Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2011
Publication Date: N/A
Mammary stem cells (MaSC) are essential for growth and maintenance of the mammary epithelium. Two main phases of mammary growth include ductal elongation prior to puberty and lobulo-alveolar growth and development during pregnancy. Some studies have utilized morphological characteristics and retention of bromodeoxyuridine (BrdU) label to identify MaSC. However, these approaches may not be feasible and require considerable expertise. An alternative approach to identify resident MaSC is based on detection of appropriate protein markers by immunohistochemstry. The focus of this study was to evaluate the staining patterns (in prepubertal and lactating mammary tissue) of 3 novel, potential protein markers for bovine MaSC. These proteins were identified as potential MaSC markers because their transcripts were highly expressed in laser microdissected-MaSC, which were identified as MaSC on the basis of BrdU label retention and position within the mammary epithelium. The 3 novel candidate markers for bovine MaSC were: nuclear receptor subfamily 5 group A member 2 (NR5A2), nucleoporin 153 (NUP153) and fibronectin type III domain containing 3B (FNDC3B). We also examined other presumptive MaSC markers that have been utilized in other species [aldehyde dehydrogenase 1 (ALDH1) and Musashi 1 (Msi1)], and differentiation factors [Notch 3 receptor (Notch3) and cytokeratins (CK) 14 and19]. We found that NR5A2 and NUP153 -positive nuclei were more abundant in prepubertal than lactating bovine mammary glands and their distribution were consistent with expectations for a MaSC marker (based upon our previous BrdU label retention studies). FNDC3B was localized in the nucleus of mammary epithelial cells of prepubertal heifers and in the cytoplasm of lactating cows. Abundant expression of ALDH1 precludes its use as a marker for bovine MaSC, whereas Msi1 staining was distributed in a fashion consistent with MaSC localization. Additionally we found that onset of lumen formation in the terminal ducts were coincident with Notch3 expression in luminal cells. This study demonstrates that NR5A2 and NUP153 are potential markers for MaSC.