Fig 2: Differentiation trajectories and TF dynamics of the PIT-1 Lineage.a Venn diagram of progenitor cells distributed in each PIT1 sublineage as shown in the pseudotime analysis. Pro.PIT1_all: the common progenitor cells of all three sublineages; Pre.Thy, the precursor cells of thyrotropes; Pre,Som: the potential precursor cells of somatotropes. b Distribution of the subtypes of the Pro.PIT1 on the UMAP plot. Dots: single cells; colors: weeks postfertilization (left) or cell types (right). c Violin and inside box plots showing the gene expression dynamics of known TFs for each PIT1 lineage. #P > 0.1, **P < 0.01 ***P < 0.001. P-values are determined by two-sided Wilcoxon test and adjusted by Bonferroni correction. d Venn diagram showing the intersections among the differentially expressed TFs between any two of the three PIT1 lineages, and the 13 TFs that were significantly upregulated in the Pro.PIT1_all cells in comparison with the stem cells, for which the names of genes are shown. e Violin with inside box plots showing representative identified TFs for each PIT1 lineage. f Heatmap showing the relative expression levels of the significantly upregulated TFs of thyrotropes along the pseudotime axis. Colors: loess-smoothed expression (red, high; blue, low). The columns represent cells being ordered along the pseudotime axis, and cell type information is shown above the heatmap. Rows represent genes being ordered by their peak expression along the pseudotime axis. g The scatterplot (left) expression and immunofluorescence staining of NKX2-2 as a somatotrope-specific TF. Scale bar, 50μm. Arrows indicate representative cells co-expressing GH and NKX2-2.

Fig 3: The effects of aberrant splicing on ESRRG.a ESRRG mRNA levels in immunoprecipitates were determined through qRT-PCR analysis (n = 3 per group). ESRRG mRNA expression levels were presented as fold enrichment ratios compared with IgG. b Cryptic ESRRG mRNA levels in immunoprecipitates of wild-type and mutant primary human prolactinoma cells were determined by qRT-PCR (n = 3 per group). Expression levels of ESRRG mRNA were presented as fold enrichment ratios compared with IgG. c–e CLIP of SF3B1-bound ESRRG mRNA in MCF7 cells c, SF3B1WT prolactinomas d, or SF3B1R625H prolactinomas e (n = 3 per group). qPCR was used to identify the region in ESRRG bound by SF3B1 protein. The amount of immunoprecipitated RNAs in each sample is represented as a signal relative to the negative (IgG) sample. Schematic representation of human ESRRG segments amplified by primer pairs for CLIP-qPCR. f GST-Pit-1 fusion protein immobilized on glutathione beads and incubated with HIS-tagged cryptic or canonical ESRRG proteins. Bound ESRRG proteins were detected by anti-HIS immunoblotting. g Immunoblotting with the indicated antibodies of FLAG immunoprecipitated from lysates of HEK293 cells co-transfected with FLAG-tagged Pit-1, HA-tagged cryptic, or canonical ESRRG. h Relative luciferase activity of PRL promoter in HEK293 cells transfected with pCDNA3.1-Pit-1 (Pit-1), pGL3-basic-PRL promoter (PRL-p), or pCDH-ESRRG-canonical/cryptic and their corresponding empty vectors including pCDNA3.1, pGL3-basic, and pCDH. pRL-TK was used as a control (n = 4 per group). Results are expressed as mean ± SD. The p values by one-way ANOVA followed by Dunnett’s multiple comparisons test in a and followed by Bonferroni’s multiple comparisons test in h are indicated. The p value by two-tailed unpaired t test is indicated in b. Source data are provided as a Source Data file.

Fig 4: Expression of cell markers in pituispheres. Representative immunofluorescence images of (A) PA02, (B) PA03, and (C) PA05 pituispheres. Cells were double-stained for (A,B) CD15 (green) and GFRα2 (red), (C) Pit-1 (green), and SF-1 (red) (B) CD15 (green) and SF-1 (red) and PA02 pituispheres were single stained for (A) Pit-1 (green) and SF-1 (red) and PA05 pituispheres were single stained for (C) Pit-1 (green) and GFRα2 (red). Isotype-matched antibodies were used for negative controls. Cell nuclei were counterstained with DAPI (blue). Scale bar, 13 μm.

Fig 5: Diversity of cell types in the human fetal pituitary.a Experimental flowchart for the scRNA-seq analysis of the human fetal pituitary. b UMAP plots showing the clusters of the cell cycle cells (CC), stem cells, the progenitor cells of PIT1 lineage (Pro.PIT1) or precursor cells of gonadotrope (Pre.Gonado) and the terminal endocrine cells (lower), and distribution of the fetal samples (upper). Dots: single cells. c Scatterplots showing expression of known markers, including TFs and hormone genes, projecting on the UMAP plot (b). Gray to red indicates no expression to high expression levels. d Bar plots showing the proportions of each cell type in each stage. Solid circles at the bottom indicate the earliest stages when a hormone producing cell type appears. e Heatmap showing the activated TFs predicated by SCENIC. For each cell type, the top 10 -log(P value) specific TFs being activated are shown, which ranked by number of cells. Columns are individual cells and rows are individual genes. White: not activated; red: activated. The expression levels of these TFs are shown in Supplementary Fig. 2c.