Fig. 5: Tissue-resident macrophages in the developing testes.

a, UMAP of immune cell states (colour) in the human scRNA-seq data (n = 20,556). Doublets and low-quality control cells were removed. Eleven samples were enriched for immune (CD45⁺) cells. Zoomed-in UMAPs show SIGLEC15⁺ and TREM2⁺ fetal testicular macrophages (ftMs) labelled by sex. b, Dot plot showing variance-scaled, log-transformed expression of marker genes (y-axis) for the identified macrophage subsets (x-axis). c, UMAP projections of integrated myeloid cells (colour) from several embryonic/fetal tissues (n = 58,948). Zoomed-in UMAPs show osteoclast and microglia signature macrophages labelled by tissue of origin. d, High-resolution imaging of representative human gonadal sections with intensity proportional to smFISH signal for RNA markers. Left, 12 PCW testis and ovary stained for CD68 (yellow, macrophages), F13A1 (red, tissue-repair macrophages) and NR2F2 (cyan, mesenchymal) (n = 2). Middle, 12 PCW testis stained for PDGFRA (green, mesenchymal), CDH5 (cyan, endothelial), CD68 (red, macrophages) and SIGLEC15 (yellow, SIGLEC15⁺ ftMs). SIGLEC15⁺ ftMs (white arrows) are outside the testis cords in proximity to endothelial cells (n = 5). Right, 8 PCW testis stained for SOX9 (magenta, Sertoli (n = 5)), POU5F1 (magenta, PGCs (n = 2)), CD68 (red, macrophages), P2RY12 (yellow, TREM2⁺ ftMs) and PDGFRA (cyan, mesenchymal). TREM2⁺ ftMs (white arrows) are adjacent to the germ and Sertoli cells. White dashed rectangles highlight gonadal regions magnified; scale bars, 100 and 10 µm in magnified regions; testicular developing cords are delineated with dashed lines. e, Schematics illustrating the spatial location of the distinct testicular macrophage populations. cDC, conventional dendritic cells; ftM, fetal testicular macrophages; ILC, innate lymphoid cells; mega, megakaryocytes; MEMP, megakaryocyte-erythroid-mast cell progenitors; mono, monocytes; neutro, neutrophils; NMP, neutrophil-myeloid progenitors; NK, natural killer cells; pDC, plasmacytoid dendritic cell; prec, precursor; Pre-B, pre-B cells; Pre-pro-B, pre-pro-B cells; Pro-B, pro-B cells; prog, progenitor; T, T cells.