Genome-wide association study identifies genomic regions associated with key reproductive traits in Korean Hanwoo cows

BACKGROUND

Conducting genome-wide association studies (GWAS) for reproductive traits in Hanwoo cattle, including age at first calving (AFC), calving interval (CI), gestation length (GL), and number of artificial inseminations per conception (NAIPC), is of paramount significance. These analyses provided a thorough exploration of the genetic basis of these traits, facilitating the identification of key markers for targeted trait improvement. Breeders can optimize their selection strategies, leading to more efficient and sustainable breeding programs, by incorporating genetic insights. This impact extends beyond individual traits and contributes to the overall productivity and profitability of the Hanwoo beef cattle industry. Ultimately, GWAS is essential in ensuring the long-term genetic resilience and adaptability of Hanwoo cattle populations. The primary goal of this study was to identify significant single nucleotide polymorphisms (SNPs) or quantitative trait loci (QTLs) associated with the studied reproductive traits and subsequently map the underlying genes that hold promise for trait improvement.

RESULTS

A genome-wide association study of reproductive traits identified 68 significant single nucleotide polymorphisms (SNPs) distributed across 29 Bos taurus autosomes (BTA). Among them, BTA14 exhibited the highest number of identified SNPs (25), whereas BTA6, BTA7, BTA8, BTA10, BTA13, BTA17, and BTA20 exhibited 8, 5, 5, 3, 8, 2, and 12 significant SNPs, respectively. Annotation of candidate genes within a 500 kb region surrounding the significant SNPs led to the identification of ten candidate genes relevant to age at first calving. These genes were: FANCG, UNC13B, TESK1, TLN1, and CREB3 on BTA8; FAM110B, UBXN2B, SDCBP, and TOX on BTA14; and MAP3K1 on BTA20. Additionally, APBA3, TCF12, and ZFR2, located on BTA7 and BTA10, were associated with the calving interval; PAX1, SGCD, and HAND1, located on BTA7 and BTA13, were linked to gestation length; and RBM47, UBE2K, and GPX8, located on BTA6 and BTA20, were linked to the number of artificial inseminations per conception in Hanwoo cows.

CONCLUSIONS

The findings of this study enhance our knowledge of the genetic factors that influence reproductive traits in Hanwoo cattle populations and provide a foundation for future breeding strategies focused on improving desirable traits in beef cattle. This research offers new evidence and insights into the genetic variants and genome regions associated with reproductive traits and contributes valuable information to guide future efforts in cattle breeding.

SWATH-MS Analysis of Blood Plasma and Circulating Small Extracellular Vesicles Enables Detection of Putative Protein Biomarkers of Fertility in Young and Aged Dairy Cows

The development of biomarkers of fertility could provide benefits for the genetic improvement of dairy cows. Circulating small extracellular vesicles (sEVs) show promise as diagnostic or prognostic markers since their cargo reflects the metabolic state of the cell of origin; thus, they mirror the physiological status of the host. Here, we employed data-independent acquisition mass spectrometry to survey the plasma and plasma sEV proteomes of two different cohorts of Young (Peripubertal; n = 30) and Aged (Primiparous; n = 20) dairy cows (Bos taurus) of high- and low-genetic merit of fertility and known pregnancy outcomes (ProteomeXchange data set identifier PXD042891). We established predictive models of fertility status with an area under the curve of 0.97 (sEV; p value = 3.302e-07) and 0.95 (plasma; p value = 6.405e-08). Biomarker candidates unique to high-fertility Young cattle had a sensitivity of 0.77 and specificity of 0.67 (*p = 0.0287). Low-fertility biomarker candidates uniquely identified in sEVs from Young and Aged cattle had a sensitivity and specificity of 0.69 and 1.0, respectively (***p = 0.0005). Our bioinformatics pipeline enabled quantification of plasma and circulating sEV proteins associated with fertility phenotype. Further investigations are warranted to validate this research in a larger population, which may lead to improved classification of fertility status in cattle.

Integrins and their potential roles in mammalian pregnancy

Integrins are a highly complex family of receptors that, when expressed on the surface of cells, can mediate reciprocal cell-to-cell and cell-to-extracellular matrix (ECM) interactions leading to assembly of integrin adhesion complexes (IACs) that initiate many signaling functions both at the membrane and deeper within the cytoplasm to coordinate processes including cell adhesion, migration, proliferation, survival, differentiation, and metabolism. All metazoan organisms possess integrins, and it is generally agreed that integrins were associated with the evolution of multicellularity, being essential for the association of cells with their neighbors and surroundings, during embryonic development and many aspects of cellular and molecular biology. Integrins have important roles in many aspects of embryonic development, normal physiology, and disease processes with a multitude of functions discovered and elucidated for integrins that directly influence many areas of biology and medicine, including mammalian pregnancy, in particular implantation of the blastocyst to the uterine wall, subsequent placentation and conceptus (embryo/fetus and associated placental membranes) development. This review provides a succinct overview of integrin structure, ligand binding, and signaling followed with a concise overview of embryonic development, implantation, and early placentation in pigs, sheep, humans, and mice as an example for rodents. A brief timeline of the initial localization of integrin subunits to the uterine luminal epithelium (LE) and conceptus trophoblast is then presented, followed by sequential summaries of integrin expression and function during gestation in pigs, sheep, humans, and rodents. As appropriate for this journal, summaries of integrin expression and function during gestation in pigs and sheep are in depth, whereas summaries for humans and rodents are brief. Because similar models to those illustrated in Fig. 1, 2, 3, 4, 5 and 6 are present throughout the scientific literature, the illustrations in this manuscript are drafted as Viking imagery for entertainment purposes.

Reconstitution of Caruncle Placenta through the 20α-HSD/Casp-3 Apoptotic Pathway during Early Pregnancy in Bovines

Trophoblast cells of endometrium during bovine pregnancy with different characteristics undergo dynamic changes during uterine remodeling, which can be observed as continuous changes, as P4 secreted by the mother is replaced by placental hormones. In this context, the present study analyzed tissues' morphological changes through uterine apoptosis during early pregnancy. In addition, the expression pattern associated with apoptosis genes and 20α-HSD was determined in the endometrium and caruncle tissues. The localization of 20α-HSD, VEGF, Casp3, and mTOR protein was also determined in endometrium and caruncle during early pregnancy. From around 30 days, caruncle trophoblast cells with very high invasiveness expanded the villus section as the gestation period progressed. The surrounding cells detached and reorganized into new cells. In addition, an analysis of the effect of apoptosis on cell reorganization in the caruncle revealed that the expression of 20α-HSD/Casp-3 signals in the villus section gradually increased from 30 to 90 days. However, on the 30th day, glandular epithelial cells occurred sporadically in the trophoblast cell section. Moreover, the apoptosis of trophoblast cells increased at 90 days. Taken together, the results of the present study show that changes in the uterus during early pregnancy promote changes during later pregnancy by inducing the reorganization through the stimulation of 20α-HSD and Casp-3, promoting uterine and caruncle tissues, unlike cell development mediated by hormone signaling.

Gene expression profile of placentomes and clinical parameters in the cows with retained placenta

BACKGROUND

Retained placenta (RP) is a prevalent disorder in cattle with many health-related and economic costs for the farm owners. Its etiology has not been clarified yet and there is no definite therapy for this disorder. In this study we conducted RNA-seq, hematologic and histologic experiments to survey the causes of RP development.

METHODS

Blood samples were collected from 4 RP and 3 healthy cows during periparturtion period for hematological assessments followed by placentome sampling within 30 min after parturition. Cows were grouped as RP and control in case the placenta was retained or otherwise expelled, respectively. Total RNA was extracted from placentome samples followed by RNA-sequencing.

RESULTS

We showed 240 differentially expressed genes (DEGs) between the RP and control groups. Enrichment analyzes indicated immune system and lipid metabolism as prominent over- and under-represented pathways in RP cows, respectively. Hormonal assessments showed that estradiol-17β (E2) was lower and cortisol tended to be higher in RP cows compared to controls at the day of parturition. Furthermore, histologic experiment showed that villi-crypt junctions remain tighter in RP cows compared to controls and the crypts layer seemed thicker in the placentome of RP cows. Complete blood cell (CBC) parameters were not significantly different between the two groups.

CONCLUSION

Overall, DEGs derived from expression profiling and these genes contributed to enrichment of immune and lipid metabolism pathways. We suggested that E2 could be involved in development of RP and the concentrations of P4 and CBC counts periparturition might not be a determining factor.

The role of dermatopontin in cell adhesion in bovine placenta during early-mid pregnancy and parturition - Pilot study

Dermatopontin (DPT) is a small protein molecule thought to have a role in the formation of the extracellular architecture and adhesion. The aim of the study was to confirm the presence of DPT and to examine its role in placental cell adhesion during pregnancy, at parturition and postpartum in cows. Placental tissue samples were obtained at abattoir from healthy pregnant cows (n = 6) while parturient samples were collected during caesarian section and retrospectively divided into released up to 6 h (R; n = 5) and not released up to 6 h (NR; n = 4) foetal membranes. Maternal epithelial cells were isolated from pregnant samples and were used for the examination of the influence of DPT (5, 50 and 100 ng/mL) on cell adhesion. Parturient samples were manually divided into maternal and foetal part and individually homogenized for Western blotting and ELISA analysis. Western blotting confirmed the presence of DPT in examined tissues. ELISA test showed significant (p < 0.05) decrease in DPT concentration within examined pregnancy period with higher concentrations in maternal part (p < 0.05). Moreover, at parturition DPT concentration further decreased in maternal (p < 0.05) but increased (p < 0.05) in fetal part. The examination of not released samples showed opposite relationship in comparison to parturient samples - the increase in maternal (p < 0.05) and the decrease in fetal (p < 0.05) part of placenta. DPT facilitated the adhesion of epithelial cells in examined periods of pregnancy in increasing manner with pregnancy course. The presence of DPT in bovine placenta during pregnancy and parturition was confirmed. This protein may influence cell adhesion during attachment and detachment of placenta. Further studies on mechanisms of action of DPT in bovine placenta are necessary.

Alpha-actinin-4 is essential for maintaining normal trophoblast proliferation and differentiation during early pregnancy

BACKGROUND

Proper differentiation of trophoblasts in the human placenta is essential for a successful pregnancy, whereas abnormal regulation of this process may lead to adverse pregnancy outcomes, especially preeclampsia (PE). However, the underlying mechanism of trophoblast differentiation remains unclear. Previous studies have reported the involvement of alpha-actinin-4 (ACTN4) in the actin cytoskeleton dynamics and motility. Hence, we hypothesized that ACTN4 may act as an important regulator in the normal proliferation and differentiation of trophoblasts during early pregnancy.

METHOD

To test this hypothesis, we collected villous tissues from women undergoing a legal pregnancy termination during 6-10 weeks of gestation and explanted them for cell culture and siRNA transfection. We also obtained placental tissues from PE patients and healthy pregnant women and isolated the primary cytotrophoblast (CTB) cells. The expression of ACTN4 in the CTBs of placental villi and during the differentiation of CTBs into STBs was detected by immunofluorescence, immunohistochemistry (IHC), and EdU proliferation assays. Besides, villous explant, Matrigel invasion, transwell migration assay, and Wound-healing assay were performed to identify the possible role of ACTN4 in the outgrowth of explants and the invasion, migration, and proliferation of cell column trophoblasts (CCTs). Western blot analysis was carried out to compare the protein expression level of AKT, Snail activities, and epithelial-to-mesenchymal transition (EMT) in the villi or HTR8/SVneo cells with ACTN4 knockdown.

RESULTS

ACTN4 was highly expressed in CTB cells and interstitial extravillous trophoblast (iEVT) cells but not found in the syncytiotrophoblast (STB) cells in the first trimester villi. Downregulation of ACTN4 led to reduced trophoblast proliferation and explant outgrowth ex vivo, as well as iEVT invasion and migration in vitro due to disrupt of actin filaments organization. Such ACTN4 inhibition also decreased AKT and Snail activities and further impeded the EMT process. In addition, ACTN4 expression was found to be downregulated in the iEVTs from preeclamptic placentas.

CONCLUSIONS

Our findings suggest that ACTN4 may act as an important regulator of trophoblast proliferation and differentiation during early pregnancy, and dysregulation of this protein may contribute to preeclampsia pathogenesis.

The distribution of some homeobox proteins in the bovine placenta during gestation

Homeobox proteins are transcription factors known to be involved in the molecular basics of body model formation and transformation. Some homeobox proteins are known to play critical roles in the control of the extraembryonic development of the placenta during gestation and in the regulation of uterine and placental physiology in adults. The gravid uteruses and placentas of 27 Holsteins cows, obtained from private slaughterhouses, were used in this study. The tissues were assigned to three groups as belonging to the first, second and third timesters of gestation, based on the fetal ages determined. Subsequently, the tissues were subjected to immunohistochemical staining using antibodies specific to the proteins investigated in the study. The evaluation of the immunohistochemical findings obtained in this study, demonstrated the presence of trimester-dependent varying intensities of immunoreactions in the uterus and placenta. Immunoreactivity was observed particularly in the luminal and glandular epithelial cells of the uterus, as well as in stromal and some endothelial cells. Furthermore, immunoreactivity for the proteins HOXA10, HOXB6, HOXC6 and Dlx-5 was determined in the smooth muscle cells. Moreover, immunoreactivity was also detected in the maternal epithelium and fetal trophoblasts found in the structure of the placenta. The results suggest that the homeobox proteins investigated may have critical roles in the regulation of endometrial functions in cows, and the proliferation and differentiation of endometrial and placental cells. It is concluded that these proteins may have physiological roles in the formation and development of the placenta, as well as in the maintenance of pregnancy.

Effect of decorin and selected glycosylation inhibitors on the adhesion of caruncular epithelial cells of pregnant cows-part I

Adhesion process ensures the formation of the appropriate connection between mother and foetus during placentation and further placental development, which determines physiological pregnancy course. Extracellular matrix of foetal membranes are a rich source of biologically active proteins, the synthesis of which is regulated by hormones. Depending on the stage of pregnancy, the protein profile of the placenta changes, thanks to which its remodelling is possible. The aim of the study was to evaluate the effect of decorin, as well as selected glycosylation inhibitors on the adhesion of caruncular epithelial cells derived from cows during pregnancy. Placental cells were isolated from healthy, pregnant (2nd and 4th month) cows after slaughter, which allowed for the establishment of 4 primary cell cultures without visible cells of fibroblast morphology. The presence of decorin in cell monolayer and cell lysates was determined by the use of immunocytochemistry and Western blotting, respectively. The viability of cells was evaluated by MTT assay. The adhesion of cells to fibronectin was measured spectrophotometrically. Protein N-glycosylation and O-glycosylation have a modulating effect on the adhesion and viability of placental cells during early-mid pregnancy. Decorin and tunicamycin were shown to have anti-adhesive properties with respect to caruncular cells of the pregnant bovine uterus.

Trophoblastic proliferation and invasion regulated by ACTN4 is impaired in early onset preeclampsia

Successful pregnancy requires normal placentation, which largely depends on the tight regulation of proliferation, invasion, and migration of trophoblast cells. Abnormal functioning of trophoblast cells may cause failure of uterine spiral artery remodeling, which may be related to pregnancy-related disorders, such as preeclampsia. Here, we reported that an actin-binding protein, α-actinin (ACTN)4, was dysregulated in placentas from early onset preeclampsia. Moreover, knockdown of ACTN4 markedly inhibited trophoblast cell proliferation by reducing AKT membrane translocation. Furthermore, E-cadherin regulated ACTN4 and β-catenin colocalization on trophoblast cell podosomes, and ACTN4 down-regulation suppressed the E-cadherin-induced cell invasion increase via depolymerizing actin filaments. Moreover, loss of ACTN4 recapitulated a number of the features of human preeclampsia. Therefore, our data indicate that ACNT4 plays a role in trophoblast function and is required for normal placental development.-Peng, W., Tong, C., Li, L., Huang, C., Ran, Y., Chen, X., Bai, Y., Liu, Y., Zhao, J., Tan, B., Luo, X., Wang, H., Wen, L., Zhang, C., Zhang, H., Ding, Y., Qi, H., Baker, P. N. Trophoblastic proliferation and invasion regulated by ACTN4 is impaired in early onset preeclampsia.

Preliminary results of the placental decorin profile in bovine pregnancy and parturition

Decorin is a small leucine-rich proteoglycan which is involved in multiple biological functions mainly as a structural and signaling molecule. Due to its biological properties in connective tissue, decorin may participate in remodeling of ECM during attachment and detachment of placenta within the course of pregnancy and at parturition in cows. The aim of the study was to detect the presence of decorin protein in bovine placental tissues and to evaluate its profile during pregnancy and at parturition. Placental tissues from healthy pregnant cows (2–5 month) were collected in abattoir (n = 10), while parturient tissues were obtained during caesarian section at physiological term (n = 6). Maternal and fetal parts were separated manually and subjected to homogenization and to quantitative ELISA and verification by Western blotting with anti-decorin antibodies. ELISA test showed that the concentration of decorin during pregnancy was higher in the fetal part of placenta compared with the maternal part (p < 0.001). Similar pattern was noted regarding to maternal and fetal samples derived from parturient cows. Our preliminary results demonstrate that the concentration of decorin is gestation time-dependent in healthy bovine placenta. Possible confirmation of the involvement of decorin in early pregnancy attachment and detachment of the placenta during parturition requires further research.

The newly established bovine endometrial gland cell line (BEGC) forms gland acini in vitro and is only IFNτ-responsive (MAPK42/44 activation) after E2 and P4-pre-incubation

INTRODUCTION

Uterine glands (UG) are crucial for the establishment of ruminant pregnancy and influenced (orchestrated manner) by estrogen (E₂), progesterone (P₄) and interferon tau (IFNτ). In the study we established a bovine endometrial glandular cell line (BGEC) and tested its functional reactivity (signaling) to IFNτ.

METHODS

BGEC was characterized by light microscopy (LM), epithelial markers (ezrin, CK18) [immunofluorescence (IF)/immunohistochemistry (IHC)] and ultrastructure (TEM/SEM) (apical microvilli). In vitro formation of gland acini and transepithelial-electric-resistance (TEER) measurements (EVOM) were done. The expression of mRNA-transcripts (RT-PCR) of steroid receptors (PR, PGRMC1/2, ESR1/2) and the IFNτ-system (IFNAR1/2, IRF1, 2, 9) was checked. BEGC was stimulated with IFNτ (10 ng/ml;1000 ng/ml) (15 min) after steroid pre-treatment [10 pg/ml E₂ (two days)/20 ng/ml P₄ (two days)]. Activation of MAPK42/44;STAT1 was evaluated (densitometrical Western Blot).

RESULTS

BGEC cells expressed epithelial markers and possessed apical microvilli. High TEER-values could be measured (2320-2620 ohm/cm²). The assembled BEGC acini (25 days) were similar to UG in vivo (markers/ultrastructure). All transcripts (steroid receptors/IFNτ-system) could be detected in BEGC (mRNA). MAPK42/44 were significantly activated after E₂/P₄ pre-treatment and IFNτ stimulation (10 ng/ml) (p < 0.05), whilst 1000 ng/ml IFNτ did not activate MAPK42/44. Neither a STAT1 (by IFNτ) nor an activation (MAPK42/44;STAT1) by IFNτ-only was observed.

DISCUSSION

BGEC retains its epithelial phenotype in culture and forms gland acini in vitro thereby confirming its glandular character. Cells were only reactive to (low) IFNτ concentrations when pre-treated with steroids thereby closely resembling implantation physiology in vivo. BEGC can be used as a bovine implantation model to study embryo-maternal communication during early pregnancy in cattle.

Extracellular matrix proteins in healthy and retained placentas, comparing hemochorial and synepitheliochorial placentas

The placenta expresses structural and biologically active proteins. Their synthesis is mainly regulated by genomic or nongenomic signals and modulated by hormones. These protein profiles are altered during different stages of pregnancy. The biological properties of extracellular matrix (ECM) proteins were defined and described in a number of tissues including placenta. These properties enable them to be the main players in the processes of attachment or invasion into the endometrium during initial placenta formation and its timely separation after delivery and detachment. In this review, we focused on the role of ECM proteins during attachment of the placenta to the uterine wall, its timely separation, and the implications of this process on retained or pathologically attached placenta. Although the amount of published information in this area is relatively scant, some of the key proteins and processes are well defined. We focused on the available data detailing the ECM protein profiles of human (histologically thin; hemochorial) and bovine (histologically thick; epitheliochorial) placentas and compared the shared and unique ECM proteins that are relevant to placental attachment and separation.

The bovine placenta in vivo and in vitro

The gross anatomic features (cotyledonary type) and histologic classification (synepitheliochorial) of the bovine placenta have been known for many years. Thorough ultrastructural analysis as well as a variety of descriptive studies dealing with the localization of cytoskeletal filaments, extracellular matrix, growth factor systems, steroid hormone receptors, and major histocompatibility complex have contributed further significant knowledge. However, this knowledge was not sufficient to solve clinical placenta-based problems, such as retained fetal membranes. Owing to the complexity of the fetomaternal interface in vitro, culture systems have been developed. As trophoblast giant cells (TGC) are thought to be key players in the cattle placenta, most cell culture models attempt to overcome the pitfall of losing the entire TGC population in vitro. Nevertheless, distinct cell line-based in vitro systems such as cell monolayers or 3-dimensional (co-culture) spheroids were generated for the fetal (trophoblast) and maternal (uterine epithelium) placental compartments. Monolayers have been used to study for example, growth factor or hormonal signaling and TGC formation, whereas spheroids served as models for, for example, trophoblast attachment, uterine epithelium depolarization, and also TGC formation. In the future, the use of more improved culture models might lead to better treatments of retained fetal membranes and increased prevention of embryonic loss. In addition, the in vitro models could shed more light on the mechanisms of the differentiation of uninucleate trophoblast into TGC.

Pregnancy boosts vaccine-induced Bovine Neonatal Pancytopenia-associated alloantibodies

Although maternal vaccination is generally considered to be safe, the occurrence of Bovine Neonatal Pancytopenia (BNP) in cattle shows that maternal vaccination may pose a risk to the offspring. Pregsure BVD-induced maternal alloantibodies cause BNP in newborn calves. The occurrence of BNP years after last Pregsure BVD vaccination indicates that alloantibody levels may remain high in dams. Since pregnancy induces alloantibodies we hypothesized that pregnancy boosts the vaccine-induced alloantibody response. Alloantibody levels in Pregsure BVD-vaccinated dams increased from conception towards the end of gestation and declined after parturition. In parallel, BVDV-antibody levels remained constant, indicating that there is specific boosting of alloantibodies. Since the rise in alloantibodies coincides with pregnancy and other alloantigen sources were excluded, we concluded that fetal alloantigens expressed during pregnancy boost the alloimmune response in the dam. These results help explain why BNP cases occur even years after Pregsure BVD has been taken off the market.

Formation of bovine placental trophoblast spheroids

INTRODUCTION

In this study, we aimed to form spheroids with the bovine placental trophoblast cell line F3. Spheroids are 3-dimensional culture models which can be used to conduct versatile in vitro and in vivo experiments.

MATERIALS AND METHODS

The spheroids were generated using the hanging drop technique, 25% methocel and matrigel. The F3 spheroids were characterized morphologically by light microscopy and transmission (TEM) and scanning electron microscopy (SEM) and immunohistochemistry (ezrin, vimentin, cytokeratin, placental lactogen). The fluorescent dyes calcein and ethidium homodimer were used to determine the viability of the spheroidal F3 cells by immunofluorescence microscopy.

RESULTS

The cell line F3 only formed spheroids by the hanging drop technique when matrigel was added. The trophoblast spheroids were delimited and fully covered by extracellular matrix (light microscopy/TEM/SEM). Cells contributing to spheroids could not be discriminated from each other (light microscopy). The outer spheroidal layer consisted of cells which possessed an apical pole with microvilli that were directed to the outside (light microscopy/TEM). All of the spheroidal F3 cells expressed ezrin, vimentin and cytokeratin, but not placental lactogen. The spheroid core contained degenerating cells whilst the F3 cells of the outer rim were viable (TEM/immunofluorescence microscopy).

DISCUSSION

We have established a 3-dimensional spheroid model for the bovine placental trophoblast cell line F3. The developed culture model might prove valuable for future in vitro studies on the differentiation of bovine trophoblast cells.