The Split-Cre system consists of two inactive polypeptides: NCre and CCre, which can be recombined into an active full-length Cre under certain conditions. This system is typically used with LoxP. To develop an efficient Split-Cre system, this study used Rma intein from Rhodothermus marinus to split Cre and screened out the split site S102 which could efficiently mediate the recombination of Cre in the "Traffic Light" reporter cell line. Moreover, the S102 Split-Cre system was delivered to mice by dual-adeno-associated virus (AAV), and it was demonstrated that the efficiency of the Rma intein-mediated S102 Split-Cre system was comparable to the full-length Cre in mice. This system lays a foundation for both basic and applied research on Split-Cre.
Inteins/genetics* ; Animals ; Integrases/biosynthesis* ; Mice ; Dependovirus/metabolism* ; Bacterial Proteins/genetics* ; Recombination, Genetic ; Humans

Very long chain polyunsaturated fatty acids (VLC-PUFAs) are unique fatty acids in tissues of mammals such as retina and testis, and the key enzyme of its biosynthesis is very long chain fatty acid elongase 4 (Elovl4). Development of an animal model of tissue-specific knockout of Elovl4 gene is conducive to the in-depth study of the biological function of VLC-PUFAs. Therefore, we constructed Stra8-Cre mice and Elovl4 floxed mice based on Cre/loxP system, and obtained the (Elovl4[flox/+], Stra8-Cre) heterozygous knockout mice by hybridization. Subsequently, female mice were selected to cross with male mice with homozygous Elovl4[flox/flox] to gain homozygous mice (Elovl4[flox/flox], Stra8-Cre) through genotype identification and screening. RT-PCR, qRT-PCR, Western blotting, immunohistochemistry and immunofluorescence techniques were used to detect the knock-out efficiency of Elovl4 in testis. The expression of Elovl4 in testis of both heterozygous and homozygous knockout mice were significantly down-regulated at mRNA and protein levels, but were not affected in other tissues. In summary, we constructed a mouse model with specific knockout of Elovl4 gene in testis, which provides a reliable animal model for studying the effect of VLC-PUFAs on the reproductive function of male mice and the underpinning molecular mechanisms.
Animals ; Disease Models, Animal ; Eye Proteins/metabolism* ; Female ; Gene Knockout Techniques ; Integrases ; Male ; Mammals/metabolism* ; Membrane Proteins/metabolism* ; Mice ; Mice, Knockout ; Testis/metabolism*

Gene expression labeling and conditional manipulation of gene function are important for elaborate dissection of gene function. However, contemporary generation of pairwise dual-function knockin alleles to achieve both conditional and geno-tagging effects with a single donor has not been reported. Here we first developed a strategy based on a flipping donor named FoRe to generate conditional knockout alleles coupled with fluorescent allele-labeling through NHEJ-mediated unidirectional targeted insertion in zebrafish facilitated by the CRISPR/Cas system. We demonstrated the feasibility of this strategy at sox10 and isl1 loci, and successfully achieved Cre-induced conditional knockout of target gene function and simultaneous switch of the fluorescent reporter, allowing generation of genetic mosaics for lineage tracing. We then improved the donor design enabling efficient one-step bidirectional knockin to generate paired positive and negative conditional alleles, both tagged with two different fluorescent reporters. By introducing Cre recombinase, these alleles could be used to achieve both conditional knockout and conditional gene restoration in parallel; furthermore, differential fluorescent labeling of the positive and negative alleles enables simple, early and efficient real-time discrimination of individual live embryos bearing different genotypes prior to the emergence of morphologically visible phenotypes. We named our improved donor as Bi-FoRe and demonstrated its feasibility at the sox10 locus. Furthermore, we eliminated the undesirable bacterial backbone in the donor using minicircle DNA technology. Our system could easily be expanded for other applications or to other organisms, and coupling fluorescent labeling of gene expression and conditional manipulation of gene function will provide unique opportunities to fully reveal the power of emerging single-cell sequencing technologies.
Alleles ; Animals ; CRISPR-Cas Systems ; DNA End-Joining Repair ; DNA, Circular/metabolism* ; Embryo, Nonmammalian ; Gene Editing/methods* ; Gene Knock-In Techniques ; Gene Knockout Techniques ; Genes, Reporter ; Genetic Loci ; Genotyping Techniques ; Green Fluorescent Proteins/metabolism* ; Integrases/metabolism* ; Luminescent Proteins/metabolism* ; Mutagenesis, Insertional ; Single-Cell Analysis ; Zebrafish/metabolism*

Animals ; Autophagy/genetics* ; Cholesterol/metabolism* ; Gene Expression Regulation ; Integrases/metabolism* ; Leydig Cells/metabolism* ; Male ; Mice, Knockout ; Multienzyme Complexes/metabolism* ; Phosphoproteins/metabolism* ; Primary Cell Culture ; Progesterone Reductase/metabolism* ; RNA Splicing Factors/metabolism* ; Scavenger Receptors, Class B/metabolism* ; Sequestosome-1 Protein/metabolism* ; Signal Transduction ; Sirtuin 1/genetics* ; Sodium-Hydrogen Exchangers/metabolism* ; Steroid 17-alpha-Hydroxylase/metabolism* ; Steroid Isomerases/metabolism* ; Testosterone/genetics*

The adrenal gland is an important endocrine organ of human body. CYP11B1 gene was specifically expressed in the zona fasciculata in adrenal cortex. In order to better study the function of genes specifically expressed in the zona fasciculata in adrenal cortex, the mice with Cre recombinase specifically expressed in the zona fasciculata in adrenal cortex were constructed. It was then confirmed that CYP11B1 was specifically expressed in adrenal glands. Then, using CRISPR/Cas9 technique, CYP11B1-2A-GfpCre recombinant vector was constructed and subsequently injected into the fertilized eggs of mice. It was confirmed that the Cre gene was mainly expressed in the zona fasciculata in adrenal cortex of CYP11B1Cre mice by using mTmG and LacZ staining. The CYP11B1Cre mice were then mated with cystathionine γ-lyase (CTH) mice, thereby generating CTH/CYP11B1Cre mice. It was also confirmed that CTH gene in the zona fasciculata in adrenal cortex was specifically knocked out in these mice. These results suggest that transgenic mice with specific Cre recombinase expression in the zona fasciculata in adrenal cortex were constructed successfully. This animal model can be a powerful tool for the study of the function of genes expressed in the zona fasciculata in adrenal cortex.
Adrenal Cortex ; enzymology ; Animals ; CRISPR-Cas Systems ; Cystathionine gamma-Lyase ; genetics ; Integrases ; genetics ; metabolism ; Mice ; Mice, Transgenic ; Zona Fasciculata ; enzymology

Cre-lox recombination system consists of two elements: Cre recombinase enzyme and lox sites. Cre recombinase can recombine the lox site sequences by specifically detecting and cutting them. The direction and position of lox sites determine the functional effects of Cre enzyme such as deletion, inversion or chromosomal translocation. The hematopoietic system of mouse consists of multi-lineages and various developmental stage hematopoietic cells that are differentiated from hematopoietic stem cells (hematopoietic stem cells, HSC). The hematopoietic stem cells are maintained in the bone marrow microenvironment (niche). Currently, a variety of floxed conditional-knockout mice, recognized by Cre-lox recombination system, are used for the study of the hematopoietic system. This review summarizes the commonly used Cre transgenic mice and their applications in the study of hematopoietic system.
Animals ; Hematopoietic Stem Cells ; cytology ; metabolism ; Integrases ; Mice ; Mice, Transgenic

In producing transgenic livestock, selectable marker genes (SMGs) are usually used to screen transgenic cells from numerous normal cells. That results in SMGs integrating into the genome and transmitting to offspring. In fact, SMGs could dramatically affect gene regulation at integration sites and also make the safety evaluation of transgenic animals complicated. In order to determine the deletion time and methods in the process of producing transgenic goats, the feasibility of deleting SMGs was explored by Cre/LoxP before or after somatic cell cloning. In addition, we compared the efficiency of protein transduction with plasmids co-transduction. We could delete 43.9% SMGs after screening out the transgenic cell clones, but these cells could not be applied to somatic cells cloning because of serious aging after two gene modifications. The SMG-free cells suitable for nuclear transfer were accessible by using the cells of transgenic goats, but this approach was more time consuming. Finally, we found that the Cre plasmid could delete SMGs with an efficiency of 7.81%, but about 30% in SMG-free cells had sequences of Cre plasmid. Compared with Cre plasmid, the integration of new exogenous gene could be avoided by TAT-CRE protein transduction, and the deletion rate of TAT-CRE transduction was between 43.9 and 72.8%. Therefore, TAT-Cre transduction could be an effective method for deleting selectable marker genes.
Animals ; Animals, Genetically Modified ; genetics ; Cloning, Organism ; veterinary ; Gene Knockout Techniques ; Gene Targeting ; methods ; Genes, Reporter ; Genetic Engineering ; Genetic Vectors ; genetics ; Goats ; genetics ; Integrases ; chemistry ; metabolism ; Recombination, Genetic ; Transgenes ; genetics

To prepare large naive phage antibody library, the host bacteria with high transformation efficiency is used in the Cre-LoxP recombination system. The variable regions of immunoglobulin light and heavy genes were amplified from lymphocytes collected from adult peripheral blood and newborn cord blood. The genes were spliced to form the single-chain variable fragments (scFv) by overlap PCR, cloned into pDAN5a vector and then transformed into XL2-blue MRF' with the Hte gene. Compared with XL1-blue strain, the size of the primary library was increased by 3.9 times. The primary library infected Cre recombinase-expressing bacteria, and the genes between phagemids created many new VH/VL combinations. The library was calculated to have a diversity of 1.7 x 10(11) and validated by the selection of antibodies against six different protein antigens. This library provides the basis for further selection of antibody-based drugs. It is the first time to report that XL2-blue MRF' can be used to improve the diversity of the library in the recombination system.
Adult ; Escherichia coli ; genetics ; immunology ; Genetic Vectors ; Humans ; Immunoglobulin Heavy Chains ; genetics ; Immunoglobulin Light Chains ; genetics ; Immunoglobulin Variable Region ; genetics ; Infant, Newborn ; Integrases ; metabolism ; Lymphocytes ; immunology ; Peptide Library ; Recombination, Genetic ; genetics ; Single-Chain Antibodies ; genetics ; metabolism ; Transformation, Genetic

The establishment of a polarized cellular morphology is essential for a variety of processes including neural tube morphogenesis and the development of the brain. Cdc42 is a Ras-related GTPase that plays an essential role in controlling cell polarity through the regulation of the actin and microtubule cytoskeleton architecture. Previous studies have shown that Cdc42 plays an indispensable role in telencephalon development in earlier embryo developmental stage (before E12.5). However, the functions of Cdc42 in other parts of brain in later embryo developmental stage or in adult brain remain unclear. Thus, in order to address the role of Cdc42 in the whole brain in later embryo developmental stage or in adulthood, we used Cre/loxP technology to generate two lines of tissue-specific Cdc42-knock-out mice. Inactivation of Cdc42 was achieved in neuroepithelial cells by crossing Cdc42/ flox mice with Nestin-Cre mice and resulted in hydrocephalus, causing death to occur within the postnatal stage. Histological analyses of the brains from these mice showed that ependymal cell differentiation was disrupted, resulting in aqueductal stenosis. Deletion of Cdc42 in the cerebral cortex also induced obvious defects in interkinetic nuclear migration and hypoplasia. To further explore the role of Cdc42 in adult mice brain, we examined the effects of knocking-out Cdc42 in radial glial cells by crossing Cdc42/flox mice with human glial fibrillary acidic protein (GFAP)-Cre mice. Inactivation of Cdc42 in radial glial cells resulted in hydrocephalus and ependymal cell denudation. Taken together, these results highlight the importance of Cdc42 for ependymal cell differentiation and maintaining, and suggest that these functions likely contribute to the essential roles played by Cdc42 in the development of the brain.
Animals ; Brain ; metabolism ; pathology ; Cell Differentiation ; Cell Polarity ; Cerebral Cortex ; cytology ; metabolism ; Constriction, Pathologic ; Embryo, Mammalian ; metabolism ; Embryonic Development ; Ependyma ; cytology ; metabolism ; Glial Fibrillary Acidic Protein ; genetics ; metabolism ; Humans ; Hydrocephalus ; metabolism ; pathology ; Integrases ; genetics ; metabolism ; Mice ; Mice, Knockout ; cdc42 GTP-Binding Protein ; genetics ; metabolism

Integrase plays a critical role in the recombination of viral DNA into the host genome. Therefore, over the past decade, it has been a hot target of drug design in the fight against type 1 human immunodeficiency virus (HIV-1). Bovine immunodeficiency virus (BIV) integrase has the same function as HIV-1 integrase. We have determined crystal structures of the BIV integrase catalytic core domain (CCD) in two different crystal forms at a resolution of 2.45 Å and 2.2 Å, respectively. In crystal form I, BIV integrase CCD forms a back-to-back dimer, in which the two active sites are on opposite sides. This has also been seen in many of the CCD structures of HIV-1 integrase that were determined previously. However, in crystal form II, BIV integrase CCD forms a novel face-to-face dimer in which the two active sites are close to each other. Strikingly, the distance separating the two active sites is approximately 20 Å, a distance that perfectly matches a 5-base pair interval. Based on these data, we propose a model for the interaction of integrase with its target DNA, which is also supported by many published biochemical data. Our results provide important clues for designing new inhibitors against HIV-1.
Animals ; Catalytic Domain ; genetics ; Cattle ; DNA ; genetics ; DNA, Viral ; HIV-1 ; genetics ; metabolism ; Humans ; Immunodeficiency Virus, Bovine ; enzymology ; genetics ; Integrases ; chemistry ; genetics ; metabolism