Fig. 1.

Distinction of undifferentiated spermatogonial subsets by ID4-EGFP expression in testes of mice. (A) Whole-mount confocal image of live seminiferous tubules from an Id4-eGfp transgenic mouse at P8. EGFP⁺ cells are ID4-expressing spermatogonia. Arrows indicate A_single with bright EGFP intensity (ID4-EGFP^Bright). Arrowhead indicates A_single with dim EGFP intensity (ID4-EGFP^Dim). Stars indicate A_pair with dim EGFP intensity (ID4-EGFP^Dim). Scale bar: 50 µm. (B) Quantitative comparison of EGFP intensity in A_single and A_pair ID4⁺ spermatogonia. Each dot represents an individual cell (n=4 different animals, 13.2 mm of tubules, 944 total cells) and the mean±s.e.m. is indicated by black bars for each population. (C) Dot plot of flow cytometric analysis (FCA) for subsets of spermatogonia based on ID4-EGFP intensity. (D) Quantitative comparison of the percentage of the ID4-EGFP⁺ population that can be classified as ID4-EGFP^Bright or ID4-EGFP^Dim from FCA. Data are mean±s.e.m. for three independent experiments. *P<0.05.