Interferon-Stimulated Gene Expression in Peripheral Blood Leucocytes as a Convenient Prediction Marker for Embryo Status in Embryo-Transferred Japanese Black Cows during the Peri-Implantation Period.

Pregnancy diagnosis during early gestation is important for cattle reproduction. The expression of interferon-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) was studied in embryo-transferred (ET) Japanese Black cattle. ISGs in PBLs-ISG15, MX1, MX2, and OAS1-were detected in multiple ovulation ET cattle using a real-time quantitative polymerase chain reaction, and receiver operating characteristic (ROC) curve analysis was performed. Gestational status was predicted using the average ISG levels during the normal estrous cycle (AVE) and the Youden index from the ROC curve analysis as cutoff values. The ISG15, MX1, and MX2 levels were significantly higher in pregnant cattle (n = 10) than in non-pregnant cattle (n = 23) on gestation day 21, whereas the levels of all ISGs were similar between non-pregnant and non-pregnant cattle with late embryonic death (n = 7). ISG15, MX1, and MX2 appropriately predicted the gestational status of ET cows. The statistical evaluation of the diagnostic accuracy in ET cows on day 21 of gestation presented higher values of sensitivity, specificity, accuracy, and positive predictive values of ISG15, MX1, and MX2 using the Youden index than using the AVE. Therefore, ISG15, MX1, and MX2 are excellent biomarkers of gestational status during the peri-implantation period in ET cattle.

Effects of oral ß-cryptoxanthin administration on the transcriptomes of peripheral neutrophil and liver tissue using microarray analysis in post-weaned Holstein calves.

We investigated the effects of oral administration of ß-cryptoxanthin (ß-CRX), a precursor of vitamin A synthesis, on the transcriptomes of peripheral neutrophils and liver tissue in post-weaned Holstein calves with immature immunity. A single oral administration of ß-CRX (0.2 mg/kg body weight) was performed in eight Holstein calves (4.0 ± 0.8 months of age; 117 ± 10 kg) on Day 0. Peripheral neutrophils (n = 4) and liver tissue (n = 4) were collected on Days 0 and 7. Neutrophils were isolated by density gradient centrifugation and treated with the TRIzol reagent. mRNA expression profiles were examined by microarray and differentially expressed genes were investigated using the Ingenuity Pathway Analysis software. The differentially expressed candidate genes identified in neutrophils (COL3A1, DCN, and CCL2) and liver tissue (ACTA1) were involved in enhanced bacterial killing and maintenance of cellular homoeostasis respectively. The changes in the expression of six of the eight common genes encoding enzymes (ADH5 and SQLE) and transcription regulators (RARRES1, COBLL1, RTKN, and HES1) were in the same direction in neutrophils and liver tissue. ADH5 and SQLE are involved in the maintenance of cellular homoeostasis by increasing the availability of substrates, and RARRES1, COBLL1, RTKN, and HES1 are associated with the suppression of apoptosis and carcinogenesis. An in silico analysis revealed that MYC, which is related to the regulation of cellular differentiation and apoptosis, was the most significant upstream regulator in neutrophils and liver tissue. Transcription regulators such as CDKN2A (cell growth suppressor) and SP1 (cell apoptosis enhancer) were significantly inhibited and activated, respectively, in neutrophils and liver tissue. These results suggest that oral administration of ß-CRX promotes the expression of candidate genes related to bactericidal ability and regulation of cellular processes in peripheral neutrophils and liver cells in response to the immune-enhancing function of ß-CRX in post-weaned Holstein calves.

Single oral ß-cryptoxanthin administration increases its serum concentration and enhances peripheral blood neutrophil function in Holstein cattle.

We investigated the effect of oral administration of ß-cryptoxanthin (ß-CRX) on its serum concentration and peripheral neutrophil functions by the chemiluminescence (CL) response in Holstein cattle. A single oral administration of ß-CRX was performed for serum ß-CRX concentration (0, 0.05, 0.1, or 0.2 mg/kg body weight [BW]) and for peak CL response of peripheral neutrophils (0.2 mg/kg BW). The serum ß-CRX concentration was peaked on 2 days after, similar to peak CL response on 3 days after ß-CRX administration. Therefore, a single oral administration of ß-CRX (0.2 mg/kg BW) induces higher serum concentration and concurrently enhances bactericidal ability of peripheral neutrophils in Holstein cattle.

Evidence for existence of insulin-like factor 3 (INSL3) hormone-receptor system in the ovarian corpus luteum and extra-ovarian reproductive organs during pregnancy in goats.

Insulin-like factor 3 (INSL3), initially described as a male hormone, is expressed in female reproductive organs during the estrous cycle and pregnancy but its function has not yet been established. This study explores the function of INSL3 in pregnant Saanen goats by characterizing the expression dynamics of INSL3 and its receptor, relaxin family peptide receptor 2 (RXFP2) and by demonstrating specific INSL3 binding in reproductive organs, using molecular and immunological approaches and ligand-receptor interaction assays. We demonstrate that the corpus luteum (CL) acts as both a source and target of INSL3 in pregnant goats, while extra-ovarian reproductive organs serve as additional INSL3 targets. The expression of INSL3 and RXFP2 in the CL reached maximum levels in middle pregnancy, followed by a decrease in late pregnancy; in contrast, RXFP2 expression levels in extra-ovarian reproductive organs were higher in the mammary glands but lower in the uterus, cervix and placenta and did not significantly change during pregnancy. The functional RXFP2 enabling INSL3 to bind was identified as an ~ 85 kDa protein in both the CL and mammary glands and localized in large and small luteal cells in the CL and in tubuloalveolar and ductal epithelial cells in the mammary glands. Additionally, INSL3 also bound to multiple cell types expressing RXFP2 in the uterus, cervix and placenta in a hormone-specific and saturable manner. These results provide evidence that an active intra- and extra-ovarian INSL3 hormone-receptor system operates during pregnancy in goats.

Use of a prediction method for early pregnancy status utilizing receiver operating characteristic curve analysis of peripheral blood leukocyte interferon-stimulated genes in Japanese-Black cattle.

A prediction method for early pregnancy status (pregnant or non-pregnant) in cattle that can be used within 3 weeks after insemination is desired. Interferon-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) have been examined as prediction molecules for determination of pregnancy status. Relative abundances of ISG15 and MX2 gene transcripts in PBLs were suitable biomarkers for the prediction of pregnancy status when there were assessments of Holstein cattle. In the present study, it was determined whether ISG biomarkers are applicable for predicting gestation in Japanese-Black (JB) cattle and evaluation of the applicability of receiver operating characteristic (ROC) analysis procedures for this purpose. There was assessment of the reliability of using average ISG values in PBLs collected during the estrous cycle (AVE) as a cutoff compared to the Youden index cutoff values. Application of AVE to assessment of pregnancy status in JB cattle indicated there was reliable predictions for pregnancy status when using ISG15 and MX2 values on day 21 after insemination, which coincided with the time of assessment in the previous study with Holstein cattle. The area under the curve values of the ROC curves confirmed the reliability of using ISGs to predict pregnancy from days 18 to 21 after insemination. Comparing AVE with Youden index values, there was confirmation of the accuracy of AVE for predicting gestation. The average mRNA transcript abundance values of ISG15 and MX2 may serve as excellent pregnancy biomarkers for cattle within 3 weeks of insemination.

Gene expression profiles in bovine granulocytes reflect the aberration of liver functions.

Liver performs several important functions; however, predicting its functions is difficult. Methods of analyzing gene expression profiles, for example, microarray, provide functional information of tissues. Liver and peripheral blood leukocytes (PBLs) were collected from Holstein cows subjected to two different physiological conditions (non-pregnant and pregnant), and PBLs were fractionated by gradient cell separation. RNA from PBLs and liver were applied to oligo-DNA microarray and reverse transcription-quantitative polymerase chain reaction (RT-qPCR). It revealed a group of stable bovine liver genes under constant physiological conditions. When they applied to physiological conditions including non-pregnant and pregnant, the profiles of some genes in liver were consistent with those in PBLs. Microarray data subjected to a principal component analysis (PCA) showed that the hepatic gene expression profiles were more consistent with those of granulocytes than mononuclear cells. The relationship of gene profiles in liver with granulocytes was confirmed by RT-qPCR and hierarchical cluster analysis. Gene profiles of granulocytes were more reliable than those of mononuclear cells, which reflected liver functions. These results suggest that the genes expressed in PBLs, particularly granulocytes, may be convenient bioindicators for the diagnosis of clinical disorder and/or detecting aberration of liver functions in cows subjected to different physiological conditions.

Characterisation of bovine embryos following prolonged culture in embryonic stem cell medium containing leukaemia inhibitory factor.

In order to help elucidate the process of epiblast and trophoblast cell differentiation in bovine embryos invitro, we attempted to develop a suitable culture medium to allow extended embryo culture. Day 7 bovine blastocysts developed in conventional medium were cultured further in embryonic stem cell medium with or without leukaemia inhibitory factor (LIF) until Day 23. At Day 14, the expression of octamer-binding transcription factor 3/4 (OCT3/4) and VIMENTIN was significantly higher in embryos cultured with than without LIF, but embryonic disc formation was not observed. Although expression of SRY (sex determining region Y)-box 17 (SOX17) mRNA was significantly lower in Day 14 embryos cultured with and without LIF than in invivo embryos, hypoblast cells formed just inside the trophoblast cells of the invitro-cultured embryos. On Day 23, expression of placental lactogen (PL) and prolactin-related protein 1 (PRP1) was not affected by LIF in invitro-cultured embryos, levels of both genes were significantly lower in the invitro than invivo embryos. Similar to invivo embryos, binucleate cell clusters seen in Day 23invitro-cultured embryos were composed of PL-negative and -positive cells. These results suggest that our culture system partially reproduced the differentiation process of trophoblast cells invivo.

A cell-based interferon-tau assay with an interferon-stimulated gene 15 promoter.

Interferon-tau (IFNT) is known as an early pregnancy recognition signal in ruminants. An accurate and convenient IFNT detection system is desirable for the diagnosis of endometrial and trophoblastic functions, including gestation status, in cows. The aim of this study was to develop a new cell-based assay, which involved the stable introduction of an interferon-stimulated gene promoter to a luciferase reporter system. The reactivity of four interferon-stimulated genes to IFNT in Madin-Darby bovine kidney (MDBK) cells was confirmed using reverse transcription-quantitative PCR. The upstream region of the interferon-stimulated gene 15 ubiquitin-like modifier (ISG15) gene as the promoter of the reporter gene, which is more responsive to IFNT and other IFNs, was determined using the luciferase assay. The reporter gene with the ISG15 upstream region was stably transfected into MDBK cells using the PiggyBac vector system; this cell line responded to type I IFNs in a dose-dependent manner. Because of its convenience, this cell line is suitable for the quantification of IFNT as well as other type I IFNs activities.

A predictive threshold value for the diagnosis of early pregnancy in cows using interferon-stimulated genes in granulocytes.

Interferon tau plays an important role in establishing bovine pregnancy. Interferon-stimulated genes (ISGs) have been examined to identify a suitable indicator for the diagnosis of early gestation in cows. Although ISGs can be specifically detected in peripheral white blood cells during early gestation, its reliability remains to be validated. In the current study, a predictive threshold level of ISGs to determine pregnancy in cows during Days 20-22 of gestation was verified by analyzing the expression of ISGs in granulocytes and peripheral blood leucocytes (a total of 57 cows were used, 28 of which were pregnant and 29 were non-pregnant). Four genes, interferon-stimulated gene 15 ubiquitin-like modifier (ISG15), MX dynamin like GTPase (MX) 1, MX2, and 2'-5'-oligoadenylate synthetase 1 (OAS1), were analyzed via quantitative RT-PCR and a receiver operating characteristic (ROC) curve was produced to visualize diagnostic accuracy measures. The expression values of the four ISGs during the estrous cycle (100 collection points from 65 cattle) were used to determine a pregnancy prediction cutoff value. Pregnancy status was determined using these cutoff values and then confirmed by ultrasonography. ROC analysis was then applied to confirm the accuracy of the pregnancy statuses (positive and negative) statistically. The statistical evaluation of the diagnostic accuracy measurements suggested that the average values of ISG15 and MX2 in granulocytes were reliable indicators of pregnancy within the three weeks after insemination with 80% accuracy. Average ISG15 and MX2 levels during the estrous cycle were more reliable biomarkers for the prediction of gestation. They predicted negative and positive pregnancies efficiently within three weeks after artificial insemination.

Generation of recombinant bovine interferon tau in the human embryonic kidney cell line and its biological activity.

The objective of this study was to generate recombinant bovine interferon tau (rbIFNT) in mammalian hosts. The complementary DNA encoding bovine IFNT2 was cloned for the construction of pRcRSV-bIFNT2 expression vector. The expression vector was transfected to 293 cells. Transfected cells harboring expression vector were selected with G418. Highly expressing clonal line was adapted to serum-free suspension culture in a spinner flask. The recombinant protein had 24 kDa apparent molecular mass, suggesting being expressed as a glycoprotein, and was purified from serum-free conditioned medium by the combination of Diethylaminoethanol Sepharose ion exchange and Sephacryl S-200 HR gel filtration. A total of 7.3 mg rbIFNT was obtained from 13.5 L conditioned medium. Generated rbIFNT was biologically active in terms of antiviral activity measured by the plaque inhibition assay with Madin-Darby bovine kidney cells and the vesicular stomatitis virus. The recombinant protein was also utilized for immunization to raise antibodies in the rabbit. The generated antibody was capable of use in both Western blotting and the binding assay. The results in the present study suggest that a certain amount of rbIFNT is raised in mammalian hosts by using conventional plasmid vector and its antibody provides useful tools for studies in the biology of bovine IFNT.

Induction of ovine trophoblast cell fusion by fematrin-1 in vitro.

Endogenous retroviruses present in the genomes take a specific role in placental formation in various vertebrates, including bovine and sheep. Fematrin-1, which is the envelope (Env) protein of bovine endogenous retrovirus found in bovine placenta, is involved in the formation of fetomaternal hybrid cells in cattle placenta. This study was conducted to clarify whether fematrin-1 possesses fusogenic activity in trophoblast cells. Another question is whether Env proteins only have species-specific activity or not. For this, fematrin-1 gene was transfected in ovine trophoblast cells, and we examined fusogenic activity with Cos-7 cells. Although fematrin-1 fusogenic activity was detected in both neutral and acidic pH conditions, acidic condition significantly enhanced it. These activities were rather weaker than those of vesicular stomatitis virus G protein as a positive control. However, the ratio of fematrin-1 and vesicular stomatitis virus G protein fusion index was confirmed similar to those in the previous reports. Some fusion cells showed multinucleate cells. These results imply that fematrin-1 is involved in the formation of trophoblast hybrid cells even in different species trophoblastic cells.

Aberrant gene expression of heparanase in ventricular hypertrophy induced by monocrotaline in rats.

The gene expression levels of heparanase, matrix metalloproteinase 2 (MMP2) and MMP9 were examined in ventricles after treatment with monocrotaline (MCT) to induce cardiac hypertrophy in rats. Rats received a single intraperitoneal injection of MCT (60 mg/kg) or saline. Twenty-five days after the injection, the right ventricle and lung wet weights were increased in MCT-treated rats compared with the control. Histological analysis revealed cardiomyocyte hypertrophy in the right ventricle of MCT-treated rats. Northern blot hybridization showed that heparanase and MMP2 expression increased significantly in the right and left ventricles of MCT-treated rats, whereas MMP9 was not induced. These findings indicate that heparanase and MMP2 might play an important role in the development of MCT-induced cardiac hypertrophy.

Nfkbiz regulates the proliferation and differentiation of keratinocytes.

Nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) inhibitor zeta (Nfkbiz) is a nuclear inhibitor of NF-κB (IκB) protein that is also termed as molecule possessing ankyrin repeats induced by lipopolysaccharide, interleukin-1-inducible nuclear ankyrin repeat protein, or IκBζ. We found previously that disrupting the Nfkbiz gene resulted in atopic dermatitis-like lesions in mice, suggesting an important role for Nfkbiz in the skin. In this study, we examined the cellular function of Nfkbiz in keratinocytes. Immunohistochemical analyses for Ki-67 revealed that Nfkbiz-/- keratinocytes were hypoproliferative. In skin from Nfkbiz-/- mice, the expression of the keratinocyte differentiation markers K10 and filaggrin were reduced, although that of K14 was unchanged. The terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay revealed that the frequency of apoptosis was comparable between control and Nfkbiz-/- keratinocytes. Interestingly, the subcellular localization of the NF-κB subunits and the transcriptional activity of NF-κB were not changed in Nfkbiz-/- keratinocytes. These findings indicate a novel possible role of Nfkbiz in controlling the proliferation and differentiation of epidermal keratinocytes through NF-κB-independent mechanisms.

The role of IFN-γ in regulating Nfkbiz expression in epidermal keratinocytes.

Nfkbiz is an inhibitor of nuclear factor κB (IκB) protein localized to the nucleus. We previously found that Nfkbiz gene-disrupted mice showed atopic dermatitis-like lesion, implying the important role of Nfkbiz in skin homeostasis. The purpose of this study was to examine the effect of interferon (IFN)-γ on Nfkbiz expression in keratinocytes. IFN-γ induced Nfkbiz expression at a comparable level to IL-1. Promoter analysis revealed that interferon-stimulated response element (ISRE) located in the Nfkbiz promoter region is important for responding to the stimulation. Interestingly, IFN-γ and IL-1 displayed synergism in terms of inducing Nfkbiz expression. By using selective inhibitors, we found that Janus activated kinase (JAK) 1 and nuclear factor (NF)-κB are important for Nfkbiz expression after IFN-γ stimulation and for synergism between IFN-γ and IL-1. These findings indicate a possible important role of Nfkbiz in modulating the progression of inflammatory diseases in which IFN-γ and IL-1 are abundant.

Development of an in vitro model for the analysis of bovine endometrium using simple techniques.

This study aimed to develop an in vitro model for the analysis of the bovine endometrium. Immunofluorescent staining revealed that the hetero-spheroids and the cultured explants showed almost similar structure in the localization of bovine endometrial epithelial cells and endometrial stromal cells, except the glandular-like structure of the epithelial cells inside the explants. Gelatin zymography revealed that the hetero-spheroids did not express matrix metalloproteinases (MMPs) after 4 days of culture, but strong MMP expressions were observed in the cultured explants until 7 days of culture. Additionally, expression of progesterone receptor (PR), estrogen receptor alpha (ERα), type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) messenger RNA was observed both in the homo- and hetero-spheroids. The expression of oxytocin receptor (OTR) mRNA in E2 and E2+P4 (1,3,5(10)-Estratrien-3, 17ß-diol + 4-Pregnen-3, 20-dinone) treated groups were significantly (P < 0.05) higher than that of the control group of spheroids. In case of cultured explants, the expression of PR and OTR mRNA were significantly (P < 0.05) higher in E2 treated groups compared to the control groups. Hepatocyte growth factor (HGF) mRNA expression was also higher in P4 treated groups at 10 days in culture (P < 0.05). In a nutshell, the in vitro model developed in this study for the analysis of the endometrium may provide a new platform for extensive research on bovine endometrial function.

SOLD1 is expressed in bovine trophoblast cell lines and regulates cell invasiveness.

BACKGROUND: Secreted protein of Ly-6 domain 1 (SOLD1), a secretory-type member of the Ly-6 superfamily, is expressed in both fetal and maternal tissues throughout gestation. SOLD1 mRNA is expressed in the endometrium and in trophoblast mononucleate and binucleate cells, suggesting it plays an important role not only in placental architecture at early gestation, but also in remodeling the endometrium at late gestation. Here, we investigate the expression of SOLD1 mRNA and protein in trophoblast cell lines. In addition, we examine the effect of SOLD1 on the invasive ability of trophoblast cells. METHODS: We measured SOLD1 gene expression in thirteen bovine trophoblast (BT) cell lines by using quantitative reverse transcription PCR (qRT-PCR). SOLD1 protein levels were examined in two cell lines, BT-C and BT-K, by using Western blotting and immunocytochemistry. In addition, we measured the invasive activity of BT cells in the presence or absence of anti-bovine SOLD1 antibodies. RESULTS: At variable levels, SOLD1 was expressed in all thirteen cell lines; however, expression remained below that of proximal fetal membrane tissue. SOLD1 protein, which was approximately 28 kDa in size, was detected in perinuclear area of the cytoplasm in BT cells. Treatment with anti-bovine SOLD1 antibody had a dose-dependent suppressive effect on the invasiveness of BT-K cell lines. CONCLUSIONS: The present study is the first to investigate SOLD1 expression in vitro, in trophoblastic cell lines. Our data suggested that SOLD1 is involved in the regulation of the trophoblast invasiveness. Therefore, SOLD1 may play an active and crucial role in mediating communication at the fetomaternal interface.

Expression profiles of perforin, granzyme B and granulysin genes during the estrous cycle and gestation in the bovine endometrium.

The conceptus is susceptible to destruction by maternal cytotoxic lymphocytes, which have cytotoxic potential. Therefore, it is expected that mechanisms for regulating cytotoxic lymphocytes exist, but little is known about the expression of cytotoxic genes in the endometrium. In the present study, we examined the spatial and temporal expression patterns of the cytotoxic genes perforin, granzyme B, and granulysin during the estrous cycle and gestation in the bovine endometrium. Endometrial tissues were collected from cows during the estrous cycle and gestation. The gene expression patterns of the three cytotoxic genes were examined using quantitative polymerase chain reaction and in situ hybridization, and cytotoxic lymphocyte subsets were characterized using immunohistochemistry. During mid- to late gestation in the intercaruncular (ICAR), granulysin expression was significantly increased, and a large number of granulysin-expressing cells were localized in the luminal epithelium. Perforin and granzyme B displayed similar expression profiles and were highly expressed in the peri-implantation endometrium, but few cells expressing these genes were found in the endometrial stroma. In conclusion, these findings suggest that in the ICAR epithelium granulysin may play important roles in the establishment and maintenance of gestation during normal pregnancy.

Dynamics of CD3⁺ T-cell distribution throughout the estrous cycle and gestation in the bovine endometrium.

T cells are the dominant lymphocytes in the endometrium and are considered to play a crucial role in implantation and in the maintenance of gestation through cytokine production and immune regulation. The mechanisms underlying immunoregulation at the feto-maternal interface are still obscure for this complex system. Understanding the role of T cells is a key factor in understanding the endometrial immune system. In this study, the distribution of endometrial CD3⁺ T cells in bovines was examined by immunohistochemical analysis. The estrous cycle and gestation was divided into 4 stages, and the number of CD3⁺-positive T cells was counted in each stage. CD3⁺ cells were found in the endometrium in significant numbers throughout the estrous cycle and were mostly located in the subepithelial area. The number of CD3⁺ cells significantly increased in the early and mid-luteal phases but decreased after implantation with the progression of gestation. No T cells were found in the placentome or specifically in the tissues near the fetus, including the trophoblastic area. In addition, very few T cells were found in stromal regions close to the myometrium of the endometrium. These findings suggest that downregulation of bovine endometrial CD3⁺ T-cell functions is closely related to the successful maintenance of gestation in a spatiotemporal manner.

Fematrin-1 is involved in fetomaternal cell-to-cell fusion in Bovinae placenta and has contributed to diversity of ruminant placentation.

During placentation, mammals employ different strategies for nourishing and supporting fetuses. Members of the Bovidae family, consisting of cloven-hoofed ruminants, utilize multiple maternal attachment points on the placenta, known as cotyledons, and hybrid cells, named trinucleate cells or syncytial plaques, made up of a fusion of fetal trophoblasts and maternal endometrial cells to provide essential hormones and maintain long gestation periods. These hybrid cells are unique to the Bovidae, as fetomaternal borders are clearly separated by syncytiotrophoblasts or epithelial cells in the placenta of other mammals. Recently, it was reported that Syncytin-Rum1 was inserted into ruminant genomes, including cattle and sheep, and was possibly involved in fetomaternal cell-to-cell fusion in both species. However, Syncytin-Rum1 alone is insufficient to explain the morphological diversity of the fetomaternal hybrids between Bovinae and Caprinae (i.e., trinucleate cells in Bovinae and syncytial plaques in Caprinae). Here we report that the bovine endogenous retrovirus K1 (BERV-K1) envelope, which we term Fematrin-1, was specifically expressed in binucleated trophoblasts throughout gestation in cattle and induced fusion with bovine endometrial cells in vitro at a significantly higher level than Syncytin-Rum1 under physiological conditions. Fematrin-1 was found to be integrated into intron 18 of FAT tumor suppressor homolog 2 (FAT2) about 18.3 to 25.4 million years ago and has been subject to purifying selection through the evolution of Bovinae. Phylogenetically, Fematrin-1 is distinct from Syncytin genes found in other mammalian species that form syncytiotrophoblasts. Our results suggest that the newly acquired endogenous retroelement has contributed to generating placentation diversity through ruminant evolution.