Single-Cell Analysis of the Gene Expression Effects of Developmental Lead (Pb) Exposure on the Mouse Hippocampus

Abstract

Lead (Pb) exposure is ubiquitous with permanent neurodevelopmental effects. The hippocampus brain region is involved in learning and memory with heterogeneous cellular composition. The hippocampus cell type-specific responses to Pb are unknown. The objective of this study is to examine perinatal Pb treatment effects on adult hippocampus gene expression, at the level of individual cells. In mice perinatally exposed to control water or a human physiologically relevant level (32 ppm in maternal drinking water) of Pb, 2 weeks prior to mating through weaning, we tested for hippocampus gene expression and cellular differences at 5 months of age. We sequenced RNA from 5258 hippocampal cells to (1) test for treatment gene expression differences averaged across all cells, (2) compare cell cluster composition by treatment, and (3) test for treatment gene expression and pathway differences within cell clusters. Gene expression patterns revealed 12 hippocampus cell clusters, mapping to major expected cell types (eg, microglia, astrocytes, neurons, and oligodendrocytes). Perinatal Pb treatment was associated with 12.4% more oligodendrocytes (p = 4.4 × 10−21) in adult mice. Across all cells, Pb treatment was associated with expression of cell cluster marker genes. Within cell clusters, Pb treatment (q < 0.05) caused differential gene expression in endothelial, microglial, pericyte, and astrocyte cells. Pb treatment upregulated protein folding pathways in microglia (p = 3.4 × 10−9) and stress response in oligodendrocytes (p = 3.2 × 10−5). Bulk tissue analysis may be influenced by changes in cell type composition, obscuring effects within vulnerable cell types. This study serves as a biological reference for future single-cell toxicant studies, to ultimately characterize molecular effects on cognition and behavior.

Prenatal Lead (Pb) Exposure and Peripheral Blood DNA Methylation (5mC) and Hydroxymethylation (5hmC) in Mexican Adolescents from the ELEMENT Birth Cohort

“…Though we were limited to analyzing whole blood samples, results from this research provide preliminary evidence that Pb exposure may affect regulation of both 5mC and 5hmC. Challenges in current developmental toxicology studies include determining whether persistent epigenetic alterations are due to global changes across all cells, altered cell-type proportions, or changes in specific cell types ( Bakulski et al. 2020 ; Jaffe and Irizarry 2014 ).…”

Single-Cell Sequencing Analysis of the db/db Mouse Hippocampus Reveals Cell-Type-Specific Insights Into the Pathobiology of Diabetes-Associated Cognitive Dysfunction

“…The protocol for dissection and single-cell dissociation were performed as previously described ( 18 ). After Morris Water Maze testing was completed, mice were immediately euthanized with sodium pentobarbital (50 mg/kg, i.p.)…”

Sodium para-aminosalicylic acid ameliorates lead-induced hippocampal neuronal apoptosis by suppressing the activation of the IP3R-Ca2+-ASK1-p38 signaling pathway

“…Once in the brain, Pb may cause various neurological deficits, including intellectual disability and behavioral deficits, and a possible link to Parkinson’s disease, Alzheimer’s disease, and amyotrophic lateral sclerosis has also been advanced ( Jiang et al, 2008 ; Liu et al, 2013 ). In particular, the hippocampus, a brain region in the temporal lobe that is central to long-term memory formation, is a key target of Pb-induced effects ( Bakulski et al, 2020 ). Once Pb crosses the blood–brain barrier (BBB) and the blood-cerebrospinal fluid (CSF) barrier into the brain and accumulates in the hippocampus ( Ouyang et al, 2019 ), it may impair hippocampal structure and function.…”