Generational Stability of Environmentally Induced Epigenetic Transgenerational Inheritance of Adult-Onset Disease
In traditional models of Drosophila flies and C. Elegans worms have shown epigenetic transgenerational inheritance has persisted and remained stable for hundreds of generations. Mammalian studies, however, have primarily investigated up to three or four generations. Environmental exposures to toxicants or other stressors have been linked to having a role in epigenetic alterations and epigenetic transgenerational inheritance. Changes within the epigenome have the potential to change gene expression and genetic processes, as well as potentially alter phenotypes and evolution in all organisms. In this study, an outcrossed mammalian colony of outbred rats was bred for twenty three successive generations and assessed for epigenetic alterations and incidence of pathological abnormalities. Sperm from male rats were analyzed for DNA methylation and pathology abnormalities in the female and male rats in successive generations. Observations showed an increase in disease incidence within the ten generations (F13) and twenty generations (F23) compared to the control lineage. Our results indicate that ten generations of transgenerational exposure led to an increase in epigenetic alterations and a higher incidence of pathological abnormalities. Ancestrally exposed rats to vinclozolin showed significant parturition abnormalities in both the maternal and paternal lineages after 16 generations. This included maternal deaths during labor and stillbirths. Pathological assessments revealed abnormalities across multiple tissue types and an increased incidence of disease. This suggests the physiological consequences of the generational stability of epigenetic inheritance. Observations establish the generational stability of epigenetic inheritance over twenty generations in a mammalian model system, however, new pathology in later generations involving parturition abnormalities were also observed. Overall design: The experimental design involved exposing the F0 generation gestating female rats to the toxicant vinclozolin through intraperitoneal injection.  The control lineage female rats were exposed to DMSO alone through intraperitoneal injection. Each generation had a maternal outcross (MOC) and paternal lineage outcross (POC) that were outbred with wild-type non-exposed Sprague Dawley rats. This generated a female lineage maternal outcross (MOC) and male lineage paternal outcross (POC) that were both investigated for generational pathology. Although sperm collection can provide millions of cells and sufficient DNA for epigenetic analysis, the very limited number of mature oocytes does not allow the female germline epigenetic analysis. Therefore, only the male sperm were used for epigenetic analysis for both the male (POC) and female (MOC) lineages for epigenetic analysis. All rats were euthanized and dissected at one year of age where tissues and epididymal sperm were collected. Further analysis was done on the collected tissue and sperm for generational stability of transgenerational epigenetic inheritance effects in the F13 and F23 generations.