A comprehensive evaluation of pre- and post-processing sperm parameters for predicting successful pregnancy rate following intrauterine insemination with the husband's sperms.

BACKGROUND: To determine the predictive values of sperm parameters pre- and post-processing by density gradient centrifugation for clinical pregnancy rates (CPRs) following artificial insemination by husband (AIH) in infertile Chinese couples. METHODS: A total of 3,522 AIH cycles from 1,918 couples were retrospectively analyzed. The parameters were compared between the pregnant and non-pregnant groups and further between different etiological groups (Male-factor, Both-male-and-female-factor, and Other-factor). Multivariate logistic regression analysis was performed to create models for predicting the CPRs of each etiological group. RESULTS: The overall CPR was 13.3%. There were significant improvements for most sperm parameters after DGC. Multivariate logistic regression analysis indicated that, in overall AIH cases, the top parameters significantly influencing the CPR of AIH were pre-STR (OR = 1.037; P = 0.048) and post-VSL (OR = 1.036; P = 0.011). In the Male-factor Group, the top influencing parameters were pre-VCL (OR = 2.096; P = 0.008), pre-LIN (OR = 1.930; P = 0.002) and post-VSL (OR = 1.316; P = 0.023). In the Both-factor Group, the top influencing parameters were pre-VCL (OR = 1.451; P = 0.008) and post-motility (OR = 1.218; P = 0.049). In the Other-factor Group, the top influencing parameters were pre-VAP (OR = 1.715; P = 0.024), pre-STR (OR = 1.20; P = 0.011) and post-VSL (OR = 1.04; P = 0.017). Moreover, receiver operating characteristic analysis showed that the logistic regression models of the Male- and Both-factor Groups had greater powers for prognostic classification than those of other groups. CONCLUSIONS: This study demonstrated that some sperm parameters have a collinearity relationship in predicting the CPR following AIH. Moreover, the predictive capacity of a multivariate logistic regression model is better than those of individual parameters, especially for the Male- and Both-factor Groups. In these cases, pre-VCL is the common top influencing factor.

Systemic delivery of fusogenic membrane glycoprotein-expressing neural stem cells to selectively kill tumor cells.

Intravenously injected neural stem cells (NSCs) can infiltrate both primary and metastatic tumor sites; thus, they are attractive tumor-targeting vehicles for delivering anticancer agents. However, because the systemic distribution of the injected NSCs involves normal organs and might induce off-target actions leading to unintended side effects, clinical applications of this approach is impeded. Given that the vesicular stomatitis virus glycoprotein (VSV-G) can promote the formation of multinucleated syncytia to kill cells in a pH-dependent manner, we engineered a pH sensor of VSV-G and generated a novel VSV-G mutant that efficiently promotes syncytium formation at the tumor extracellular pH (pHe) but not at pH 7.4. Using transduced NSCs derived from induced pluripotent stem cells (iPSCs), the VSV-G mutant was delivered into mice with metastatic breast cancers in the lung through tail vein injection. Compared with the conventional stem cell-based gene therapy that uses the herpes simplex virus thymidine kinase (HSVtk) suicide gene, this treatment did not display toxicity to normal non-targeted organs while retaining therapeutic effects in tumor-bearing organs. Our findings demonstrate the effectiveness of a new approach for achieving tumor-selective killing effects following systemic stem cell administration. Its potential in stem cell-based gene therapy for metastatic cancer is worthy of further exploration.

Development and clinical validation of a dual ddPCR assay for detecting carbapenem-resistant Acinetobacter baumannii in bloodstream infections.

Objective: Acinetobacter baumannii (A. baumannii, AB) represents a major species of Gram-negative bacteria involved in bloodstream infections (BSIs) and shows a high capability of developing antibiotic resistance. Especially, carbapenem-resistant Acinetobacter baumannii (CRAB) becomes more and more prevalent in BSIs. Hence, a rapid and sensitive CRAB detection method is of urgent need to reduce the morbidity and mortality due to CRAB-associated BSIs. Methods: A dual droplet digital PCR (ddPCR) reaction system was designed for detecting the antibiotic resistance gene OXA-23 and AB-specific gene gltA. Then, the specificity of the primers and probes, limit of detection (LOD), linear range, and accuracy of the assay were evaluated. Furthermore, the established assay approach was validated on 37 clinical isolates and compared with blood culture and drug sensitivity tests. Results: The dual ddPCR method established in this study demonstrated strong primer and probe specificity, distinguishing CRAB among 21 common clinical pathogens. The method showed excellent precision (3 × 10-4 ng/µL, CV < 25%) and linearity (OXA-23: y = 1.4558x + 4.0981, R2 = 0.9976; gltA: y = 1.2716x + 3.6092, R2 = 0.9949). While the dual qPCR LOD is 3 × 10-3 ng/µL, the dual ddPCR's LOD stands at 3 × 10-4 ng/µL, indicating a higher sensitivity in the latter. When applied to detect 35 patients with BSIs of AB, the results were consistent with clinical blood culture identification and drug sensitivity tests. Conclusion: The dual ddPCR detection method for OXA-23 and gltA developed in this study exhibits good specificity, excellent linearity, and a higher LOD than qPCR. It demonstrates reproducibility even for minute samples, making it suitable for rapid diagnosis and precision treatment of CRAB in BSIs.

Competing endogenous RNA network analysis of Turner syndrome patient-specific iPSC-derived cardiomyocytes reveals dysregulation of autosomal heart development genes by altered dosages of X-inactivation escaping non-coding RNAs.

BACKGROUND: A 45,X monosomy (Turner syndrome, TS) is the only chromosome haploinsufficiency compatible with life. Nevertheless, the surviving TS patients still suffer from increased morbidity and mortality, with around one-third of them subjecting to heart abnormalities. How loss of one X chromosome drive these conditions remains largely unknown. METHODS: Here, we have generated cardiomyocytes (CMs) from wild-type and TS patient-specific induced pluripotent stem cells and profiled the mRNA, lncRNA and circRNA expression in these cells. RESULTS: We observed lower beating frequencies and higher mitochondrial DNA copies per nucleus in TS-CMs. Moreover, we have identified a global transcriptome dysregulation of both coding and non-coding RNAs in TS-CMs. The differentially expressed mRNAs were enriched of heart development genes. Further competing endogenous RNA network analysis revealed putative regulatory circuit of autosomal genes relevant with mitochondrial respiratory chain and heart development, such as COQ10A, RARB and WNT2, mediated by X-inactivation escaping lnc/circRNAs, such as lnc-KDM5C-4:1, hsa_circ_0090421 and hsa_circ_0090392. The aberrant expressions of these genes in TS-CMs were verified by qPCR. Further knockdown of lnc-KDM5C-4:1 in wild-type CMs exhibited significantly reduced beating frequencies. CONCLUSIONS: Our study has revealed a genomewide ripple effect of X chromosome halpoinsufficiency at post-transcriptional level and provided insights into the molecular mechanisms underlying heart abnormalities in TS patients.

The gene regulatory role of non-coding RNAs in non-obstructive azoospermia.

Non-coding RNAs are classified as small non-coding RNAs, long non-coding RNAs and circular RNAs, which are involved in a variety of biological processes, including cell differentiation, proliferation, apoptosis and pathological conditions of various diseases. Many studies have shown that non-coding RNAs are related to spermatogenesis, maturation, apoptosis, function, etc. In addition, the expression of non-coding RNAs in testicular tissue and semen of patients with non-obstructive azoospermia was different. However, the role of non-coding RNAs in the pathogenesis of non-obstructive azoospermia has not been fully elucidated, and the role of non-coding RNAs in non-obstructive azoospermia is rarely reviewed. Here we summarize the research progress of non-coding RNAs in the pathogenesis of non-obstructive azoospermia.

Sperm DNA integrity is critically impacted by male age but does not influence outcomes of artificial insemination by husband in the Chinese infertile couples.

The sperm chromatin structure assay (SCSA) is crucial for assessing male fertility. However, the predictive value of the SCSA parameters, including the DNA fragment indices (DFI) and the percentages of high DNA stainability (HDS), for outcomes of artificial insemination by husband (AIH) remains controversial. This study aims to evaluate the correlations between SCSA parameters and male aging as well as other routine semen parameters, and explore their prognostic powers on AIH outcomes of the Chinese infertile couples. A total of 809 AIH cycles were retrospectively analyzed. The results showed that DFI in the age groups < 35 years were significantly lower than that in the age groups ≥ 35 years (P < 0.001). Meanwhile, there was no statistical difference in HDS between the age groups (P = 0.063). DFI and HDS are negatively correlated with most routine semen parameters (all P < 0.05). The chi-square and generalized linear model tests indicated that neither DFI nor HDS influenced the clinical pregnancy rate of AIH. In summary, this study found that aging is a critical factor leading to increased sperm DFI but not HDS. DFI and HDS are negatively correlated with most semen parameters but do not significantly influence AIH outcomes.

Chlamydia trachomatis infection in the genital tract is associated with inflammation and hypospermia in the infertile male of China.

Chlamydia trachomatis (CT) infection is the most prevalent sexually transmitted bacterial disease worldwide. However, unlike that in female infertility, the role of CT infection in male infertility remains controversial. The objective of this retrospective study was to explore the impacts of CT infection in the genital tract on sperm quality, sperm acrosin activity, antisperm antibody levels, and inflammation in a large cohort of infertile males in China. A total of 7154 semen samples were collected from infertile male subjects, 416 of whom were CT positive (CT+ group) and 6738 of whom were CT negative (CT- group), in our hospital between January 2016 and December 2018. Routine semen parameters (semen volume, pH, sperm concentration, viability, motility, morphology, etc.), granulocyte elastase levels, antisperm antibody levels, and sperm acrosin activity were compared between the CT+ and CT- groups. Our results showed that CT infection was significantly correlated with an abnormally low semen volume, as well as an increased white blood cell count and granulocyte elastase level (all P < 0.05) in the semen of infertile males; other routine semen parameters were not negatively impacted. The antisperm antibody level and sperm acrosin activity were not affected by CT infection. These findings suggested that CT infection might contribute to inflammation and hypospermia but does not impair sperm viability, motility morphology, and acrosin activity or generate antisperm antibodies in the infertile males of China.

Application of Human Induced Pluripotent Stem Cell-Derived Cellular and Organoid Models for COVID-19 Research.

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its rapid international spread has caused the coronavirus disease 2019 (COVID-19) pandemics, which is a global public health crisis. Thus, there is an urgent need to establish biological models to study the pathology of SARS-CoV-2 infection, which not only involves respiratory failure, but also includes dysregulation of other organs and systems, including the brain, heart, liver, intestines, pancreas, kidneys, eyes, and so on. Cellular and organoid models derived from human induced pluripotent stem cells (iPSCs) are ideal tools for in vitro simulation of viral life cycles and drug screening to prevent the reemergence of coronavirus. These iPSC-derived models could recapitulate the functions and physiology of various human cell types and assemble the complex microenvironments similar with those in the human organs; therefore, they can improve the study efficiency of viral infection mechanisms, mimic the natural host-virus interaction, and be suited for long-term experiments. In this review, we focus on the application of in vitro iPSC-derived cellular and organoid models in COVID-19 studies.

Targeted integration of EpCAM-specific CAR in human induced pluripotent stem cells and their differentiation into NK cells.

BACKGROUND: Redirection of natural killer (NK) cells with chimeric antigen receptors (CAR) is attractive in developing off-the-shelf CAR therapeutics for cancer treatment. However, the site-specific integration of a CAR gene into NK cells remains challenging. METHODS: In the present study, we genetically modified human induced pluripotent stem cells (iPSCs) with a zinc finger nuclease (ZFN) technology to introduce a cDNA encoding an anti-EpCAM CAR into the adeno-associated virus integration site 1, a "safe harbour" for transgene insertion into human genome, and next differentiated the modified iPSCs into CAR-expressing iNK cells. RESULTS: We detected the targeted integration in 4 out of 5 selected iPSC clones, 3 of which were biallelically modified. Southern blotting analysis revealed no random integration events. iNK cells were successfully derived from the modified iPSCs with a 47-day protocol, which were morphologically similar to peripheral blood NK cells, displayed NK phenotype (CD56+CD3-), and expressed NK receptors. The CAR expression of the iPSC-derived NK cells was confirmed with RT-PCR and flow cytometry analysis. In vitro cytotoxicity assay further confirmed their lytic activity against NK cell-resistant, EpCAM-positive cancer cells, but not to EpCAM-positive normal cells, demonstrating the retained tolerability of the CAR-iNK cells towards normal cells. CONCLUSION: Looking ahead, the modified iPSCs generated in the current study hold a great potential as a practically unlimited source to generate anti-EpCAM CAR iNK cells.

Generation of an induced pluripotent stem cell line GZHMCi008-A derived from a patient with SRY-positive 46,XX testicular disorder of sex development.

The testicular disorder of sex development (TDSD) is a rare condition characterized by a male appearance with a female karyotype. The most frequent cause of TDSD is misplacement of the sex determining region Y (SRY) gene on the X chromosome. Here, we report the generation of an induced pluripotent stem cell (iPSC) line from peripheral blood mononuclear cells of a patient with SRY-positive 46,XX TDSD. This cell line offers an unprecedented cellular model to investigate the profound manifestations like infertility of the male sex reversal patients, and serves as a useful tool to develop therapies for the disease.

Evaluation of Prognostic Factors for Clinical Pregnancy Rate Following Artificial Insemination by Husband in the Chinese Population.

Background: To determine the independent prognostic factors and develop a multivariate logistic regression model for predicting successful pregnancy following artificial insemination by husband (AIH) in infertile Chinese couples. Methods: A total of 3,015 AIH cycles with superovulation from 1,853 infertile Chinese couples were retrospectively analyzed. The clinical characteristics and sperm parameters were compared between the pregnant and non-pregnant groups. Multivariate logistic regression analysis was performed to remove the confounding factors and create an equation to predict the successful pregnancy. Receiver operating characteristic (ROC) curves were constructed for evaluating the abilities for prognostic classification of the independent predictors and the equation. Results: The overall pregnancy rate was 13.0%. The pregnancy rate of double intrauterine insemination (IUI) (18.9%) was significantly higher than that of single IUI (11.4%). The pregnancy rate of the stimulated cycle (14.4%) was significantly higher than that of the natural cycle (9.0%). The pregnancy rates of the age groups <40 years are ~3 times higher than that of the ≥40 years age group. Among sperm parameters, the influencing factors included straight-line velocity (VSL), sperm deformity index (SDI), and normal form rate (all P < 0.05). A multivariate logistic regression equation was created based on the above influencing factors. ROC analysis showed that the prognostic power of the equation is better than those of individual predictors. Conclusion: Cycle treatment options, single/double IUI, female age, sperm VSL, SDI, and normal form rate could predict successful pregnancy following AIH in China. The multivariate logistic regression equation exhibited a greater value for prognostic classification than single predictors.

Single-Cell Transcriptome Analysis of Mouse Liver Cell-Specific Tropism and Transcriptional Dysregulation Following Intravenous Administration of AAVrh.10 Vectors.

Capitalizing on liver tropism of adeno-associated viral (AAV) vectors, intravenous vector administration is commonly used to genetically modify hepatocytes, a strategy currently in clinical trials for a number of liver-based hereditary disorders. Although hepatocytes are known to exhibit extensive phenotypic heterogeneity influenced by liver zonation and dietary cycle, there is little data available for the tropism capacity, as well as the potential transcriptional dysregulation, of AAV vectors for specific liver cell types. To assess these issues, we employed single-cell RNA sequencing of the mouse liver after intravenous administration of the liver tropic AAVrh.10 vector to characterize cell-specific AAV-mediated transgene expression and transcriptome dysregulation. Wild-type 8-week-old male C57Bl/6 mice under normal feed cycle were randomly divided into three groups and intravenously administered phosphate-buffered saline (PBS), AAVrh.10Null (no transgene), or AAVrh.10mCherry (marker gene). Overall, a total of 46,500 liver cells were sequenced. The single-cell transcriptomic profiles were grouped into three separate clusters of hepatocytes (Ttr-enriched "Hep1," Tat-enriched "Hep2," and Alb-enriched "Hep3") and multiple other cell types. The hepatocyte diversity was driven by glucose and lipid homeostasis signaling. Assessment of the transgene expression demonstrated that AAVrh.10 is primarily Hep1-tropic, with a 10-gene signature positively correlated with AAVrh.10-mediated transgene expression. The transgene expression was less in Hep2 and Hep3 cells with a high receptor tyrosine kinase phenotype. Importantly, AAVrh.10 vector interactions with the liver markedly altered the transcriptional patterns of all cell types, with modified genes enriched in pathways of complement and coagulation cascade, cytochrome P450, peroxisome, antigen processing and presentation, and endoplasmic reticulum protein processing. These observations provide insights into the liver cell-specific consequences of AAV-mediated liver gene transfer, far beyond the well-known organ-specific expression of the vector-delivered transgene.

Regional methylome profiling reveals dynamic epigenetic heterogeneity and convergent hypomethylation of stem cell quiescence-associated genes in breast cancer following neoadjuvant chemotherapy.

BACKGROUND: Neoadjuvant chemotherapy (NAC) induces a pathological complete response (pCR) in ~ 30% of patients with breast cancer. However, aberrant DNA methylation alterations are frequent events during breast cancer progression and acquisition of chemoresistance. We aimed to characterize the inter- and intra-tumor methylation heterogeneity (MH) in breast cancer following NAC. METHODS: DNA methylation profiles of spatially separated regions of breast tumors before and after NAC treatment were investigated using high-density methylation microarray. Methylation levels of genes of interest were further examined using multiplexed MethyLight droplet digital PCR (ddPCR). RESULTS: We have discovered different levels of intra-tumor MH in breast cancer patients. Moreover, NAC dramatically altered the methylation profiles and such changes were highly heterogeneous between the patients. Despite the high inter-patient heterogeneity, we identified that stem cell quiescence-associated genes ALDH1L1, HOPX, WNT5A and SOX9 were convergently hypomethylated across all the samples after NAC treatment. Furthermore, by using MethyLight ddPCR, we verified that the methylation levels of these 4 genes were significantly lower in breast tumor samples after NAC than those before NAC. CONCLUSIONS: Our study has revealed that NAC dramatically alters epigenetic heterogeneity in breast cancer and induces convergent hypomethylation of stem cell quiescence-associated genes, ALDH1L1, HOPX, WNT5A and SOX9, which can potentially be developed as therapeutic targets or biomarkers for chemoresistance.

Generation of an induced pluripotent stem cell line from an adult male with 45,X/46,XY mosaicism.

Turner syndrome (TS) with 45,X/46,XY mosaic karyotype is a rare sex chromosome disorder with an occurrence of 0.15‰ at birth. We report the generation of an induced pluripotent stem cell (iPSC) line from peripheral blood mononuclear cells of a Chinese adult male with 45,X/46,XY mosaicism. The iPSC line retains the original 45,X/46,XY mosaic karyotype, expresses pluripotency markers and undergoes trilineage differentiation. Therefore, it offers an unprecedented cellular model to investigate the profound symptoms like infertility of TS in the male, and serve as a useful tool to develop therapies for the disease.

Single-Cell Transcriptome Analysis Reveals Estrogen Signaling Coordinately Augments One-Carbon, Polyamine, and Purine Synthesis in Breast Cancer.

Estrogen drives breast cancer (BCa) progression by directly activating estrogen receptor α (ERα). However, because of the stochastic nature of gene transcription, it is important to study the estrogen signaling pathway at the single-cell level to fully understand how ERα regulates transcription. Here, we performed single-cell transcriptome analysis on ERα-positive BCa cells following 17ß-estradiol stimulation and reconstructed the dynamic estrogen-responsive transcriptional network from discrete time points into a pseudotemporal continuum. Notably, differentially expressed genes show an estrogen-stimulated metabolic switch that favors biosynthesis but reduces estrogen degradation. Moreover, folate-mediated one-carbon metabolism is reprogrammed through the mitochondrial folate pathway and polyamine and purine synthesis are upregulated coordinately. Finally, we show AZIN1 and PPAT are direct ERα targets that are essential for BCa cell survival and growth. In summary, our study highlights the dynamic transcriptional heterogeneity in ERα-positive BCa cells upon estrogen stimulation and uncovers a mechanism of estrogen-mediated metabolic switch.

Targeted Inhibition of the miR-199a/214 Cluster by CRISPR Interference Augments the Tumor Tropism of Human Induced Pluripotent Stem Cell-Derived Neural Stem Cells under Hypoxic Condition.

The human induced pluripotent stem cell (hiPSC) provides a breakthrough approach that helps overcoming ethical and allergenic challenges posed in application of neural stem cells (NSCs) in targeted cancer gene therapy. However, the tumor-tropic capacity of hiPSC-derived NSCs (hiPS-NSCs) still has much room to improve. Here we attempted to promote the tumor tropism of hiPS-NSCs by manipulating the activity of endogenous miR-199a/214 cluster that is involved in regulation of hypoxia-stimulated cell migration. We first developed a baculovirus-delivered CRISPR interference (CRISPRi) system that sterically blocked the E-box element in the promoter of the miR-199a/214 cluster with an RNA-guided catalytically dead Cas9 (dCas9). We then applied this CRISPRi system to hiPS-NSCs and successfully suppressed the expression of miR-199a-5p, miR-199a-3p, and miR-214 in the microRNA gene cluster. Meanwhile, the expression levels of their targets related to regulation of hypoxia-stimulated cell migration, such as HIF1A, MET, and MAPK1, were upregulated. Further migration assays demonstrated that the targeted inhibition of the miR-199a/214 cluster significantly enhanced the tumor tropism of hiPS-NSCs both in vitro and in vivo. These findings suggest a novel application of CRISPRi in NSC-based tumor-targeted gene therapy.

Yeast Actin-Related Protein ARP6 Negatively Regulates Agrobacterium-Mediated Transformation of Yeast Cell.

The yeasts, including Saccharomyces cerevisiae and Pichia pastoris, are single-cell eukaryotic organisms that can serve as models for human genetic diseases and hosts for large scale production of recombinant proteins in current biopharmaceutical industry. Thus, efficient genetic engineering tools for yeasts are of great research and economic values. Agrobacterium tumefaciens-mediated transformation (AMT) can transfer T-DNA into yeast cells as a method for genetic engineering. However, how the T-DNA is transferred into the yeast cells is not well established yet. Here our genetic screening of yeast knockout mutants identified a yeast actin-related protein ARP6 as a negative regulator of AMT. ARP6 is a critical member of the SWR1 chromatin remodeling complex (SWR-C); knocking out some other components of the complex also increased the transformation efficiency, suggesting that ARP6 might regulate AMT via SWR-C. Moreover, knockout of ARP6 led to disruption of microtubule integrity, higher uptake and degradation of virulence proteins, and increased DNA stability inside the cells, all of which resulted in enhanced transformation efficiency. Our findings have identified molecular and cellular mechanisms regulating AMT and a potential target for enhancing the transformation efficiency in yeast cells.

Integrative Analysis of CRISPR/Cas9 Target Sites in the Human HBB Gene.

Recently, the clustered regularly interspaced short palindromic repeats (CRISPR) system has emerged as a powerful customizable artificial nuclease to facilitate precise genetic correction for tissue regeneration and isogenic disease modeling. However, previous studies reported substantial off-target activities of CRISPR system in human cells, and the enormous putative off-target sites are labor-intensive to be validated experimentally, thus motivating bioinformatics methods for rational design of CRISPR system and prediction of its potential off-target effects. Here, we describe an integrative analytical process to identify specific CRISPR target sites in the human ß-globin gene (HBB) and predict their off-target effects. Our method includes off-target analysis in both coding and noncoding regions, which was neglected by previous studies. It was found that the CRISPR target sites in the introns have fewer off-target sites in the coding regions than those in the exons. Remarkably, target sites containing certain transcriptional factor motif have enriched binding sites of relevant transcriptional factor in their off-target sets. We also found that the intron sites have fewer SNPs, which leads to less variation of CRISPR efficiency in different individuals during clinical applications. Our studies provide a standard analytical procedure to select specific CRISPR targets for genetic correction.

A Double-Switch Cell Fusion-Inducible Transgene Expression System for Neural Stem Cell-Based Antiglioma Gene Therapy.

Recent progress in neural stem cell- (NSC-) based tumor-targeted gene therapy showed that NSC vectors expressing an artificially engineered viral fusogenic protein, VSV-G H162R, could cause tumor cell death specifically under acidic tumor microenvironment by syncytia formation; however, the killing efficiency still had much room to improve. In the view that coexpression of another antitumoral gene with VSV-G can augment the bystander effect, a synthetic regulatory system that triggers transgene expression in a cell fusion-inducible manner has been proposed. Here we have developed a double-switch cell fusion-inducible transgene expression system (DoFIT) to drive transgene expression upon VSV-G-mediated NSC-glioma cell fusion. In this binary system, transgene expression is coregulated by a glioma-specific promoter and targeting sequences of a microRNA (miR) that is highly expressed in NSCs but lowly expressed in glioma cells. Thus, transgene expression is "switched off" by the miR in NSC vectors, but after cell fusion with glioma cells, the miR is diluted and loses its suppressive effect. Meanwhile, in the syncytia, transgene expression is "switched on" by the glioma-specific promoter. Our in vitro and in vivo experimental data show that DoFIT successfully abolishes luciferase reporter gene expression in NSC vectors but activates it specifically after VSV-G-mediated NSC-glioma cell fusion.