MicroRNA-mRNA Gene Regulatory Circuitry Orchestrates the Epigenetic and Transcriptional Reprogramming from Pluripotency to Murine Mammary Epithelial stem-like-Cells lactogenic differentiation

MicroRNAs (miRNAs) are small non-coding RNAs that post-transcriptionally regulate gene expression via mRNA degradation or translational repression. While miRNAs are established regulators of development and differentiation, their role in the dynamic mRNA transitions during lactogenic differentiation of mammary epithelial cells remains incompletely characterized. In this study, we profiled miRNA expression across four distinct developmental states: embryonic stem cells (ESCs), and three progressive stages of HC11 murine mammary epithelial differentiation, including undifferentiated growth factor-maintained cells (HC11-N), glucocorticoid-primed cells (HC11-P), and prolactin-induced lactogenic cells (HC11-PRL). By integrating these signatures with parallel mRNA expression profiles, we identified stage-specific miRNA-mRNA regulatory axes. Our analysis revealed miRNAs coordinate networks of transcription factors and epigenetic regulators to shape the lactogenic transcriptome. While ESCs and undifferentiated HC11 cells were characterized by pathways associated with pluripotency and oncogenic signalling, the pregnancy-like priming stage showed enrichment in, neurotrophin signalling. Crucially, the lactation-like state was dominated by PI3K-Akt and mTOR signalling-- critical drivers of epithelial proliferation and milk synthesis. Furthermore, the integration of miRNAs with transcriptional and epigenetic regulators highlighted the modulation of prolactin signalling and extracellular matrix-receptor interactions during lactation. This study provides a comprehensive map of the miRNA-associated post-transcriptional landscape of lactogenesis, offering a mechanistic framework for understanding mammary gland development and associated pathologies.