Brain-centred transcriptomic convergence in autism spectrum disorder: synaptic, immune-glial and mitochondrial-transcriptional axes.

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental condition in which transcriptomic findings vary across cohorts, brain regions, developmental stages, and analytical platforms. This narrative review synthesises human ASD transcriptomic evidence with primary emphasis on post-mortem cerebral cortex and examines whether recurrent biological programs emerge despite substantial heterogeneity between studies. Across cortical datasets, the most reproducible pattern is not a single universal molecular signature but partial convergence at the level of synaptic and neuronal programs, immune-glial activation, and mitochondrial-transcriptional regulation. Bulk RNA-seq has defined broad tissue-level shifts, whereas single-cell and single-nucleus approaches refine these signals at cell-type resolution and long-read transcriptomics extends interpretation to isoform structure and splicing complexity. Peripheral blood transcriptomic studies are discussed only as secondary contextual observations because immune-cell composition and clinical-state effects limit direct inference about central nervous system mechanisms. Overall, current evidence supports a brain-centred model of transcriptomic convergence in ASD that is mechanistically informative but constrained by regional specificity, cohort heterogeneity, and methodological variation.