Fig. 1
From: Acoel regeneration mechanisms indicate an ancient role for muscle in regenerative patterning
PCGs are expressed in a common differentiated cell type. a A phylogenetic tree representing the relative position of acoels within the Metazoa. Phylogenetic analyses support the position of acoels as the sister group to other bilaterian lineages, diverging shortly after the origin of the Bilateria > 550 million years ago17, 18, 20. b As a marker for cycling cells, piwi-1 expression is sensitive to irradiation and is ablated by 7 days post-irradiation with 10,000 rads17. PCG expression domains17 were maintained, suggesting that they are primarily expressed in non-cycling, differentiated cells. c Fluorescent image of a transverse optical section in the anterior. ep epidermis. PCG pool comprised of simultaneously hybridized sFRP-1, frizzled-11, bmp, admp, notum, wnt-1, and frizzled-1 RNA probes. d Eighteen RNA probe pairs were used in double-FISH experiments. The denominator for each quantification is the total number of cells in the channel indicated (i.e., magenta or green); the numerator is the total number of double-positive cells for that pair. Quantification was performed in area indicated by the white box, and inset panels below are higher magnification images of cells for this region. See Supplementary Fig. 1b for remaining pairs. Scale bars: b 100 μm; c 10 μm; d 100 μm, overview image; 10 μm, cell inset. D dorsal view, V ventral view, L lateral view. Overview images are representative of 5/5 animals examined
