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Introduction: Human induced pluripotent stem cells (iPSCs), with their ability to generate human neural cells (astrocytes and neurons) from patients, hold great promise for understanding the pathophysiology of major neuropsychiatric diseases such as schizophrenia and bipolar disorders, which includes alterations in cerebral development. Indeed, the in vitro neurodifferentiation of iPSCs, while recapitulating certain major stages of neurodevelopment in vivo, makes it possible to obtain networks of living human neurons. The culture model presented is particularly attractive within this framework since it involves iPSC-derived neural cells, which more specifically differentiate into cortical neurons of diverse types (in particular glutamatergic and GABAergic) and astrocytes. However, these in vitro neuronal networks, which may be heterogeneous in their degree of differentiation, remain challenging to bring to an appropriate level of maturation. It is therefore necessary to develop tools capable of analyzing a large number of cells to assess this maturation process. Calcium (Ca2+) imaging, which has been extensively developed, undoubtedly offers an incredibly good approach, particularly in its versions using genetically encoded calcium indicators. However, in the context of these iPSC-derived neural cell cultures, there is a lack of studies that propose Ca2+ imaging methods that can finely characterize the evolution of neuronal maturation during the neurodifferentiation process. Methods: In this study, we propose a robust and reliable method for specifically measuring neuronal activity at two different time points of the neurodifferentiation process in such human neural cultures. To this end, we have developed a specific Ca2+ signal analysis procedure and tested a series of different AAV serotypes to obtain expression levels of GCaMP6f under the control of the neuron-specific human synapsin1 (hSyn) promoter. Results: The retro serotype has been found to be the most efficient in driving the expression of the GCaMP6f and is compatible with multi-time point neuronal Ca2+ imaging in our human iPSC-derived neural cultures. An AAV2/retro carrying GCaMP6f under the hSyn promoter (AAV2/retro-hSyn-GCaMP6f) is an efficient vector that we have identified. To establish the method, calcium measurements were carried out at two time points in the neurodifferentiation process with both hSyn and CAG promoters, the latter being known to provide high transient gene expression across various cell types. Discussion: Our results stress that this methodology involving AAV2/retro-hSyn-GCaMP6f is suitable for specifically measuring neuronal calcium activities over multiple time points and is compatible with the neurodifferentiation process in our mixed human neural cultures. [ABSTRACT FROM AUTHOR]

IntroductionHuman induced pluripotent stem cells (iPSCs), with their ability to generate human neural cells (astrocytes and neurons) from patients, hold great promise for understanding the pathophysiology of major neuropsychiatric diseases such as schizophrenia and bipolar disorders, which includes alterations in cerebral development. Indeed, the in vitro neurodifferentiation of iPSCs, while recapitulating certain major stages of neurodevelopment in vivo, makes it possible to obtain networks of living human neurons. The culture model presented is particularly attractive within this framework since it involves iPSC-derived neural cells, which more specifically differentiate into cortical neurons of diverse types (in particular glutamatergic and GABAergic) and astrocytes. However, these in vitro neuronal networks, which may be heterogeneous in their degree of differentiation, remain challenging to bring to an appropriate level of maturation. It is therefore necessary to develop tools capable of analyzing a large number of cells to assess this maturation process. Calcium (Ca2+) imaging, which has been extensively developed, undoubtedly offers an incredibly good approach, particularly in its versions using genetically encoded calcium indicators. However, in the context of these iPSC-derived neural cell cultures, there is a lack of studies that propose Ca2+ imaging methods that can finely characterize the evolution of neuronal maturation during the neurodifferentiation process.MethodsIn this study, we propose a robust and reliable method for specifically measuring neuronal activity at two different time points of the neurodifferentiation process in such human neural cultures. To this end, we have developed a specific Ca2+ signal analysis procedure and tested a series of different AAV serotypes to obtain expression levels of GCaMP6f under the control of the neuron-specific human synapsin1 (hSyn) promoter.ResultsThe retro serotype has been found to be the most efficient in driving the expression of the GCaMP6f and is compatible with multi-time point neuronal Ca2+ imaging in our human iPSC-derived neural cultures. An AAV2/retro carrying GCaMP6f under the hSyn promoter (AAV2/retro-hSyn-GCaMP6f) is an efficient vector that we have identified. To establish the method, calcium measurements were carried out at two time points in the neurodifferentiation process with both hSyn and CAG promoters, the latter being known to provide high transient gene expression across various cell types.DiscussionOur results stress that this methodology involving AAV2/retro-hSyn-GCaMP6f is suitable for specifically measuring neuronal calcium activities over multiple time points and is compatible with the neurodifferentiation process in our mixed human neural cultures.

Abstract Human pluripotent stem cells, including induced pluripotent stem cells (iPSCs) and embryonic stem cells, hold great promise for cell‐based therapies, but safety concerns that complicate consideration for routine clinical use remain. Installing a “safety switch” based on the inducible caspase‐9 (iCASP9) suicide gene system should offer added control over undesirable cell replication or activity. Previous studies utilized lentiviral vectors to integrate the iCASP9 system into T cells and iPSCs. This method results in random genomic insertion of the suicide switch and inefficient killing of the cells after the switch is “turned on” with a small molecule (eg, AP1903). To improve the safety and efficiency of the iCASP9 system for use in iPSC‐based therapy, we precisely installed the system into a genomic safe harbor, the AAVS1 locus in the PPP1R12C gene. We then evaluated the efficiencies of different promoters to drive iCASP9 expression in human iPSCs. We report that the commonly used EF1α promoter is silenced in iPSCs, and that the endogenous promoter of the PPP1R12C gene is not strong enough to drive high levels of iCASP9 expression. However, the CAG promoter induces strong and stable iCASP9 expression in iPSCs, and activation of this system with AP1903 leads to rapid killing and complete elimination of iPSCs and their derivatives, including MSCs and chondrocytes, in vitro. Furthermore, iPSC‐derived teratomas shrank dramatically or were completely eliminated after administration of AP1903 in mice. Our data suggest significant improvements on existing iCASP9 suicide switch technologies and may serve as a guide to other groups seeking to improve the safety of stem cell‐based therapies.

The loss of photoreceptors in individuals with retinal degenerative diseases leads to partial or complete blindness. Optogenetic therapy is a promising approach for restoring vision to the blind. Multiple strategies have been employed by targeting genetically encoded light sensors, particularly channelrhodopsins, to surviving retinal neurons in animal models. In particular, the strategy of targeting retinal bipolar cells has commonly been expected to result in better vision than ubiquitous expression in retinal ganglion cells. However, a direct comparison of the channelrhodopsin-restored vision between these two strategies has not been performed. Here, we compared the restored visual functions achieved by adeno-associated virus (AAV)-mediated expression of a channelrhodopsin in ON-type bipolar cells and retinal ganglion cells driven by an improved mGluR6 promoter and a CAG promoter, respectively, in a blind mouse model by performing electrophysiological recordings and behavioral assessments. Unexpectedly, the efficacy of the restored vision based on light sensitivity and visual acuity was much higher following ubiquitous retinal ganglion cell expression than that of the strategy targeting ON-type bipolar cells. Our study suggests that, at least based on currently available gene delivery techniques, the expression of genetically encoded light sensors in retinal ganglion cells is likely a practical and advantageous strategy for optogenetic vision restoration.

There is wide variability in the propensity of somatic cells to reprogram into pluripotency in response to the Yamanaka factors. How to segregate these variabilities to enrich for cells of specific traits that reprogram efficiently remains challenging. Here we report that the variability in reprogramming propensity is associated with the activity of the MKL1/SRF transcription factor and concurs with small cell size as well as rapid cell cycle. Reprogramming progressive cells can be prospectively identified by their low activity of a widely used synthetic promoter, CAG. CAGlow cells arise and expand during cell cycle acceleration in the early reprogramming culture of both mouse and human fibroblasts. Our work illustrates a molecular scenario underlying the distinct reprogramming propensities and demonstrates a convenient practical approach for their enrichment. [ABSTRACT FROM AUTHOR]

Background Research on the biogenesis of tick-borne encephalitis virus (TBEV) would benefit gene therapy. Due to specific arrangements of genes along the TBEV genome, its viral-like particles (VLPs) could be exploited as shuttles to deliver their replicon, which carries therapeutic genes, to immune system cells. Objective To develop a flaviviral vector for gene delivery as a part of gene therapy research that can be expressed in secretable VLP suicidal shuttles and provide abundant unique molecular and structural data supporting this gene therapy concept. Method TBEV structural gene constructs of a Swedish Torö strain were cloned into plasmids driven by the promoters CAG and CMV and then transfected into various cell lines, including COS-1 and BHK-21. Time-course sampling of the cells, culture fluid, cell lysate supernatant, and pellet specimens were performed. Western blotting and electron microscopy analyses of collected specimens were used to investigate molecular and structural processing of TBEV structural proteins. Results Western blotting analysis showed differences between promoters in directing the gene expression of the VLPs constructs. The premature flaviviral polypeptides as well as mature VLPs could be traced. Using electron microscopy, the premature and mature VLP accumulation in cellular compartments—and also endoplasmic reticulum proliferation as a virus factory platform—were observed in addition to secreted VLPs. Conclusions The abundant virologic and cellular findings in this study show the natural processing and safety of inserting flaviviral structural genes into suicidal VLP shuttles. Thus, we propose that these VLPs are a suitable gene delivering system model in gene therapy. [ABSTRACT FROM AUTHOR]

Fowl adenoviruses (FAdVs) are promising vectors for poultry vaccines and gene therapy. The commonly used human cytomegalovirus (CMV) promoter in recombinant FAdV-9 viruses (recFAdV-9s) leads to foreign gene expression that elicits an antibody response. Despite its strength, studies have shown that the CMV promoter is prone to silencing by methylation hampering the in vivo application of vectors containing this promoter. Therefore, to improve our virus vector system and circumvent potential limitations of silencing, we engineered recFAdV-9s with foreign gene expression cassettes carrying the CMV enhancer/chicken β-actin (CAG) or the human elongation factor 1 alpha (EF1α) promoters with or without the posttranscriptional regulatory element of woodchuck hepatitis virus (WPRE). Chicken hepatoma cells (CH-SAH) infected with recFAdV-9s carrying either CAG or EF1α promoters expressed higher levels of foreign protein than those infected with recFAdV-9 carrying the CMV promoter. Incorporation of the WPRE element rendered lower gene expression regardless of promoter type. Surprisingly, most chickens inoculated with recFAdV-9 containing the CMV promoter had the highest antibody response to foreign protein compared to other promoters. Our findings suggest the importance of promoter selection for candidate virus vector vaccines based on humoral immune response rather than foreign protein expression levels in vitro . [ABSTRACT FROM AUTHOR]

Transgenic animals have been established for studying gene function, improving animals' production traits, and providing organ models for the exploration of human diseases. However, the stability of inheritance and transgene expression in transgenic animals has gained extensive attention. The unstable expression of transgene through DNA methyltransferase (DNMT) targeting to the methylation of transgenic DNA such as CAG promoter and Egfp coding region in homozygous transgenic animals is still unknown. In the present study, the offspring from the same litter of homozygous transgenic mice carrying ubiquitously expressed enhanced green fluorescence protein driven by CMV early enhancer/chicken β- actin (CAG) promoter was observed to have unstable expression of transgene Egfp, quantitative PCR, western blot and bisulfite sequencing were conducted to quantify the expressional characteristics and methylation levels in various tissues. The correlation between transgene expression and methylation was analyzed. We have found that transgene expression is dependent on the methylation of CAG promoter, but not Egfp coding region. We have also characterized the correlation between the methylation of CAG promoter and DNMT, and found that only Dnmt3b expression is correlated with the methylation of CAG promoter. In conclusion, Dnmt3b-related methylation of CAG promoter can inhibit the transgene expression and may result in the unstable expression of transgene in the offspring from the same litter of homozygous transgenic mice. [ABSTRACT FROM AUTHOR]

Abstract: The fat-1 gene was isolated from roundworm Caenorhabditis elegans, and built into pIRES2-EGFP expression vectors driven by cytomegalovirus (CMV) promoter or cytomegalovirus enhancer and chickenβ-actin (CAG) promoter. Both CMV- and CAG-driven expression vectors were transfected to sheep fetal fibroblast cells. Positive transfected cells were used as donors for somatic cell nuclear transfer (SCNT) and the cloned embryos were transferred into the oviducts of synchronized recipient sheep. Two lambs derived from CMV vector and three lambs derived from CAG vector developed to term. Although Southern analyses using tissues from the two lambs derived from CMV vectors indicated integration of fat-1 gene into the genome, fat-1 mRNAs were not detected by RT-PCR. However, there was fat-1 expression (detected by RT-PCR) in tissues from transgenic lambs driven by CAG vectors. To investigate potential mechanisms involved in the two transgene models, methylation state of the vector promoters were examined. In CMV-driven transgenics, CMV promoters had almost no methylation in transfected cells and the resultant cloned embryos, whereas high methylations were detected in tissues and organs in transgenic lambs. In the CAG-driven transgenics, there were almost no methylations in transgenic cells and transgenic cloned embryos, and cloned lambs expressed fat-1 mRNA (detected by RT-PCR). Moreover, although SV40 promoters which drove neo/kan marker gene in CMV vectors were highly methylated in tissues from transgenic lambs, they were without methylation in cells and embryos. Therefore, we concluded that highly methylated CMV promoters induced the silence of fat-1 transgene expression in sheep. Furthermore, CAG promoter, but not CMV promoter was suitable for generation of fat-1 transgenic sheep. [Copyright &y& Elsevier]

Human embryonic stem (HuES) cells represent a new potential tool for cell-therapy and gene-therapy applications. However, these approaches require the development of efficient, stable gene delivery, and proper progenitor cell and tissue separation methods. In HuES cell lines, we have generated stable, enhanced green fluorescent protein (EGFP)-expressing clones using a transposon-based (Sleeping Beauty) system. This method yielded high percentage of transgene integration and expression. Similarly to a lentiviral expression system, both the undifferentiated state and the differentiation pattern of the HuES cells were preserved. By using the CAG promoter, in contrast to several other constitutive promoter sequences (such as CMV, elongation factor 1a, or phosphoglycerate kinase), an exceptionally high EGFP expression was observed in differentiated cardiomyocytes. This phenomenon was independent of the transgene sequence, methods of gene delivery, copy number, and the integration sites. This ''doublefeature'' promoter behavior, that is providing a selectable marker for transgene expressing undifferentiated stem cells, and also specifically labeling differentiated cardiomyocytes, was assessed by transcriptional profiling. We found a positive correlation between CAG promoter-driven EGFP transcription and expression of cardiomyocyte-specific genes. Our experiments indicate an efficient applicability of transposon-based gene delivery into HuES cells and provide a novel approach to identify differentiated tissues by exploiting a nontypical behavior of a constitutively active promoter, thereby avoiding invasive drug selection methods. [ABSTRACT FROM AUTHOR]

Abstract: Fabry disease is caused by the deficiency of lysosomal α-galactosidase A (α-gal A) and usually develops clinical manifestations during childhood/adolescence. Adult Fabry model mice have been successfully treated by various viral vectors. Here, in order to examine the feasibility of preventive gene therapy, we compared AAV vector-mediated gene transfer into neonatal and adult model mice. AAV serotype 1 vector (AAV1) carrying human α-gal A cDNA driven by the CAG promoter was intravenously injected into adult (12 weeks old) and neonatal (2 days old) Fabry model mice, and were sacrificed for detailed examination 25 weeks after vector injection. AAV1 vector preferentially transduced the liver in male adult and sustained high concentration of α-gal A was detected in the liver, heart and plasma. In contrast, AAV1-mediated gene expression was suppressed in similarly treated female adult mice. When the vector was systemically injected into neonates, moderate increase in plasma α-gal A and cardiac-specific expression of α-gal A were observed independently of mouse sex. The high levels of α-gal A activity in the heart appear to be due to the strong activity of the CAG promoter in the heart. Globotriaosylceramide (Gb3) accumulation was efficiently inhibited in the liver and heart by a single injection into both adult and neonatal animals. The biodistribution of the AAV1 vector and levels of α-gal A expression are markedly different between adult and neonatal mice. Neonatal injection is effective to inhibit Gb3 accumulation and therefore, might help prevent failure of major organs during adulthood. [Copyright &y& Elsevier]

Fabry disease is an X-linked recessive inborn metabolic disorder in which a deficiency in lysosomal enzyme α-galactosidase A (Gal A) causes the systemic accumulation of globotriaosylceramide (Gb3). Although many investigators have attempted to treat α-Gal A knock-out mice (Fabry mice) with gene therapy, no report has demonstrated therapeutic effects by the retrograde renal vein injection of naked DNA. We recently developed a naked plasmid vector-mediated kidney-targeted gene transfer technique. A solution containing naked plasmid DNA encoding human α-Gal A (pKSCX-α-Gal A) was rapidly injected into the left kidney of Fabry mice (pKSCX-α-Gal A mice). pKSCX was used for mock transfections (pKSCX mice). We confirmed that vector-derived human α-Gal A mRNA was present in the left kidney but not in other tissues, by reverse transcriptase polymerase chain reaction. Compared with the pKSCX mice, the pKSCX-α-Gal A mice showed partial therapeutic effects: increased α-Gal A activity in the injected kidney and in the liver, heart, and plasma, and decreased Gb3 in the injected kidney, contralateral kidney, liver, heart, and spleen. Our results demonstrated that, although further studies are needed to improve the outcome, this method has promise as a potential treatment option for Fabry disease. [ABSTRACT FROM AUTHOR]

Recently, we developed a kidney-targeted gene transfer technique, in which naked DNA was injected into the renal vein while the renal vein and artery were clamped. Kidney-targeted DNA transfer with only the renal vein clamped is an important modification that may permit less invasive catheter-based gene transfer in future clinical applications. The preparation of PCR-amplified DNA fragments is less time-consuming than that of naked plasmid DNA. We examined rat erythropoietin (Epo) plasmid, pCAGGS-Epo, or PCR-amplified DNA fragment, fCAGGS-Epo, transfer into the rat kidney with only the renal vein clamped. The Epo level peaked at week 3 and then was sustained for 24 weeks, which resulted in significant erythropoiesis. This modified technique, allowing long-term expression of both PCR-amplified DNA fragments and naked plasmid DNA, could potentially be used for catheter-based gene transfer in humans, and could help determine the physiological functions of putative genes. [ABSTRACT FROM PUBLISHER]

Kidney-targeted gene transfer is expected to revolutionize the treatment of renal diseases. Recently, we demonstrated that naked plasmid deoxyribonucleic acid (DNA) can be transferred into renal interstitial fibroblasts near the peritubular capillaries (PTCs) in normal rats, by retrograde injection into the renal vein with the renal vein and artery clamped. The PTC network is a main target of kidney transplant rejection and of progressive tubulointerstitial fibrosis, which typifies all progressive renal diseases. We retrogradely injected a lacZ expression plasmid in Ringer’s solution into the renal vein of rats using a 24-gage catheter. We detected lacZ expression exclusively in the interstitial fibroblasts near the PTCs of the kidney by immunoelectron microscopy. Nephrotoxicity from the gene transfer was not apparent. We then used a rat erythropoietin (Epo) expression plasmid vector pCAGGS-Epo in a reporter assay. We obtained maximal Epo expression when the DNA solution was injected within 5 s in a volume of 1.0 mL. We detected transgene-derived Epo messenger ribonucleic acid by reverse transcriptase polymerase chain reaction only in the kidneys receiving pCAGGS-Epo. In this article, protocols for naked plasmid DNA transfer into rat kidney using this hydrodynamics-based transfection method and the immunoelectron microscopic technique to determine the lacZ gene transfer site are described in detail. [ABSTRACT FROM AUTHOR]

We recently developed a novel kidney-targeted gene transfer technique in rats, using the retrograde renal vein injection of naked plasmid DNA. Many animal disease models are created in mice by transgenic or knockout technologies. However, it is much harder to perform renal vein injection in mice than in rats because they have a thin and short vein. Here we transferred the mouse interleukin (IL)-10 gene into mice by retrograde renal vein injection, using an IL-10 and immunoglobulin fusion protein (IL-10/Fc) (96-kDa) expression plasmid, pCAGGS-IL10/Fc. We observed a dose–response relationship between serum IL-10 levels and the amount of injected DNA. The serum IL-10 levels peaked at day 1 and then were sustained for at least 2 weeks. These results demonstrate that the kidney-targeted naked plasmid DNA transfer of mice by retrograde renal vein injection can be achieved, and the kidney serves as a depot organ for the production of large proteins. [Copyright &y& Elsevier]

The recombinant adeno-associated virus 8 (rAAV8) vector is a widely used tool in basic research and clinical trials. The cytomegalovirus immediate-early enhancer/chicken β-actin (CAG) promoter is a synthetic promoter used in adenoviral constructs with a wide spectrum and notable efficiency. The thyroxine binding globulin (TBG) promoter is a liver-specific promoter, which directs transgene expression in hepatocytes. However, the transduction efficiency of the rAAV vector is dependent on both the administration routes and the promoter elements. In the present study, the transduction efficiency in the liver following intraperitoneal (IP) and intravenous (IV) injections of rAAV8 with the CAG, TBG669 and TBG410 promoters was compared. Enhanced green fluorescent protein (EGFP) expression was used as the biomarker to indicate efficiency. Among the three different promoters, CAG exhibited the highest efficiency from both IV and IP injections. Following IV administration, EGFP expression, induced by the CAG promoter, was 67-fold higher compared with that in the TBG410 promoter group and 26-fold higher compared with that in the TBG669 promoter group. EGFP protein expression was higher with IV injection compared with that for IP injection for both the CAG and TBG669 promoters (P<0.05). With the CAG promoter, EGFP protein expression was 1.5-fold higher with the use of IV injection than with IP injection. With the TBG410 promoter, no differences were observed between the two administrations. In conclusion, these findings demonstrated that the CAG promoter was much more efficient at driving gene expression in the liver compared with that for the TBG promoters in rAAV8. In addition, IP administration produced comparable efficiency for gene delivery via the rAAV8 vector, particularly with the promoter TBG410. [ABSTRACT FROM AUTHOR]