Jian Zhou1,2,13, Claudia Cattoglio3,4,13, Yingyao Shao1,2,5,13, Harini P. Tirumala1,2, Carlo Vetralla3,4,6, Sameer S. Bajikar1,2, Yan Li1,2, Hu Chen2,7, Qi Wang2,7, Zhenyu Wu2,7, Bing Tang2,7, Mahla Zahabiyon1,2, Aleksandar Bajic1,2, Xiangling Meng2,8, Jack J. Ferrie3,4, Anel LaGrone9, Ping Zhang8, Jean J. Kim9,10, Jianrong Tang2,7, Zhandong Liu2,7, Xavier Darzacq3, Nathaniel Heintz11, Robert Tjian3,4 and Huda Y. Zoghbi1,2,5,7,8,12 1Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA; 2Jan and Dan Duncan Neurological Research Institute at Texas Children's Hospital, Houston, Texas 77030, USA; 3Department of Molecular and Cell Biology, Li Ka Shing Center for Biomedical and Health Sciences, California Institute for Regenerative Medicine (CIRM) Center of Excellence, University of California, Berkeley, Berkeley, California 94720, USA; 4Howard Hughes Medical Institute, Berkeley, California 94720, USA; 5Program in Developmental Biology, Baylor College of Medicine, Houston, Texas 77030, USA; 6School of Medicine and Surgery, University of Milan-Bicocca, Milano 20126, Italy; 7Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030, USA; 8Department of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA; 9Advanced Technology Cores, Baylor College of Medicine, Houston, Texas 77030, USA; 10Department of Molecular and Cellular Biology, Stem Cells and Regenerative Medicine Center, Baylor College of Medicine, Houston, Texas 77030, USA; 11Laboratory of Molecular Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10065, USA; 12Howard Hughes Medical Institute, Baylor College of Medicine, Houston, Texas 77030, USA Corresponding authors: hzoghbibcm.edu, jmlimberkeley.edu

↵13 These authors contributed equally to this work.

Abstract

Loss-of-function mutations in MECP2 cause Rett syndrome (RTT), a severe neurological disorder that mainly affects girls. Mutations in MECP2 do occur in males occasionally and typically cause severe encephalopathy and premature lethality. Recently, we identified a missense mutation (c.353G>A, p.Gly118Glu [G118E]), which has never been seen before in MECP2, in a young boy who suffered from progressive motor dysfunction and developmental delay. To determine whether this variant caused the clinical symptoms and study its functional consequences, we established two disease models, including human neurons from patient-derived iPSCs and a knock-in mouse line. G118E mutation partially reduces MeCP2 abundance and its DNA binding, and G118E mice manifest RTT-like symptoms seen in the patient, affirming the pathogenicity of this mutation. Using live-cell and single-molecule imaging, we found that G118E mutation alters MeCP2's chromatin interaction properties in live neurons independently of its effect on protein levels. Here we report the generation and characterization of RTT models of a male hypomorphic variant and reveal new insight into the mechanism by which this pathological mutation affects MeCP2's chromatin dynamics. Our ability to quantify protein dynamics in disease models lays the foundation for harnessing high-resolution single-molecule imaging as the next frontier for developing innovative therapies for RTT and other diseases.

Received April 20, 2023. Accepted October 5, 2023.