ABSTRACT: Pathogenic DNA variants in chromatin-related genes cause an important minority of neurodevelopmental disorders (NDDs). Epigenetic mechanisms, including chromatin regulation, are associated with the etiopathogenesis of NDDs. Therapeutic strategies targeting chromatin dysregulation, such as histone deacetylase inhibition with butyrate, show promise; however, its effects remain poorly understood. We performed single-cell RNA sequencing (scRNA seq) on 101,539 peripheral immune cells from four children with functionally impairing NDDs (median age 11.2 years, IQR = 3.5 years; 3 females): three with de novo pathogenic variants in chromatin-related genes (KMT2D, CHD7, and MECP2), and one without a monogenic diagnosis (non-monogenic), compared with two sex-matched healthy controls (median age 12.5 years, IQR = 0.94 years; 1 female). Patient cells also underwent scRNA seq sequencing after in vitro butyrate treatment. Untreated patient cells showed dysregulation of ribosomal and immune pathways compared to controls. Specifically, KMT2D, CHD7, and the non-monogenic patients exhibited downregulation of ribosomal pathways, and upregulation of immune pathways. In contrast, the MECP2 patient displayed upregulation of ribosomal pathways and mixed regulation of immune pathways. Butyrate treatment largely reversed these pathways, normalizing ribosomal and immune pathways in KMT2D, CHD7, and non-monogenic patient cells, with partial effects in MECP2. Overall, butyrate induced up-regulation of ribosome, GTPase, cytoskeletal, mitochondrial pathways, and down-regulation of epigenetic (histone, transcription factors) and immune pathways. We propose that chromatin dysregulation is associated with a common RNA signature involving ribosomal pathways and immune dysregulation. Butyrate is a potential modulator of epigenetic and immune dysregulation in NDDs associated with chromatin dysregulation.
