Bisphenol A disrupts circadian locomotor rhythms via m⁶A-dependent nr1d1 destabilization in zebrafish larvae

Bisphenol A (BPA), an environmental endocrine disruptor, has been shown to disrupt circadian rhythms and affect neurological development; however, its underlying molecular mechanisms remain unclear. The present study employed an early-life exposure model in zebrafish to investigate whether BPA disrupts circadian locomotor rhythms by regulating the N6-methyladenosine (m⁶A)-dependent clock gene nr1d1. The results indicated that BPA elevated total m6A levels in zebrafish embryos, upregulated the methyltransferase Mettl14, and disrupted its rhythmic expression. Molecular docking analysis revealed a direct interaction between BPA and Mettl14. BPA enhanced m⁶A enrichment at site 2449 in the nr1d1 3'UTR, decreasing mRNA stability and expression. The nr1d1 instability diminishes the amplitude of spontaneous locomotor rhythms in juvenile zebrafish, while leaving period and phase unaffected. The methyltransferase inhibitor S-adenosylhomocysteine (SAH) rescues nr1d1 expression and rhythmic amplitude, while knocking out the reading protein prevents BPA-induced nr1d1 instability. In summary, BPA disrupts the circadian rhythm and stability of the clock gene nr1d1 via Mettl14-mediated m⁶A modification, revealing nr1d1 as a vulnerable BPA target molecule. The m⁶A-Mettl14-nr1d1 axis has been demonstrated to represent a critical link between environmental pollutants and circadian dysfunction, offering new insights into the effects of environmental pollutants on early neurodevelopment.