Abstract / Summary
Benzo[a]pyrene (BaP), a widespread polycyclic aromatic hydrocarbon, is associated with adverse reproductive outcomes, mainly described at the gonadal level, while its effects on neuroendocrine regulation remain poorly characterized. Reproductive function is controlled by gonadotropin-releasing hormone (GnRH) neurons, which undergo a regulated migratory process during development. Using human fetal GnRH neuroblasts (FNCB4 cells), we previously showed that BaP exposure (10 µM, 24 h) impairs GnRH neuron migration and maturation. Here, we used RNA sequencing to clarify the molecular mechanisms through which BaP affects human GnRH neuron development. Transcriptomic analysis identified 585 significantly differentially expressed genes (DEGs; FDR < 0.05) in BaP-treated FNCB4 cells. Both functional and pathway enrichment analyses revealed that BaP primarily affected the expression of genes related to cell adhesion, cell migration and extracellular matrix organization processes. In particular, BaP exposure changed the expression of key genes involved in GnRH neuron development and migration, including adhesion-related molecules (SDC2, SDC4, ITGB5), guidance receptors and ligands (FGFR1, SEMA5A, ROBO2, EFNA5, and EPHA5) and the Notch pathway ligand JAG1. Interestingly, network analysis showed that several DEGs are functionally connected to RhoA, a central regulator of cytoskeletal dynamics. Consistent with this finding, immunofluorescence analysis demonstrated that BaP inhibited RhoA membrane translocation, indirectly suggesting a reduced RhoA activation likely linked to altered cytoskeletal remodelling essential for GnRH neuron motility. Although obtained in a single in vitro GnRH neuroblast model, overall these findings suggest that BaP can directly compromise GnRH neuron development, providing a molecular basis for its reproductive toxicity at the central nervous system level.