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Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis and RNA expression in Holstein heifer calves.

ABSTRACT: 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.

ORGANISM(S): Bos taurus

PROVIDER: GSE121715 | GEO | 2019/09/21

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:Effect of breed in mid lactation Holstein (H) and Montbéliarde (M) cows on mammary glande miRNA profile. Genetic polymorphisms are known to influence milk production and composition. However, genomic mechanisms involved in the genetic regulation of milk component synthesis are not completely understood. MicroRNAs (miRNA) regulate gene expression. The objective of the present study was to compare mammary gland miRNomes of two dairy cow breeds, Holstein and Montbéliarde, with different dairy performances. Milk, fat, protein, and lactose yields were lower in Montbéliarde than in Holstein cows. MiRNomes obtained using RNA-Seq technology from the mammary glands of Holstein (n = 5) and Montbéliarde (n = 6) lactating cows revealed 623 distinct expressed miRNAs, among which 596 were known and 27 were predicted miRNAs. The comparison of their abundance in the mammary gland of Holstein versus Montbéliarde cows showed 22 differentially expressed miRNAs (Padj ≤ 0.05). Among them, 11 presented a fold change ≥2, with 2 highly expressed miRNAs (miR-100 and miR-146b). Without taking into account the fold change, the differential miRNA with the highest abundance was miR-186, which is known to inhibit cell proliferation and epithelial-to-mesenchymal transition. Data mining showed that the 17 differentially expressed miRNAs with more than 20 reads on average, regulate mammary gland plasticity and may be related to the observed differences in milk production between Holstein and Montbéliarde, which are two breeds with different mammogenic potential. Some of the 17 miRNAs could potentially target mRNAs involved in signaling pathways (such as mTOR) and in lipid metabolism, thereby suggesting that they could influence milk composition. In conclusion, we showed differences in mammary gland miRNomes of two dairy bovine breeds. These differences suggest a potential role of miRNAs in mammary gland plasticity and in milk component synthesis related to milk production and composition.

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Preweaning nutrient supply alters mammary gland transcriptome expression relating to morphology, lipid accumulation, DNA synthesis and RNA expression in Holstein heifer calves.

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