Environmentally relevant lead exposure impacts gene expression in SH-SY5Y cells throughout neuronal differentiation

Lead (Pb) causes learning and memory impairments, but the molecular effects of continuous, environmentally relevant levels of exposure on key neurodevelopmental processes are not fully characterized. Here, we examine the effects of a range of environmentally relevant Pb concentrations (0.16, 1.26, and 10 µM Pb) relative to control on neural differentiation in the SH-SY5Y cell model. Pb exposure began on differentiation day 5 and was continuous for the remaining days, and we assessed the transcriptome via RNA sequencing at several time points. The bulk of detected changes in gene expression occurred with the 10 µM Pb condition. Interestingly, changes associated with the lower 2 exposures were differentiation stage-specific, with aberrant expression of several genes (e.g. COL3A1, HMOX1, NQO1, and CCL2) observed during differentiation on days 9, 12, and 15 in both the 0.16 and 1.26 µM Pb conditions, which disappeared by the time differentiation concluded on day 18. We observed 6 co-expression clusters of genes during differentiation, and 10 µM Pb significantly perturbed 2 clusters, one involved in cell cycling and DNA repair and the other in protein synthesis. Benchmark concentration analysis identified many genes affected by levels of Pb at or below the current US reference value (3.5 µg/dl), and Pb-affected genes were enriched for pathways including stress responses, DNA repair, misfolded protein response, mitosis, and neurotransmitter production. This work highlights potential new mechanisms by which environmentally relevant concentrations of Pb impact gene expression throughout neural differentiation and may result in long-lasting implications for neural health and cognition.