Transcriptome analysis of fat globules in milk of cows with differential genotype for β-casein

In the framework of A2 milk production, a better understanding of the molecular mechanisms of the milk synthesis is needed. The transcriptome profiling of mamamry gland of Holstein cows with A1A1 genotype (n = 7) and A2A2 genotype (n = 7) for β-casein was analysed by RNA-seq technology. Total RNA was isolated from milk fat globules (non-invasive source of mammary RNA). Out of the 11,180 and 11,257 genes expressed in milk fat globules (identified with DESeq2 and EdgeR packages, respectively), only two genes were detected as differentially expressed between A1A1 and A2A2 genotype cows, indicating that both groups had very similar mammary gland transcriptome profiles. The majority of the highly expressed genes in milk fat globulesduring lactation (FPKM ≥500) were involved in biological process and molecular functions related to protein synthesis and energy production, as lactation is one of the most energetically demanding process for female mammals. To investigate the milk fat globules transcriptome of two groups of cows with differential genotype for β-casein, a total of 14 milk fat globule RNA samples from Holstein cows were analysed. 7 milk samples were collected from cows with A1A1 genotype for β-casein and 7 samples were collected from cows with A2A2 genotype.