Expression of putative stem cell markers related to developmental stage of sheep mammary glands.

It is thought that the regenerative capacity of the mammary gland following post-lactation involution resides in multipotent stem cells within the luminal tissue. Adult stem cells make up a small percentage of the cells found in mature organ systems, however to define useful markers has long been a challenge. c-Kit (KIT) and its ligand stem cell factor (KITLG), ATP-binding cassette sub-family G member 2 (ABCG2) and Musashi 1 (MSI1) are good candidate to identify progenitor cells in their niche. Using real-time PCR we showed that KIT, KITLG and MSI1 expressions were up regulated before lambing and at involution relatively to prepubertal stage. The in situ hybridization analysis for KIT gene confirmed and localized the expression in luminal epithelial cells. The changes in the expression profile of putative stem cell markers in mammary glands of sheep suggest that they modify with the progression of lactation cycle, being up regulated during differentiation and down regulated during lactation.