Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 52 4 2023 04 08 703 712 EN Rong Zhang 1. Department of Gynecology and Obstetrics, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, China 2. State Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou, 215123, China Huifen Xu Department of Pharmacy, Children’s Hospital, Zhejiang University School of Medicine, Hangzhou, 310057, China Jin Lu Department of Gynecology and Obstetrics, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, China Ying Chen Department of Gynecology and Obstetrics, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, China Yahui Zhang Department of Gynecology and Obstetrics, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, China Li Xiao 1. Department of Gynecology and Obstetrics, the Second Affiliated Hospital of Soochow University, Suzhou, 215004, China 2. State Key Laboratory of Radiation Medicine and Protection, Soochow University, Suzhou, 215123, China 2022 09 07 2023 01 24 Background: Fragile X syndrome (FXS) is a genetic disease with intellectual disabilities. FXS is often caused by the CGG-repeat expansion mutation in the FMR1 gene with suppressed FMR1 transcription and decreased protein levels in the brain of the patients. The RNA-guided CRISPR/Cas9 system is a promising targeted genomic editing tool in gene therapy of FXS. In order to evaluate its feasibility, the present study used CRISPR/Cas9 system to target the FMR1 5’-UTR sites in cultured human neuroblastoma cells. Methods: PCR and DNA clone were used to construct plasmids. CRISPR function was tested by Western blot and flow cytometry. Data were analyzed by a two-tailed unpaired Student’s t-test using GraphPad software. This research was conducted from 2020 to 2022 in the Second Affiliated Hospital of Soochow University, Suzhou, China. Results: Cell cycle analysis showed significant differences in G1, S and G2/M phases between the two groups (P<0.05). In the knockout cells, apoptosis was accelerated (P<0.05) with a significantly down-regulated (P<0.05) expression of FMRP as compared with the control group. Conclusion: This study provides further understanding about the FMRP function and molecular mechanism of FMR1 gene in nerve cells, and suggests the feasibility of gene therapy in FXS by CRISPR/Cas9 gene editing system.   https://ijph.tums.ac.ir/index.php/ijph/article/view/29740 https://ijph.tums.ac.ir/index.php/ijph/article/download/29740/7901