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Assessment of the effect of nutrition level on transcriptome of mammary gland structural components (parenchyma (PAR) and fat pad (MFP)) and liver in dairy calves mammary gland in dairy calves

ABSTRACT: The aim of this study was to identify changes in transcriptome of parenchyma (PAR), fat pad (MFP) and liver in dairy calves. Our earlier results showed that feeding management regulates the dynamics of organ growth in preweaned heifers. We observed that a daily dose of 5.3 kg of milk replacer inhibits mammary gland development. Therefore, this research aims at evaluation of the influence of the nutritional level in the early life period of calves on the biological processes related to the development of the mammary gland through transcriptomic alterations.

ORGANISM(S): Bos taurus

PROVIDER: GSE241557 | GEO | 2024/12/31

REPOSITORIES: GEO

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Project description:Background: To reduce costs of rearing replacement heifers, researchers have focused on decreasing age at breeding and first calving, and to increase returns upon initiation of lactation the focus has been on increasing mammary development prior to onset of first lactation. Enhanced plane of nutrition pre-weaning may benefit the entire replacement heifer operation by promoting mammary gland development and greater future production. Methods: Twelve Holstein heifer calves (<1 wk old) were reared on 1 of 2 dietary treatments (n = 6/group) for 8 wk: a control group fed a restricted milk replacer at 0.45 kg/d (R, 20% crude protein, 20% fat), or an accelerated group fed an enhanced milk replacer at 1.13 kg/d (EH, 28% crude protein, 25% fat). At weaning (8 wk), calves were euthanized and sub-samples of mammary parenchyma (PAR) and mammary fat pad (MFP) were harvested upon removal from the body. Total RNA from both tissues was extracted and sequenced using the Illumina HiSeq2500 platform. The Dynamic Impact Approach (DIA) and Ingenuity Pathway Analysis (IPA) were used for pathway analysis and functions, gene networks, and cross-talk analyses of the two tissues. Results: When comparing EH vs R 1,561 genes (↑895, and ↓666) and 970 genes (↑506, and ↓464) were found differentially expressed in PAR and MFP, respectively. DIA and IPA results highlight a greater proliferation and differentiation activity in both PAR and MFP, supported by an increased metabolic activity. When calves were fed EH, the PAR displayed transcriptional signs of greater overall organ development, with higher ductal growth and branching, together with a supportive blood vessel and nerve network. These activities were mediated by intracellular cascades, such as AKT, SHH, MAPKs, and Wnt, probably activated by hormones, growth factors, and endogenous molecules. The analysis also revealed strong communication between MFP and PAR, with the first enhancing the development of PAR through secreted growth factors and the recruitment of immune cells. Conclusion: The transcriptomics and bioinformatics approach highlighted the mechanisms that mediate the mammary gland response to a higher plane of nutrition in the pre-weaning period.

Project description:Direct transcriptomics comparison corroborated by functional and gene network analyses of pre-weaned bovine mammary parenchyma and fat pad shed light on potential cross-talk between these developing tissues. Transcriptomic characterization of mammary parenchyma and fat pad and their interaction is still incomplete. In the present experiment, the molecular epithelial-fat pad cross-talk during mammary development was assessed by transcript profiling and functional analyses. Background: Interactions between bovine mammary parenchyma (PAR) and fat pad (MFP) during neonatal tissue development are still not fully understood. It is thought that the MFP surrounding the parenchymal tissue exerts proliferative effects on the PAR through secretion of local modulators of growth induced by systemic hormones. Main objectives in the present study were to use bioinformatics tools to characterize differences in transcript profiles between mammary PAR and MFP from Holstein heifers at ca. 65 d age and uncover potential cross-talk between the two tissues via the analyses of signaling molecules (e.g., cytokines and growth factors) preferentially expressed in one tissue relative to the other. Results: Over 9,000 differentially expressed genes (DEG; False discovery rate ≤ 0.05) were found of which 1,478 had a ≥1.5-fold difference. Within these DEG in PAR vs. MFP (n = 736) we noted enrichment of functions related to cell cycle, structural organization, signaling, and DNA/RNA metabolism. Few canonical pathways were among DEG and were mostly involved in cell cycle and tissue organization (p53 signaling). Enriched among DEG more highly-expressed in MFP vs. PAR (n = 742) were genes involved in lipid metabolism, signaling, cell movement, and immune-related functions. Canonical pathways associated with metabolism (fatty acid metabolism) and signaling, particularly immune- (acute phase response) and metabolism-related (cAMP signaling), 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 revealed a central role of PPARG, KLF2, EGR2, and EPAS1 in regulating expression of highly-expressed DEG in MFP vs. PAR. Analyses revealed putative crosstalk between tissues via differential expression of cytokines and growth factors highly-expressed in PAR (angiopoietin-1, osteopontin, interleukin-1β) or in MFP (adiponectin, interleukin-13, fibroblast growth factor-2, leptin) during bovine mammary development. Conclusions: We uncovered specific transcriptomic signatures characterizing MFP and PAR tissue. Not surprisingly, the expression profile of the MFP is characteristic of adipose tissue, and the one of PAR is characteristic of an epithelial tissue undergoing expansion and remodeling. Overall, our data highlighted a large degree of interaction between the two tissues and allowed envisaging a reciprocal influence in determining the biological features (and perhaps the fate) of each of the two tissues during this stage of development. This is strongly suggested by the potential effect that the signaling molecules released preferentially by PAR have on lipid metabolism-related pathways, which from our data was what most distinguished the MFP from PAR. Similarly, the cytokines and growth factors largely expressed in MFP potentially affect the pathways related to cell cycle, development, and proliferation in PAR, which our data highlighted as the main functions represented among the genes highly expressed in PAR vs. MFP. Based on the current analysis, the number of cytokines and growth factors that potentially are secreted by each tissue and affect molecules in the other underscores the concept of crosstalk. Ultimately, these bidirectional interactions might be required to coordinate mammary tissue development under normal circumstances or in response to environmental stimuli, such as nutrition.

Project description:The objective of this study was to analyze the mammary gland transcriptome to determine how preweaning nutrient supply alters the molecular mechanisms that regulate preweaning mammary development. Holstein heifers were fed via milk replacer either an elevated level of nutrient intake (ELE; on average, 5.9 ± 0.2 Mcal ME in 8.4 L of milk replacer (MR)/d, n = 6) or a restricted amount of nutrients (RES; 2.8 ± 0.2 Mcal ME in 4L MR/day, n = 5) for 54 d postnatal, at which point they were slaughtered and samples of mammary parenchyma tissue were obtained. Parenchymal mRNA was analyzed and the fold changes (FC) of 18,111 genes (ELE relative to RES) were uploaded to Ingenuity Pathway Analysis (IPA) software for transcriptomic analysis. Using a threshold of P < 0.05, IPA identified that the FC of 1,931 of 18,811 differentially expressed genes (DEG) could be utilized for the analysis. A total 18 molecular and cellular functions were relevant (P < 0.05) to DE genes arising from the treatments, with Cell Death and Survival, Cellular Movement, Cellular Development, Cellular Growth and Proliferation, and Lipid Metabolism being the 5 most associated functions with DEG. Based on the directional FC of DEG, the mammary gland of ELE heifers was predicted to have increased Epithelial-Mesenchymal Transition (Z = 2.685) and Accumulation of Lipid (Z = 2.322), while the Synthesis of DNA (Z = -2.137), Transactivation of RNA (Z = -2.254), Expression of RNA (Z = -2.405), Transcription (Z = -2.482) and Transactivation (Z = -2.611) were all predicted to be decreased. Additionally, IPA predicted the activation status of 13 upstream regulators with direct influence on DEG as affected by ELE feeding that were either ligand-dependent nuclear receptors (n = 2), enzyme (n = 1), or transcription regulators (n = 10). Of these, 6 were activated (Z > 2) and 7 were inhibited (Z < -2). In summary, feeding ELE preweaning altered the mammary transcriptome of Holstein heifers affecting cell functions involved in the morphological and physiological development of the mammary gland.