Identification of estrogen-responsive genes in the parenchyma and fat pad of the bovine mammary gland by microarray analysis

Characterization of interferon gamma gene in relation to immunological responses in Haemonchus contortus resistant and susceptible Garole sheep

Garole sheep exhibits within-breed difference in resistance to natural gastrointestinal nematode infection predominated by Haemonchus contortus. In the present study, interferon gamma gene (IFN-γ) was characterized in relation to parasitological, haematological, and immune response against H. contortus in resistant and susceptible Garole sheep. Resistant and susceptible Garole sheep were selected from the field based on consistent low faecal egg counts (FEC) for one year and single nucleotide polymorphisms (SNPs) in the IFN-γ gene. The partial amplification of IFN-γ gene (1282 bp) revealed 4 SNPs exclusively in resistant sheep and 3 SNPs were shared between resistant and susceptible Garole sheep. The selected resistant and susceptible Garole sheep were challenged with H. contortus infection. The parasitological, haematological, immunological responses, and expression of IFN-γ gene were compared between the resistant and susceptible Garole sheep. The FEC of resistant sheep was significantly (P < 0.05) lower than the susceptible sheep infected with H. contortus. There was spontaneous elimination of H. contortus from 28 to 33 days post infection (DPI) in resistant sheep. Haemoglobin and packed cell volume were significantly (P < 0.05) higher in resistant sheep than the susceptible sheep. The serum concentration of immunoglobulin (Ig)G₁ and IgA and cytokine IFN-γ activity and also the expression of IFN-γ gene were significantly (P < 0.05) higher in the infected resistant sheep from 14 to 28 DPI compared to the susceptible sheep. In resistant sheep, IgA and IgG₁ and cytokine IFN-γ positively correlated with expression of IFN-γ gene, and the SNPs recorded in the resistant sheep only might play an important role in conferring resistance against H. contortus. Further studies are required to elucidate the role of IFN-γ gene in H. contortus resistance in Garole sheep.

The role of the IGF system in mammary physiology of ruminants

The IGF system plays a central role in all stages of mammary development, lactation and involution. IGFs exert their effects on the mammary gland through both endocrine and paracrine/autocrine mechanisms and the importance of circulating versus local IGF action remains an open question, especially in ruminants. At the whole organ level, a critical role for IGFs in ductal morphogenesis and lobuloalveolar development has been established, while at the cellular level the ability of IGFs to stimulate cell proliferation and control cell survival contributes to the number of milk-secreting cells in the gland. Much of this work has been conducted in rodents which provide an affordable research model and allow for genetic manipulation of specific components of the IGF system. Research into the role of the IGF system in dairy cows has generally supported information obtained with rodents though large gaps in our knowledge remain and species differences are not well defined. Examples include whether exogenous somatotropin exerts its effects on the mammary gland through local IGF-1 synthesis which is accepted dogma in rodents, what the role of IGF-1 versus IGF-2 is in the mammary gland, and how the IGFBPs regulate IGF bioactivity. This last area is particularly under-investigated in ruminants both at the whole animal and the cellular and molecular levels. Given that the IGF system may underlie many management practices that could contribute to enhancing productive efficiency of lactation, more research into the basic biology of this important system is warranted.

Unique Transcriptomic Changes Underlie Hormonal Interactions During Mammary Histomorphogenesis in Female Pigs

Successful lactation and the risk for developing breast cancer depend on growth and differentiation of the mammary gland (MG) epithelium that is regulated by ovarian steroids (17β-estradiol [E] and progesterone [P]) and pituitary-derived prolactin (PRL). Given that the MG of pigs share histomorphogenic features present in the normal human breast, we sought to define the transcriptional responses within the MG of pigs following exposure to all combinations of these hormones. Hormone-ablated female pigs were administered combinations of E, medroxyprogesterone 17-acetate (source of P), and either haloperidol (to induce PRL) or 2-bromo-α-ergocryptine. We subsequently monitored phenotypic changes in the MG including mitosis, receptors for E and P (ESR1 and PGR), level of phosphorylated STAT5 (pSTAT5), and the frequency of terminal ductal lobular unit (TDLU) subtypes; these changes were then associated with all transcriptomic changes. Estrogen altered the expression of approximately 20% of all genes that were mostly associated with mitosis, whereas PRL stimulated elements of fatty acid metabolism and an inflammatory response. Several outcomes, including increased pSTAT5, highlighted the ability of E to enhance PRL action. Regression of transcriptomic changes against several MG phenotypes revealed 1669 genes correlated with proliferation, among which 29 were E inducible. Additional gene expression signatures were associated with TDLU formation and the frequency of ESR1 or PGR. These data provide a link between the hormone-regulated genome and phenome of the MG in a species having a complex histoarchitecture like that in the human breast, and highlight an underexplored synergy between the actions of E and PRL during MG development.

Suprabasin-A Review

Among the ~22,000 human genes, very few remain that have unknown functions. One such example is suprabasin (SBSN). Originally described as a component of the cornified envelope, the function of stratified epithelia-expressed SBSN is unknown. Both the lack of knowledge about the gene role under physiological conditions and the emerging link of SBSN to various human diseases, including cancer, attract research interest. The association of SBSN expression with poor prognosis of patients suffering from oesophageal carcinoma, glioblastoma multiforme, and myelodysplastic syndromes suggests that SBSN may play a role in human tumourigenesis. Three SBSN isoforms code for the secreted proteins with putative function as signalling molecules, yet with poorly described effects. In this first review about SBSN, we summarised the current knowledge accumulated since its original description, and we discuss the potential mechanisms and roles of SBSN in both physiology and pathology.

mRNAs biotinylated within the 5' cap and protected against decapping: new tools to capture RNA-protein complexes

The 5'-terminus of eukaryotic mRNAs comprises a 7-methylguanosine cap linked to the first transcribed nucleotide via a 5'-5' triphosphate bond. This cap structure facilitates numerous interactions with molecules participating in mRNA processing, turnover and RNA translation. Here, we report the synthesis and biochemical properties of a set of biotin-labelled cap analogues modified within the triphosphate bridge and increasing mRNA stability while retaining biological activity. Successful co-transcriptional incorporation of the cap analogues allowed for the quantification of cap-dependent translation efficiency, capping efficiency and the susceptibility to decapping by Dcp2. The utility of such cap-biotinylated RNAs as molecular tool was demonstrated by ultraviolet-cross-linking and affinity capture of protein-RNA complexes. In conclusion, RNAs labelled with biotin via the 5' cap structure can be applied to a variety of biological experiments based on biotin-avidin interaction or by means of biotin-specific antibodies, including protein affinity purification, pull-down assays, in vivo visualization, cellular delivery and many others.This article is part of the theme issue '5' and 3' modifications controlling RNA degradation'.

Transcriptional profiling of two different physiological states of the yak mammary gland using RNA sequencing

Yak milk is superior to common cow milk in nutrients including protein, fat and calories. However, the milk yield of the yak is very much lower compared with other dairy bovines. To understand the molecular mechanisms of lactogenesis, lactation and mammary gland development, mammary tissue samples were taken from five yaks during a dry period (DP, n = 3) and lactation period (LP, n = 2). Two types of cDNA sequence libraries that reflected the different physiological states of the mammary gland were constructed using RNA sequencing technology. After removing reads containing adapters, reads containing poly-N and low-quality reads from the raw data, 45,423,478 to 53,274,976 clean reads were obtained from these libraries. A total of 74.72% to 80.65% of the high-quality sequence reads were uniquely aligned to the BosGru v2.0 yak reference genome. Using the DESeq R package, 360 differentially expressed genes were detected between the two groups when the adjusted P value (padj < 0.05) was used as the cutoff value; this included 192 upregulated and 168 downregulated genes in the yak mammary gland tissue of the DP compared to the LP. A gene ontology analysis revealed that the most enriched GO terms were protein binding, multi-organism process, immune system and others. KEGG pathway analysis indicated that the differentially expressed genes were mostly enriched in Hippo signaling, insulin signaling, steroid biosynthesis and others. The analysis of the up- and downregulated genes provides important insights into the molecular events involved in lactogenesis, lactation and mammary gland development and will guide further research to enhance milk yield and optimize the constituents of yak milk.

BASP1 interacts with oestrogen receptor α and modifies the tamoxifen response

Tamoxifen binds to oestrogen receptor α (ERα) to elicit distinct responses that vary by cell/tissue type and status, but the factors that determine these differential effects are unknown. Here we report that the transcriptional corepressor BASP1 interacts with ERα and in breast cancer cells, this interaction is enhanced by tamoxifen. We find that BASP1 acts as a major selectivity factor in the transcriptional response of breast cancer cells to tamoxifen. In all, 40% of the genes that are regulated by tamoxifen in breast cancer cells are BASP1 dependent, including several genes that are associated with tamoxifen resistance. BASP1 elicits tumour-suppressor activity in breast cancer cells and enhances the antitumourigenic effects of tamoxifen treatment. Moreover, BASP1 is expressed in breast cancer tissue and is associated with increased patient survival. Our data have identified BASP1 as an ERα cofactor that has a central role in the transcriptional and antitumourigenic effects of tamoxifen.

TRIENNIAL LACTATION SYMPOSIUM: Nutrigenomics in livestock: Systems biology meets nutrition

The advent of high-throughput technologies to study an animal's genome, proteome, and metabolome (i.e., "omics" tools) constituted a setback to the use of reductionism in livestock research. More recent development of "next-generation sequencing" tools was instrumental in allowing in-depth studies of the microbiome in the rumen and other sections of the gastrointestinal tract. Omics, along with bioinformatics, constitutes the foundation of modern systems biology, a field of study widely used in model organisms (e.g., rodents, yeast, humans) to enhance understanding of the complex biological interactions occurring within cells and tissues at the gene, protein, and metabolite level. Application of systems biology concepts is ideal for the study of interactions between nutrition and physiological state with tissue and cell metabolism and function during key life stages of livestock species, including the transition from pregnancy to lactation, in utero development, or postnatal growth. Modern bioinformatic tools capable of discerning functional outcomes and biologically meaningful networks complement the ever-increasing ability to generate large molecular, microbial, and metabolite data sets. Simultaneous visualization of the complex intertissue adaptations to physiological state and nutrition can now be discerned. Studies to understand the linkages between the microbiome and the absorptive epithelium using the integrative approach are emerging. We present examples of new knowledge generated through the application of functional analyses of transcriptomic, proteomic, and metabolomic data sets encompassing nutritional management of dairy cows, pigs, and poultry. Published work to date underscores that the integrative approach across and within tissues may prove useful for fine-tuning nutritional management of livestock. An important goal during this process is to uncover key molecular players involved in the organismal adaptations to nutrition.

A Preclinical Model for ERα-Positive Breast Cancer Points to the Epithelial Microenvironment as Determinant of Luminal Phenotype and Hormone Response

Seventy-five percent of breast cancers are estrogen receptor α positive (ER⁺). Research on these tumors is hampered by lack of adequate in vivo models; cell line xenografts require non-physiological hormone supplements, and patient-derived xenografts (PDXs) are hard to establish. We show that the traditional grafting of ER⁺ tumor cells into mammary fat pads induces TGFβ/SLUG signaling and basal differentiation when they require low SLUG levels to grow in vivo. Grafting into the milk ducts suppresses SLUG; ER⁺ tumor cells develop, like their clinical counterparts, in the presence of physiological hormone levels. Intraductal ER⁺ PDXs are retransplantable, predictive, and appear genomically stable. The model provides opportunities for translational research and the study of physiologically relevant hormone action in breast carcinogenesis.

Localization and quantitation of macrophages, mast cells, and eosinophils in the developing bovine mammary gland

Prepubertal mammary development involves elongation and branching of ducts and stromal tissue remodeling. This process is highly regulated and in mice is known to be affected by the presence of innate immune cells. Whether or not such immune cells are present or involved in bovine mammary development is unknown. For the first time, we determined the presence, location (relative to mammary ductal structures), and changes in numbers of eosinophils, mast cells, and macrophages in prepubertal bovine mammary tissue, and evaluated the effects of age, ovariectomy, and exogenous estrogen on numbers of each cell type. Chemical stains and immunofluorescence were used to identify the 3 cell types in formalin-fixed, paraffin-embedded mammary tissue from prepubertal female calves from 3 archived tissue sets. The ontogeny tissue set included samples of mammary tissue from female calves (n=4/wk) from birth to 6 wk of age. The ovary tissue set contained samples from ovary intact and ovariectomized heifers allowing us to investigate the influence of the ovaries on immune cells in the developing mammary gland in prepubertal heifers. Nineteen animals were intact or ovariectomized 30 d before sampling; they were 90, 120, or 150 d old at the time of sampling. A third tissue set, the estrogen set, allowed us to determine the effect of exogenous estrogen on innate immune cells in the gland. Eosinophils were identified via Luna staining, mast cells by May-Grunwald Giemsa staining, and macrophages with immunofluorescence. Key findings were that more eosinophils and mast cells were observed in near versus far stroma in the ontogeny and ovary tissue sets but not estrogen. More macrophages were observed in near versus far stroma in ontogeny animals. Eosinophils were more abundant in the younger animals, and fewer macrophages tended to be observed in ovariectomized heifers as compared with intact heifers and estrogen treatment resulted in a reduction in cell numbers. In summary, we show for the first time that innate immune cells are present in prepubertal bovine mammary tissue, localization varies by immune cell type, and abundance is related to proximity of epithelial structures and physiological state. We suggest a likely role for these cells in control of bovine mammary growth and ductal development.

Functional development of the adult ovine mammary gland--insights from gene expression profiling

Background

The mammary gland is a dynamic organ that undergoes dramatic physiological adaptations during the transition from late pregnancy to lactation. Investigation of the molecular basis of mammary development and function will provide fundamental insights into tissue remodelling as well as a better understanding of milk production and mammary disease. This is important to livestock production systems and human health.

Here we use RNA-seq to identify differences in gene expression in the ovine mammary gland between late pregnancy and lactation.

Results

Between late pregnancy (135 days of gestation ± 2.4 SD) and lactation (15 days post partum ± 1.27 SD) 13 % of genes in the sheep genome were differentially expressed in the ovine mammary gland. In late pregnancy, cell proliferation, beta-oxidation of fatty acids and translation were identified as key biological processes. During lactation, high levels of milk fat synthesis were mirrored by enrichment of genes associated with fatty acid biosynthesis, transport and lipogenesis. Protein processing in the endoplasmic reticulum was enriched during lactation, likely in support of active milk protein synthesis. Hormone and growth factor signalling and activation of signal transduction pathways, including the JAK-STAT and PPAR pathways, were also differently regulated, indicating key roles for these pathways in functional development of the ovine mammary gland. Changes in the expression of epigenetic regulators, particularly chromatin remodellers, indicate a possible role in coordinating the large-scale transcriptional changes that appear to be required to switch mammary processes from growth and development during late pregnancy to synthesis and secretion of milk during lactation.

Conclusions

Coordinated transcriptional regulation of large numbers of genes is required to switch between mammary tissue establishment during late pregnancy, and activation and maintenance of milk production during lactation. Our findings indicate the remarkable plasticity of the mammary gland, and the coordinated regulation of multiple genes and pathways to begin milk production. Genes and pathways identified by the present study may be important for managing milk production and mammary development, and may inform studies of diseases affecting the mammary gland.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1947-9) contains supplementary material, which is available to authorized users.

Ovariectomy in young prepubertal dairy heifers causes complete suppression of mammary progesterone receptors

Mammary growth and development depends on ovarian steroids and particularly interaction of estrogen and progesterone with their intracellular receptors. The objectives of this study were to determine the effect of ovariectomy on the expression of protein and messenger RNA for estrogen receptor-alpha (ESR1) and progesterone receptor (PGR) and their relation to mammary ductal development and cell proliferation. Prepubertal Holstein heifers 2, 3, or 4 mo of age were randomly assigned to one of 2 treatments, ovariectomized (OVX; n = 8) or sham operated (INT; n = 12). Mammary parenchymal (PAR) tissue samples were harvested 30 d after surgery. Localization and quantitation of ESR1 and PGR in PAR were determined by immunohistochemistry and quantitative multispectral imaging. Relative messenger RNA expression of ESR1 and PGR in PAR was measured by quantitative real time polymerase chain reaction. We observed the complete absence of PGR-positive epithelial cell nuclei and reduced PGR transcript abundance in mammary parenchyma of OVX heifers. The percent of epithelial cells expressing ESR1 did not differ by treatment but was decreased with age. However, average intensity of ESR1 expression per cell was reduced in OVX heifers. The abundance of Ki67 labeled epithelial cells and stromal cells was reduced after ovariectomy. These data suggest that reduced mammary development after ovariectomy may be mediated by loss of PGR expression and reduced ESR1 expression in positive cells. A presumptive relationship with ovarian-derived circulating estradiol remains unresolved, but data suggest other ovarian-derived agents may play a role. Use of specific antagonists to manipulate expression or action of PGR and ESR1 receptors should provide direct evidence for roles of these receptors in prepubertal bovine mammary development.

Transcriptional regulators transforming growth factor-β1 and estrogen-related receptor-α identified as putative mediators of calf rumen epithelial tissue development and function during weaning

Molecular mechanisms regulating rumen epithelial development remain largely unknown. To identify gene networks and regulatory factors controlling rumen development, Holstein bull calves (n=18) were fed milk replacer only (MRO) until 42 d of age. Three calves each were euthanized at 14 and 42 d of age for tissue collection to represent preweaning, and the remaining calves were provided diets of either milk replacer + orchard grass hay (MH; n=6) to initiate weaning without development of rumen papillae, or milk replacer + calf starter (MG; n=6) to initiate weaning and development of rumen papillae. At 56 and 70 d of age, 3 calves from the MH and MG groups were euthanized for collection of rumen epithelium. Total RNA and protein were extracted for microarray analysis and to validate detected changes in selected protein expression, respectively. As expected, calves fed MRO had no rumen papillae and development of papillae was greater in MG versus MH calves. Differentially expressed genes between the MRO diet at d 42 (preweaning) versus the MG or MH diets at d 56 (during weaning) were identified using permutation analysis of differential expression. Expression of 345 and 519 transcripts was uniquely responsive to MG and MH feeding, respectively. Ingenuity Pathway Analysis (Qiagen, Redwood City, CA) indicated that the top-ranked biological function affected by the MG diet was the cell cycle, and TFGB1, FBOX01, and PPARA were identified as key transcriptional regulators of genes responsive to the MG diet and associated with development of rumen papillae. Increased expressions of TGFB1 mRNA and protein in response to the MG diet were confirmed by subsequent analyses. The top-ranking biological function affected by the MH diet was energy production. Receptors for IGF-1 and insulin, ESRRA, and PPARD were identified by ingenuity pathway analysis as transcriptional regulators of genes responsive to the MH diet. Further analysis of TGFB1 and ESRRA mRNA expression in rumen epithelium obtained from a separate ontogenic study of Holstein calves (n=26) euthanized every 7d from birth to 42 d of age showed increases in transcript expression with advancing age, supporting their roles in mediating rumen epithelial development and function during weaning. Additional evaluation of gene expression in the rumen epithelium of adult cows ruminally infused with butyrate also suggested that observed changes in ESRRA mRNA expression in developing calf rumen may be mediated by increased butyrate concentration. Our results identify TGFB1 and ESRRA as likely transcriptional regulators of rumen epithelial development and energy metabolism, respectively, and provide targets for modulation of rumen development and function in the growing calf.

Estrogen receptor α in cancer-associated fibroblasts suppresses prostate cancer invasion via modulation of thrombospondin 2 and matrix metalloproteinase 3

The prostate cancer (PCa) microenvironment contains active stromal cells known as cancer-associated fibroblasts (CAF) that may play important roles in influencing tumor progression. Here we studied the role of CAF estrogen receptor alpha (ERα) and found that it could protect against PCa invasion. Immunohistochemistry on prostatectomy specimens showed that PCa patients with ERα-positive stroma had a significantly lower risk for biochemical recurrence. In vitro invasion assays further confirmed that the stromal ERα was able to reduce PCa cell invasion. Dissection of the molecular mechanism revealed that the CAF ERα could function through a CAF-epithelial interaction via selectively upregulating thrombospondin 2 (Thbs2) and downregulating matrix metalloproteinase 3 (MMP3) at the protein and messenger RNA levels. Chromatin immunoprecipitation assays further showed that ERα could bind to an estrogen response element on the promoter of Thbs2. Importantly, knockdown of Thbs2 led to increased MMP3 expression and interruption of the ERα mediated invasion suppression, providing further evidence of an ERα-Thbs2-MMP3 axis in CAF. In vivo studies using athymic nude mice injected with CWR22Rv1 (22Rv1) PCa epithelial cells and CAF cells ± ERα also confirmed that mice coimplanted with PCa cells and CAF ERα+ cells had less tumor foci in the pelvic lymph nodes, less metastases, and tumors showed less angiogenesis, MMP3, and MMP9 (an MMP3 downstream target) positive staining. Together, these data suggest that CAF ERα could play protective roles in suppressing PCa metastasis. Our results may lead to developing new and alternative therapeutic approaches to battle PCa via controlling ERα signaling in CAF.

Lysine metabolism in mammalian brain: an update on the importance of recent discoveries

The lysine catabolism pathway differs in adult mammalian brain from that in extracerebral tissues. The saccharopine pathway is the predominant lysine degradative pathway in extracerebral tissues, whereas the pipecolate pathway predominates in adult brain. The two pathways converge at the level of ∆(1)-piperideine-6-carboxylate (P6C), which is in equilibrium with its open-chain aldehyde form, namely, α-aminoadipate δ-semialdehyde (AAS). A unique feature of the pipecolate pathway is the formation of the cyclic ketimine intermediate ∆(1)-piperideine-2-carboxylate (P2C) and its reduced metabolite L-pipecolate. A cerebral ketimine reductase (KR) has recently been identified that catalyzes the reduction of P2C to L-pipecolate. The discovery that this KR, which is capable of reducing not only P2C but also other cyclic imines, is identical to a previously well-described thyroid hormone-binding protein [μ-crystallin (CRYM)], may hold the key to understanding the biological relevance of the pipecolate pathway and its importance in the brain. The finding that the KR activity of CRYM is strongly inhibited by the thyroid hormone 3,5,3'-triiodothyronine (T3) has far-reaching biomedical and clinical implications. The inter-relationship between tryptophan and lysine catabolic pathways is discussed in the context of shared degradative enzymes and also potential regulation by thyroid hormones. This review traces the discoveries of enzymes involved in lysine metabolism in mammalian brain. However, there still remain unanswered questions as regards the importance of the pipecolate pathway in normal or diseased brain, including the nature of the first step in the pathway and the relationship of the pipecolate pathway to the tryptophan degradation pathway.

Estradiol and progesterone exhibit similar patterns of hepatic gene expression regulation in the bovine model

Female sex steroid hormones, estradiol-17β (E2-17β) and progesterone (P4) regulate reproductive function and gene expression in a broad range of tissues. Given the central role of the liver in regulating homeostasis including steroid hormone metabolism, we sought to understand how E2-17β and P4 interact to affect global gene expression in liver. Ovariectomized cows (n = 8) were randomly assigned to 4 treatment groups applied in a replicated Latin Square design: 1) No hormone supplementation, 2) E2-17β treatment (ear implant), 3) P4 treatment (intravaginal inserts), and 4) E2-17β combined with P4. After 14 d of treatment, liver biopsies were collected, allowing 28 d intervals between periods. Changes in gene expression in the liver biopsies were monitored using bovine-specific arrays. Treatment with E2-17β altered expression of 479 genes, P4 472 genes, and combined treatment significantly altered expression of 468 genes. In total, 578 genes exhibited altered expression including a remarkable number (346 genes) that responded similarly to E2-17β, P4, or combined treatment. Additional evidence for similar gene expression actions of E2-17ß and/or P4 were: principal component analysis placed almost every treatment array at a substantial distance from controls; Venn diagrams indicated overall treatment effects for most regulated genes; clustering analysis indicated the two major clusters had all treatments up-regulating (172 genes) or down-regulating (173 genes) expression. Thus, unexpectedly, common biological pathways were regulated by E2-17β and/or P4 in liver. This indicates that the mechanism of action of these steroid hormones in the liver might be either indirect or might occur through non-genomic pathways. This unusual pattern of gene expression in response to steroid hormones is consistent with the idea that there are classical and non-classical tissue-specific responses to steroid hormone actions. Future studies are needed to elucidate putative mechanism(s) responsible for overlapping actions of E2-17β and P4 on the liver transcriptome.

Granule exocytosis of granulysin and granzyme B as a potential key mechanism in vaccine-induced immunity in cattle against the nematode Ostertagia ostertagi

Ostertagia ostertagi is considered one of the most economically important bovine parasites. As an alternative to anthelmintic treatment, an experimental host-protective vaccine was previously developed on the basis of ASP proteins derived from adult worms. Intramuscular injection of this vaccine, combined with QuilA as an adjuvant, significantly reduced fecal egg counts by 59%. However, the immunological mechanisms triggered by the vaccine are still unclear. Therefore, in this study, the differences in immune responses at the site of infection, i.e., the abomasal mucosa, between ASP-QuilA-vaccinated animals and QuilA-vaccinated control animals were investigated on a transcriptomic level by using a whole-genome bovine microarray combined with histological analysis. Sixty-nine genes were significantly impacted in animals protected by the vaccine, 48 of which were upregulated. A correlation study between the parasitological parameters and gene transcription levels showed that the transcription levels of two of the upregulated genes, those for granulysin (GNLY) and granzyme B (GZMB), were negatively correlated with cumulative fecal egg counts and total worm counts, respectively. Both genes were also positively correlated with each other and with another upregulated gene, that for the IgE receptor subunit (FCER1A). Surprisingly, these three genes were also correlated significantly with CMA1, which encodes a mast cell marker, and with counts of mast cells and cells previously described as globule leukocytes. Furthermore, immunohistochemical data showed that GNLY was present in the granules of globule leukocytes and that it was secreted in mucus. Overall, the results suggest a potential role for granule exocytosis by globule leukocytes, potentially IgE mediated, in vaccine-induced protection against O. ostertagi.

Comparison of the transcriptomes of long-term label retaining-cells and control cells microdissected from mammary epithelium: an initial study to characterize potential stem/progenitor cells

Background: Previous molecular characterizations of mammary stem cells (MaSC) have utilized fluorescence-activated cell sorting or in vitro cultivation of cells from enzymatically dissociated tissue to enrich for MaSC. These approaches result in the loss of all histological information pertaining to the in vivo locale of MaSC and progenitor cells. Instead, we used laser microdissection to excise putative progenitor cells and control cells from their in situ locations in cryosections and characterized the molecular properties of these cells. MaSC/progenitor cells were identified based on their ability to retain bromodeoxyuridine for an extended period.

Results: We isolated four categories of cells from mammary epithelium of female calves: bromodeoxyuridine label retaining epithelial cells (LREC) from basal (LRECb) and embedded layers (LRECe), and epithelial control cells from basal and embedded layers. Enriched expression of genes in LRECb was associated with stem cell attributes and identified WNT, TGF-β, and MAPK pathways of self renewal and proliferation. Genes expressed in LRECe revealed retention of some stem-like properties along with up-regulation of differentiation factors.

Conclusion: Our data suggest that LREC in the basal epithelial layer are enriched for MaSC, as these cells showed increased expression of genes that reflect stem cell attributes; whereas LREC in suprabasal epithelial layers are enriched for more committed progenitor cells, expressing some genes that are associated with stem cell attributes along with those indicative of cell differentiation. Our results support the use of DNA label retention to identify MaSC and also provide a molecular profile and novel candidate markers for these cells. Insights into the biology of stem cells will be gained by confirmation and characterization of candidate MaSC markers identified in this study.

Application of Top-Down and Bottom-up Systems Approaches in Ruminant Physiology and Metabolism

Systems biology is a computational field that has been used for several years across different scientific areas of biological research to uncover the complex interactions occurring in living organisms. Applications of systems concepts at the mammalian genome level are quite challenging, and new complimentary computational/experimental techniques are being introduced. Most recent work applying modern systems biology techniques has been conducted on bacteria, yeast, mouse, and human genomes. However, these concepts and tools are equally applicable to other species including ruminants (e.g., livestock). In systems biology, both bottom-up and top-down approaches are central to assemble information from all levels of biological pathways that must coordinate physiological processes. A bottom-up approach encompasses draft reconstruction, manual curation, network reconstruction through mathematical methods, and validation of these models through literature analysis (i.e., bibliomics). Whereas top-down approach encompasses metabolic network reconstructions using ‘omics’ data (e.g., transcriptomics, proteomics) generated through DNA microarrays, RNA-Seq or other modern high-throughput genomic techniques using appropriate statistical and bioinformatics methodologies. In this review we focus on top-down approach as a means to improve our knowledge of underlying metabolic processes in ruminants in the context of nutrition. We also explore the usefulness of tissue specific reconstructions (e.g., liver and adipose tissue) in cattle as a means to enhance productive efficiency.

Markers/parameters for the evaluation of natural resistance status of small ruminants against gastrointestinal nematodes

The high prevalence of anthelmintic-resistant gastrointestinal nematodes (GINs) throughout the world has led to the need for alternative worm control strategies. One of the possible substitutes to reduce the problems of drug resistance and residue is the evaluation/breeding of small ruminants for greater resistance to the GINs (organically produced), which in turn would be a helpful tool to predict the performance of an animal. At present, the existing diversity in the genetic potential to resist/tolerate GINs infection both within and between breeds has been validated. Successful selection of animals to define the genotype and identified resistance is related to the employed markers. A number of phenotypic traits such as faecal egg count (FEC), worm burden, serum antibodies, peripheral eosinophilia, packed cell volume, live weight, serum protein and albumin concentrations have been used for this purpose both in natural and artificial infections. Relatively resistant/tolerant animals have also been found to have mastocytosis, globule leucocytes, high levels of histamine and immunoglobulin (Ig) A and IgE concentrations. Of these traits, the principal and most practical measurement used to assess resistance status in animals undergoing similar parasite challenges is FEC. FEC has a positive/negative correlation with other biochemical, cellular and immunological parameters; however, the reliability of individual trial is often questioned and valuable information regarding the genetic makeup can be obtained from pooled data of a large number of trials and parameters. This paper covers all the aspects reported in the literature on various parameters considered to evaluate the resistance status of a range of small ruminant breeds.

Effect of staged ovariectomy on measures of mammary growth and development in prepubertal dairy heifers

Previous studies in prepubertal heifers suggest that the magnitude of reduction in mammary parenchymal growth in response to ovariectomy varies with the age at which surgery is performed. We hypothesized that ovarian secretions are essential for initiating mammary development but not required to maintain allometric mammary growth in prepubertal dairy heifers. The objectives of this study were to determine the effect of staged ovariectomy during the prepubertal period on mammary growth and tissue composition and the expression of selected genes. Prepubertal Holstein heifers at 2, 3 or 4 months of age were randomly assigned to one of two treatments, ovariectomized (OVX; n = 12) or sham operated (INT; n = 12). Mammary parenchyma (PAR) and fat pad (MFP) were harvested 30 days after surgery. Proximate composition of PAR and MFP (DNA, protein and lipid) as well as expression of the selected estrogen-responsive genes stanniocalcin1 (STC1), tissue factor pathway inhibitor precursor (TFPI) and proliferating cell nuclear antigen (PCNA) were determined in PAR and MFP by quantitative real-time PCR. The relative amount of epithelium and proportion of epithelia cell nuclei expressing the proliferation marker Ki67 were determined by histological and immunohistochemical analyses, respectively. MFP mass was not impacted by treatment but was decreased with age as was lipid content and concentration (P ⩽ 0.01). The mass of mammary PAR was reduced in OVX and increased with age (P ⩽ 0.01). Parenchymal tissue tended to have less total DNA, protein and lipid in OVX heifers. Parenchymal tissue concentrations of protein and DNA were increased with age and there was an age × treatment interaction. Treatment had no effect on either the Ki67 labeling index or percent epithelial area. The relative abundances of STC1, TFPI and PCNA mRNA in PAR were reduced in OVX. We did not find a significant impact of ovariectomy on mRNA expression when surgery was performed at 2 months compared with surgery at 3 or 4 months of age. However, having nearly undetectable PAR in two heifers ovariectomized at the earliest period (2 months of age) suggests that early ovariectomy is especially detrimental to subsequent parenchymal development.

Bovine mammary stem cells: cell biology meets production agriculture

Mammary stem cells (MaSC) provide for net growth, renewal and turnover of mammary epithelial cells, and are therefore potential targets for strategies to increase production efficiency. Appropriate regulation of MaSC can potentially benefit milk yield, persistency, dry period management and tissue repair. Accordingly, we and others have attempted to characterize and alter the function of bovine MaSC. In this review, we provide an overview of current knowledge of MaSC gained from studies using mouse and human model systems and present research on bovine MaSC within that context. Recent data indicate that MaSC retain labeled DNA for extended periods because of their selective segregation of template DNA strands during mitosis. Relying on this long-term retention of bromodeoxyuridine-labeled DNA, we identified putative bovine MaSC. These label-retaining epithelial cells (LREC) are in low abundance within mammary epithelium (<1%). They are predominantly estrogen receptor (ER)-negative and localized in a basal or suprabasal layer of the epithelium throughout the gland. Thus, the response of MaSC to estrogen, the major mitogen in mammary gland, is likely mediated by paracrine factors released by cells that are ER-positive. This is consistent with considerable evidence for cross-talk within and between epithelial cells and surrounding stromal cells. Excision of classes of cells by laser microdissection and subsequent microarray analysis will hopefully provide markers for MaSC and insights into their regulation. Preliminary analyses of gene expression in laser-microdissected LREC and non-LREC are consistent with the concept that LREC represent populations of stem cells and progenitor cells that differ with regard to their properties and location within the epithelial layer. We have attempted to modulate the MaSC number by infusing a solution of xanthosine through the teat canal and into the ductal network of the mammary glands of prepubertal heifers. This treatment increased the number of putative stem cells, as evidenced by an increase in the percentage of LREC and increased telomerase activity within the tissue. The exciting possibility that stem cell expansion can influence milk production is currently under investigation.

ER and PR signaling nodes during mammary gland development

The ovarian hormones estrogen and progesterone orchestrate postnatal mammary gland development and are implicated in breast cancer. Most of our understanding of the molecular mechanisms of estrogen receptor (ER) and progesterone receptor (PR) signaling stems from in vitro studies with hormone receptor-positive cell lines. They have shown that ER and PR regulate gene transcription either by binding to DNA response elements directly or via other transcription factors and recruiting co-regulators. In addition they cross-talk with other signaling pathways through nongenomic mechanisms. Mouse genetics combined with tissue recombination techniques have provided insights about the action of these two hormones in vivo. It has emerged that hormones act on a subset of mammary epithelial cells and relegate biological functions to paracrine factors. With regards to hormonal signaling in breast carcinomas, global gene expression analyses have led to the identification of gene expression signatures that are characteristic of ERα-positive tumors that have stipulated functional studies of hitherto poorly understood transcription factors. Here, we highlight what has been learned about ER and PR signaling nodes in these different systems and attempt to lay out in which way the insights may converge.

Proteomic analysis of the nuclear phosphorylated proteins in dairy cow mammary epithelial cells treated with estrogen

Estrogen regulates a variety of physiological processes, including mammary gland growth, morphogenesis of the mammary gland, proliferation and differentiation, and elevating the expression of milk proteins. Many nuclear phosphorylated proteins such as pStat5 and mTOR regulate milk protein synthesis. But the detail of milk protein synthesis controlled at the transcript level and posttranslational level is not well-known. To contribute to the understanding of the molecular mechanism underlying estrogen action on the dairy cow mammary epithelial cells (DCMECs), nuclear phosphorylated proteins regulated by estrogen in DCMECs were identified. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization/time of flight mass spectrometry were used to identify the changes of nuclear phosphorylated proteins in DCMECs treated with estrogen. Seven proteins were identified differentially up-expressed in DCMECs after 24-h estrogen exposure: including glycyl-tRNA synthetase, previously reported in milk protein synthesis of DCMECs, belonging to the class-II aminoacyl-tRNA synthetase family; proteins involved in other cellular functions, such as translation initiation factors, GTP-binding nuclear proteins, heat-shock proteins, and proteins belonging to ubiquitin-proteasome system. This screening reveals that estrogen influences the levels of nuclear phosphorylated proteins of DCMECs which opens new avenue for the study of the molecular mechanism linking to milk synthesis.

Alpha-Tocopherol Alters Transcription Activities that Modulates Tumor Necrosis Factor Alpha (TNF-α) Induced Inflammatory Response in Bovine Cells

To further investigate the potential role of α-tocopherol in maintaining immuno-homeostasis in bovine cells (Madin-Darby bovine kidney epithelial cell line), we undertook in vitro experiments using recombinant TNF-α as an immuno-stimulant to simulate inflammation response in cells with or without α-tocopherol pre-treatment. Using microarray global-profiling and IPA (Ingenuity Pathways Analysis, Ingenuity^® Systems, http://www.ingenuity.com) data analysis on TNF-α-induced gene perturbation in those cells, we focused on determining whether α-tocopherol treatment of normal bovine cells in a standard cell culture condition can modify cell’s immune response induced by TNF-α challenge. When three datasets were filtered and compared using IPA, there were a total of 1750 genes in all three datasets for comparison, 97 genes were common in all three sets; 615 genes were common in at least two datasets; there were 261 genes unique in TNF-α challenge, 399 genes were unique in α-tocopherol treatment, and 378 genes were unique in the α-tocopherol plus TNF-α treatment. TNF-α challenge induced significant change in gene expression. Many of those genes induced by TNF-α are related to the cells immune and inflammatory responses. The results of IPA data analysis showed that α-tocopherol-pretreatment of cells modulated cell’s response to TNF-α challenge. In most of the canonical pathways, α-tocopherol pretreatment showed the antagonistic effect against the TNF-α-induced pro-inflammatory responses. We concluded that α-tocopherol pre-treatment has a significant antagonistic effect that modulates the cell’s response to the TNF-α challenge by altering the gene expression activities of some important signaling molecules.

Small ruminant resistance against gastrointestinal nematodes: a case of Haemonchus contortus

Gastrointestinal nematode (GIN) infections are a common constraint to small ruminant industry throughout the world, and among those, haemonchosis has its own significance. Control of GIN primarily relies on the use of anthelmintics, but this approach has become less reliable due to the development of resistance in GINs against commonly used anthelmintics and an increased consumer demand for environmentally friendly animal products. These issues have stimulated investigations to find alternative sustainable control strategies, which are less reliant on anthelmintic input. One of such strategies is breeding of small ruminants for their resistance to the GINs. The susceptibility and resistance of animals to GIN infections varies within and between breeds. Various parasitological, biochemical and immunological parameters are employed to evaluate natural resistance status of animals both in natural pasture and artificial infections. The immune mechanisms responsible for resistance are not completely understood, but it has a significant effect in inherited resistance. Relatively resistant or tolerant animals show better local and generalised immune response as compared to susceptible. Immune response against GINs is influenced by many physiological factors. Determination of specific genes linked with host resistance will provide a valuable approach to find out the molecular mechanism of host resistance to GINs. Resistance has been reported to reduce pasture contamination, which in turn reduces re-infection and thus the requirement of the frequent anthelmintic treatments. The efficiency of control can be increased through objective and accurate identification of genetically tolerant individuals by natural and artificial infections with GINs. Complete resistance is the ultimate solution, but this has generally been ignored as a commercial reality. This paper reviews the published reports on natural resistance in small ruminants and discusses the prospects of developing small ruminants, which could be resistant to GINs.

Transcriptome analysis of epithelial and stromal contributions to mammogenesis in three week prepartum cows

Transcriptome analysis of bovine mammary development has provided insight into regulation of mammogenesis. However, previous studies primarily examined expression of epithelial and stromal tissues combined, and consequently did not account for tissue specific contribution to mammary development. Our objective was to identify differences in gene expression in epithelial and intralobular stromal compartments. Tissue was biopsied from non-lactating dairy cows 3 weeks prepartum, cut into explants and incubated for 2 hr with insulin and hydrocortisone. Epithelial and intralobular stromal tissues were isolated with laser capture microdissection. Global gene expression was measured with Bovine Affymetrix GeneChips, and data were preprocessed using RMA method. Moderated t-tests from gene-specific linear model analysis with cell type as a fixed effect showed more than 3,000 genes were differentially expressed between tissues (P<0.05; FDR<0.17). Analysis of epithelial and stromal transcriptomes using Database for Annotation, Visualization and Integrated Discovery (DAVID) and Ingenuity Pathways Analysis (IPA) showed that epithelial and stromal cells contributed distinct molecular signatures. Epithelial signatures were enriched with gene sets for protein synthesis, metabolism and secretion. Stromal signatures were enriched with genes that encoded molecules important to signaling, extracellular matrix composition and remodeling. Transcriptome differences also showed evidence for paracrine interactions between tissues in stimulation of IGF1 signaling pathway, stromal reaction, angiogenesis, neurogenesis, and immune response. Molecular signatures point to the dynamic role the stroma plays in prepartum mammogenesis and highlight the importance of examining the roles of cell types within the mammary gland when targeting therapies and studying mechanisms that affect milk production.

The vitamin D receptor and inducible nitric oxide synthase associated pathways in acquired resistance to Cooperia oncophora infection in cattle

Cooperia oncophora is an economically important gastrointestinal nematode in ruminants. Acquired resistance to Cooperia oncophora infection in cattle develops rapidly as a result of prior infections. Naïve cattle, when given a primary infection of high-dose infective L3 larvae, develop a strong immunity to subsequent reinfection. Compared to primary infection, reinfection resulted in a marked reduction in worm establishment. In order to understand molecular mechanisms underlying the development of acquired resistance, we characterized the transcriptomic responses of the bovine small intestine to a primary infection and reinfection. A total of 23 pathways were significantly impacted during infection. The vitamin D receptor activation was strongly induced only during reinfection, suggesting that this pathway may play an important role in the development of acquired resistance via its potential roles in immune regulation and intestinal mucosal integrity maintenance. The expression of inducible nitric oxide synthase (NOS2) was strongly induced during reinfection but not during primary infection. As a result, several canonical pathways associated with NOS2 were impacted. The genes involved in eicosanoid synthesis, including prostaglandin synthase 2 (PTGS2 or COX2), remained largely unchanged during infection. The rapid development of acquired resistance may help explain the lack of relative pathogenicity by Cooperia oncophora infection in cattle. Our findings facilitate the understanding of molecular mechanisms underlying the development of acquired resistance, which could have an important implication in vaccine design.

Alpha-Tocopherol Modulates Transcriptional Activities that Affect Essential Biological Processes in Bovine Cells

Using global expression profiling and pathway analysis on α-tocopherol-induced gene perturbation in bovine cells, this study has generated comprehensive information on the physiological functions of α-tocopherol. The data confirmed α-tocopherol is a potent regulator of gene expression and α-tocopherol possesses novel transcriptional activities that affect essential biological processes. The genes identified fall within a broad range of functional categories and provide the molecular basis for its distinctive effects. Enrichment analyses of gene regulatory networks indicate α-tocopherol alter the canonical pathway of lipid metabolism and transcription factors SREBP1 and SREBP2, (Sterol regulatory element binding proteins), which mediate the regulatory functions of lipid metabolism. Transcription factors HNF4-α (Hepatocyte nuclear factor 4), c-Myc, SP1 (Sp1 transcription factor), ESR1 (estrogen receptor 1, nuclear), and androgen receptor, along with several others, were centered as the hubs of transcription regulation networks. The data also provided direct evidence that α-tocopherol is involved in maintaining immuno-homeostasis through targeting the C3 (Complement Component 3) gene.

Mastitis associated transcriptomic disruptions in cattle

Mastitis is ranked as the top disease for dairy cattle based on traditional cost analysis. Greater than 100 organisms from a broad phylogenetic spectrum are able to cause bovine mastitis. Transcriptomic characterization facilitates our understanding of host-pathogen relations and provides mechanistic insight into host resistance to mastitis. In this review, we discuss effector mechanisms and transcriptomic changes within the mammary gland in response to experimental infections. We compare temporal, spatial and pathogen-specific local transcriptomic disruptions in the mammary gland as well as pathogen-induced systemic responses and transcriptional changes in distant organs. We attempt to explain why studies on transcriptomic changes during critical physiological periods and in response to non-mastitic pathogens may have important implications for mastitis studies. Future perspectives on revealing bidirectional molecular cross-talk between mastitis pathogens and host cells using cutting-edge genomic technologies are also discussed.

Localized complement activation in the development of protective immunity against Ostertagia ostertagi infections in cattle

The abomasal nematode Ostertagia ostertagi is a major causal agent contributing to production inefficiencies in the cattle industry in temperate regions of the world. Protective immunity to infections develops very slowly and resistance to reinfection manifests only after prolonged exposure. Mechanisms underlying the development of protective immunity remain largely unexplored. Immune animals, which have significantly reduced worm burdens, were developed after multiple drug-attenuated experimental infections and were compared to a primary infected group and their respective uninfected controls. In this study, transcriptomic analysis identified three signaling pathways significantly impacted during both primary and repeat infections, the complement system, leukocyte extravasation and acute phase responses. Increased mRNA levels of complement components C3, factor B (CFB) and factor I (CFI) in the abomasal mucosa of the infected cattle were confirmed using quantitative PCR while Western blot analysis established the presence of elevated levels of activated C3 proteins in the mucosa. One of the initiators of local complement activation could be related to secretory IgA and IgM because infections significantly up-regulated expression of J chain (IGJ), as well as polymeric Ig receptor (PIGR) and an IgM-specific receptor (FAIM3), suggesting sustained increases in both synthesis and transepithelial transport of IgA and IgM during the infection. The elevated levels of pro-inflammatory cytokines, such as IL-4 and IL-1β, during infection may be involved in gene regulation of complement components. Our results suggest enhanced tissue repair and mucin secretion in immune animals may also contribute to protective immunity. These results are the first evidence that local complement activation may be involved in the development of long-term protective immunity and provide a novel mechanistic insight into resistance against O. ostertagi in cattle.

Microarray analysis of equine endometrium at days 8 and 12 of pregnancy

Establishment and maintenance of pregnancy in equids is only partially understood. To provide new insights into early events of this process, we performed a systematic analysis of transcriptome changes in the endometrium at Days 8 and 12 of pregnancy. Endometrial biopsy samples from pregnant and nonpregnant stages were taken from the same mares. Composition of the collected biopsy samples was analyzed using quantitative stereological techniques to determine proportions of surface and glandular epithelium and blood vessels. Microarray analysis did not reveal detectable changes in gene expression at Day 8, whereas at Day 12 of pregnancy 374 differentially expressed genes were identified, 332 with higher and 42 with lower transcript levels in pregnant endometrium. Expression of selected genes was validated by quantitative real-time RT-PCR. Gene set enrichment analysis, functional annotation clustering, and cocitation analysis were performed to characterize the genes differentially expressed in Day 12 pregnant endometrium. Many known estrogen-induced genes and genes involved in regulation of estrogen signaling were found, but also genes known to be regulated by progesterone and prostaglandin E2. Additionally, differential expression of a number of genes related to angiogenesis and vascular remodeling suggests an important role of this process. Furthermore, genes that probably have conserved functions across species, such as CRYAB, ERRFI1, FGF9, IGFBP2, NR2F2, STC1, and TNFSF10, were identified. This study revealed the potential target genes and pathways of conceptus-derived estrogens, progesterone, and prostaglandin E2 in the equine endometrium probably involved in the early events of establishment and maintenance of pregnancy in the mare.

Functional and gene network analyses of transcriptional signatures characterizing pre-weaned bovine mammary parenchyma or fat pad uncovered novel inter-tissue signaling networks during development

BACKGROUND

The neonatal bovine mammary fat pad (MFP) surrounding the mammary parenchyma (PAR) is thought to exert proliferative effects on the PAR through secretion of local modulators of growth induced by systemic hormones. We used bioinformatics to characterize transcriptomics differences between PAR and MFP from approximately 65 d old Holstein heifers. Data were mined to uncover potential crosstalk through the analyses of signaling molecules preferentially expressed in one tissue relative to the other.

RESULTS

Over 9,000 differentially expressed genes (DEG; False discovery rate <or= 0.05) were found of which 1,478 had a >or=1.5-fold difference between PAR and MFP. Within the DEG highly-expressed in PAR vs. MFP (n = 736) we noted significant enrichment of functions related to cell cycle, structural organization, signaling, and DNA/RNA metabolism. Only actin cytoskeletal signaling was significant among canonical pathways. DEG more highly-expressed in MFP vs. PAR (n = 742) belong to lipid metabolism, signaling, cell movement, and immune-related functions. Canonical pathways associated with metabolism and signaling, particularly immune- and metabolism-related were significantly-enriched. Network analysis uncovered a central role of MYC, TP53, and CTNNB1 in controlling expression of DEG highly-expressed in PAR vs. MFP. Similar analysis suggested a central role for PPARG, KLF2, EGR2, and EPAS1 in regulating expression of more highly-expressed DEG in MFP vs. PAR. Gene network analyses revealed putative inter-tissue crosstalk between cytokines and growth factors preferentially expressed in one tissue (e.g., ANGPTL1, SPP1, IL1B in PAR vs. MFP; ADIPOQ, IL13, FGF2, LEP in MFP vs. PAR) with DEG preferentially expressed in the other tissue, particularly transcription factors or pathways (e.g., MYC, TP53, and actin cytoskeletal signaling in PAR vs. MFP; PPARG and LXR/RXR Signaling in MFP vs. PAR).

CONCLUSIONS

Functional analyses underscored a reciprocal influence in determining the biological features of MFP and PAR during neonatal development. This was exemplified by the potential effect that the signaling molecules (cytokines, growth factors) released preferentially (i.e., more highly-expressed) by PAR or MFP could have on molecular functions or signaling pathways enriched in the MFP or PAR. These bidirectional interactions might be required to coordinate mammary tissue development under normal circumstances or in response to nutrition.

Mucin biosynthesis in the bovine goblet cell induced by Cooperia oncophora infection

Mucin hypersecretion is considered to be one of the most common components of the immune response to gastrointestinal nematode infection. However, investigations have not been conducted in the Cattle-Cooperia oncophora system to verify the findings largely derived from murine models. In this study, we examined the expression of seven mucins and seven enzymes in the mucin biosynthesis pathway involved in O-linked glycosylation in the bovine small intestine including goblet cells enriched using laser capture microdissection during a primary C. oncophora infection. At the mRNA level, MUC2 expression was significantly higher in both lamina propria and goblet cells at 28 days post-infection compared to the naive control. MUC5B expression at the mRNA level was also higher in lamina propria at 28dpi. Expression of MUC1, MUC4, MUC5AC, and MUC6 was extremely low or not detectable in goblet cells, columnar epithelial cells, and lamina propria from both naive control and infected animals. Among the seven enzymes involved in post-translational O-linked glycosylation of mucins, GCNT3, which may represent one of the key rate-limiting steps in mucin biosynthesis, was up-regulated in goblet cells, columnar epithelial cells, lamina propria, and gross small intestine tissue during the course of infection. Western blot analysis revealed that MUC2 glycoprotein was strongly induced by infection in both gross small intestine tissue and its mucosal layer. In contrast, the higher MUC5B protein expression was observed only in the mucosal layer. Immunohistochemistry provided further evidence of the mucin glycoprotein production and localization. Our results provided insight into regulation of mucin biosynthesis in various cell types in the bovine small intestine during gastrointestinal nematode infection and will facilitate our understanding of mucins and their role in immune response against parasitic nematodes.

In vivo expansion of the mammary stem/ progenitor cell population by xanthosine infusion

Mammary stem cells provide for growth and maintenance of the mammary gland and are therefore of considerable interest as determinants of productivity and efficiency of dairy animals and as targets of carcinogenesis in humans. Xanthosine treatment was previously shown to promote expansion of hepatic stem cells in vitro. The objective of this study was to determine if in vivo treatment with xanthosine can increase the mammary stem cell population. Xanthosine was infused into the right mammary glands of four female Holstein calves for 5 consecutive days. Immediately after each xanthosine treatment, calves were injected intravenously with 5-bromo-2-deoxyuridine (BrdU). Forty days after the final treatment, calves were euthanized and mammary tissue harvested. BrdU-label retaining epithelial cells (LREC) were detected immunohistochemically and quantified. Retention of BrdU was used as a marker for putative bovine mammary stem cells. Infusion of xanthosine into the bovine mammary gland significantly increased the number of LREC in treated glands compared to contralateral control glands (P < 0.05). LREC averaged 0.4% of epithelial cells in control glands and 0.8% in xanthosine-treated glands. The increase in LREC in xanthosine-treated glands was supported by a concomitant increase in telomerase activity (P < 0.01) and a correlation between LREC and telomerase (P < 0.05; r (2) = 0.7). Data indicate that in vivo treatment with xanthosine can be used to increase the number of mammary stem cells. This is the first demonstration of an in vivo treatment to increase the endogenous population of mammary stem cells, with utility for biomedical research and dairy management.

Mammary Fat Can Adjust Prolactin Effect on Mammary Epithelial Cells via Leptin and Estrogen

Leptin, like estrogen, is one of the endo/paracrine factors, which are synthesized in and secreted from mature adipocytes. The roles of the mammary fat pad and mammary adipocytes in the initiation of lactation are not clear. In this study, we showed that combination of prolactin, leptin and estrogen elevated the expression of the milk protein beta-lactoglobulin. We also showed that after prolactin stimulate the secretion of leptin from the mammary fat, leptin upregulated the expression of estrogen receptor alpha in the mammary epithelial cells. Also, prolactin affected aromatase mRNA expression in the bovine mammary fat and we demonstrated that leptin and prolactin can affect cholesterol secretion from explants in culture to the medium. Therefore, we suggest that prolactin initiates estrogen expression (as represented by aromatase mRNA) in the mammary fat pad, whereas leptin stimulates estrogen receptor alpha expression in the mammary epithelial cells. We hypothesize that leptin and estrogen, secreted from the mammary fat regulate lactation after stimulation of prolactin.

ASAS centennial paper: Lactation biology for the twenty-first century

Knowledge of general aspects of mammary gland function, including metabolic pathways and hormonal regulation of mammary gland development and lactation, in livestock species was obtained several decades ago. As basic biological information of growth factor action, apoptotic mechanisms, and signal transduction events has exploded, the mouse became the model of choice for studying fundamental mechanisms regulating mammary function. A complete sequenced genome also has made the mouse amenable for studies of mammary gene network expression. Advances in molecular biology techniques currently allow researchers to genetically modify mice to either overexpress or completely lack specific genes, thereby studying their function in an in vivo setting. Furthermore, the use of mammary-specific promoters has allowed genes related to mammary gland function to be eliminated from the mammary gland in a developmental and tissue-specific manner. These studies have demonstrated the complexity that underlies mammary gland development and function in rodents and may provide insight into the mechanisms that ultimately allow the ruminant or swine mammary gland to function in a coordinated fashion throughout puberty, pregnancy, lactation, and involution. The challenge facing animal scientists is how to obtain similar information in much larger and expensive livestock. One possible approach is to manipulate gene expression in vitro using mammary cell culture models derived from domestic animals (e.g., genes can be "knocked down" using small interfering RNA approaches). Ultimately, major advances in understanding lactation biology may come from coupling basic mechanistic information with functional genomics, proteomics, and metabolomics approaches. A strong foundation in bioinformatics will also be required to optimize use of these new technologies. Stem cell biology also represents an exciting area in the next decade that holds promise for improving lactation efficiency. Strong training of our future scientists in these areas should facilitate livestock-focused mammary gland research that will allow basic information to be gained at unprecedented amounts, ultimately leading to optimization of livestock production.

Identification of putative bovine mammary epithelial stem cells by their retention of labeled DNA strands

Stem cells appear to retain labeled DNA for extended periods because of their selective segregation of template DNA strands during mitosis. In this study, proliferating cells in the prepubertal bovine mammary gland were labeled using five daily injections of 5-bromo-2-deoxyuridine (BrdU). Five weeks later, BrdU-labeled mammary epithelial cells were still evident. The percentage of BrdU-labeled epithelial cells was greatest in the lower region of the mammary gland, near the gland cistern, and was decreased toward the periphery of the parenchymal region, where the ducts were invading the mammary fat pad. Increased numbers of BrdU-labeled epithelial cells in basal regions of the gland are likely a consequence of decreased proliferation rates and increased cell cycle arrest in this area. In peripheral regions of mammary parenchyma, the percentage of heavily labeled epithelial cells averaged 0.24%, a number that is consistent with estimates of the frequency of stem cells in the mouse mammary gland. Epithelial label-retaining cells seemingly represent a slowly proliferating population of cells, as 5.4% of heavily labeled cells were positive for the nuclear proliferation antigen Ki67. Because epithelial label-retaining cells contain estrogen receptor (ER)-negative and ER-positive cells, they apparently comprise a mixed population, which I suggest is composed of ER-negative stem cells and ER-positive progenitors. Continuing studies will address the usefulness of this technique to identify bovine mammary stem cells and to facilitate studies of stem cell biology.

Canonical pathways and networks regulated by estrogen in the bovine mammary gland

Many attempts have been made to identify estrogen-responsive genes using high-throughput approaches such as microarray, serial analysis of gene expression (SAGE), and in silico prediction. However, few studies have systematically analyzed regulatory networks and pathways affected by estrogen. In this report, we analyzed transcript profiles obtained from 16 prepubertal heifers in a 2 x 2 factorial experiment, with ovarian status (intact or ovariectomized) as the first factor and estrogen treatment as the second (control or estradiol). After 54 h of estrogen treatment, gene expression was evaluated in the parenchyma and fat pad of the bovine mammary gland using a high-density oligonucleotide microarray. The genes significantly regulated by estrogen were subject to pathway and regulatory network analysis using Ingenuity Pathways Analysis software. Approximately 2,344 genes responded significantly to estrogen treatment. Of these, 1016 genes were influenced by estrogen regardless of tissue or ovarian status, while the remaining genes were significant in one of four specific effects of tissue or ovarian status. The canonical pathways significantly regulated by estrogen (P < 0.05) included protein ubiquitination, G2/M cell cycle control, IGF1 signaling, N-glycan biosynthesis, sterol biosynthesis, and oxidative phosphorylation. A total of 23 regulatory networks were identified as estrogen responsive. The results provide insight into the molecular mechanisms through which estrogen regulates bovine mammary gland growth and development, supporting the concept that interaction between tissues within the mammary gland promotes mammary epithelial growth.

Regulation of gene expression in the bovine mammary gland by ovarian steroids

It is well established that estrogen is required for mammary epithelial cell proliferation and ductal development in the growing animal, and that lobuloalveolar development during gestation is dependent on progesterone. The effects of these steroid hormones on gene expression in the mammary gland are mediated primarily by their respective nuclear hormone receptors, which function as hormone-bound transcription factors. To gain insight into how estrogen and progesterone regulate mammary gland growth and function in cattle, we and others have characterized the expression patterns of their cognate nuclear hormone receptors in the bovine mammary gland throughout development, pregnancy, and lactation. This work has identified a lack of expression of estrogen receptor beta and a greater abundance of progesterone receptor during lactation in the bovine mammary gland, compared with the rodent gland. We speculate that interactions among the estrogen receptor isoforms that regulate progesterone receptor expression may contribute to these species differences. Further, demonstrated expression of substantial quantities of estrogen receptor within the prepubertal bovine mammary fat pad, along with coordinated insulin-like growth factor-I expression, suggests that this tissue may stimulate parenchymal growth via an estrogen-responsive paracrine mechanism. In addition, the recent availability of bovine genomic sequence information and microarray technologies has permitted the study of global gene expression in the mammary gland in response to the steroid environment. We have identified more than 100 estrogen-responsive genes, of which the majority are novel estrogen gene targets. Estrogen-induced changes in gene expression were consistent with increased mammary epithelial cell proliferation, increased extracellular matrix turnover in parenchyma, and increased extracellular matrix deposition in the fat pad. A comparison of estrogen-responsive genes in the mammary glands of humans, mice, and cattle suggests considerable variation among species, as well as potential differences in regulatory elements in common estrogen receptor gene targets. Continuing studies using advanced molecular techniques should assist in elucidating the complex regulation of mammary function at the transcript level.

Combining mouse mammary gland gene expression and comparative mapping for the identification of candidate genes for QTL of milk production traits in cattle

Background

Many studies have found segregating quantitative trait loci (QTL) for milk production traits in different dairy cattle populations. However, even for relatively large effects with a saturated marker map the confidence interval for QTL location by linkage analysis spans tens of map units, or hundreds of genes. Combining mapping and arraying has been suggested as an approach to identify candidate genes. Thus, gene expression analysis in the mammary gland of genes positioned in the confidence interval of the QTL can bridge the gap between fine mapping and quantitative trait nucleotide (QTN) determination.

Results

We hybridized Affymetrix microarray (MG-U74v2), containing 12,488 murine probes, with RNA derived from mammary gland of virgin, pregnant, lactating and involuting C57BL/6J mice in a total of nine biological replicates. We combined microarray data from two additional studies that used the same design in mice with a total of 75 biological replicates. The same filtering and normalization was applied to each microarray data using GeneSpring software. Analysis of variance identified 249 differentially expressed probe sets common to the three experiments along the four developmental stages of puberty, pregnancy, lactation and involution. 212 genes were assigned to their bovine map positions through comparative mapping, and thus form a list of candidate genes for previously identified QTLs for milk production traits. A total of 82 of the genes showed mammary gland-specific expression with at least 3-fold expression over the median representing all tissues tested in GeneAtlas.

Conclusion

This work presents a web tool for candidate genes for QTL (cgQTL) that allows navigation between the map of bovine milk production QTL, potential candidate genes and their level of expression in mammary gland arrays and in GeneAtlas. Three out of four confirmed genes that affect QTL in livestock (ABCG2, DGAT1, GDF8, IGF2) were over expressed in the target organ. Thus, cgQTL can be used to determine priority of candidate genes for QTN analysis based on differential expression in the target organ.

Local inflammation as a possible mechanism of resistance to gastrointestinal nematodes in Angus heifers

Understanding mechanisms of resistance to gastrointestinal nematodes is important in developing effective and sustainable control programs. A resource population of Angus cattle consisting of approximately 600 animals with complete pedigree records has been developed. The majority of these animals were completely characterized for their resistance to natural challenge by gastrointestinal nematodes. As the first step towards understanding the molecular basis of disease resistance, we investigated expression profiles of 17 cytokines, cytokine receptors, and chemokines using real-time RT-PCR in animals demonstrating resistance or susceptibility to pasture challenge. The animals exposed to natural infection for approximately 6 months were treated to remove existing parasites and then experimentally challenged with both Ostertagia ostertagi and Cooperia oncophora. The mRNA expression profiles of these genes in abomasal and mesenteric lymph nodes (ALN, MLN), fundic and pyloric abomasa (FA, PA), and small intestine (SI) were compared between resistant and susceptible animals. Resistant heifers exhibited elevated expression of inflammatory cytokines such as TNFalpha, IL-1beta, and MIP-1alpha in fundic and pyloric abomasa 7 days post infection. Expression levels of IL-10, polymeric immunoglobullin receptor gene (PIGR), and WSX-1 were also 2.7-19.9-folds higher in resistant than susceptible heifers in these tissues. No difference in expression of CXCL6, CXCL10, IFN-gamma, IL-2, IL-4, IL-6, IL-8, IL-12 p40, IL-13, IL-15 and IL-18 was observed between the two groups. The expression of MIP-1alpha, IL-6, and IL-10 was also elevated in small intestines in resistant animals. In contrast, little difference in expression of these genes was detected between resistant and susceptible groups in the draining lymph nodes. These data indicate that resistant animals can better maintain inflammatory responses at the site of infection, suggesting a possible novel mechanism of resistance.