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The bovine dry period is a dynamic non-lactating phase where the mammary gland undergoes extensive cellular turnover. Utilizing RNA sequencing, we characterized novel genes and pathways involved in this process and determined the impact of dry period heat stress. We identified 3, differentially expressed genes DEGs between late lactation and early involution, and DEGs later in the involution process.
DEGs, pathways, and upstream regulators during early involution support the downregulation of functions such as anabolism and milk component synthesis , and upregulation of cell death , cytoskeleton degradation , and immune response. The impact of environmental heat stress was less significant, yet genes, pathways, and upstream regulators involved in processes such as ductal branching morphogenesis, cell death, immune function, and protection against tissue stress were identified.
Our research advances understanding of the mammary gland transcriptome during the dry period, and under heat stress insult. Individual genes, pathways, and upstream regulators highlighted in this study point towards potential targets for dry period manipulation and mitigation of the negative consequences of heat stress on mammary function.
In dairy cows, the dry period is a six to eight-week non-lactating state initiated between lactations that allows for optimal milk yield in the subsequent lactation through the turnover of worn, senescent mammary epithelial cells MEC with new, active cells 1. It consists of three phases known as active involution, steady state involution, and redevelopment. Involution is the natural process whereby the mammary gland transitions from a lactating to a non-lactating state 2. It begins after the cessation of milk removal and is characterized by a decrease in milk secretion and rise in mammary pressure, apoptosis and autophagy of MEC, and immune response 3 , 4 , 5.
