Latour, B. L. | bioRxiv Science

bioRxiv2025

THE NSL COMPLEX PROMOTES NEURAL DEVELOPMENT BY PREVENTING R-LOOP INDUCED REPLICATION STRESS

Early neuronal development relies on the proliferation of neural progenitor cells, making this developmental stage particularly vulnerable to DNA replication impediments. Here, we identify a non-canonical role for the non-specific lethal (NSL) complex in safeguarding DNA replication during neurodevelopment. The NSL complex, which acetylates histone 4 at gene promoters and is mutated in Koolen-de Vries syndrome (KdVS), prevents unscheduled R-loop accumulation at weakly transcribed promoters that are typically devoid of R-loops. Single-cell sequencing reveals that loss of NSL causes replisome stalling and delayed S-phase progression. Neural organoids derived from KdVS patients exhibit impaired DNA replication, developmental abnormalities, and reduced synapse formation, driven entirely by unscheduled R-loop accumulation. These findings reveal that faithful DNA replication is critical for early neurodevelopment.

genomics↗

bioRxiv2025

Evolutionary hotspots of structural variation drive inter-individual differences in the expression of fusion transcripts in the human brain

While most protein-coding regions in our genome are highly conserved, phenotypic variation largely arises from differences in gene transcription, splicing, and translation. Intra-gene splicing variations are a known source of inter-individual differences. However, inter-gene splicing events, which generate fusion transcripts--RNA molecules combining exons from multiple distinct genes--are less explored. Fusion transcripts are well-studied in cancer, but their expression and inter-individual variability in normal human tissues has not been thoroughly investigated. We conducted a genome-wide fusion transcript analysis in postmortem human brain tissues from 276 individuals, identifying 717 distinct fusion transcripts. Many had protein coding potential, further supported in some cases by ribosome profiling data. Fusion transcripts that were present in only part of the human population were predominantly located within segmental duplication (SD) "hotspots"; highly copy number-variable genomic regions linked to neurodevelopmental and neurodegenerative diseases. None of these variable fusion transcripts were present in chimpanzee or rhesus macaque, suggesting they are human-specific. We confirmed that SD-derived fusion transcripts arise from structural genomic rearrangements in the human population, previously associated with neurodevelopmental and neurodegenerative disease risk. Inter-individual variation in fusion transcript expression represents an overlooked source of genetic diversity, with potential to contribute to differences in disease susceptibility.

molecular biology↗