Various genetic switches have been developed to let engineered cells perform designed functions. However, a sustained input is often needed to maintain the on/off state, which is energy-consuming and sensitive to perturbation. Therefore, we developed a set of transcriptional switches for cell states control that were constructed by the inversion effect of site-specific recombinases on terminators. Such a switch could respond to a pulse signal and maintain the new state by itself until the next input. With a bottom-up design principle, we first characterized the terminators and recombinases. Then the mutual interference was studied to select compatible pairs, which were used to achieve one-time and two-time state transitions. Finally, we constructed a biological seven-segment display as a demonstration to prove such switch's immense potential for application.
Recombinases ; metabolism

Genetically engineered mouse models are commonly preferred for studying the human disease due to genetic and pathophysiological similarities between mice and humans. In particular, Cre-loxP system is widely used as an integral experimental tool for generating the conditional. This system has enabled researchers to investigate genes of interest in a tissue/cell (spatial control) and/or time (temporal control) specific manner. A various tissue-specific Cre-driver mouse lines have been generated to date, and new Cre lines are still being developed. This review provides a brief overview of Cre-loxP system and a few commonly used promoters for expression of tissue-specific Cre recombinase. Also, we finally introduce some available links to the Web sites that provides detailed information about Cre mouse lines including their characterization.
Animals ; Humans ; Mice* ; Recombinases

Animal models, particularly pigs, have come to play an important role in translational biomedical research. There have been many pig models with genetically modifications via somatic cell nuclear transfer (SCNT). However, because most transgenic pigs have been produced by random integration to date, the necessity for more exact gene-mutated models using recombinase based conditional gene expression like mice has been raised. Currently, advanced genome-editing technologies enable us to generate specific gene-deleted and -inserted pig models. In the future, the development of pig models with gene editing technologies could be a valuable resource for biomedical research.
Animals ; Gene Expression ; Gene Transfer Techniques* ; Mice ; Models, Animal ; Recombinases ; Swine

Animals ; Biological Assay ; Nucleic Acid Amplification Techniques ; Phlebovirus/isolation & purification* ; Psychodidae/virology* ; Recombinases/metabolism* ; Reverse Transcription

Objective: To establish an ultra-sensitive, ultra-fast, visible detection method for Vibrio parahaemolyticus (VP) . Methods: We established a new method for detecting the tdh and trh genes of VP using clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 12a (CRISPR/Cas12a) combined with recombinase polymerase amplification and visual detection (CRISPR/Cas12a-VD). Results: CRISPR/Cas12a-VD accurately detected target DNA at concentrations as low as 10 ^-18 M (single molecule detection) within 30 min without cross-reactivity against other bacteria. When detecting pure cultures of VP, the consistency of results reached 100% compared with real-time PCR. The method accurately analysed pure cultures and spiked shrimp samples at concentrations as low as 10 ² CFU/g. Conclusion The novel CRISPR/Cas12a-VD method for detecting VP performed better than traditional detection methods, such as real-time PCR, and has great potential for preventing the spread of pathogens.
CRISPR-Cas Systems ; Nucleic Acid Amplification Techniques/methods* ; Recombinases/genetics* ; Vibrio parahaemolyticus/genetics*

Antimicrobial resistance has become a major public health issue of global concern. Conjugation is an important way for fast spreading drug-resistant plasmids, during which the type Ⅳ pili plays an important role. Type Ⅳ pili can adhere on the surfaces of host cell and other medium, facilitating formation of bacterial biofilms, bacterial aggregations and microcolonies, and is also a critical factor in liquid conjugation. PilV is an adhesin-type protein found on the tip of type Ⅳ pili encoded by plasmid R64, and can recognize the lipopolysaccharid (LPS) molecules that locate on bacterial membrane. The shufflon is a clustered inversion region that diversifies the PilV protein, which consequently affects the recipient recognition and conjugation frequency in liquid mating. The shufflon was firstly discovered on an IncI1 plasmid R64 and has been identified subsequently in plasmids IncI2, IncK and IncZ, as well as the pathogenicity island of Salmonella typhi. The shufflon consists of four segments including A, B, C, and D, and a specific recombination site named sfx. The shufflon is regulated by its downstream-located recombinase-encoding gene rci, and different rearrangements of the shufflon region in different plasmids were observed. Mobile colistin resistance gene mcr-1, which has attracted substantial attentions recently, is mainly located in IncI2 plasmid. The shufflon may be one of the contributors to fast spread of mcr-1. Herein, we reviewed the discovery, structure, function and prevalence of plasmid mediated shufflon, aiming to provide a theoretical basis on transmission mechanism and control strategy of drug-resistant plasmids.
Plasmids/genetics* ; Proteins/genetics* ; Bacteria/genetics* ; Recombinases ; Genes, Bacterial ; Anti-Bacterial Agents

OBJECTIVE: To evaluate the performance of recombinase-aided amplification (RAA) assay in detection of Clonorchis sinensis metacercariae in freshwater fish samples, so as to provide insights into standardization and field application of this assay. METHODS: Wild freshwater fish samples were collected in the rivers of administrative villages where C. sinensis-infected residents lived in Jiangyan District, Xinghua County and Taixing County of Taizhou City, Jiangsu Province from June to September 2022. Genomic DNA was extracted from six freshwater fish specimens (5 g each) containing 0, 1, 2, 4, 8 and 16 C. sinensis metacercariae for fluorescent RAA assay, and the diagnostic sensitivity was evaluated. Fluorescent RAA assay was performed with genomic DNA from C. sinensis, Metorchis orientalis, Haplorchis pumilio and Centrocestus formosanus metacercariae as templates to evaluate its cross-reactions. In addition, the detection of fluorescent RAA assay and direct compression method for C. sinensis metacercariae was compared in field-collected freshwater fish samples. RESULTS: Positive amplification was found in fresh-water fish specimens containing different numbers of C. sinensis metacercariae, and fluorescent RAA assay was effective to detect one C. sinensis metacercaria in 5 g freshwater fish specimens within 20 min. Fluorescent RAA assay tested negative for DNA from M. orientalis, H. pumilio and C. formosanus metacercariae. Fluorescent RAA assay and direct compression method showed 5.36% (93/1 735) and 2.88% (50/1 735) detection rates for C. sinensis metacercariae in 1 735 field-collected freshwater fish samples, with a statistically significant difference seen (χ² = 478.150, P < 0.001). There was a significant difference in the detection of C. sinensis metacercariae in different species of freshwater fish by both the direct compression method (χ² = 11.20, P < 0.05) and fluorescent RAA assay (χ² = 20.26, P < 0.001), and the detection of C. sinensis metacercariae was higher in Pseudorasbora parva than in other fish species by both the direct compression method and fluorescent RAA assay (both P values < 0.05). CONCLUSIONS Fluorescent RAA assay has a high sensitivity for detection of C. sinensis metacercariae in freshwater fish samples, and has no cross-reactions with M. orientalis, H. pumilio or C. formosanus metacercariae. Fluorescent RAA assay shows a higher accuracy for detection of C. sinensis infections in field-collected freshwater fish than the direct compression method.
Animals ; Clonorchis sinensis/genetics* ; Metacercariae/genetics* ; Recombinases ; Fresh Water ; Fishes ; DNA ; Fish Diseases/diagnosis*

This investigation is to delete the most of the coding sequence (1104 bp) of the IV a2 gene in an adenovirus genome by a lambda-Red recombinase system-mediated PCR-targeting approach and rescue a recombinant adenovirus with IV a2 deletion. First, the template pAK of PCR targeting, containing kanamycin cassette, was constructed. Then, a linear fragment for PCR targeting, which had 39 bp homologous arms at both of its terminus, was amplified by PCR from the pAK. The pFG140 and the linear fragment were electroporated into E. coli BW25113/pIJ790 sequentially and the recombinant pFG140-deltaIV a2 (1104) was established by homologous recombination between the linear fragment and the pFG140 with aid of X-Red recombinase. The precise deletion of 1 104 bp fragment from IV a2 was confirmed by restriction endonucleases digestion and DNA sequencing. ORF of IV a2 was amplified by PCR from pFG140 and then cloned into the pAAV2neo vector. The recombinant adenovirus Ad5delta IV a2 (1104) was rescued by co-transfection of pFG140-deltaIV a2 (1104) and pAAV2neo-IV a2 into HEK293 cells. It was shown by Western Blot that IV a2 could not be detected in the Ad5deltaIV a2 (1104)- infected HEK293 cells. This study established a PCR-targeting strategy for manipulating adenovirus genome directly by a lambda-Red recombinase system, and a recombinant adenovirus with IV a2 deletion was obtained.
Adenoviridae ; genetics ; Genome, Viral ; HEK293 Cells ; Humans ; Polymerase Chain Reaction ; Recombinases ; metabolism ; Sequence Deletion ; Viral Proteins ; genetics ; Virus Assembly

The aim of this study was to understand the roles of Sonic Hedgehog (SHH) signaling during tooth root and periodontium formation. In this study, we generated the dental mesenchyme-specific Smoothened (Smo) activated/inactivated mice with the activity of Cre recombinase under the control of osteocalcin promoter.In the Smo activated mutant molar sections at the postnatal 28 days, we found extremely thin root dentin and widened pulp chamber. Picrosirius red staining showed loosely arranged fibers in the periodontal space and decreased cellular cementum with some root resorption. Immunohistochemical staining showed less localization of matrix proteins such as Bsp, Dmp1, Pstn, and Ank in the cementum, periodontal ligament, and/or cementoblast.In the Smo inactivated mutant mouse, there was not any remarkable differences in the localization of these matrix proteins compared with the wild type. These findings suggest that adequate suppressing regulation of SHH signaling is required in the development of tooth root and periodontium.
Animals ; Dental Cementum ; Dental Pulp Cavity ; Dentin ; Hedgehogs ; Mice ; Molar ; Osteocalcin ; Periodontal Ligament ; Periodontium ; Recombinases ; Root Resorption ; Tooth Root ; Tooth

Adeno-associated virus (AAV)-mediated gene delivery has been proposed to be an essential tool of gene therapy for various brain diseases. Among several cell types in the brain, astrocyte has become a promising therapeutic target for brain diseases, as more and more contribution of astrocytes in pathophysiology has been revealed. Until now, genetically targeting astrocytes has been possible by utilizing the glial fibrillary acidic protein (GFAP) promoter. In some brain areas including thalamus, however, the GFAP expression in astrocytes is reported to be low, making it difficult to genetically target astrocytes using GFAP promoter. To study the function of astrocytes in thalamus, which serves as a relay station, there is a great need for identifying an alternative astrocyte-specific promoter in thalamus. Recently, a new astrocyte-specific promoter of ALDH1L1 has been identified. However, it has not been examined in thalamus. Here we developed and characterized an AAV vector expressing Cre recombinase under the human ALDH1L1 promoter, AAV-hALDH1L1-Cre. To test the cell-type specific expression of AAV-hALDH1L1-Cre, AAV virus was injected into several brain regions of Ai14 (RCL-tdTomato) mouse, which reports Cre activity by tdTomato expression. In thalamus, we observed that tdTomato was found mostly in astrocytes (91.71%), with minimal occurrence in neurons (2.67%). In contrast, tdTomato signal was observed in both neurons and astrocytes of the amygdala (neuron: 68.13%, astrocyte: 28.35%) and hippocampus (neuron: 76.25%, astrocyte: 18.00%), which is consistent with the previous report showing neuronal gene expression under rat ALDH1L1 promoter. Unexpectedly, tdTomato was found mostly in neurons (91.98%) with minimal occurrence in astrocytes (6.66%) of the medial prefrontal cortex. In conclusion, hALDH1L1 promoter shows astrocyte-specificity in thalamus and may prove to be useful for targeting thalamic astrocytes in mouse.
Amygdala ; Animals ; Astrocytes ; Brain ; Brain Diseases ; Dependovirus ; Gene Expression* ; Genetic Therapy ; Glial Fibrillary Acidic Protein ; Hippocampus ; Humans* ; Mice* ; Neurons ; Prefrontal Cortex ; Rats ; Recombinases ; Thalamus* ; Ventral Thalamic Nuclei