Fetal hypothyroidism induces sex-specific epigenetic and transcriptomic alterations in the porcine placenta

Biology of Reproduction · 2026-03-07

The placenta is critical for fetal development, supporting nutrient transport, while also isolating the developing conceptus from adverse maternal signals. The porcine placenta creates an enzymatic barrier for thyroid hormones following activation of the fetal endocrine system in early gestation. Perturbation of the fetal thyroid system can have significant developmental consequences. However, research examining the relationship between fetal thyroid hormone availability, the placental epigenome, and global effects on placental gene expression is limited, particularly in swine. Existing work on select placental genes suggests a potential compensatory response to fetal endocrine disruption during late gestation. We hypothesize that global placental epigenetic and transcriptomic changes may arise in response to induced fetal hypothyroidism. To address this hypothesis, we analyzed placental tissues from gestation day 86 fetuses exposed to 21-day maternal methimazole (MMI) treatment and matched controls. CUT&RUN profiling revealed differential histone mark enrichment, with enrichment of both marks predominantly gained in MMI samples. The placental histone mark status from female fetuses was more substantially altered in response to maternal MMI treatment than placental tissue from male fetuses. In contrast, while differential gene expression was apparent between control and MMI conditions, transcriptional changes were more pronounced in placental tissue from male fetuses. Integration of these datasets revealed treatment- and sex-dependent epigenetic and transcriptional variation. This work expands our understanding of the intricate interplay between fetal thyroid hormone levels and placental gene expression regulation and provides novel insights into the existence of sex-specific differences in placental epigenetic and transcriptomic responses to fetal endocrine disruption.

Surgical alteration of uterine space influences embryonic loss and fetal growth in the contemporary pig

BMC Veterinary Research · 2025-05-20 · 2 citations

BACKGROUND: Litter size is a key economic trait in the swine industry, and ongoing selection for this trait has increased ovulation rates without producing a corresponding increase in uterine capacity. Overcrowding, intensifies competition between fetuses, increasing within-litter variation and the occurrence of intrauterine growth restriction (IUGR). METHODS: We utilized a combination of unilateral oviductal ligation (UOL) and unilateral hysterectomy-ovariectomy (UHO), to create apposing biological extremes of intrauterine crowding. A total of twenty gilts including N = 7 UHO, N = 7 UOL and N = 6 unaltered controls (CON) were synchronized and bred via artificial insemination. Embryonic loss and fetal viability were evaluated on gestation day 95. The fetal population intensively phenotyped including morphometric assessment of skull shape. RESULTS: As expected, UOL significantly reduced litter size, but increased embryonic survival, fetal viability, body weight and uniformity compared to CON. In contrast, UHO significantly increased early embryonic loss, but did not alter fetal viability, body weight or uniformity within litter. UOL increased the absolute weight of all organs compared to UHO and CON, with the exception of the brain (BRN) resulting in a significant reduction in BRN consistent with the established brain-sparing effect. The ratio of skull curve-to-linear length (C: L) was significantly reduced in UOL fetuses and found to be strongly correlated with brain-to-liver weight ratio (BRN: LVR). CONCLUSIONS: The results of this study confirm the negative effects of uterine crowding on fetal growth. They further suggest that contemporary gilts approach the limit of uterine capacity, such that increased crowding results in additional early embryonic loss.

Chromatin profiling and state predictions reveal insights into epigenetic regulation during early porcine development

Epigenetics & Chromatin · 2024 · 1 citations

• Computer Science
• Biology
• Computational biology

BACKGROUND: Given their physiological similarities to humans, pigs are increasingly used as model organisms in human-oriented biomedical studies. Additionally, their value to animal agriculture across the globe has led to the development of numerous studies to investigate how to improve livestock welfare and production efficiency. As such, pigs are uniquely poised as compelling models that can yield findings with potential implications in both human and animal contexts. Despite this, many gaps remain in our knowledge about the foundational mechanisms that govern gene expression in swine across different developmental stages, particularly in early development. To address some of these gaps, we profiled the histone marks H3K4me3, H3K27ac, and H3K27me3 and the SWI/SNF central ATPase BRG1 in two porcine cell lines representing discrete early developmental time points and used the resulting information to construct predicted chromatin state maps for these cells. We combined this approach with analysis of publicly available RNA-seq data to examine the relationship between epigenetic status and gene expression in these cell types. RESULTS: In porcine fetal fibroblast (PFF) and trophectoderm cells (PTr2), we saw expected patterns of enrichment for each of the profiled epigenetic features relative to specific genomic regions. H3K4me3 was primarily enriched at and around global gene promoters, H3K27ac was enriched in promoter and intergenic regions, H3K27me3 had broad stretches of enrichment across the genome and narrower enrichment patterns in and around the promoter regions of some genes, and BRG1 primarily had detectable enrichment at and around promoter regions and in intergenic stretches, with many instances of H3K27ac co-enrichment. We used this information to perform genome-wide chromatin state predictions for 10 different states using ChromHMM. Using the predicted chromatin state maps, we identified a subset of genomic regions marked by broad H3K4me3 enrichment, and annotation of these regions revealed that they were highly associated with essential developmental processes and consisted largely of expressed genes. We then compared the identities of the genes marked by these regions to genes identified as cell-type-specific using transcriptome data and saw that a subset of broad H3K4me3-marked genes was also specifically expressed in either PFF or PTr2 cells. CONCLUSIONS: These findings enhance our understanding of the epigenetic landscape present in early swine development and provide insight into how variabilities in chromatin state are linked to cell identity. Furthermore, this data captures foundational epigenetic details in two valuable porcine cell lines and contributes to the growing body of knowledge surrounding the epigenetic landscape in this species.

Identification of SWI/SNF Subcomplex GBAF Presence, Intra-Complex Interactions, and Transcriptional Dynamics during Early Porcine Development

Animals · 2024 · 1 citations

• Biology
• Computational biology
• Genetics

Understanding the complex interplay between genetics and environmental factors is vital for enhancing livestock production efficiency while safeguarding animal health. Despite extensive studies on production-specific genes in livestock, exploring how epigenetic mechanisms and heritable modifications govern animal growth and development remains an under-explored frontier with potential implications across all life stages. This study focuses on the GBAF chromatin remodeling complex and evaluates its presence during embryonic and fetal development in swine. Immunocytochemistry and co-immunoprecipitation techniques were employed to investigate the presence and interactions of GBAF subunits BRD9 and GLTSCR1 in porcine oocytes, preimplantation embryos, and cell lines, and transcriptional dynamics of GBAF subunits across these key developmental stages were analyzed using existing RNA-seq datasets. BRD9 and GLTSCR1 were identified across all represented stages, and an interaction between GLTSCR1 and BAF170 was shown in PTr2 and PFF cells. Our findings highlight the ubiquitous presence of GBAF in porcine early development and the potentially novel association between GLTSCR1 and BAF170 in swine. The transcriptional dynamics findings may suggest GBAF-specific contributions during key developmental events. This study contributes to the growing understanding of epigenetic regulators in both swine and mammalian development, emphasizing the implications of GBAF as a modulator of key developmental events.

Depletion of SMARCB1 and BRD7, two SWI/SNF chromatin remodelling complex subunits, differentially impact porcine embryo development

Reproduction Fertility and Development · 2022 · 1 citations

• Biology
• Cell biology
• Genetics

CONTEXT: SWI/SNF chromatin remodelling complexes are composed of multiple protein subunits and can be categorised into three sub-families, including the BAF, PBAF, and GBAF complexes. We hypothesised that depletion of SMARCB1 and BRD7, two subunits unique to different SWI/SNF sub-families, would differentially impact porcine embryo development. AIM: The aim of these experiments was to determine the developmental requirements of two SWI/SNF subunits, SMARCB1 and BRD7. METHODS: RNA interference assays were used to determine the developmental requirements of SMARCB1 and BRD7 in porcine embryos. KEY RESULTS: Our findings indicate that knockdown of SMARCB1 dramatically reduces embryo developmental potential, with few embryos developing beyond the pronuclear stage. The knockdown of BRD7 had a less severe impact on developmental potential. CONCLUSIONS: Our findings also demonstrate that knockdown of SMARCB1 alters the expression of NANOG and POU5F1 (also referred to as OCT4 ). IMPLICATIONS: These findings highlight the unique developmental requirements for sub-families of SWI/SNF chromatin remodelling complexes. This new knowledge will enable us to determine how discrete genomic loci are differentially remodelled during key points in embryo development.

Nuclear trafficking dynamics of Bromodomain-containing protein 7 (BRD7), a switch/sucrose non-fermentable (SWI/SNF) chromatin remodelling complex subunit, in porcine oocytes and cleavage-stage embryos

Reproduction Fertility and Development · 2019-05-13 · 2 citations

In the work presented here, we investigated how bromodomain-containing protein 7 (BRD7), a subunit associated with switch/sucrose non-fermentable (SWI/SNF) chromatin remodelling complexes, is trafficked between cellular compartments during embryo development. SWI/SNF complexes are multi-subunit complexes that contain a core catalytic subunit (SWI/SNF related, Matrix associated, Actin dependent Regulator of Chromatin, subfamily A, member 4, or member 2; SMARCA4 or SMARCA2) and a collection of additional subunits that guide the complexes to their appropriate loci; BRD7 is one of these additional subunits. We hypothesised that BRD7 is exported from the nuclei of porcine oocytes and embryos in a Chromosome Region Maintenance 1 (CRM1)-dependent manner and imported into the nuclei using the karyopherin α/β1 heterodimer. Porcine oocytes and embryos were treated with inhibitors of CRM1-mediated nuclear export and karyopherin α/β1-mediated nuclear import to test this hypothesis. An RNA interference assay and a dominant negative overexpression assay were also performed to determine if karyopherin α7 serves a specific role in BRD7 trafficking. Our findings indicate that BRD7 shuttles between nuclear and cytoplasmic compartments during cleavage development. The shuttling of BRD7 indicates that it serves a unique role in remodelling chromatin during this developmental window.

Chromatin remodeling in mammalian embryos

Reproduction · 2018-01-16 · 33 citations

The mammalian embryo undergoes a dramatic amount of epigenetic remodeling during the first week of development. In this review, we discuss several epigenetic changes that happen over the course of cleavage development, focusing on covalent marks (e.g., histone methylation and acetylation) and non-covalent remodeling (chromatin remodeling via remodeling complexes; e.g., SWI/SNF-mediated chromatin remodeling). Comparisons are also drawn between remodeling events that occur in embryos from a variety of mammalian species.

Differential expression of key subunits of SWI/SNF chromatin remodeling complexes in porcine embryos derived in vitro or in vivo

Molecular Reproduction and Development · 2017-10-10 · 6 citations

In vitro embryo production is an established method for both humans and animals, but is fraught with inferior development and health issues in offspring born after in vitro fertilization procedures. Analysis of epigenetic changes caused by exposure to in vitro conditions should shed light on potential sources of these phenotypes. Using immunocytochemistry, we investigated the localization and relative abundance of components associated with the SWI/SNF (Switch/Sucrose non-fermentable) chromatin-remodeling complex-including BAF155, BAF170, BAF180, BAF53A, BAF57, BAF60A, BAF45D, ARID1A, ARID1B, ARID2, SNF5, and BRD7-in oocytes and in in vitro-produced and in vivo-derived porcine embryos. Differences in the localization of BAF155, BAF170, BAF60A, and ARID1B among these sources indicate that improper timing of chromatin remodeling and cellular differentiation might occur in early preimplantation embryos produced and cultured in vitro.

ARID1A, a component of SWI/SNF chromatin remodeling complexes, is required for porcine embryo development

Molecular Reproduction and Development · 2017-11-26 · 15 citations

Mammalian embryos undergo dramatic epigenetic remodeling that can have a profound impact on both gene transcription and overall embryo developmental competence. Members of the SWI/SNF (Switch/Sucrose non-fermentable) family of chromatin-remodeling complexes reposition nucleosomes and alter transcription factor accessibility. These large, multi-protein complexes possess an SNF2-type ATPase (either SMARCA4 or SMARCA2) as their core catalytic subunit, and are directed to specific loci by associated subunits. Little is known about the identity of specific SWI/SNF complexes that serve regulatory roles during cleavage development. ARID1A, one of the SWI/SNF complex subunits, can affect histone methylation in somatic cells; here, we determined the developmental requirements of ARID1A in porcine oocytes and embryos. We found ARID1A transcript levels were significantly reduced in 4-cell porcine embryos as compared to germinal vesicle-stage oocytes, suggesting that ARID1A would be required for porcine cleavage-stage development. Indeed, injecting in vitro-matured and fertilized porcine oocytes with double-stranded interfering RNAs that target ARID1A, and evaluating their phenotype after seven days, revealed that the depletion of ARID1A results in significantly fewer cells than their respective control groups (p < 0.001).

Maternal Exercise Does Not Significantly Alter Adult Rat Offspring Vascular Function

Medicine & Science in Sports & Exercise · 2015-03-20 · 10 citations

PURPOSE: Research has revealed the role of adverse behaviors during pregnancy on metabolic and cardiovascular health outcomes in offspring. However, minimal attention has been focused on positive prenatal behaviors, such as exercise, and the effect on offspring health outcomes. The objective of this investigation was to test the hypothesis that mothers who voluntarily exercise during pregnancy would improve endothelial function in offspring from exercising compared with sedentary mothers. METHODS: Female Sprague Dawley rats were divided into sedentary (n = 10) or exercise (n = 9) groups with, the exercise group having voluntary access to a running wheel throughout gestation. Litter characteristics (weight and size) were taken 1 d after birth. After weaning, offspring were placed in sedentary cages where they remained until 4 or 8 months of age. Offspring food consumption and cage activity were assessed during a 72-h interval at 2, 4, 6, and 8 months of age. The abdominal aortas of offspring were harvested at 4 or 8 months of age, and vascular function was assessed using cumulative doses of endothelium-dependent (acetylcholine/10(-10)-10(-4) M) and independent (sodium nitroprusside/10(-10)-10(-4) M) vasodilators. RESULTS: There were no significant differences in litter size and litter weight at weaning between the sedentary and exercise groups. Food consumption and wheel running activity did not differ between the sedentary and exercise offspring at 2, 4, 6, or 8 months of age. Vasorelaxation response to acetylcholine or sodium nitroprusside did not differ between the offspring from sedentary and exercise dams. CONCLUSIONS: Maternal voluntary wheel running during pregnancy does not significantly alter behavior or vascular function in adult offspring.