A NEW genomic technology is uncovering previously hidden autism gene variants, helping explain long standing gaps in genetic understanding of autism. Researchers report that long-read genome sequencing can reveal complex structural mutations missed by conventional DNA sequencing approaches.
Long-Read Sequencing Advances Autism Gene Discovery
Autism spectrum disorder has a strong genetic component, yet a large proportion of its heritability remains unexplained. This gap, often referred to as missing heritability, reflects the difficulty of detecting complex genomic changes using traditional sequencing techniques. Standard short read sequencing analyses DNA in small fragments, which can obscure larger structural rearrangements and repetitive regions of the genome.
Long-read whole genome sequencing offers a different approach by analysing much larger segments of DNA at once. This allows scientists to map complex genomic structures and identify variants that are difficult to detect with conventional methods. Researchers used this technology to explore whether long-read sequencing could improve detection of autism-related variants and clarify how these mutations affect gene regulation and brain development.
Study Methods
The study analysed 267 individuals from 63 families, using long-read whole genome sequencing combined with short read data to create an integrated variant dataset. Researchers identified over 44,000 structural variants, with approximately 60% considered novel compared with variants detected through standard sequencing approaches.
Long-read sequencing increased detection of gene disrupting structural variants by 33% and tandem repeat variants by 38%. The technology also identified approximately 11,500 tandem repeat variants per subject with length deviations of ≥50 bp, more than twice the number typically detectable with short read sequencing.
Investigators also discovered previously undescribed complex structural rearrangements, including a class of nested duplication deletion events. By combining structural variant analysis with DNA methylation data, the researchers were able to identify deletions in imprinted genes and examine how intermediate tandem repeat expansions of 35–54 CGG influence methylation of the FMR1 promoter, a region associated with intellectual disability.
Implications for Understanding Autism Genetics
The findings highlight how long-read sequencing could transform the study of autism gene variants by revealing genomic changes that were previously invisible. Researchers estimated that rare structural variants, tandem repeats, and damaging single nucleotide variants together account for 7.4% of autism spectrum disorder heritability (95% CI, 2.7%–17%).
Improved detection of autism gene variants may help scientists better understand the biological mechanisms underlying autism and support the development of more precise diagnostic tools. As sequencing technologies continue to advance, they may help close the missing heritability gap and guide more personalised approaches to autism research and clinical care.
Reference
Mortazavi M et al. Long-read genome sequencing improves detection and functional interpretation of structural and repeat variants in autism. medRxiv. 2025;2025-07.
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