUND

Among the techniques used to induce and control gene expression, a non-invasive, physical approach based on local heat in combination with a heat-sensitive promoter represents a promising alternative but requires accurate temperature control in vivo. MRI-guided focused ultrasound (MRI-FUS) with real-time feedback control allows automatic execution of a predefined temperature-time trajectory. The purpose of this study was to demonstrate temporal and spatial control of transgene expression based on a well-defined local hyperthermia generated by MRI-FUS.

METHODS

Expression of the green fluorescent protein (GFP) marker gene was used. Two cell lines were derived from C6 glioma cells. The GFP expression of the first one is under the control of the CMV promoter, whereas it is under the control of the HSP70 promoter in the second one and thus inducible by heat. Subcutaneous tumours were generated by injection in immuno-deficient mice and rats. Tumours were subjected to temperatures varying from 42 to 50 degrees C for 3 to 25 min controlled by MRI-FUS and analyzed 24 h after the heat-shock. Endogenous HSP70 expression and C6 cell distribution were also analyzed.

RESULTS

The results demonstrate strong expression at 50 degrees C applied during a short time period (3 min) without affecting cell viability. Induced expression was also clearly shown for temperature in the range 44-48 degrees C but not at 42 degrees C.

CONCLUSIONS

Heating with MRI-FUS allows a tight and non-invasive control of transgene expression in a tumour.