Risk Factors and Nomogram Model for Hepatocellular Carcinoma Development in Chronic Hepatitis B Patients with Low-Level Viremia.

Background and aim: Patients with chronic hepatitis B patients (CHB) with low-level viremia (LLV) are not necessarily at low risk of developing hepatocellular carcinoma (HCC). The question of whether CHB patients with LLV require immediate antiviral agent (AVT) or long-term AVT remains controversial. The study aims to investigate the risk of HCC development and the risk factors in CHB patients with LLV and construct a nomogram model predicting the risk of HCC. Methods: We conducted a retrospective cohort study that enrolled 16,895 CHB patients from January 2008 to December 2020. The patients were divided into three groups for comparison: the LLV group, maintained virological response (MVR) group and HBV-DNA>2000 group. The cumulative incidence of progression to HCC was assessed. Cox regression analysis was performed to determine the final risk factors, and a nomogram model was constructed. The 10-fold Cross-Validation method was utilized for internal validation. Results: A total of 408 new cases of HCC occurred during the average follow-up period of 5.78 years. The 3, 5, and 10-year cumulative HCC risks in the LLV group were 3.56%, 4.96%, and 9.51%, respectively. There was a significant difference in the cumulative risk of HCC between the HBV-DNA level > 2000 IU/mL and LLV groups (p = 0.049). Independent risk factors for HCC development in LLV group included male gender, age, presence of cirrhosis, and platelets count. The Area Under the Curve (AUC) values for the 3-year and 5-year prediction from our HCC risk prediction model were 0.75 and 0.76, respectively. Conclusion: Patients with LLV and MVR are still at risk for developing HCC. The nomogram established for CHB patient with LLV, incorporating identified significant risk factors, serves as an effective tool for predicting HCC-free outcomes. This nomogram model provides valuable information for determining appropriate surveillance strategies and prescribing AVT.

Dynamic Information-Hiding Method with High Capacity Based on Image Interpolating and Bit Flipping.

In this era of rapid information exchange in public networks, there is a risk to information security. Data hiding is an important technique for privacy protection. Image interpolation is an important data-hiding technique in image processing. This study proposed a method called neighbor mean interpolation by neighboring pixels (NMINP) that calculates a cover image pixel by neighbor mean interpolation and neighboring pixels. To reduce image distortion, NMINP limits the number of bits when embedding secret data, making NMINP have a higher hiding capacity and peak signal-to-noise ratio (PSNR) than other methods. Furthermore, in some cases, the secret data are flipped, and the flipped data are treated in ones' complement format. A location map is not needed in the proposed method. Experimental results comparing NMINP with other state-of-the-art methods show that NMINP improves the hiding capacity by more than 20% and PSNR by 8%.

Associations between short-term ambient ozone exposure and cause-specific mortality in rural and urban areas of Jiangsu, China.

Most previous studies on the acute health effects of ozone are limited to urban areas, largely due to the paucity of air pollutant measurements in rural areas. We here estimated the county-specific daily maximum 8-h average ozone concentration in Jiangsu Province, China during 2015-2018, using a recently developed spatiotemporal machine learning model at a spatial resolution of 0.1° × 0.1° (∼11 × 11 km). Counties were equally divided into urban and rural groups based on the median of the percentage of urban residents across Jiangsu counties obtained from the National Population Census in 2010. We first conducted time-series analyses to estimate the county-specific effect of ozone using generalized linear models, then pooled the effect estimates by random-effects modeling. A 10 µg/m3 increase in the 4-day moving average (lag 0-3) of ambient ozone exposure was associated with increases of 0.66% (95% confidence interval [CI] 0.36%-0.95%) in daily nonaccidental mortality in rural areas and 0.42% in urban areas (95% CI, 0.27%-0.56%). Short-term ambient ozone exposure was associated with an increased risk of mortality caused by chronic obstructive pulmonary disease, hypertension, ischemic heart disease, and stroke. Our finding suggests that both urban and rural residents suffer adverse health effects from short-term ozone exposure.

High EREG Expression Is Predictive of Better Outcomes in Rectal Cancer Patients Receiving Neoadjuvant Concurrent Chemoradiotherapy.

BACKGROUND/AIM: A great proportion of patients with rectal cancer initially present with locally advanced disease and can potentially benefit from neoadjuvant concurrent chemoradiotherapy (CCRT) for downstaging before surgery. However, risk and clinical outcome stratification remain a great challenge. We aimed to find the potential biomarker to predict the effect of neoadjuvant CCRT on rectal cancer. METHODS: We identified epiregulin (EREG) as the most significant predictive marker for neoadjuvant CCRT response from the published rectal cancer transcriptome data set GSE35452. We collected 172 biopsy specimens from rectal cancer patients who received neoadjuvant CCRT followed by radical proctectomy, performed EREG immunohistochemistry, and analyzed the H-scores. We further examined the correlations between the expression level of EREG and clinicopathological features, tumor regression grade, and survival, including disease-specific survival (DSS), locoregional recurrence-free survival (LRFS), and metastasis-free survival (MeFS). RESULTS: High EREG expression was significantly related to early pretreatment (pre-Tx) and posttreatment (post-Tx) tumor status (T1, T2, p = 0.047 and p < 0.001), pre-Tx and post-Tx negative nodal status (N0, p < 0.001 and p = 0.004), less vascular and perineurial invasion (p = 0.015 and p = 0.023), and higher tumor regression grade (p < 0.001). In the survival analysis, high EREG expression was significantly associated with better DSS (p < 0.0001), LRFS (p = 0.0004), and MeFS (p < 0.0001). In the multivariate analysis, high EREG expression remained prognostically significant for better DSS (p = 0.003; hazard ratio: 5.599). CONCLUSION: These data suggest that EREG is a potential predictive marker and therapeutic target in rectal cancer patients receiving neoadjuvant CCRT.

Cryptanalysis and Improvement of a Chaotic Map-Based Image Encryption System Using Both Plaintext Related Permutation and Diffusion.

In theory, high key and high plaintext sensitivities are a must for a cryptosystem to resist the chosen/known plaintext and the differential attacks. High plaintext sensitivity can be achieved by ensuring that each encrypted result is plaintext-dependent. In this work, we make detailed cryptanalysis on a published chaotic map-based image encryption system, where the encryption process is plaintext Image dependent. We show that some designing flaws make the published cryptosystem vulnerable to chosen-plaintext attack, and we then proposed an enhanced algorithm to overcome those flaws.

Mammalian hyperplastic discs homolog EDD regulates miRNA-mediated gene silencing.

MicroRNAs (miRNAs) regulate gene expression through translation repression and mRNA destabilization. However, the molecular mechanisms of miRNA silencing are still not well defined. Using a genetic screen in mouse embryonic stem (ES) cells, we identify mammalian hyperplastic discs protein EDD, a known E3 ubiquitin ligase, as a key component of the miRNA silencing pathway. ES cells deficient for EDD are defective in miRNA function and exhibit growth defects. We demonstrate that E3 ubiquitin ligase activity is dispensable for EDD function in miRNA silencing. Instead, EDD interacts with GW182 family proteins in the Argonaute-miRNA complexes. The PABC domain of EDD is essential for its silencing function. Through the PABC domain, EDD participates in miRNA silencing by recruiting downstream effectors. Among the PABC-interactors, DDX6 and Tob1/2 are both required and sufficient for silencing mRNA targets. Taken together, these data demonstrate a critical function for EDD in miRNA silencing.

Gender differences in the associations between perceived environment and walking for recreation in Taiwanese adults.

This study examined gender differences in the associations between perceived environmental factors and walking for recreation in Taiwanese adults. In 2014, a telephone-based, cross-sectional survey targeting Taiwanese adults (20-64 years) was conducted. Data on nine items about environmental perception, time spent in walking for recreation, and socio-demographic variables were obtained from 1,065 adults using the International Physical Activity Questionnaire-long version and its environmental module. Adults who perceived good aesthetics (adjusted odds ratio [AOR] = 1.74; 95% confidence interval [CI]: 1.36-2.23) and reported seeing people being active (AOR = 1.58; 95% CI: 1.21-2.06) were more likely to perform 150 minutes of recreational walking per week. Furthermore, significant interactions regarding walking for recreation were observed between gender and five environmental correlates: access to shops (p = .046), the presence of sidewalks (p < .001), access to recreational facilities (p = .02), seeing people being active (p = .001), and aesthetics (p < .001). These five perceived environmental factors were positively associated with recreational walking in women but not in men. Gender is a potential modifier between perceived environment and walking for recreation in adults. Perceived environmental factors appear to be more critical for women in performing health-enhancing levels of recreational walking than they are for men.

In situ forming hydrogel composed of hyaluronate and polygalacturonic acid for prevention of peridural fibrosis.

Hyaluronic acid-based hydrogels can reduce postoperative adhesion. However, the long-term application of hyaluronic acid is limited by tissue mediated enzymatic degradation. To overcome this limitation, we developed a polygalacturonic acid and hyaluronate composite hydrogel by Schiff's base crosslinking reaction. The polygalacturonic acid and hyaluronate composite hydrogels had short gelation time (less than 15 s) and degraded by less than 50 % in the presence of hyaluronidase for 7 days. Cell adhesion and migration assays showed polygalacturonic acid and hyaluronate composite hydrogels prevented fibroblasts from adhesion and infiltration into the hydrogels. Compared to hyaluronate hydrogels and commercial Medishield™ gels, polygalacturonic acid and hyaluronate composite hydrogel was not totally degraded in vivo after 4 weeks. In the rat laminectomy model, polygalacturonic acid and hyaluronate composite hydrogel also had better adhesion grade and smaller mean area of fibrous tissue formation over the saline control and hyaluronate hydrogel groups. Polygalacturonic acid and hyaluronate composite hydrogel is a system that can be easy to use due to its in situ cross-linkable property and potentially promising for adhesion prevention in spine surgeries.

Overexpression of MTFR1 promotes cancer progression and drug-resistance on cisplatin and is related to the immune microenvironment in lung adenocarcinoma.

OBJECTIVE: The roles of MTFR1 in the drug resistance of lung adenocarcinoma (LAC) to cisplatin remain unexplored. In this study, the expression, clinical values and mechanisms of MTFR1 were explored, and the relationship between MTFR1 expression and immune microenvironment was investigated in LAC using bioinformatics analysis, cell experiments, and meta-analysis. METHODS: MTFR1 expression and clinical values, and the relationship between MTFR1 expression and immunity were explored, through bioinformatics analysis. The effects of MTFR1 on the growth, migration and cisplatin sensitivity of LAC cells were identified using cell counting kit-8, wound healing and Transwell experiments. Additionally, the mechanisms of drug resistance of LAC cells involving MTFR1 were investigated using western blotting. RESULTS: MTFR1 was elevated in LAC tissues. MTFR1 overexpression was associated with sex, age, primary therapy outcome, smoking, T stage, unfavourable prognosis and diagnostic value and considered an independent risk factor for an unfavourable prognosis in patients with LAC. MTFR1 co-expressed genes involved in the cell cycle, oocyte meiosis, DNA replication and others. Moreover, interfering with MTFR1 expression inhibited the proliferation, migration and invasion of A549 and A549/DDP cells and promoted cell sensitivity to cisplatin, which was related to the inhibition of p-AKT, p-P38 and p-ERK protein expression. MTFR1 overexpression was associated with stromal, immune and estimate scores along with natural killer cells, pDC, iDC and others in LAC. CONCLUSIONS: MTFR1 overexpression was related to the unfavourable prognosis, diagnostic value and immunity in LAC. MTFR1 also participated in cell growth and migration and promoted the drug resistance of LAC cells to cisplatin via the p-AKT and p-ERK/P38 signalling pathways.

The Efficacy of On-Site Integration Screening and Microelimination Programs for Chronic Hepatitis C in a Detection Center: A Comparison of the Treatment Outcomes and Characteristics of Incarcerated Patients and Outpatients.

We aimed to analyze the different patient characteristics and treatment outcomes (such as sustained viral response, SVR) between incarcerated patients with chronic hepatitis C (CHC) and those with CHC from the outpatient department through an on-site integrated screening and microelimination program in a detection center. In this retrospective study, which ran from May 2021 to April 2022, we included 32 consenting male prisoners aged at least 20 years who were willing to participate in the study. Members of the control group (who received DAAs in an outpatient setting) were selected from the treated CHC patient databank of individuals who received DAA regimens at Chi Mei Hospital between January 2021 and December 2022. The patients in the two groups did not differ significantly in terms of age, FIB-4 score, HCV RNA, HBV coinfection, hemogram findings, coagulation profiles, and renal function tests. However, the patients in the incarcerated group had a significantly different genotype distribution compared to the control group, significantly lower liver enzyme levels, and higher albumin and bilirubin levels compared to those in the control group. The rate of SVR to DAA treatment obtained among incarcerated patients did not differ significantly from that obtained among patients in the control group. Loss to follow-up (for several reasons) is a major reason for treatment discontinuation among these patients.

Finite element analysis of optimized novel additively manufactured non-articulating prostheses for cervical total disc replacement.

Ball-and-socket designs of cervical total disc replacement (TDR) have been popular in recent years despite the disadvantages of polyethylene wear, heterotrophic ossification, increased facet contact force, and implant subsidence. In this study, a non-articulating, additively manufactured hybrid TDR with an ultra-high molecular weight polyethylene core and polycarbonate urethane (PCU) fiber jacket, was designed to mimic the motion of normal discs. A finite element (FE) study was conducted to optimize the lattice structure and assess the biomechanical performance of this new generation TDR with an intact disc and a commercial ball-and-socket Baguera®C TDR (Spineart SA, Geneva, Switzerland) on an intact C5-6 cervical spinal model. The lattice structure of the PCU fiber was constructed using the Tesseract or the Cross structures from the IntraLattice model in the Rhino software (McNeel North America, Seattle, WA) to create the hybrid I and hybrid II groups, respectively. The circumferential area of the PCU fiber was divided into three regions (anterior, lateral and posterior), and the cellular structures were adjusted. Optimal cellular distributions and structures were A2L5P2 in the hybrid I and A2L7P3 in the hybrid II groups. All but one of the maximum von Mises stresses were within the yield strength of the PCU material. The range of motions, facet joint stress, C6 vertebral superior endplate stress and path of instantaneous center of rotation of the hybrid I and II groups were closer to those of the intact group than those of the Baguera®C group under 100 N follower load and pure moment of 1.5 Nm in four different planar motions. Restoration of normal cervical spinal kinematics and prevention of implant subsidence could be observed from the FE analysis results. Superior stress distribution in the PCU fiber and core in the hybrid II group revealed that the Cross lattice structure of a PCU fiber jacket could be a choice for a next-generation TDR. This promising outcome suggests the feasibility of implanting an additively manufactured multi-material artificial disc that allows for better physiological motion than the current ball-and-socket design.

Proteomics analysis reveals overlapping functions of clustered protocadherins.

The three tandem-arrayed protocadherin (Pcdh) gene clusters, namely Pcdh-alpha, Pcdh-beta, and Pcdh-gamma, play important roles in the development of the vertebrate central nervous system. To gain insight into the molecular action of PCDHs, we performed a systematic proteomics analysis of PCDH-gamma-associated protein complexes. We identified a list of 154 non-redundant proteins in the PCDH-gamma complexes. This list includes nearly 30 members of clustered Pcdh-alpha, -beta, and -gamma families as core components of the complexes and additionally over 120 putative PCDH-associated proteins. We validated a selected subset of PCDH-gamma-associated proteins using specific antibodies. Analysis of the identities of PCDH-associated proteins showed that the majority of them overlap with the proteomic profile of postsynaptic density preparations. Further analysis of membrane protein complexes revealed that several validated PCDH-gamma-associated proteins exhibit reduced levels in Pcdh-gamma-deficient brain tissues. Therefore, PCDH-gamma s are required for the integrity of the complexes. However, the size of the overall complexes and the abundance of many other proteins remained unchanged, raising a possibility that PCDH-alphas and PCDH-betas might compensate for PCDH-gamma function in complex formation. As a test of this idea, RNA interference knockdown of both PCDH-alphas and PCDH-gamma s showed that PCDHs have redundant functions in regulating neuronal survival in the chicken spinal cord. Taken together, our data provide evidence that clustered PCDHs coexist in large protein complexes and have overlapping functions during vertebrate neural development.

Enhanced Piezocatalytic Activity in Bi1/2Na1/2TiO3 for Water Splitting by Oxygen Vacancy Engineering.

Piezoelectric materials have demonstrated applicability in clean energy production and environmental wastewater remediation through their ability to initiate a number of catalytic reactions. In this study, we used a conventional sol-gel method to synthesize lead-free rhombohedral R3c bismuth sodium titanate (BNT) particles of various sizes. When used as a piezocatalyst to generate H2 through water splitting, the BNT samples provided high production rates (up to 506.70 µmol g-1 h-1). These piezocatalysts also degraded the organic pollutant methylene blue (MB, 20 mg L-1) with high efficiency (up to k = 0.039 min-1), suggesting their potential to treat polluted water. Finally, we found that the piezopotential caused band tilting in the semiconductor and aided charge transfer such that recombination was suppressed and the rate of H2 production increased. The mechanism of piezoelectric catalysis involved oxygen vacancies, the size of the catalyst, and the internal electric field playing important roles to enhance electron-hole separation, which further enhanced the catalysis reactions.

Improved Mass-Transfer Enhances Photo-Driven Dye Degradation and H2 Evolution over a Few-Layer WS2/ZnO Heterostructure.

In this study, we observed the enhanced photocatalytic activity of a few-layer WS2/ZnO (WZ) heterostructure toward dye degradation and H2 production. The few-layer WS2 acted as a co-catalyst that separated photogenerated electron/hole pairs and provided active sites for reactions, leading to the rate of photocatalytic H2 production of WZ being 35% greater than that over the bare ZnO nanoparticles. Moreover, vortex-stirring accelerated the mass-transfer of the reactants, leading to the efficiency of dye photodegradation being 3 times higher than that obtained without high-speed stirring. We observed a similar effect for H2 production, with greater photocatalytic performance arising from the increased mass-transfer of H2 from the catalyst surface to the atmosphere.

Pediatric sigmoid colonic perforation with Campylobacter enterocolitis: a case report and review of the literature.

BACKGROUND: Campylobacter-related infectious gastroenteritis is common and usually self-limited. Intestinal perforation is a rare complication of the infectious colitis caused by Campylobacter, and only handful of cases have been reported. This is the first published case report of pediatric Campylobacter intestinal perforation located in the sigmoid colon. CASE PRESENTATION: A 15-year-old previously Taiwanese healthy boy presented with 5 days of fever up to 39.8 °C, with right lower quadrant abdominal pain and watery diarrhea. Although he received antimotility agents and antipyretics at a local clinic to relieve symptoms, he came to the emergency department with signs of shock manifesting as hypothermia to 35.2 °C, tachycardia, and low blood pressure. Laboratory testing demonstrated leukocytosis with left shift and significant elevation of C-reactive protein. Stool and blood cultures were obtained, and he was admitted for fluid challenge and antibiotic treatment. On the second day of admission, he suffered from sudden onset of severe, diffuse abdominal pain. Physical examination revealed muscle guarding, rebounding tenderness, and silent bowel sound. Abdominal X-ray showed subdiaphragmatic free air at standing view. The patient underwent emergent exploratory laparotomy, which revealed sigmoid colon perforation about 0.5 cm. Enterolysis and repair of sigmoid colon were performed. Intraoperative stool specimen nucleic acid amplification testing had turned positive for Campylobacter spp. with negative results for other bacterial pathogens. His symptoms improved and he tolerated food well, and was discharged 15 days after admission. CONCLUSIONS: We present this case because of the rarity of Campylobacter-induced sigmoid colon perforation in the pediatric population. It is important to keep in mind that sigmoid colon perforation can be due to an infectious cause, and one of the culprits can be Campylobacter. Infectious colitis caused by Campylobacter spp. should be managed cautiously and the use of antimotility agents in such conditions should be considered judiciously.

Upregulated Ubiquitin D is a Favorable Prognostic Indicator for Rectal Cancer Patients Undergoing Preoperative Concurrent Chemoradiotherapy.

Purpose: For locally advanced rectal cancer, neoadjuvant concurrent chemoradiotherapy (CCRT) allows tumor downstaging and makes curative radical proctectomy possible. However, we lack a genetic biomarker to predict cancer prognosis or treatment response. We investigated the association between ubiquitin D (UBD) expression and clinical outcomes in rectal cancer patients receiving CCRT. Patients and Methods: We analyzed the genes associated with the protein modification process (GO:0036211) and identified the UBD gene as the most relevant among the top 7 differentially expressed genes associated with CCRT resistance. We collected tissue specimens from 172 rectal cancer patients who had received CCRT followed by a curative proctectomy. We examine the relationship between UBD expression and patient characteristics, pathological findings, and patient survival, such as metastasis-free survival (MeFS) and disease-specific survival. Results: Upregulated UBD expression was associated with lower pre-CCRT tumor T stage (P = 0.009), lower post-CCRT tumor T stage (P < 0.001), lower post-CCRT nodal stage (P < 0.001), less vascular invasion (P = 0.015), and better tumor regression (P < 0.001). Using univariate analysis, we found that high UBD expression was correlated with better disease-free survival (DFS) (P < 0.0001), local recurrence-free survival (LRFS) (P < 0.0001) and MeFS (P < 0.0001). Moreover, multivariate analysis demonstrated that high UBD expression was associated with superior DFS (P < 0.001), LRFS (P = 0.01), and MeFS (P = 0.004). Conclusion: UBD upregulation was linked to better clinical prognosis, favorable pathological features, and good treatment response in rectal cancer patients undergoing CCRT. These results suggest UBD is a biomarker for rectal cancer.

Iatrogenic Kaposi sarcoma of the small bowel in Crohn's disease following short-term use of immunomodulators: a case report and review of the literature.

BACKGROUND: Kaposi sarcoma is a vascular tumor highly related to human herpesvirus-8 and Kaposi sarcoma-associated herpesvirus. Kaposi sarcoma usually manifests as skin or mucosal lesions; involvement in visceral organs such as the gastrointestinal tract is rare. Kaposi sarcoma can occur in immunocompromised patients receiving immunosuppressive therapy, in which case it is known as iatrogenic Kaposi sarcoma or drug-induced Kaposi sarcoma. Intestinal Kaposi sarcoma in patients with inflammatory bowel disease is extremely rare. CASE PRESENTATION: A 46-year-old East Asian male with recently diagnosed Crohn's disease was administered azathioprine and prednisolone; however, the patient complained of persistent abdominal pain and diarrhea following treatment. Endoscopy revealed small bowel Kaposi sarcoma. The patient was treated with systemic chemotherapy successfully without relapse. CONCLUSIONS: This is the fifth case of Kaposi sarcoma developed over the small intestine in a patient with Crohn's disease following administration of immunomodulators. Additionally, this case indicated that even short-term immunomodulator use can induce Kaposi sarcoma in patients with inflammatory bowel disease. Thus, in patients with inflammatory bowel disease, if symptoms are aggravated or do not abate after immunomodulators prescription, and before intending to upgrade immunomodulators, endoscopy should be considered. Finally, chemotherapy can also be considered if both medication withdrawal and surgical intervention are not feasible.

PDCD10/CCM3 acts downstream of {gamma}-protocadherins to regulate neuronal survival.

γ-Protocadherins (PCDH-γ) regulate neuronal survival in the vertebrate central nervous system. The molecular mechanisms of how PCDH-γ mediates this function are still not understood. In this study, we show that through their common cytoplasmic domain, different PCDH-γ isoforms interact with an intracellular adaptor protein named PDCD10 (programmed cell death 10). PDCD10 is also known as CCM3, a causative genetic defect for cerebral cavernous malformations in humans. Using RNAi-mediated knockdown, we demonstrate that PDCD10 is required for the occurrence of apoptosis upon PCDH-γ depletion in developing chicken spinal neurons. Moreover, overexpression of PDCD10 is sufficient to induce neuronal apoptosis. Taken together, our data reveal a novel function for PDCD10/CCM3, acting as a critical regulator of neuronal survival during development.

PiggyBac transgenic strategies in the developing chicken spinal cord.

The chicken spinal cord is an excellent model for the study of early neural development in vertebrates. However, the lack of robust, stable and versatile transgenic methods has limited the usefulness of chick embryos for the study of later neurodevelopmental events. Here we describe a new transgenic approach utilizing the PiggyBac (PB) transposon to facilitate analysis of late-stage neural development such as axon targeting and synaptic connection in the chicken embryo. Using PB transgenic approaches we achieved temporal and spatial regulation of transgene expression and performed stable RNA interference (RNAi). With these new capabilities, we mapped axon projection patterns of V2b subset of spinal interneurons and visualized maturation of the neuromuscular junction (NMJ). Furthermore, PB-mediated RNAi in the chick recapitulated the phenotype of loss of agrin function in the mouse NMJ. The simplicity and versatility of PB-mediated transgenic strategies hold great promise for large-scale genetic analysis of neuronal connectivity in the chick.

Chromosomal transposition of PiggyBac in mouse embryonic stem cells.

Transposon systems are widely used for generating mutations in various model organisms. PiggyBac (PB) has recently been shown to transpose efficiently in the mouse germ line and other mammalian cell lines. To facilitate PB's application in mammalian genetics, we characterized the properties of the PB transposon in mouse embryonic stem (ES) cells. We first measured the transposition efficiencies of PB transposon in mouse embryonic stem cells. We next constructed a PB/SB hybrid transposon to compare PB and Sleeping Beauty (SB) transposon systems and demonstrated that PB transposition was inhibited by DNA methylation. The excision and reintegration rates of a single PB from two independent genomic loci were measured and its ability to mutate genes with gene trap cassettes was tested. We examined PB's integration site distribution in the mouse genome and found that PB transposition exhibited local hopping. The comprehensive information from this study should facilitate further exploration of the potential of PB and SB DNA transposons in mammalian genetics.