Global Gene Expression Analysis Reveals Dynamic and Developmental Stage–Dependent Enrichment of Lead-Induced Neurological Gene Alterations

Background: The underlying genetic mechanisms specific to subtle neurological alterations associated with environmental lead (Pb) exposures have not been clearly elucidated. Objectives: The goal of this study was to identify novel gene targets and the underlying genetic mechanisms associated with developmental Pb neurotoxicity. Methods: We first exposed zebrafish embryos to a range of Pb concentrations throughout early development to establish relative toxicity. Using the data from that experiment, we exposed another group of zebrafish embryos to a sublethal dose of Pb (100 ppb) immediately after fertilization through 72 or 120 hr postfertilization (hpf). Global gene expression was then analyzed for molecular pathways and gene ontology enrichment, and Western blot analysis was performed to investigate the translation of gene expression changes to protein levels. Results: After 72 hpf, we identified 231 probes representing 90 nonredundant genes with well-established function or orthology to human genes as being altered by Pb exposure. This gene set was both confirmatory and novel in nature and was highly enriched for neurological development, function, and disease. Moreover, gene changes at this time point were correlated to altered protein levels. Alternatively, the gene set at 120 hpf did not share association with neurological development. Conclusions: Global gene expression alterations associated with developmental Pb exposure were dynamic and dependent on developmental stage. Gene expression alterations at the 72‑hpf time point were highly enriched with genes and molecular pathways associated with neurological development and disease. Moreover, we identified a number of novel targets for future exploration We treated zebrafish embryos from approximately 1 hour post fertilization through 72 hours post fertilization (embryogenesis) or 120 hours post fertilization to 0 or 100 ppb Pb (lead acetate). Following the chemical exposure period, larvae were collected and processed for transcriptomic analysis to determine differences between control and Pb treatment at each time point (n=3 pools of ~50 larvae per time point).