The anterior pituitary gland plays a central role in regulating various physiological processes, including body growth, reproduction, metabolism and stress response. Here, we perform single-cell RNA-sequencing (scRNA-seq) of 4113 individual cells from human fetal pituitaries. We characterize divergent developmental trajectories with distinct transitional intermediate states in five hormone-producing cell lineages. Corticotropes exhibit an early intermediate state prior to full differentiation. Three cell types of the PIT-1 lineage (somatotropes, lactotropes and thyrotropes) segregate from a common progenitor coexpressing lineage-specific transcription factors of different sublineages. Gonadotropes experience two multistep developmental trajectories. Furthermore, we identify a fetal gonadotrope cell subtype expressing the primate-specific hormone chorionic gonadotropin. We also characterize the cellular heterogeneity of pituitary stem cells and identify a hybrid epithelial/mesenchymal state and an early-to-late state transition. Here, our results provide insights into the transcriptional landscape of human pituitary development, defining distinct cell substates and subtypes and illustrating transcription factor dynamics during cell fate commitment.

垂体前叶在调节身体生长、生殖、新陈代谢和应激反应等多种生理过程中发挥着核心作用。在这里，我们对来自人类胎儿垂体的 4113 个单个细胞进行了单细胞 RNA 测序 (scRNA-seq)。我们描述了五种激素产生细胞谱系中具有不同过渡中间状态的不同发育轨迹。促肾上腺皮质激素在完全分化之前表现出早期中间状态。 PIT-1谱系的三种细胞类型（生长激素、催乳剂和促甲状腺激素）从共表达不同亚谱系的谱系特异性转录因子的共同祖细胞中分离出来。促性腺激素经历两个多步骤的发育轨迹。此外，我们还鉴定了表达灵长类动物特异性激素绒毛膜促性腺激素的胎儿促性腺细胞亚型。我们还描述了垂体干细胞的细胞异质性，并确定了混合的上皮/间质状态和早期到晚期的状态转变。在这里，我们的结果提供了对人类垂体发育的转录景观的见解，定义了不同的细胞亚状态和亚型，并说明了细胞命运决定过程中的转录因子动态。