Our understanding of the molecular events underpinning the development of mammalian organ systems has been increasing rapidly in recent years. With the advent of new and improved next-generation sequencing methods, we are now able to dig deeper than ever before into the genomic and epigenomic events that play critical roles in determining the fates of stem and progenitor cells during the development of an embryo into an adult. In this review, we detail and discuss the genes and pathways that are involved in mammary gland development, from embryogenesis, through maturation into an adult gland, to the role of pregnancy signals in directing the terminal maturation of the mammary gland into a milk producing organ that can nurture the offspring. We also provide an overview of the latest research in the single-cell genomics of mammary gland development, which may help us to understand the lineage commitment of mammary stem cells (MaSCs) into luminal or basal epithelial cells that constitute the mammary gland. Finally, we summarize the use of 3D organoid cultures as a model system to study the molecular events during mammary gland development. Our increased investigation of the molecular requirements for normal mammary gland development will advance the discovery of targets to predict breast cancer risk and the development of new breast cancer therapies.

近年来，我们对支撑哺乳动物器官系统发育的分子事件的了解不断加深。随着新的和改进的下一代测序方法的出现，我们现在能够比以往更深入地研究基因组和表观基因组事件，这些事件在胚胎发育成胚胎的过程中在决定干细胞和祖细胞的命运方面发挥着关键作用。成人。在这篇综述中，我们详细讨论了乳腺发育中涉及的基因和途径，从胚胎发生，到成熟为成人腺体，再到妊娠信号在引导乳腺最终成熟为产奶器官中的作用才能养育后代。我们还概述了乳腺发育的单细胞基因组学的最新研究，这可能有助于我们了解乳腺干细胞（MaSC）向构成乳腺的管腔或基底上皮细胞的谱系定向。最后，我们总结了使用 3D 类器官培养物作为模型系统来研究乳腺发育过程中的分子事件。我们对正常乳腺发育的分子需求的增加研究将促进预测乳腺癌风险的靶标的发现和新乳腺癌疗法的开发。