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. 2020 Sep 24;9:e54573. doi: 10.7554/eLife.54573

Figure 4. Vas2+ germ cells in juvenile gonad rudiments.

(A) Schematic diagram of Nematostella polyp anatomy depicts the gametogenic mesenteries at the mid-body level. (B) A mid-body level cross section through a juvenile polyp, note the enlarged primary mesenteries (yellow arrows). Nuclei are counter stained by DAPI (green). (C and D) Representative images of maturing mesenteries with corresponding schematic diagrams. Putative PGCs are labeled by Vas2 immunofluorescence in red. (E) Whole-mount juvenile female mesentery shows Vas2-labeled putative PGCs and germ cells in close proximity (red), suggesting maturing oocytes originate from the continuous PGC lineage. (F) Whole-mount juvenile male mesentery shows Vas2-labeled putative PGC and germ cell populations, including the rudimentary sperm cysts. Insets 1–4 of E and F are xz plane views at the indicated levels. Scale bar = 100 µm in B; 20 µm in C–F.

Figure 4.

Figure 4—figure supplement 1. Adult PGC-like lineages localize adjacent to the mature gonad and migrate aborally.

Figure 4—figure supplement 1.

(A) Along the oral-aboral axis, adult Nematostella can be regionally subdivided into the disc (mouth and tentacle base), capitulum (pharynx), scapus (gametogenic region) and physa (non-gametogenic region; Williams, 1975). (B–E’) Female and male cross sections were immunolabeled with Vas2 (red) and counter-stained for nuclei (green). PGC-like cells (arrows in B–B’ and C’) localize next to the maturing oocytes and sperm stem cells (spermatogonia, arrowheads in C–C’), which divide and give rise to sperm in the sperm cyst lumen. Note there are Vas2 puncta surrounding the nuclei of spermatogonia. (D–E’) PGC-like cells also localize aborally in the physa, the site of occasional asexual fission (Hand and Uhlinger, 1995; Burton and Finnerty, 2009). Aboral migration may thus ensure fertility in asexually-produced progeny. (F) Schematic diagrams depict the cross-sectional localization of PGC-like cells (red) in adult mesenteries. The boundaries of mesentery are delineated by gray lines. Scale bar = 50 µm in B; 100 µm in C, D, and E; 20 µm in B’, C’, D’, and E’.
Figure 4—figure supplement 2. PGC-like cells are proliferative.

Figure 4—figure supplement 2.

In the aboral region of mesenteries, some PGC-like cells (gray) incorporate EdU (green) in their nuclei, consistent with proliferative activity. Scale bar = 50 µm in A; 20 µm in A’.