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Tzeng CP, Whitwam T, Boxer LD, Li E, Silberfeld A, Trowbridge S, Mei K, Lin C, Shamah R, Griffith EC, Renthal W, Chen C, Greenberg ME. Activity-induced MeCP2 phosphorylation regulates retinogeniculate synapse refinement. Proc Natl Acad Sci U S A 2023; 120:e2310344120. [PMID: 37871205 PMCID: PMC10623012 DOI: 10.1073/pnas.2310344120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 09/25/2023] [Indexed: 10/25/2023] Open
Abstract
Mutations in MECP2 give rise to Rett syndrome (RTT), an X-linked neurodevelopmental disorder that results in broad cognitive impairments in females. While the exact etiology of RTT symptoms remains unknown, one possible explanation for its clinical presentation is that loss of MECP2 causes miswiring of neural circuits due to defects in the brain's capacity to respond to changes in neuronal activity and sensory experience. Here, we show that MeCP2 is phosphorylated at four residues in the mouse brain (S86, S274, T308, and S421) in response to neuronal activity, and we generate a quadruple knock-in (QKI) mouse line in which all four activity-dependent sites are mutated to alanines to prevent phosphorylation. QKI mice do not display overt RTT phenotypes or detectable gene expression changes in two brain regions. However, electrophysiological recordings from the retinogeniculate synapse of QKI mice reveal that while synapse elimination is initially normal at P14, it is significantly compromised at P20. Notably, this phenotype is distinct from the synapse refinement defect previously reported for Mecp2 null mice, where synapses initially refine but then regress after the third postnatal week. We thus propose a model in which activity-induced phosphorylation of MeCP2 is critical for the proper timing of retinogeniculate synapse maturation specifically during the early postnatal period.
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Affiliation(s)
| | - Tess Whitwam
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
- Program in Neuroscience, Harvard Medical School, Boston, MA02115
| | - Lisa D. Boxer
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Emmy Li
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | | | - Sara Trowbridge
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Kevin Mei
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Cindy Lin
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Rebecca Shamah
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Eric C. Griffith
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - William Renthal
- Department of Neurobiology, Harvard Medical School, Boston, MA02115
| | - Chinfei Chen
- Department of Neurology, F.M. Kirby Neurobiology Center, Children’s Hospital, Boston, MA02115
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