Abstract
SynopsisThe mammary gland has evolved to accommodate the developmental needs of offspring in species-specific ways. This is particularly true for marsupials. Marsupial milk content changes dramatically throughout lactation in ways appearing timed with neonatal ontogeny and behavior. Here we investigate morphological restructuring within the mammaries throughout lactation in the gray short-tailed opossum, Monodelphis domestica. Substantial remodeling of the mammaries occurs throughout the first half of active lactation. It is not until the latter half of lactation that opossum mammaries appear histologically similar to active eutherian mammaries. Noteworthy was the presence of eosinophils in early developing mammary tissue, which correlated with elevated abundance of transcripts encoding the chemokine IL-16. The presence and abundance of whey protein transcripts within the opossum mammaries were also quantified. Whey acidic protein (WAP) transcript abundance peaked in the latter half of lactation and remained elevated through weaning. Minimal transcripts for the marsupial-specific Early and Late Lactation Proteins (ELP/LLP) were detected during active lactation. Elevated abundance of LLP transcripts was only detected prior to parturition. Overall, the results support the role of eosinophils in mammary restructuring appearing early in mammalian evolution, and describe key similarities and differences in nutritional protein transcript abundance among marsupial species.
Highlights
A defining trait of mammals is the presence of a specialized mammary gland for milk production
Noteworthy was the presence of eosinophils in early developing mammary tissue, which correlated with elevated abundance of transcripts encoding the chemokine IL-16
Whey acidic protein (WAP) transcript abundance peaked in the latter half of lactation and remained elevated through weaning
Summary
A defining trait of mammals is the presence of a specialized mammary gland for milk production. This is found in all three extant mammalian lineages: Prototheria, Metatheria, and Eutheria (Lefevre et al 2010). In eutherian species investigated, remodeling occurs during pregnancy in preparation for lactogenesis. This includes an increase in secondary and tertiary ductal branching, providing the network for the development of the alveoli, where milk synthesis and storage occurs (Djonov et al 2001; Macias and Hinck 2012). Proliferating epithelial cells generate alveolar buds that progressively cleave and differentiate into distinct alveoli, which become milk-secreting lobules during lactation (Macias and Hinck 2012). By late pregnancy the alveoli encompass the majority of the fat pad and some secretory activity has been noted as pregnancy approaches term (Djonov et al 2001)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
