Heritable Alterations Research Articles

Epigenetics Primer: Why the Clinician Should Care About Epigenetics

Epigenetics describes heritable alterations of gene expression that do not involve DNA sequence variation and are changeable throughout an organism's lifetime. Not only can epigenetic status influence drug response, but it can also be modulated by drugs. In this review, the three major epigenetic mechanisms are described: covalent DNA modification, histone protein modification, and regulation by noncoding RNA. Further, this review describes how drug therapy can influence, and be influenced by, these mechanisms. Drugs with epigenetic mechanisms are already in use, with many more likely to be approved within the next few years. As the understanding of epigenetic processes improves, so will the ability to use these data in the clinic to improve patient care.

Heritable genome editing in C. elegans via a CRISPR-Cas9 system.

CRISPR-Cas systems have been used with single-guide RNAs for accurate gene disruption and conversion in multiple biological systems. Here we report the use of the endonuclease Cas9 to target genomic sequences in the C. elegans germline, utilizing single-guide RNAs that are expressed from a U6 small nuclear RNA promoter. Our results demonstrate that targeted, heritable genetic alterations can be achieved in C. elegans, providing a convenient and effective approach for generating loss-of-function mutants.

Inter-species grafting caused extensive and heritable alterations of DNA methylation in Solanaceae plants.

BackgroundGrafting has been extensively used to enhance the performance of horticultural crops. Since Charles Darwin coined the term “graft hybrid” meaning that asexual combination of different plant species may generate products that are genetically distinct, highly discrepant opinions exist supporting or against the concept. Recent studies have documented that grafting enables exchanges of both RNA and DNA molecules between the grafting partners, thus providing a molecular basis for grafting-induced genetic variation. DNA methylation is known as prone to alterations as a result of perturbation of internal and external conditions. Given characteristics of grafting, it is interesting to test whether the process may cause an alteration of this epigenetic marker in the grafted organismal products.Methodology/Principal FindingsWe analyzed relative global DNA methylation levels and locus-specific methylation patterns by the MSAP marker and locus-specific bisulfite-sequencing in the seed plants (wild-type controls), self- and hetero-grafted scions/rootstocks, selfed progenies of scions and their seed-plant controls, involving three Solanaceae species. We quantified expression of putative genes involved in establishing and/or maintaining DNA methylation by q-(RT)-PCR. We found that (1) hetero-grafting caused extensive alteration of DNA methylation patterns in a locus-specific manner, especially in scions, although relative methylation levels remain largely unaltered; (2) the altered methylation patterns in the hetero-grafting-derived scions could be inherited to sexual progenies with some sites showing further alterations or revisions; (3) hetero-grafting caused dynamic changes in steady-state transcript abundance of genes encoding for a set of enzymes functionally relevant to DNA methylation.Conclusions/SignificanceOur results demonstrate that inter-species grafting in plants could produce extensive and heritable alterations in DNA methylation. We suggest that these readily altered, yet heritable, epigenetic modifications due to interspecies hetero-grafting may shed one facet of insight into the molecular underpinnings for the still contentious concept of graft hybrid.

Epigenetics in Ocular Diseases

Epigenetics pertains to heritable alterations in gene expression that do not involve modification of the underlying genomic DNA sequence. Historically, the study of epigenetic mechanisms has focused on DNA methylation and histone modifications, but the concept of epigenetics has been more recently extended to include microRNAs as well. Epigenetic patterning is modified by environmental exposures and may be a mechanistic link between environmental risk factors and the development of disease. Epigenetic dysregulation has been associated with a variety of human diseases, including cancer, neurological disorders, and autoimmune diseases. In this review, we consider the role of epigenetics in common ocular diseases, with a particular focus on DNA methylation and microRNAs. DNA methylation is a critical regulator of gene expression in the eye and is necessary for the proper development and postmitotic survival of retinal neurons. Aberrant methylation patterns have been associated with age-related macular degeneration, susceptibility to oxidative stress, cataract, pterygium, and retinoblastoma. Changes in histone modifications have also been observed in experimental models of diabetic retinopathy and glaucoma. The expression levels of specific microRNAs have also been found to be altered in the context of ocular inflammation, retinal degeneration, pathological angiogenesis, diabetic retinopathy, and ocular neoplasms. Although the complete spectrum of epigenetic modifications remains to be more fully explored, it is clear that epigenetic dysregulation is an important contributor to common ocular diseases and may be a relevant therapeutic target.

Methylation's mark on inheritance

Epigenetic changes to the genome can have heritable effects. An epigenome-wide study of wild plants identifies shared patterns of such modifications and their associations with genetic information. See Article p.193 Like natural genetic variation, natural epigenetic variation — heritable alterations in gene expression caused by mechanisms other than changes in DNA sequence —is a source of phenotypic diversity. How epigenetic variants form and how genetic variation is linked to epigenetic variation at the population level, however, has been little studied. These authors present the first whole-genome, base-resolution, population-level epigenomic analysis by sequencing the genomes, methylomes and transcriptomes of a population of more than 150 accessions of the plant Arabidopsis thaliana isolated from across the Northern Hemisphere. Thousands of DNA-methylation variants were identified, many of them linked to genetic variants. The analyses also reveal that genes targeted by RNA-directed DNA methylation may have co-opted a mechanism that silences transposons to maintain their silenced state in vegetative tissues and to ensure correct expression in pollen, seed and germ line development.

The role of high-throughput technologies in clinical cancer genomics

Cancer is a genetic disease driven by both heritable and somatic alterations in DNA, which underpin not only oncogenesis but also progression and eventual metastasis. The major impetus for elucidating the nature and function of somatic mutations in cancer genomes is the potential for the development of effective targeted anticancer therapies. Over the last decade, high-throughput technologies have allowed us unprecedented access to a host of cancer genomes, leading to an influx of new information about their pathobiology. The challenge now is to integrate such emerging information into clinical practice to achieve tangible benefits for cancer patients. This review examines the roles array-based comparative genomic hybridization and next-generation sequencing are playing in furthering our understanding of both hematological and solid-organ tumors. Furthermore, the authors discuss the current challenges in translating the role of these technologies from bench to bedside.

Third Jesús Culebras Lecture - Molecular biology and clinical nutrition; where do we stand and where do we go?

Nutrition plays a fundamental role in the maintenance of health and the treatment of disease, and serves as the crossroads for many disciplines. Biochemistry and Molecular Biology represents a key brand of science to ascertain the mechanism of action of nutrients and other food bioactive compounds in health and disease. The aim of the present Jesús M. Culebras lecture is to consider the future of the relationships between Molecular Biology and Clinical Nutrition and to discuss the use of molecular and genetic tools to study molecular responses to dietary factors and the metabolic consequences of food and to consider major challenges on human nutrition sciences in the 21(st) century. Particular emphasis is given to the identification and use of novel biomarkers in inflammatory diseases. Likewise, the importance of the human microbiome and how microorganisms can be safely utilized in the prevention and management of infectious and chronic diseases are discussed. Moreover, the key role of nutrigenetics, nutrigenomics and epigenetics in the new era of nutrition is considered. Nutrigenetics refers to the role of DNA sequence variation in the responses to nutrients, whereas nutrigenomics is the study of the role of nutrients in gene expression. Epigenetics is the study of mitotically heritable alterations in gene expression potential that are not caused by DNA sequence alterations. In the past decade, it has increasingly been recognized that dysregulation of epigenetic mechanisms may play an important role in human disease. Indeed, there is increasing interest in epigenetic mechanisms underlying phenotype modification modulated by nutrients. Further research in those areas should contribute to evaluate functionality of specific nutrients and bioactive compounds in Clinical Nutrition and allow personalized nutritional advice.

Enhanced Genetic Integrity in Mouse Germ Cells1

Genetically based diseases constitute a major human health burden, and de novo germline mutations represent a source of heritable genetic alterations that can cause such disorders in offspring. The availability of transgenic rodent systems with recoverable, mutation reporter genes has been used to assess the occurrence of spontaneous point mutations in germline cells. Previous studies using the lacI mutation reporter transgenic mouse system showed that the frequency of spontaneous mutations is significantly lower in advanced male germ cells than in somatic cell types from the same individuals. Here we used this same mutation reporter transgene system to show that female germ cells also display a mutation frequency that is lower than that in corresponding somatic cells and similar to that seen in male germ cells, indicating this is a common feature of germ cells in both sexes. In addition, we showed that statistically significant differences in mutation frequencies are evident between germ cells and somatic cells in both sexes as early as mid-fetal stages in the mouse. Finally, a comparison of the mutation frequency in a general population of early type A spermatogonia with that in a population enriched for Thy-1-positive spermatogonia suggests there is heterogeneity among the early spermatogonial population such that a subset of these cells are predestined to form true spermatogonial stem cells. Taken together, these results support the disposable soma theory, which posits that genetic integrity is normally maintained more stringently in the germ line than in the soma and suggests that this is achieved by minimizing the initial occurrence of mutations in early germline cells and their subsequent gametogenic progeny relative to that in somatic cells.

Reduced limbic metabolism and fronto-cortical volume in rats vulnerable to alcohol addiction

Alcohol abuse is associated with long-term reductions in fronto-cortical volume and limbic metabolism. However, an unanswered question in alcohol research is whether these alterations are the sole consequence of chronic alcohol use, or contain heritable contributions reflecting biological propensity toward ethanol addiction. Animal models of genetic predisposition to alcohol dependence can be used to investigate the role of inborn brain abnormalities in the aetiology of alcoholism. Here we used magnetic resonance imaging (MRI) in the Marchigian-Sardinian (msP) alcohol-preferring rats to assess the presence of inherited structural or functional brain alterations. Alcohol-naïve msP (N=22) and control rats (N=26) were subjected to basal cerebral blood volume (bCBV) mapping followed by voxel-based morphometry (VBM) of grey matter and tract-based spatial statistics mapping of white matter fractional anisotropy. msP rats exhibited significantly reduced bCBV, an established marker of resting brain function, in focal cortico-limbic and thalamic areas, together with reduced grey matter volume in the thalamus, ventral tegmental area, insular and cingulate cortex. No statistically significant differences in fractional anisotropy were observed between groups. These findings highlight the presence of inborn grey matter and metabolic abnormalities in alcohol-naïve msP rats, the localization and sign of which are remarkably similar to those mapped in abstinent alcoholics and subjects at high risk for alcohol dependence. Collectively, these results point for a significant role of heritable neurofunctional brain alterations in biological propensity toward ethanol addiction, and support the translational use of advanced imaging methods to describe the circuital determinants of vulnerability to drug addiction.

Heritable alteration in salt-tolerance in rice induced by introgression from wild rice (Zizania latifolia)

BackgroundIntrogression as a means of generating phenotypic novelty, including altered stress tolerance, is increasingly being recognized as common. The underlying basis for de novo genesis of phenotypic variation in the introgression lines remains largely unexplored. In this investigation, we used a rice line (RZ35) derived from introgressive hybridization between rice (Oryza sativa L.) and wild rice (Zizania latifolia Griseb.), along with its rice parental line (cv. Matsumae) as the experimental materials. We compared effects of salt stress on growth, ion homeostasis, and relevant gene expression between RZ35 and Matsumae, to explore possible mechanisms of heritable alteration in stress tolerance induced by the introgression.ResultsContrary to our expectation, the results showed that the inhibitory effect of salt stress on growth of RZ35 was significantly greater than that of Matsumae. We further found that a major underlying cause for this outcome is that the introgression process weakened the capacity in Na+ exclusion under the salt stress condition, and hence, escalated the injuries of Na+ and Cl- in shoots of RZ35. Accordingly, based on q-RT-PCR analysis, four genes known to be involved in the Na+ exclusion, i.e., OsHKT1;5, OsSOS1, OsCIPK24 and OsCBL4, were found to be significantly down-regulated in roots of RZ35 relative to its rice parental line under the salt stress condition, thus implicating a gene expression regulation-based molecular mechanism underlying the difference in salt stress-tolerance between the introgression line and its rice parental line.ConclusionsWe show that introgression represents a potent means for rapidly generating de novo heritable variations in physiological traits like stress tolerance in plants, although the direction of the alteration appears unpredictable.Electronic supplementary materialThe online version of this article (doi:10.1186/1939-8433-5-36) contains supplementary material, which is available to authorized users.

DNA methylation as a mechanism of nutritional plasticity: limited support from horned beetles.

Epigenetic changes to DNA, potentially heritable alterations above the sequence level, such as DNA methylation, are thought to underlie many instances of adaptive phenotypic plasticity. Our understanding of the links between epigenetic variation and adaptive phenotypic plasticity in natural populations is limited. If DNA methylation underlies adaptive responses to different nutritional environments, methylation patterns should be correlated with differences in performance across nutritional environments, and respond to changes in the environment. Additionally, genotypes that can cope with a broader range of nutritional environments are expected to have greater flexibility in methylation patterns. We tested these predictions using horned beetles (genus Onthophagus), which can cope with a wide range of variation in larval nutrition. We surveyed levels of methylation across several methylated loci in lab-reared beetles originating from natural populations using a methylation-specific amplified fragment length polymorphism (AFLP) analysis. For less than half the of the loci investigated, methylation level was correlated with performance, measured as adult body size attained on a given diet, in different nutritional environments, with an overall greater effect in males (the more nutritionally plastic sex) than females. Methylation levels at most sites were influenced more by genotype (iso-female line) than by environment (dung type). Only 1 site (of 12) showed a significant genotype-by-environment interaction. Taken together, our results provide modest support for the hypothesis that DNA methylation underlies nutritional plasticity, as only 8-16% of methylated sites conformed to all of our predictions.

Mutagenesis by an Antisense Oligonucleotide and Its Degradation Product

The European Medicines Agency has expressed concern regarding (1) the potential for antisense oligonucleotide (ASO) therapeutics to induce sequence-specific mutation at genomic DNA and (2) the capability of ASO degradation products (nucleotide analogues) to incorporate into newly synthesized genomic DNA via DNA polymerase and cause mutation if base pairing occurs with reduced fidelity. Treating human lymphoblastoid cells with a biologically active antisense molecule induced sequence-specific mutation within genomic DNA over fourfold, in a system where RAD51 protein expression was induced. This finding has implications for ASO therapeutics with individuals with an induced DNA damage response, such as cancer patients. Furthermore, a phosphorothioate nucleotide analogue potently induced mutation at genomic DNA two orders of magnitude above control. This study shows that a biologically active ASO molecule can induce heritable sequence alterations, and if degraded, its respective analogue may incorporate into genomic DNA with mutagenic consequences.

The Implications of Inheritance for Clinical Management

Since the advent of genotyping, recognition of heritable disease has been perceived as an opportunity for genetic diagnosis or new gene identification studies to advance understanding of pathogenesis. Until recently, however, clinical application of DNA-based testing was confined largely to Mendelian disorders. Even within this remit, predictive testing of relatives is cost-effective only in diseases in which the majority of families harbor mutations in known causal genes, such as adult polycystic kidney disease and hypertrophic cardiomyopathy, but not dilated cardiomyopathy. Confirmatory genetic testing of index cases with borderline clinical features may be economic in the still smaller subset of diseases with limited locus heterogeneity, such as Marfan syndrome. Furthermore, Mendelian diseases account for ≈5% of total disease burden.1 Genome-wide association studies have made headway in elucidating the genetic contribution to the more common, complex diseases, and high throughput techniques promise to facilitate integration of genetic analysis into clinical practice. Nevertheless, many genes remain to be identified and implementation of genomic profiling as a population screening tool would not be cost-effective at present. The implications of heredity, however, extend beyond serving as a platform for genetic analysis, influencing diagnosis, prognostication, and treatment of both index cases and relatives, and enabling rational targeting of genotyping resources. This review covers acquisition of a family history, evaluation of heritability and inheritance patterns, and the impact of inheritance on subsequent components of the clinical pathway. Eliciting a family history is the first step to determining whether a known diagnosis is heritable or symptoms of unknown etiology have a hereditary basis. Both narrative and diagrammatic approaches are integral to data collection, the former including questioning for diseases that recur within the family and the latter involving construction of a pedigree or family tree. Incorporation of psychosocial and interactional data, such as emotional relationships (harmony, apathy, …

Environmental exposures, epigenetics and cardiovascular disease

Epigenetic modifications are heritable alterations of the genome, which can govern gene expression without altering the DNA sequence. The purpose of this review is to render an overview of the possible mechanisms of epigenetic regulation of gene expression in response to environmental pollutants leading to cardiovascular diseases (CVD). An era of cataloging epigenetic marks of the various diseased states has recently commenced, including those within the genes responsible for atherosclerosis, ischemia, hypertension and heart failure. From varied study approaches directed either toward the general understanding of the key pathway regulatory genes, or sampling population cohorts for global and gene-specific changes, it has been possible to identify several epigenetic signatures of environmental exposure relevant to CVD. Signatures of epigenetic dysregulation can be detected in peripheral blood samples, even within a few hours of environmental exposure. However, the field now faces the demand for thorough, systematic, rationalized approaches to establish the relation of exposure-driven epigenetic changes to clinical outcomes, by using sophisticated and reliable research designs and tools. An understanding of chromatin remodelling in response to environmental stimuli conducive to CVD is emerging, with the promise of novel diagnostic and therapeutic candidates.

Epigenetic modifications associated with suicide and common mood and anxiety disorders: a systematic review of the literature

Epigenetic modifications are those reversible, mitotically heritable alterations in genomic expression that occur independent of changes in gene sequence. Epigenetic studies have the potential to improve our understanding of the etiology of mood and anxiety disorders and suicide by bridging the gap in knowledge between the exogenous environmental exposures and pathophysiology that produce common mood and anxiety disorders and suicide. We systematically reviewed the English-language peer-reviewed literature about epigenetic regulation in these disorders between 2001–2011, summarizing and synthesizing this literature with respect to directions for future work. Twenty-one articles met our inclusion criteria. Twelve studies were concerned with epigenetic changes among suicide completers; other studies considered epigenetic regulation in depression, post-traumatic stress disorder, and panic disorder. Several studies focused on epigenetic regulation of amine, glucocorticoid, and serotonin metabolism in the production of common mood and anxiety disorders and suicide. The literature is nascent and has yet to reach consensus about the roles of particular epigenetic modifications in the etiology of these outcomes. Future studies require larger sample sizes and measurements of environmental exposures antecedent to epigenetic modification. Further work is also needed to clarify the link between epigenetic modifications in the brain and peripheral tissues and to establish ‘gold standard’ epigenetic assays.

Epigenetically Heritable Alteration of Fly Development in Response to Toxic Challenge

Developing organisms have evolved a wide range of mechanisms for coping with recurrent environmental challenges. How they cope with rare or unforeseen challenges is, however, unclear as are the implications to their unchallenged offspring. Here, we investigate these questions by confronting the development of the fly, D. melanogaster, with artificial tissue distributions of toxic stress that are not expected to occur during fly development. We show that under a wide range of toxic scenarios, this challenge can lead to modified development that may coincide with increased tolerance to an otherwise lethal condition. Part of this response was mediated by suppression of Polycomb group genes, which in turn leads to derepression of developmental regulators and their expression in new domains. Importantly, some of the developmental alterations were epigenetically inherited by subsequent generations of unchallenged offspring. These results show that the environment can induce alternative patterns of development that are stable across multiple generations.

Quantitative proteomic analysis of mitochondrial proteins reveals prosurvival mechanisms in the perpetuation of radiation-induced genomic instability

Radiation-induced genomic instability is a well-studied phenomenon that is measured as mitotically heritable genetic alterations observed in the progeny of an irradiated cell. The mechanisms that perpetuate this instability are unclear; however, a role for chronic oxidative stress has consistently been demonstrated. In the chromosomally unstable LS12 cell line, oxidative stress and genomic instability were correlated with mitochondrial dysfunction. To clarify this mitochondrial dysfunction and gain insight into the mechanisms underlying radiation-induced genomic instability we have evaluated the mitochondrial subproteome and performed quantitative mass spectrometry analysis of LS12 cells. Of 98 quantified mitochondrial proteins, 17 met criteria for fold changes and reproducibility; and 11 were statistically significant in comparison with the stable parental GM10115 cell line. Previous observations implicated defects in the electron transport chain (ETC) in the LS12 cell mitochondrial dysfunction. Proteomic analysis supports these observations, demonstrating significantly reduced levels of mitochondrial cytochrome c, the intermediary between complexes III and IV of the ETC. Results also suggest that LS12 cells compensate for ETC dysfunction and oxidative stress through increased levels of tricarboxylic acid cycle enzymes and upregulation of proteins that protect against oxidative stress and apoptosis. More than one cellular defect is likely to contribute to the genomic instability phenotype, and evaluation of gene and microRNA expression suggests that epigenetics play a role in the phenotype. These data suggest that LS12 cells have adapted mechanisms that allow survival under suboptimal conditions of oxidative stress and compromised mitochondrial function to perpetuate genomic instability.

Role of epigenetic and miR‐22 and miR‐29b alterations in the downregulation of Mat1a and Mthfr genes in early preneoplastic livers in rats induced by 2‐acetylaminofluorene

Carcinogenesis is a multistep sequential process of clonal expansion of initiated cells associated with the accumulation of multiple cancer-specific heritable phenotypes. The acquisition of these heritable cancer-specific alterations may be triggered by mutational and/or non-mutational changes in the genome that affect the regulation of gene expression. Currently, cancer-specific epigenetically mediated changes in gene expression are regarded as driving events in tumorigenesis. In the present study, we investigated the role of gene-specific expression changes in the mechanism of rat hepatocarcinogenesis induced by the complete hepatocarcinogen 2-acetylaminofluorene (2-AAF). The results of the present study demonstrate significant alterations in gene expression, especially of Mat1a and Mthfr genes, during early stages of rat 2-AAF-induced liver carcinogenesis. Both of these genes were downregulated in the livers of 2-AAF-treated male rats. Inhibition of Mat1a expression was associated with an increase in histone H3 lysine 27 trimethylation and a decrease in histone H3 lysine 18 acetylation at the gene promoter/first exon region. Additionally, we demonstrate for the first time a critical contribution of miR-22 and miR-29b microRNAs in the inhibition of Mat1a and Mthfr gene expression during 2-AAF-induced rat hepatocarcinogenesis. The downregulation of Mat1a and Mthfr genes was accompanied by marked functional alterations in one-carbon metabolism. The results of the present study suggest that downregulation of the Mat1a and Mthfr genes may be one of the main driver events that promote liver carcinogenesis by causing a profound accumulation of subsequent epigenetic abnormalities during progression of the carcinogenic process.

DNA Nicks Promote Efficient and Safe Targeted Gene Correction

Targeted gene correction employs a site-specific DNA lesion to promote homologous recombination that eliminates mutation in a disease gene of interest. The double-strand break typically used to initiate correction can also result in genomic instability if deleterious repair occurs rather than gene correction, possibly compromising the safety of targeted gene correction. Here we show that single-strand breaks (nicks) and double-strand breaks both promote efficient gene correction. However, breaks promote high levels of inadvertent but heritable genomic alterations both locally and elsewhere in the genome, while nicks are accompanied by essentially no collateral local mutagenesis, and thus provide a safer approach to gene correction. Defining efficacy as the ratio of gene correction to local deletion, nicks initiate gene correction with 70-fold greater efficacy than do double-strand breaks (29.0±6.0% and 0.42±0.03%, respectively). Thus nicks initiate efficient gene correction, with limited local mutagenesis. These results have clear therapeutic implications, and should inform future design of meganucleases for targeted gene correction.

Developmental Dioxin Exposure Negatively Affects Fertility and Pregnancy Outcomes in Mice for Multiple Generations.

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) is an ubiquitous environmental contaminant and known endocrine disruptor, capable of interfering with multiple aspects of mammalian reproduction. Mammals are most sensitive to toxicant exposure during early development; thus we developed a mouse model of in utero TCDD exposure in order to examine the impact of this toxicant on adult reproductive function. For our study, pregnant C57bl/6 mice were provided a single dose of TCDD (10 μg/kg) by gavage on gestation day 15.5 (E15.5) and the dams were observed until normal delivery. Female offspring (F1) of TCDD exposed dams and several subsequent generations (F2-F4) were examined at sexual maturity for fertility, uterine decidualization capacity and pregnancy outcomes. Our initial studies of F1 animals revealed diminished uterine progesterone receptor (PR) expression and the majority of mice were infertile or exhibited a poor decidualization response leading to early pregnancy failure. Among mice which were able to achieve pregnancy, preterm birth (PTB) was common. Examination of surviving F3/F4 mice also revealed a significant number of infertile animals, and this transgenerational effect of TCDD was also correlated with diminished uterine PR and impaired decidualization. In F3/F4 mice which were able to become pregnant, ancestral toxicant exposure was associated with a significant increased risk of PTB. In order to further evaluate pregnancy failure in toxicant-exposed mice, in a subsequent study, we euthanized both control and F1 mice during late pregnancy (E18.5) for qRT-PCR analysis of selected genes at the maternal-fetal interface. These studies revealed that a history of developmental toxicant exposure was associated with a premature placental loss of PR mRNA expression and a concomitant increase in expression of toll-like receptor-4 mRNA, a mediator of inflammation. Since immunosuppression is a major function of progesterone related to the timing of birth, we speculated that a loss of PR in our toxicant-exposed mice may lead to PTB as a consequence of a heightened inflammatory response. To test this theory, we examined the ability of pregnant F1 and F3 mice to resist an inflammatory challenge mediated by intraperitoneal injection of lipopolysaccharide (LPS). Following the identification of a dose of LPS that did not induce PTB in control mice (200 μg/kg), F1 and F3 mice were subjected to an identical LPS challenge on E15.5 of pregnancy. In contrast to control animals, which were resistant to the LPS challenge, 100% of mice with a history of TCDD exposure (F1) or their descendants (F3) delivered within 16 hrs of treatment. Our data suggest that TCDD exposure during early development affects multiple aspects of reproductive tract function in adult animals. Significantly, following early life TCDD exposure, we observed a multigenerational incidence of PTB associated with increased sensitivity to non-microbial inflammation at the maternal-fetal interface. The rate of PTB in women in industrialized countries continues to increase despite better health care and patient awareness. Our experimental model in mice supports the possibility that ancestral, early life TCDD exposure may lead to heritable epigenetic alterations affecting fertility and birth outcomes. In humans, the risk of PTB may be yet another adult condition with its origins in the fetal environment. Support: NIEHS ES014942, NCCAM AT006245 and The Endometriosis Association (platform)