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

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.

TET1 Regulates Skeletal Stem-Cell Mediated Cartilage Regeneration.

OBJECTIVE: Adult skeletal stem cells (SSCs) that give rise to chondrocytes, osteocytes, and stromal cells as progeny have been shown to contribute to cartilage regeneration in osteoarthritis (OA). Understanding extrinsic and intrinsic regulators of SSC fate and function can therefore identify putative candidate factors to enhance cartilage regeneration. This study explores how the DNA hydroxymethylase Tet1 regulates SSC function in OA. METHODS: We investigated the differences in the SSC lineage tree and differentiation potential in neonatal and adult Tet1+/+ and Tet1-/- mice with and without injury and upon OA induction and progression. Using RNA sequencing, the transcriptomic differences between SSCs and bone cartilage stroma progenitor cells (BCSPs) were identified in Tet1+/+ mice and Tet1-/- mice. RESULTS: Loss of Tet1 skewed the SSC lineage tree by expanding the SSC pool and enhanced the chondrogenic potential of SSCs and BCSPs. Tet1 inhibition led to enhanced chondrogenesis in human SSCs and chondroprogenitors isolated from human cartilage. Importantly, TET1 inhibition in vivo in late stages of a mouse model of OA led to increased cartilage regeneration. Transcriptomic analyses of SSCs and BCSPs lacking Tet1 revealed pathway alterations in transforming growth factor ß signaling, melatonin degradation, and cartilage development-associated genes. Lastly, we report that use of the hormone melatonin can dampen inflammation and improve cartilage health. CONCLUSION: Although Tet1 is a broad epigenetic regulator, melatonin can mimic the inhibition ability of TET1 to enhance the chondrogenic ability of SSCs. Melatonin administration has the potential to be an attractive stem cell-based therapy for cartilage regeneration.

Laminin-associated integrins mediate Diffuse Intrinsic Pontine Glioma infiltration and therapy response within a neural assembloid model.

Diffuse Intrinsic Pontine Glioma (DIPG) is a highly aggressive and fatal pediatric brain cancer. One pre-requisite for tumor cells to infiltrate is adhesion to extracellular matrix (ECM) components. However, it remains largely unknown which ECM proteins are critical in enabling DIPG adhesion and migration and which integrin receptors mediate these processes. Here, we identify laminin as a key ECM protein that supports robust DIPG cell adhesion and migration. To study DIPG infiltration, we developed a DIPG-neural assembloid model, which is composed of a DIPG spheroid fused to a human induced pluripotent stem cell-derived neural organoid. Using this assembloid model, we demonstrate that knockdown of laminin-associated integrins significantly impedes DIPG infiltration. Moreover, laminin-associated integrin knockdown improves DIPG response to radiation and HDAC inhibitor treatment within the DIPG-neural assembloids. These findings reveal the critical role of laminin-associated integrins in mediating DIPG progression and drug response. The results also provide evidence that disrupting integrin receptors may offer a novel therapeutic strategy to enhance DIPG treatment outcomes. Finally, these results establish DIPG-neural assembloid models as a powerful tool to study DIPG disease progression and enable drug discovery.

Chromatin alterations during the epididymal maturation of mouse sperm refine the paternally inherited epigenome.

BACKGROUND: Paternal lifestyle choices and male exposure history have a critical influence on the health and fitness of the next generation. Accordingly, defining the processes of germline programming is essential to resolving how the epigenetic memory of paternal experiences transmits to their offspring. Established dogma holds that all facets of chromatin organization and histone posttranslational modification are complete before sperm exits the testes. However, recent clinical and animal studies suggest that patterns of DNA methylation change during epididymal maturation. In this study, we used complementary proteomic and deep-sequencing approaches to test the hypothesis that sperm posttranslational histone modifications change during epididymal transit. RESULTS: Using proteomic analysis to contrast immature spermatozoa and mature sperm isolated from the mouse epididymis, we find progressive changes in multiple histone posttranslational modifications, including H3K4me1, H3K27ac, H3K79me2, H3K64ac, H3K122ac, H4K16ac, H3K9me2, and H4K20me3. Interestingly, some of these changes only occurred on histone variant H3.3, and most involve chromatin modifications associated with gene enhancer activity. In contrast, the bivalent chromatin modifications, H3K4me3, and H3K27me3 remained constant. Using chromatin immunoprecipitation coupled with deep sequencing, we find that changes in histone h3, lysine 27 acetylation (H3K27ac) involve sharpening broad diffuse regions into narrow peaks centered on the promoter regions of genes driving embryonic development. Significantly, many of these regions overlap with broad domains of H3K4me3 in oocytes and ATAC-seq signatures of open chromatin identified in MII oocytes and sperm. In contrast, histone h3, lysine 9 dimethylation (H3K9me2) becomes enriched within the promoters of genes driving meiosis and in the distal enhancer regions of tissue-specific genes sequestered at the nuclear lamina. Maturing sperm contain the histone deacetylase enzymes HDAC1 and HDAC3, suggesting the NuRD complex may drive some of these changes. Finally, using Western blotting, we detected changes in chromatin modifications between caput and caudal sperm isolated from rams (Ovis aries), inferring changes in histone modifications are a shared feature of mammalian epididymal maturation. CONCLUSIONS: These data extend our understanding of germline programming and reveal that, in addition to trafficking noncoding RNAs, changes in histone posttranslational modifications are a core feature of epididymal maturation.

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

Using a mouse model, studies by our group reveal that paternal preconception alcohol intake affects offspring fetal-placental growth, with long-lasting consequences on adult metabolism. Here, we tested the hypothesis that chronic preconception male alcohol exposure impacts histone enrichment in sperm and that these changes are associated with altered developmental programming in the placenta. Using chromatin immunoprecipitation, we find alcohol-induced increases in sperm histone H3 lysine 4 trimethylation (H3K4me3) that map to promoters and presumptive enhancer regions enriched in genes driving neurogenesis and craniofacial development. Given the colocalization of H3K4me3 with the chromatin binding factor CTCF across both sperm and embryos, we next examined CTCF localization in the placenta. We find global changes in CTCF binding within placentae derived from the male offspring of alcohol-exposed sires. Furthermore, altered CTCF localization correlates with dysregulated gene expression across multiple gene clusters; however, these transcriptional changes only occur in male offspring. Finally, we identified a correlation between genomic regions exhibiting alcohol-induced increases in sperm H3K4me3 and increased CTCF binding in male placentae. Collectively, our analysis demonstrates that the chromatin landscape of sperm is sensitive to chronic alcohol exposure and that a subset of these affected regions exhibits increased placental CTCF enrichment.

Paternal alcohol exposures program intergenerational hormetic effects on offspring fetoplacental growth.

Hormesis refers to graded adaptive responses to harmful environmental stimuli where low-level toxicant exposures stimulate tissue growth and responsiveness while, in contrast, higher-level exposures induce toxicity. Although the intergenerational inheritance of programmed hormetic growth responses is described in plants and insects, researchers have yet to observe this phenomenon in mammals. Using a physiologically relevant mouse model, we demonstrate that chronic preconception paternal alcohol exposures program nonlinear, dose-dependent changes in offspring fetoplacental growth. Our studies identify an inverse j-shaped curve with a threshold of 2.4 g/Kg per day; below this threshold, paternal ethanol exposures induce programmed increases in placental growth, while doses exceeding this point yield comparative decreases in placental growth. In male offspring, higher paternal exposures induce dose-dependent increases in the placental labyrinth layer but do not impact fetal growth. In contrast, the placental hypertrophy induced by low-level paternal ethanol exposures associate with increased offspring crown-rump length, particularly in male offspring. Finally, alterations in placental physiology correlate with disruptions in both mitochondrial-encoded and imprinted gene expression. Understanding the influence of ethanol on the paternally-inherited epigenetic program and downstream hormetic responses in offspring growth may help explain the enormous variation observed in fetal alcohol spectrum disorder (FASD) phenotypes and incidence.

Preconception paternal alcohol exposure exerts sex-specific effects on offspring growth and long-term metabolic programming.

BACKGROUND: Although clinical data support an association between paternal alcohol use and deficits in child neurocognitive development, the relationship between paternal drinking and alcohol-induced growth phenotypes remains challenging to define. Using an established mouse model of chronic exposure, previous work by our group has linked preconception paternal alcohol use to sex-specific patterns of fetal growth restriction and placental dysfunction. The aim of the present study was to investigate the long-term impact of chronic preconception paternal alcohol use on offspring growth and metabolic programming. RESULTS: Preconception paternal alcohol exposure induced a prolonged period of fetal gestation and an increased incidence of intrauterine growth restriction, which affected the male offspring to a greater extent than the females. While the female offspring of ethanol-exposed males were able to match the body weights of the controls within the first 2 weeks of postnatal life, male offspring continued to display an 11% reduction in weight at 5 weeks of age and a 6% reduction at 8 weeks of age. The observed growth deficits associated with insulin hypersensitivity in the male offspring, while in contrast, females displayed a modest lag in their glucose tolerance test. These metabolic defects were associated with an up-regulation of genes within the pro-fibrotic TGF-ß signaling pathway and increased levels of cellular hydroxyproline within the livers of the male offspring. We observed suppressed cytokine profiles within the liver and pancreas of both the male and female offspring, which correlated with the up-regulation of genes in the LiverX/RetinoidX/FarnesoidX receptor pathways. However, patterns of gene expression were highly variable between the offspring of alcohol-exposed sires. In the adult offspring of alcohol-exposed males, we did not observe any differences in the allelic expression of Igf2 or any other imprinted genes. CONCLUSIONS: The impact of paternal alcohol use on child development is poorly explored and represents a significant gap in our understanding of the teratogenic effects of ethanol. Our studies implicate paternal exposure history as an additional and important modifier of alcohol-induced growth phenotypes and challenge the current maternal-centric exposure paradigm.

Alterations in sperm-inherited noncoding RNAs associate with late-term fetal growth restriction induced by preconception paternal alcohol use.

Using a mouse model, our group recently described an association between chronic paternal alcohol use prior to conception and deficits in offspring growth. Here, we sought to determine the impact of alcohol exposure on male reproductive physiology and the association of sperm-inherited noncoding RNAs with the transmission of the observed growth defects. Alcohol exposure did not appreciably alter male reproductive physiology or fertility. However, chronic alcohol use reproducibly induced late-term fetal growth restriction in the offspring, which correlated with a shift in the proportional ratio of transfer RNA-derived small RNAs to Piwi-interacting RNAs, as well as altered enrichment of microRNAs miR21, miR30, and miR142 in alcohol-exposed sperm. Although our dataset share similarities to prior works examining the impact of paternal stress on offspring phenotype, we were unable to identify any changes in plasma corticosterone, indicating alcohol may alter sperm-inherited noncoding RNAs through distinct mechanisms.

Programmed increases in LXRα induced by paternal alcohol use enhance offspring metabolic adaptation to high-fat diet induced obesity.

OBJECTIVES: Paternally inherited alterations in epigenetic programming are emerging as relevant factors in numerous disease states, including the growth and metabolic defects observed in fetal alcohol spectrum disorders. In rodents, chronic paternal alcohol use induces fetal growth restriction, as well as sex-specific alterations in insulin signaling and lipid homeostasis in the offspring. Based on previous studies, we hypothesized that the observed metabolic irregularities are the consequence of paternally inherited alterations liver x receptor (LXR) activity. METHODS: Male offspring of alcohol-exposed sires were challenged with a high-fat diet and the molecular pathways controlling glucose and lipid homeostasis assayed for LXR-induced alterations. RESULTS: Similar to findings in studies employing LXR agonists we found that the male offspring of alcohol-exposed sires display resistance to diet-induced obesity and improved glucose homeostasis when challenged with a high-fat diet. This improved metabolic adaptation is mediated by LXRα trans-repression of inflammatory cytokines, releasing IKKß inhibition of the insulin signaling pathway. Interestingly, paternally programmed increases in LXRα expression are liver-specific and do not manifest in the pancreas or visceral fat. CONCLUSIONS: These studies identify LXRα as a key mediator of the long-term metabolic alterations induced by preconception paternal alcohol use.

Disconnect between alcohol-induced alterations in chromatin structure and gene transcription in a mouse embryonic stem cell model of exposure.

Alterations to chromatin structure induced by environmental insults have become an attractive explanation for the persistence of exposure effects into subsequent life stages. However, a growing body of work examining the epigenetic impact that alcohol and other drugs of abuse exert consistently notes a disconnection between induced changes in chromatin structure and patterns of gene transcription. Thus, an important question is whether perturbations in the 'histone code' induced by prenatal exposures to alcohol implicitly subvert gene expression, or whether the hierarchy of cellular signaling networks driving development is such that they retain control over the transcriptional program. To address this question, we examined the impact of ethanol exposure in mouse embryonic stem cells cultured under 2i conditions, where the transcriptional program is rigidly enforced through the use of small molecule inhibitors. We find that ethanol-induced changes in post-translational histone modifications are dose-dependent, unique to the chromatin modification under investigation, and that the extent and direction of the change differ between the period of exposure and the recovery phase. Similar to in vivo models, we find post-translational modifications affecting histone 3 lysine 9 are the most profoundly impacted, with the signature of exposure persisting long after alcohol has been removed. These changes in chromatin structure associate with dose-dependent alterations in the levels of transcripts encoding Dnmt1, Uhrf1, Tet1, Tet2, Tet3, and Polycomb complex members Eed and Ezh2. However, in this model, ethanol-induced changes to the chromatin template do not consistently associate with changes in gene transcription, impede the process of differentiation, or affect the acquisition of monoallelic patterns of expression for the imprinted gene Igf2R. These findings question the inferred universal relevance of epigenetic changes induced by drugs of abuse and suggest that changes in chromatin structure cannot unequivocally explain dysgenesis in isolation.

DNA methylation-independent growth restriction and altered developmental programming in a mouse model of preconception male alcohol exposure.

The preconception environment is a significant modifier of dysgenesis and the development of environmentally-induced disease. To date, fetal alcohol spectrum disorders (FASDs) have been exclusively associated with maternal exposures, yet emerging evidence suggests male-inherited alterations in the developmental program of sperm may be relevant to the growth-restriction phenotypes of this condition. Using a mouse model of voluntary consumption, we find chronic preconception male ethanol exposure associates with fetal growth restriction, decreased placental efficiency, abnormalities in cholesterol trafficking, sex-specific alterations in the genetic pathways regulating hepatic fibrosis, and disruptions in the regulation of imprinted genes. Alterations in the DNA methylation profiles of imprinted loci have been identified in clinical studies of alcoholic sperm, suggesting the legacy of paternal drinking may transmit via heritable disruptions in the regulation of imprinted genes. However, the capacity of sperm-inherited changes in DNA methylation to broadly transmit environmentally-induced phenotypes remains unconfirmed. Using bisulphite mutagenesis and second-generation deep sequencing, we find no evidence to suggest that these phenotypes or any of the associated transcriptional changes are linked to alterations in the sperm-inherited DNA methylation profile. These observations are consistent with recent studies examining the male transmission of diet-induced phenotypes and emphasize the importance of epigenetic mechanisms of paternal inheritance beyond DNA methylation. This study challenges the singular importance of maternal alcohol exposures and suggests paternal alcohol abuse is a significant, yet overlooked epidemiological factor complicit in the genesis of alcohol-induced growth defects, and may provide mechanistic insight into the failure of FASD children to thrive postnatally.

Mono-(2-ethylhexyl) phthalate induces apoptosis through miR-16 in human first trimester placental cell line HTR-8/SVneo.

Phthalates have been linked to adverse pregnancy complications. Mono-(2-ethylhexyl) phthalate, an active metabolite of di-(2-ethylhexyl) phthalate and an endocrine disruptor, has been shown to induce apoptosis in various cell types including placental cells. However, the mechanism of action of MEHP induced apoptosis is still unknown. We hypothesized that apoptosis may be mediated in part through altered microRNA(s) in placenta under MEHP exposure. In the present study, we report that MEHP increases miR-16 expression in a time- and dose-dependent manner (p<0.05), while inducing apoptosis in HTR-8/SVneo. Cells treated with MEHP showed a dose-dependent increase in cytotoxicity and reactive oxygen species along with decreased cell viability. Consistent with significant increase in apoptosis analyzed by flow cytometry, we detected decreased anti-apoptotic BCL-2 at transcriptional and translational levels with MEHP (p<0.05). Knockdown of miR-16 did not decrease the BCL-2/BAX protein expression ratio in the presence of MEHP when compared to negative control demonstrating that MEHP induces apoptosis directly through miR-16. In conclusion, our study demonstrates for the first time that MEHP induces miR-16, which in turn, alters BCL-2/BAX ratio leading to increased apoptosis. This study provides a novel insight into MEHP induced epigenetic regulation in placental apoptosis which may lead to pregnancy complications.

The plasticizer BBP selectively inhibits epigenetic regulator sirtuins.

The plasticizer benzyl butyl phthalate (BBP) is a well-known endocrine disruptor. Widespread human exposure to phthalates has raised substantial public concern due to its detrimental health effects. However, molecular mechanisms of the phthalates effect require elucidation. In this study, we analyzed: 1) the binding interaction of several phthalates and persistent organic pollutants with epigenetic regulator sirtuins and 2) the effect of BBP on the sirtuins in HepG2 cells. AutoDock molecular docking analysis showed that BBP binds to Sirt1 and Sirt3 proteins similarly to the native ligands with shortest binding free energies (ΔGb) of -7.35 and -8.3 kcal/mol, respectively; and inhibition constants (Ki) of 4.07 µM and 0.82 µM, respectively. Furthermore, BBP was superimposed onto the co-crystallized ligands within the least root-mean-square deviation (RMSD) of 0.96Å and 1.55Å for Sirt1 and Sirt3, respectively, and bound into the sites with a sufficient number of hydrogen bonds, implying the best fit compared to other sirtuins. In HepG2 cells, BBP significantly down-regulated Sirt1 and Sirt3 (p<0.05) gene expression at a concentration as low as 10nM; other sirtuins remained unaffected. Consistent with decreased gene expression, Sirt1 and Sirt3 protein levels were significantly decreased at 48 h (p<0.05). In addition, mitochondrial biogenesis regulators PGC-1α, NRF-1, and NRF-2, were decreased (p<0.05). SiRNA studies showed that BBP did not regulate PGC-1α via sirtuin and BBP requires sirtuin's presence to regulate NRF-1 or NRF-2. BBP significantly increased ROS production (p<0.05) and ROS may be chiefly regulated by NRF-1 and NRF-2 in HepG2 cells under Sirt1 and Sirt3 silenced condition. This is the first report to demonstrate that BBP selectively disrupts specific sirtuins in HepG2 cells. In conclusion, our study suggests that BBP can impair two vital epigenetic regulators and mitochondrial biogenesis regulators in liver cells.

Pyrroloquinoline quinone increases the expression and activity of Sirt1 and -3 genes in HepG2 cells.

Sirtuin (Sirt) 1 and Sirt 3 are nicotinamide adenine dinucleotide ((+))-dependent protein deacetylases that are important to a number of mitochondrial-related functions; thus, identification of sirtuin activators is important. Herein, we hypothesize that pyrroloquinoline quinone (PQQ) can act as a Sirt1/Sirt3 activator. In HepG2 cell cultures, PQQ increased the expression of Sirt1 and Sirt3 gene, protein, and activity levels (P < .05). We also observed a significant increase in nicotinamide phosphoribosyltransferase gene expression (as early as 18 hours) and increased NAD(+) activity at 24 hours. In addition, targets of Sirt1 and Sirt3 (peroxisome proliferator-activated receptor γ coactivator 1α, nuclear respiratory factor 1 and 2, and mitochondrial transcription factor A) were increased at 48 hours. This is the first report that demonstrates PQQ as an activator of Sirt1 and Sirt3 expression and activity, making it an attractive therapeutic agent for the treatment of metabolic diseases and for healthy aging. Based on our study and the available data in vivo, PQQ has the potential to serve as a therapeutic nutraceutical, when enhancing mitochondrial function.