MECP2 mutations rewire human ESC fate and bias cortical lineage commitment.
Marion Guillon, Margaux Brin, Elodie Gabet, Justine Gromaire, Mathéa Bernard, Laetitia Laurent, Théo Rabin, Lisa Bianchin, Marie Veziano, Julie Kloda, Alexia Bernard, Laila Asali, Yi Liu, Anthony Flamier
Abstract
Rett syndrome arises from loss-of-function mutations in the X-linked chromatin regulator MECP2, yet the earliest molecular derailments in development are poorly defined. Using isogenic human embryonic stem cell (hESC) models carrying three patient-derived MECP2 mutations, we followed the transcriptome from pluripotency through neuroectoderm, neural stem/progenitor stages. Developmental stage dominated transcriptional variance, but mutants shared a secondary program enriched for synaptic-membrane and extracellular matrix genes. Single-cell/bulk profiling at the embryonic stem cell (ESC) stage revealed partial naïve-like drift, marked by the up-regulation of the naïve-enriched factor ZFP42/REX1 and related markers in MECP2-mutant lines. Among convergently dysregulated genes, the cortical determinant EMX1 showed an abnormal developmental trajectory, early repression followed by overshoot, and was consistently altered across independent Rett PSC models. Single-nucleus RNA-seq of cerebral organoids uncovered allele-specific yet convergent disturbances in cortical lineage allocation. These data chart a continuous developmental trajectory for MECP2-mutant cells and nominate naïve-like drift and mis-timed EMX1 expression as tractable entry points for dissecting Rett pathogenesis.