Base editors: development and applications in biomedicine / 医学前沿

Base editor (BE) is a gene-editing tool developed by combining the CRISPR/Cas system with an individual deaminase, enabling precise single-base substitution in DNA or RNA without generating a DNA double-strand break (DSB) or requiring donor DNA templates in living cells. Base editors offer more precise and secure genome-editing effects than other conventional artificial nuclease systems, such as CRISPR/Cas9, as the DSB induced by Cas9 will cause severe damage to the genome. Thus, base editors have important applications in the field of biomedicine, including gene function investigation, directed protein evolution, genetic lineage tracing, disease modeling, and gene therapy. Since the development of the two main base editors, cytosine base editors (CBEs) and adenine base editors (ABEs), scientists have developed more than 100 optimized base editors with improved editing efficiency, precision, specificity, targeting scope, and capacity to be delivered in vivo, greatly enhancing their application potential in biomedicine. Here, we review the recent development of base editors, summarize their applications in the biomedical field, and discuss future perspectives and challenges for therapeutic applications.

Generation of genetic modified pigs devoid of GGTA1 and expressing the human leukocyte antigen-G5 / 生物工程学报

Pigs are considered as ideal donors for xenotransplantation because they have many physiological and anatomical characteristics similar to human beings. However, antibody-mediated immunity, which includes both natural and induced antibody responses, is a major challenge for the success of pig-to-primate xenotransplantation. Various genetic modification methods help to tailor pigs to be appropriate donors for xenotransplantation. In this study, we applied transcription activator-like effector nuclease (TALEN) to knock out the porcine α-1, 3-galactosyltransferase gene GGTA1, which encodes Gal epitopes that induce hyperacute immune rejection in pig-to-human xenotransplantation. Meanwhile, human leukocyte antigen-G5 gene HLA-G5, which acts as an immunosuppressive factor, was co-transfected with TALEN into porcine fetal fibroblasts. The cell colonies of GGTA1 biallelic knockout with positive transgene for HLA-G5 were chosen as nuclear donors to generate genetic modified piglets through a single round of somatic cell nuclear transfer. As a result, we successfully obtained 20 modified piglets that were positive for GGTA1 knockout (GTKO) and half of them expressed the HLA-G5 protein. Gal epitopes on the cell membrane of GTKO/HLA-G5 piglets were completely absent. Western blotting and immunofluorescence showed that HLA-G5 was expressed in the modified piglets. Functionally, the fibroblasts from the GTKO/HLA-G5 piglets showed enhanced resistance to complement-mediated lysis ability compared with those from GTKO-only or wild-type pigs. These results indicate that the GTKO/HLA-G5 pigs could be a valuable donor model to facilitate laboratory studies and clinics for xenotransplantation.

Establishment and application of genetically modified pig tool models / 中国实验动物学报

Genetically modified tool animal models are the animal models,which are generated by modifying a defined gene and can be used as a tool to help realize other objective.Genetically modified large animals have wide applications in agriculture and biomedicine.Tool animal models play important role in biological research and development of new drugs in biomedicine,especially,have made tremendous contribution in revealing gene function and pathway of signal transduction.Pigs are not only an economically important agriculture animals,but also an ideal animal model in biomedicine due to its close similarity to human in physiology,as well as organ structure and size.Thanks to the breakthrough of newly emerged gene editing technology,striking progress has made in establishment of genetically modified tool pig models which include the ones used for monitoring pluripotency of cells,tracing cell lineages,replacing genes mediated by Cre recombinase,mimicking immunodeficiency,as well as gene editing in vivo.These tool models have been widely applied in biological research.Here,we will review the progress in generation of genetically modified tool pig models and their applications.

Brief report of series study on Rongshui miniature pig as laboratory animal / 中国比较医学杂志

The provenances of Rongshui miniature pigs ( RMPs) were purchased from Rongshui, Guangxi, in 2012.130 RMPs were transported to Sanshui, Guangdong,China, which were breed according to the laboratory animal standards.83 RMPs were selected randomly from the first filial generations ( F1 ).The basic data were collected including breed characteristics, reproductive performance, grow curve, hematology, biochemical markers of serum and urine, organ coefficient, Chromosome analysis.According to the national and local standards, the quality control standards of RMP were set up including microbiological, parasitic, environment and facilities, fodder, pathology, genetic.The results showed that RMPs adapt to the climate of Guangdong.The natural mating and conceive rate was 88.3% with the pregnancy of 112 days.The average number of firstborn and still-born was 6.1 and 7.9 respectively.RMP was small body size with the adult body weight of 17.21 ±5.20 kg and 16.35 ±5.23 kg in female and male respectively.RMP was very tame.The mitochondrial genome analysis suggested RMP belonged a typical miniature pig breed in China, which is ancient than Lanyu pig.RMP could be breed as a new kind of laboratory animal.