Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen
Ali Altıntaş (Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen)| Jie Liu (The Lundquist Institute)| Odile Fabre (Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen)| Tsai-Der Chuang (The Lundquist Institute)| Ying Wang (The Lundquist Institute)| Reiko Sakurai (The Lundquist Institute)| Galal Nazih Chehabi (Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen)| Romain Barrès (Novo Nordisk Foundation Center for Basic Metabolic Research, University of Copenhagen)| Virender Rehan (The Lundquist Institute)
Background: Perinatal nicotine exposure alters the offspring’s lung development and causes asthma-like phenotype. The mechanism underlying the transgenerational inheritance of asthma-like phenotype is unknown, but epigenetic modulations, including DNA methylation, most likely play a role. Germ cells are the sole bridge between generations, and alterations in their epigenetic machinery might explain environmentally induced, heritable asthma phenotype.
Objectives: This study aims to determine F1 offspring’s sperm DNA methylation pattern upon perinatal administration of nicotine to F0 mother.
Methods: Pregnant (F0) rat dams were subcutaneously administered nicotine or placebo once daily from embryonic day 6 of gestation to the end of lactation (postnatal day 21). Sperms from litters (F1) were collected (n=10 per group) and reduced representation bisulfite sequencing (RRBS) was performed to identify differentially methylated regions (DMRs). Top regulated gene bodies and promoter DMRs were tested for lung gene expression levels using qPCR. Immunoblotting was performed for key proteins involved in lung development and repair.
Results: The overall CpG methylation in F1 sperm cells across gene bodies, promoters, 5’ UTRs, exons, introns, and 3’UTRs was not affected by nicotine treatment although methylation levels were different between different genomic regions. We found 138 CpG sites, 35 gene bodies, and 8 promoters differentially methylated (FDR < 0.10). Gene enrichment analysis of DMRs revealed pathways involved in oxidative stress, nicotine response, alveolar and brain development, and cellular signaling. Among DMRs, Dio1 and Nmu were the most hypermethylated and hypo-methylated genes, respectively. qPCR expression results showed that the gene expression and DNA methylation were incongruous. Key proteins involved in lung development and repair were all significantly different (FDR < 0.05) between the nicotine and placebo-treated groups.
Discussion: Collectively, these findings suggest that DNA methylation is reprogrammed in sperm cells upon perinatal nicotine exposure. The transgenerational asthma-like lung phenotype might be regulated by these epigenetic alterations.