Dynamic allelic expression in mouse mammary gland across the adult developmental cycle
The mammary gland, which primarily develops postnatally, undergoes significant changes during pregnancy and lactation to facilitate milk production. Through the generation and analysis of 480 transcriptomes,this study provides the first detailed allelic expression map of the mammary gland, cataloguing cell-type specific expression from ex-vivo purified cell populations over 10 developmental stages of the reproductive cycle enabling comparative analysis of cellular properties during this critical process.Genomic imprinting, a mechanism regulating gene expression based on parental origin, plays a crucial role in controlling gene dosage and stem cell potential throughout development and adult life. Although some imprinted genes have been identified in the mammary gland, a comprehensive assessment has been lacking. Our analysis identified 25 imprinted genes that are monoallelically expressed in the mammary gland, with several showing allele-specific expression in distinct cell types. No imprinted genes showed biallelic expression and novel imprinted genes were not identified.This research highlights known transcriptional dynamics within mammary gland cell types and identifies novel candidate genes potentially significant in the mammary gland as it develops during gestation and lactation. Additionally, our findings suggest that, unlike in brain, selective absence of imprinting does not serve as a mechanism for gene dosage control in the mammary gland. Furthermore, we integrate GWAS data to explore genetic links to lactation disorders and postpartum breast cancer.Overall, this comprehensive atlas of cell type, parent-of-origin, and stage-specific expression in the mammary gland represents a valuable resourcefor future studies on expression and transcriptional dynamics in mammary gland cell types.