The Cre-loxP system and its derivative systems: methodology research and applications in neuroscience / 药学学报

In scientific research, it is often needed to knock in, knock out, knock down, or overexpress a specific gene in model organisms or specific types of cells to achieve precise regulation of experimental independent variables. In this case, various transgenic mice are required. The cyclization recombinase (Cre) can directly interact with different loxP (locus X over P1) DNA sequences without any cofactors to perform specific gene knock-in or knock-out at specific targets. Because of its advantages of simple action principles, high spatial specificity, and high reorganization efficiency, the Cre-loxP system is widely used in scientific research. Furthermore, the CreERT2 system (mutant of the fusion protein of Cre and estrogen receptor ligand binding domain) and the tetracycline (Tet)-on/off system, derived from the Cre-loxP system, have made the recombination of the target gene occur in temporal-specificity on the basis of spatial-specificity. This dual specificity of time and space is indispensable for research in specific directions such as fear memory and engram cells on the basis of reducing the impacts on experimental animals. Therefore, these derived systems have broad application prospects.

Construction, Expression and Internalization Study of Human Anti-HBsAg Single Chain Antibody/EGFP Fusion Proteins Containing Arg9 / 中国生物工程杂志

Objective: To construct, express and purify ScFvl4/EGFP fusion proteins which containing Arg9, and to study their binding activities and internalization functions. Methods: Arg9 gene was recombined into 5' terminal, 3' terminal of ScFv/EGFP gene and between them respectively before they were cloned into the expression vector pET32a. After induced in E. coli BL21 and purified, their binding activities and internalization were respectively analyzed by indirect ELISA and indirect immunofluorescence analysis. Results: DNA sequencing and restriction endonuclease digestion proved that the four fusion genes were correctly constructed. SDS-PAGE analysis and Western blot showed that they were successfully expressed and purified. Indirect ELISA confirmed that the expressed products had antigen specific binding activities. Indirect immunofluorescence analysis revealed the fusion protein containing Arg9 at its N terminal had much better internalization function, but never internalized into the cells which do not express HBsAg. Conclusion: The four fusion genes were constructed, expressed and purified successfully. The purified fusion proteins maintained the binding activities to HBsAg and the fusion protein containing Arg9 at its N terminal had much better internalization effect.

Prevalence of major external birth defects in high and low risk areas in China, 2003 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To study the prevalence rates of birth defects in high and low risk areas in China.</p><p><b>METHODS</b>A population-based surveillance system on birth defects was used to obtain the prevalence rates of 24 kinds of major external birth defects from > or = 20 weeks of gestation to 7 days of life in selected areas in Shanxi and Jiangsu provinces.</p><p><b>RESULTS</b>The birth prevalence of birth defects (232.4 per 10,000 births) and neural tube defects (NTDs) (138.7 per 10,000 births) in four counties of Shanxi province were significantly higher than that in Taiyuan city (75.3 and 28.2 per 10,000 births, respectively). There was no significant difference for all selected birth defects between Wuxi city and Xishan counties in low risk areas. There was a 6.1-fold of higher prevalence for NTDs in Taiyuan city compared with that in Wuxi areas (4.6 per 10,000 births). In four counties of Shanxi province, the prevalence rates of anencephaly, spina bifida, hydrocephaly, cleft palate alone and polydactyly were significantly higher than in Wuxi areas. The NTDs prevalence rate in four counties of Shanxi was 30.2 times higher than in Wuxi areas. When compared with previous surveillance data, the NTDs prevalence rate did not present obvious declining trend in high risk areas. The birth prevalence rate had a 31.8% decrease when births were calculated after 28 gestational weeks and compared with those from 20 gestational weeks.</p><p><b>CONCLUSION</b>NTDs remained to be the most common birth defect seen in Shanxi province. The birth prevalence rate of NTDs in some areas of Shanxi province was among the highest that ever reported in the world in comparison with data from other countries and regions. The current prevalence rate in high risk areas in Shanxi province did not clearly show a declining trend. Programs on surveillance and prenatal diagnosis were proved to have made big impact on the rates of major external birth defects.</p>