Mutation of SOCS2 induces structural and functional changes in mammary development.

Lactation is an essential process for mammals. In sheep, the R96C mutation in Suppressor Of Cytokine Signaling 2 (SOCS2) protein is associated with greater milk production and increased mastitis sensitivity. To shed light on the involvement of R96C mutation in mammary gland development and lactation, we developed a mouse model carrying this mutation (SOCS2KI/KI). Mammary glands from virgin adult SOCS2KI/KI mice presented a branching defect and less epithelial tissue, which were not compensated in later stages of mammary development. Mammary epithelial cell subpopulations were modified, with mutated mice having three times as many basal cells accompanied by a decrease in luminal cells. The SOCS2KI/KI mammary gland remained functional; however, MECs contained more lipid droplets vs. fat globules and milk lipid composition was modified. Moreover, the gene expression dynamic from virgin to pregnancy state resulted in the identification of about 3,000 differentially expressed genes specific to SOCS2KI/KI or control mice. Our results show that SOCS2 is important for mammary gland development and milk production. In the long term, this would allow for adequate milk production without compromising animal health and welfare.