Fig. 4: The neuropeptide Dh44, secreted by brain Dh44-PI neurons, and its receptor Dh44-R2, expressed in GSC niche cells, are essential for venerose-induced GSC proliferation.

a A schematic illustrating inter-organ signaling between the brain and the ovary, where Dh44, secreted into the hemolymph by Dh44-PI neurons, stimulates GSC proliferation through its receptor expressed in the TF cells of the GSC niche. b-d Representative confocal Z-projection images of germaria from Dh44-R2 > mCD8-EGFP females immunostained with anti-GFP, anti-LamC (a GSC niche cell marker), and anti-Tj (a cap cell marker) (n = 24). All examined germaria exhibited one of three types of Dh44-R2 expression in TF and TC cells at the following frequencies: TF + TC + 54% (b), TF- TC + 38% (c), TF + TC- 8% (d). TF and TC cells are indicated by yellow and white arrow heads, respectively. Scale bars, 5 µm. e–j Frequencies of germaria containing 1, 2, or 3 GSCs (left y-axis) and the average number of GSCs per germarium (right y-axis). e Virgin ovaries of w¹¹¹⁸ cultured for 24 h in a medium containing Dh44 at the indicated concentrations. f Virgin ovaries of the indicated genotypes and cultured for 24 h with or without 10 nM Dh44. g Virgin ovaries of the indicated genotypes and cultured for 24 h in 10 mM venerose along with female virgin w¹¹¹⁸ brains. h Ovaries from virgin females of the indicated genotypes that received an injection of vehicle or 0.8 nmol venerose. Ovaries were examined 24 h post-injection. i Ovaries isolated from virgin females exposed to 24 h of light activation. Females were fed vehicle or all-trans-retinal (ATR) immediately after eclosion. j Virgin ovaries of w¹¹¹⁸ cultured for 24 h in 10 mM venerose along with virgin female brains of the indicated genotypes. The schematics illustrate the experimental protocols. The numbers in parentheses indicate n. The numbers above the columns indicate the p-values for the indicated comparisons (*p < 0.05, **p < 0.01). Exact p-values are in Supplementary Data 4. Kruskal-Wallis tests with Dunn post-hoc tests (e, f, h). Two-tailed Mann Whitney tests (g, i, j). Source data are provided as a Source Data file.