Ggta1, encoding α1,3-galactosyltransferase, is crucial for the biosynthesis of galactosyl-alpha 1,3-galactose. This carbohydrate epitope, known as the α-Gal antigen, is the primary xenoantigen recognized by the human immune system, thus playing a significant role in xenotransplantation-related immune responses [1,2,3,4,5,6,7,8,9].

Genetic knockout of Ggta1 in various animal models has been extensively studied. In rabbits, CRISPR/Cas9-mediated Ggta1 gene disruption led to a high mutation efficiency (92.3% in F0 pups), with α-Gal antigen expression in major organs decreased by over 99.96% compared to wild-type rabbits. Specific anti-Gal IgG and IgM antibody levels in F1 rabbits increased with age [1]. In pigs, Ggta1-KO pigs showed removal of α-Gal-terminating N-glycans, along with changes in other glycan levels [2]. Generation of Ggta1-modified pigs via electroporation of the CRISPR/Cas9 system into in vitro-fertilized zygotes was efficient, and biallelic mutant piglets had deficient Ggta1 function [6]. Additionally, Ggta1/iGb3S double-knockout mice were sensitive to Gal antigen-positive xenogeneic grafts, useful for evaluating α-Gal-mediated immunogenic risk [7].

In conclusion, Ggta1 is essential in the synthesis of a major xenoantigen. Gene-knockout models in animals, especially in rabbits, pigs, and mice, have revealed its role in xenotransplant-related immunogenicity. These models contribute significantly to understanding the mechanisms of xenograft rejection and developing strategies to improve the success of xenotransplantation [1,2,6,7].

References:

1. Wei, Lina, Mu, Yufeng, Deng, Jichao, Qu, Shuxin, Xu, Liming. 2022. α-Gal antigen-deficient rabbits with GGTA1 gene disruption via CRISPR/Cas9. In BMC genomic data, 23, 54. doi:10.1186/s12863-022-01068-4. https://pubmed.ncbi.nlm.nih.gov/35820824/

2. Morticelli, Lucrezia, Rossdam, Charlotte, Cajic, Samanta, Buettner, Falk F R, Hilfiker, Andres. 2023. Genetic knockout of porcine GGTA1 or CMAH/GGTA1 is associated with the emergence of neo-glycans. In Xenotransplantation, 30, e12804. doi:10.1111/xen.12804. https://pubmed.ncbi.nlm.nih.gov/37148126/

3. Ko, Nayoung, Shim, Joohyun, Kim, Hyoung-Joo, Kim, Hyunil, Choi, Kimyung. 2022. A desirable transgenic strategy using GGTA1 endogenous promoter-mediated knock-in for xenotransplantation model. In Scientific reports, 12, 9611. doi:10.1038/s41598-022-13536-z. https://pubmed.ncbi.nlm.nih.gov/35688851/

4. Shim, Joohyun, Ko, Nayoung, Kim, Hyoung-Joo, Kim, Hyunil, Choi, Kimyung. 2021. Human immune reactivity of GGTA1/CMAH/A3GALT2 triple knockout Yucatan miniature pigs. In Transgenic research, 30, 619-634. doi:10.1007/s11248-021-00271-w. https://pubmed.ncbi.nlm.nih.gov/34232440/

5. Wang, Yi, Chen, Gang, Pan, Dengke, Zhang, Kang, Chen, Zhonghua K. 2024. Pig-to-human kidney xenotransplants using genetically modified minipigs. In Cell reports. Medicine, 5, 101744. doi:10.1016/j.xcrm.2024.101744. https://pubmed.ncbi.nlm.nih.gov/39317190/

6. Tanihara, Fuminori, Hirata, Maki, Nguyen, Nhien Thi, Doi, Masako, Otoi, Takeshige. 2020. Efficient generation of GGTA1-deficient pigs by electroporation of the CRISPR/Cas9 system into in vitro-fertilized zygotes. In BMC biotechnology, 20, 40. doi:10.1186/s12896-020-00638-7. https://pubmed.ncbi.nlm.nih.gov/32811500/

7. Shao, Anliang, Ling, You, Chen, Liang, Xu, Liming, Wang, Chengbin. 2020. GGTA1/iGb3S Double Knockout Mice: Immunological Properties and Immunogenicity Response to Xenogeneic Bone Matrix. In BioMed research international, 2020, 9680474. doi:10.1155/2020/9680474. https://pubmed.ncbi.nlm.nih.gov/32596401/

8. Fu, Rui, Fang, Minghui, Xu, Kai, Zhou, Qi, Hu, Zheng. . Generation of GGTA1-/-β2M-/-CIITA-/- Pigs Using CRISPR/Cas9 Technology to Alleviate Xenogeneic Immune Reactions. In Transplantation, 104, 1566-1573. doi:10.1097/TP.0000000000003205. https://pubmed.ncbi.nlm.nih.gov/32732833/

9. Burlak, Christopher, Taylor, R Travis, Wang, Zheng Yu, Tector, A Joseph. 2020. Human anti-α-fucose antibodies are xenoreactive toward GGTA1/CMAH knockout pigs. In Xenotransplantation, 27, e12629. doi:10.1111/xen.12629. https://pubmed.ncbi.nlm.nih.gov/32697003/