Summary: A recent study has identified abnormal DNA methylation patterns in the dorsal raphe, a brain region central to serotonin signaling, in individuals with autism spectrum disorder (ASD). By analyzing postmortem brain tissue, researchers detected epigenetic alterations in genes linked to sensory perception, serotonin regulation, and synaptic function, revealing potential molecular pathways that contribute to ASD.
The study reports hypermethylation of the serotonin receptor gene HTR2C and the olfactory receptor gene OR2C3, alongside hypomethylation in the promoter region of RABGGTB—a gene not previously associated with ASD. These methylation changes were correlated with altered gene expression and suggest that environmental and epigenetic factors may influence ASD development, pointing to new directions for research, diagnosis, and therapy.
Key Facts:
- Serotonin connection: DNA methylation alterations in the dorsal raphe affect genes involved in serotonin signaling.
- New candidate gene: Hypomethylation and increased expression of RABGGTB highlight a novel autism-related target.
- Epigenetic regulation: ASD brains can show gene expression changes driven by methylation without underlying DNA sequence mutations.
Source: University of Fukui
Background: Autism spectrum disorder (ASD) affects brain development and commonly alters how individuals process sensory information and social cues. In addition to genetic contributors, growing evidence points to environmental exposures and epigenetic mechanisms—particularly DNA methylation—as important influences on ASD risk and neurodevelopment.
The dorsal raphe (DR) nucleus is a key regulator of serotonin and other neurotransmitter systems and has been implicated in ASD. Despite its importance, comprehensive DNA methylation profiling of the DR in ASD had not been performed prior to this investigation, leaving a gap in our understanding of region-specific epigenetic regulation in autism.
To address this gap, a Japanese research team led by Professor Hideo Matsuzaki at the Research Center for Child Mental Development, University of Fukui, together with Dr. Keiko Iwata from Wakayama Medical University, conducted genome-wide methylation profiling on postmortem DR tissue from individuals with and without ASD. The study was published in Psychiatry and Clinical Neurosciences on April 24, 2025.
The researchers applied the Infinium HumanMethylation450 BeadChip (Illumina) for DNA methylation analysis across the genome and used quantitative RT-PCR to measure expression levels of differentially methylated genes. Site-specific methylation findings were further validated with targeted amplicon sequencing.
Results revealed widespread methylation abnormalities across promoters, gene bodies, and intergenic regions in the DR of ASD cases compared with controls. Notably, the olfactory receptor gene OR2C3 and the serotonin receptor gene HTR2C displayed hypermethylation in ASD samples—changes that may relate to altered sensory processing and serotonin signaling observed in many individuals with autism.
Conversely, the promoter region of RABGGTB, a gene involved in autophagy and synaptic function, was hypomethylated in ASD samples and showed corresponding increases in expression. According to Professor Matsuzaki, RABGGTB is not listed in the SFARI gene database, making it a novel candidate for further study in autism research. He suggests that this gene could offer new insights into ASD mechanisms and might eventually contribute to biomarker development.
While these findings illuminate potential epigenetic mechanisms underlying ASD, the authors emphasize the need for further research combining methylome and transcriptome analyses across larger cohorts and multiple brain regions. Such integrative studies will be necessary to clarify how methylation changes translate into altered RNA and protein function and how they interact with genetic and environmental risk factors.
In summary, this exploratory study enhances understanding of the epigenetic landscape in the dorsal raphe of individuals with ASD, highlighting serotonin-related pathways and introducing RABGGTB as a promising novel target. The work underscores the importance of region-specific epigenetic profiling for uncovering molecular contributors to neurodevelopmental disorders and for guiding future diagnostic and therapeutic strategies.
About this genetics and autism research news
Author: Naoki Tsukamoto
Source: University of Fukui
Contact: Naoki Tsukamoto – University of Fukui
Image: The image is credited to Neuroscience News
Original Research: Open access. “Title of original paper: Genome-wide DNA methylation profiles in the raphe nuclei of patients with autism spectrum disorder” by Hideo Matsuzaki et al., Psychiatry and Clinical Neurosciences.
Abstract
Title of original paper: Genome-wide DNA methylation profiles in the raphe nuclei of patients with autism spectrum disorder
Aim
ASD has a substantial genetic component, but genetic factors alone do not explain all cases. Environmental exposures and epigenetic modifications, especially DNA methylation, are increasingly recognized as key contributors to ASD risk. This exploratory study examines DNA methylation in the dorsal raphe—a brain region involved in neurotransmitter regulation—to better understand epigenetic contributions to ASD.
Methods
Genome-wide DNA methylation profiles were analyzed in dorsal raphe tissue from seven control and five ASD postmortem samples using the Infinium HumanMethylation450 BeadChip. Quantitative PCR assessed mRNA levels of genes showing differential methylation in an extended sample set (11 controls and six ASD). Site-specific methylation was validated with targeted amplicon sequencing.
Results
Differentially methylated regions were identified across promoters, gene bodies, and intergenic regions. Hypermethylation was observed in genes associated with olfaction and serotonin signaling, including OR2C3 and HTR2C. Promoter hypomethylation of RABGGTB corresponded with increased expression, linking epigenetic change to transcriptional alteration.
Conclusions
The study demonstrates extensive DNA methylation changes in the dorsal raphe of individuals with ASD and identifies RABGGTB as a novel candidate gene deserving further investigation. These results expand our understanding of epigenetic contributions to ASD and underscore the need for integrated studies that combine methylation and transcriptome data to elucidate functional consequences.