Maternal background alters the penetrance of growth phenotypes and sex‐specific placental adaptation of offspring sired by alcohol‐exposed males

Abstract

Epigenetic mechanisms of paternal inheritance are an emerging area of interest in our efforts to understand fetal alcohol spectrum disorders. In rodent models examining maternal alcohol exposures, different maternal genetic backgrounds protect or sensitize offspring to alcohol‐induced teratogenesis. However, whether maternal background can mitigate sperm‐inherited alterations in developmental programming and modify the penetrance of growth defects induced by preconception paternal alcohol exposures remains unaddressed. In our previous studies examining pure C57Bl/6J crosses, the offspring of alcohol‐exposed sires exhibited fetal growth restriction, enlarged placentas, and decreased placental efficiency. Here, we find that in contrast to our previous studies, the F1 offspring of alcohol‐exposed C57Bl/6J sires and CD‐1 dams do not exhibit fetal growth restriction, with male fetuses developing smaller placentas and increased placental efficiencies. However, in these hybrid offspring, preconception paternal alcohol exposure induces sex‐specific changes in placental morphology. Specifically, the female offspring of alcohol‐exposed sires displayed structural changes in the junctional and labyrinth zones, along with increased placental glycogen content. These changes in placental organization are accompanied by female‐specific alterations in the expression of imprinted genes Cdkn1c and H19. Although male placentae do not display overt changes in placental histology, using RNA‐sequencing, we identified programmed alterations in genes regulating oxidative phosphorylation, mitochondrial function, and Sirtuin signaling. Collectively, our data reveal that preconception paternal alcohol exposure transmits a stressor to developing offspring, that males and females exhibit distinct patterns of placental adaptation, and that maternal genetic background can modulate the effects of paternal alcohol exposure.

Alcohol induced increases in sperm Histone H3 lysine 4 trimethylation correlate with increased placental CTCF occupancy and altered developmental programming

“…We suspect that similar to previous studies, reduced CTCF destabilizes Enhancer-Promoter interactions required to maintain appropriate gene expression patterns 29 . Further, reductions in these critical transport proteins may contribute to the growth deficits we observe in alcohol-exposed offspring 31 – 33 , 36 .…”

“…To this end, we used our published Drinking in the Dark model to expose adult (postnatal day 90) C57BL/6 J males to either water or 10% ethanol (EtOH) for ten weeks. After verifying the impact of the preconception EtOH treatment on placental growth 36 , we euthanized the sires and generated sperm ChIP-seq libraries from control and EtOH-exposed males (n = 3 and 4), with an average of 50 million unique reads per sample.…”

“…This developmental stage represents the earliest phase in which we can detect alterations in placental efficiency and gene expression patterns 32 , and allows the investigation of epigenetic inheritance without the technical challenges of working with ultra-low-input samples. Given that placental growth phenotypes induced by paternal alcohol exposure are more severe in the male offspring 31 , 32 , 36 , we focused our analysis on male placentae.…”

“…Our previous studies of preconception paternal alcohol exposures have identified several sex-specific outcomes, including sexually dimorphic changes in gene expression and histology 31 – 33 , 36 . We, therefore, assayed the expression of genes within the albumin , apolipoprotein , and fibrinogen gene clusters, along with a selection of other candidate genes in placentae isolated from the female offspring of alcohol-exposed sires.…”

“…Using a physiologically relevant mouse model that simulates chronic binge drinking, our group has identified a correlation between preconception male alcohol exposures and defects in fetal-placental growth that precede long-term alterations in offspring health 31 – 36 . However, we observed minimal impacts of chronic alcohol use on sperm DNA methylation 32 .…”