Bi-FoRe: an efficient bidirectional knockin strategy to generate pairwise conditional alleles with fluorescent indicators

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.

New insights of growth hormone (GH) actions from tissue-specific GH receptor knockouts in mice

ABSTRACT In order to provide new insights into the various activities of GH in specific tissues, recent advances have allowed for the generation of tissue-specific GHR knockout mice. To date, 21 distinct tissue-specific mouse lines have been created and reported in 28 publications. Targeted tissues include liver, muscle, fat, brain, bone, heart, intestine, macrophage, pancreatic beta cells, hematopoietic stem cells, and multi-tissue "global". In this review, we provide a brief history and description of the 21 tissue-specific GHR knockout mouse lines. Arch Endocrinol Metab. 2019;63(6):557-67

Establishment and Phenotype Analysis of SHBG Knockout Mouse Model / 中国生物工程杂志

Objective:To generate sex hormone binding globulin(SHBG) conditional knockout mice model.In order to investigate the physiological function of SHBG in vivo and to provide experimental means for the study of the relationship between SHBG and gestational diabetes mellitus.Methods:The mouse genomic DNA sequence of SHBG was verified through bioinformatic analysis.According to the SHBG genomic DNA sequence,the gene targeting and knockout vector were constructed.Transfection of the vectors to ES cells by electroporation was performed according to common protocol.Positive ES cells were screened and identified by PCR.Therefore,the dual selected ES cells were microinjected into blastula,then blastula transplantations into the host mice.The chimeric mice were mated with C57BL/6J mice,and the Flox mice were obtained after screening.The Flox mice were hybridized with EIIA-Cre transgenic mice,and the progeny of the SHBG gene knockout (SHBG-/-) mice were obtained by autocopuation for several times.Results:Several Flox homozygous mice and SHBG gene knockout mice were successfully obtained.Compared with control mice,homozygous mice of SHBG gene knockout were well developed and had reproductive ability.The growth and development of SHBG knockout mice were not significantly different from that of wild type mice.Conclusion:Homozygous mice model of SHBG gene knockout was successfully established,which laid the foundation for further study of the role of SHBG in the gestational diabetes.The SHBG gene knockout mouse model was successfully established and the preliminary phenotypic analysis was performed,which laid the foundation for further study on the role of SHBG in gestational diabetes mellitus.SHBG gene knockout mice were normal in appearance.Due to the limited number of samples and many unknown biological characteristics of gene knockout mice,it needs further study.

Construction of Targeting Vector for Conditional Knockout of Murine Shbg / 中国医科大学学报

Objective To construct the targeting vector for conditional gene knockout of sex hormone?binding globulin(Shbg)in mice. Methods Based on Red/ET,two LoxP were inserted into both sides of extron 4 and extron 7 for conditional gene knockout of murine Shbg. Firstly,the Shbg gene and its upstream,downstream genes obtained from BAC DNA by PCR were cloned into plasmid pBR322?MK,which was named pBR322?MK?AB. The retrieve plasmid(pBR322?Shbg?Re)was obtained by homologous recombination between the plasmid and BAC.Then a great quantity of Neo fragments obtained from PL452 and PL451 were inserted into the targeting vector after another round of Red/ET and then the final targeting vec?tor(pBR322?MK?SHBG?cko)was achieved. Results The correct structures of the targeting vectors such as pBR322?MK?AB,pBR322?Shbg?Re, SHBG?Ln and pBR322?MK?Shbg?cko were confirmed by restriction enzyme digestion and sequencing analysis. Conclusion The targeting vector for conditional knockout of murine SHBG was successfully constructed. The construction of targeting vector paved the way for conditional knockout mouse strain generated by targeted mutation of Shbg.

Conditional knockout of brca1/2 and p53 in mouse ovarian surface epithelium: Do they play a role in ovarian carcinogenesis?

Alterations of genes are known to be critical for the induction of tumorigenesis, but the mechanism of ovarian carcinogenesis is little understood and remains to be elucidated. In this study, we investigated the roles of brca1, brca2 and p53 genes in the development of ovarian cancer using conditional knockout mice generated by a Cre-loxP recombinant system. Following the application of recombinant adenovirus expressing Cre in vitro, the proliferation of ovarian surface epithelium (OSE) was increased. For instance, a significant increase in cell growth was observed in OSE cells in vitro by conditional knockout isolated from the mice bearing concurrent floxed copies of brca1 and brca2/p53. However, the proliferative effect of the ovarian cells was not observed in concurrent brca1/brca2 or p53 knockout mice in vivo, indicating that we could not observe the direct evidence of the involvement of brca1, brca2, and p53 in ovarian carcinogenesis. Since morphological changes including tumor formation were not observed in mice bearing floxed copies of concurrent brca1/brca2 or p53, the inactivation of brca1/2 or p53 is not sufficient for the induction of tumor formation. Taken together, these results suggest that the deficiency of these genes may not be involved directly in the mechanism of ovarian carcinogenesis.