Abstract
BackgroundGenetic polymorphisms are known to influence milk production and composition. However, the genomic mechanisms involved in the genetic regulation of milk component synthesis are not completely understood. MicroRNAs (miRNAs) regulate gene expression. Previous research suggests that the high developmental potential of the mammary gland may depend in part on a specific miRNA expression pattern. The objective of the present study was to compare the mammary gland miRNomes of two dairy cow breeds, Holstein and Montbéliarde, which have different mammogenic potentials that are related to differences in dairy performance.ResultsMilk, fat, protein, and lactose yields were lower in Montbéliarde cows than in Holstein cows. We detected 754 distinct miRNAs in the mammary glands of Holstein (n = 5) and Montbéliarde (n = 6) midlactating cows using RNA-Seq technology, among which 738 were known and 16 were predicted miRNAs. The 25 most abundant miRNAs accounted for 90.6% of the total reads. The comparison of their abundances in the mammary glands of Holstein versus Montbéliarde cows identified 22 differentially expressed miRNAs (Padj ≤ 0.05). Among them, 11 presented a fold change ≥2, and 2 (miR-100 and miR-146b) were highly expressed. Among the most abundant miRNAs, miR-186 is known to inhibit cell proliferation and epithelial-to-mesenchymal transition.Data mining showed that 17 differentially expressed miRNAs with more than 20 reads were involved in the regulation of mammary gland plasticity. Several of them may potentially target mRNAs involved in signaling pathways (such as mTOR) and lipid metabolism, thereby indicating that they could influence milk composition.ConclusionWe found differences in the mammary gland miRNomes of two dairy cattle breeds. These differences suggest a potential role for miRNAs in mammary gland plasticity and milk component synthesis, both of which are related to milk production and composition. Further research is warranted on the genetic regulation of miRNAs and their role in milk synthesis.
Highlights
Genetic polymorphisms are known to influence milk production and composition
These differences are in agreement with those found in previous studies comparing lactating Holstein and Montbéliarde cows fed diets based on maize silage [2] and grazed grass [1]
Global description of mammary miRNomes Five and six libraries were constructed using RNA extracted from the mammary gland (MG) of lactating Holstein and Montbéliarde cows, respectively
Summary
Genetic polymorphisms are known to influence milk production and composition. the genomic mechanisms involved in the genetic regulation of milk component synthesis are not completely understood. The mammogenic potential in dairy heifers in comparison with beef heifers is facilitated by an increased number of mammary stem cells and the differential expression of genes involved in the development of the mammary stem cell niche. These genes influence the proliferation, migration, differentiation, and remodeling of mammary tissue and the regulation of adipocyte transdifferentiation [4]. Genetic polymorphisms that differentiate species and breeds influence milk production and composition. Despite the increase in knowledge about the genetics of dairy cows in recent decades, the genomic mechanisms influencing milk secretion and composition are not fully understood
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