Hydractinia single-cell atlas represented as a labeled UMAP and validation of several cell-type markers using fluorescent in situ hybridization (FISH). (A) Hydractinia single-cell atlas UMAP with 18 clusters (C0–C17). (B–F) UMAP expression of select marker genes (left) and spatial expression pattern of marker gene in polyps via FISH (right). Blue staining indicates Hoechst; pink, marker gene. Piwi1 (B) and PCNA (C) expression in the i-cell band in the middle of the body column of a feeding polyp. (D) Ncol1 expression in nematoblasts in the lower body column of a feeding polyp. (E) SLC9C1 expression in mature sperm cells in gonads of male sexual polyps. (F) Nematocilin A expression in a subset of nematocytes in the tentacles of a feeding polyp. Close-up view of tentacles in panels F′′ and F′′′ both show higher magnification images from the same polyp as in panel F′, showing expression is specific to cnidocytes. Panel F′′′ adds DIC. (G) ARSTNd2-like expression in a subset of nematocytes in the body column of a feeding polyp. Panels G′′ and G′′′ both show higher magnification images from the same polyp as in panel G′, showing expression is specific to cnidocytes. Panel G′′′ adds DIC. (H) Chitinase1 expression in gland cells in the endodermal epithelial cell layer of a feeding polyp. Panel H′′ and H′′′ both show higher magnification images from the same polyp as in panel H′, showing expression is specific to gland cells. Panel H′′′ adds DIC. All images shown were projected from confocal stacks. All scale bars = 100 µm. Abbreviations in A: (ecEP) ectodermal epithelial cell, (enEP) endodermal epithelial cell, (germ) germ cell, (ISC) interstitial stem cell, (Mgc) mucous gland cell, (nb) nematoblast, (nem) nematocyte, (prog) progenitor, (sprm) sperm, and (Zgc) zymogen gland cell.
