A Comparative Analysis of the Gene Expression Profiles in the Mammary Glands of Lactating and Nonlactating Mares at the Second Month of Gestation.

Simple Summary: To explore molecular regulation related to lactation during pregnancy, the mammary glands of pregnant Mongolian mares during lactation and non-lactation were sequenced and analyzed for differentially expressed genes. We screened milk protein-related genes (CSN1S1, CSN3, and LALBA), genes related to the lipid metabolism process (DGAT1, LEP, and LEPR), and genes closely related to lactation events (FAT1 and LTF), which can be used as candidate genes for selecting lactation traits in Mongolian mares. To investigate molecular regulation involved in lactation during pregnancy, this study focused on the transcriptomic profiles of mammary tissue from lactating and non-lactating Mongolian mares at the second month of gestation. A total of 4197 differentially expressed genes were identified by comparing mammary tissues from pregnant mares at two different states, including 1974 differentially expressed genes such as the milk protein-related genes a-s1-casein (CSN1S1), k-casein (CSN3), lactalbumin (LALBA), and lactoferrin (LTF), which were highly expressed in the lactating mares group, and overall, these differentially expressed genes were mainly associated with biological processes such as endoplasmic reticulum protein processing, the Toll-like receptor signaling pathway, steroid biosynthesis, cytokine–cytokine receptor interactions, and amino sugar and nucleotide glycolysis. These findings serve as a foundation for investigating the molecular underpinnings of lactation in pregnant equids. [ABSTRACT FROM AUTHOR]