Figure 2

Seminiferous epithelium stage-dependent distribution of LIN28-positive spermatogonia. (A) Expression of LIN28 in representative tubules. Adult testis sections were immunostained with anti-LIN28 antibody (green) and anti-ACRV1 antibody (red). Chromatin was stained with DAPI (blue) but was presented in black and white in the second row of panels to show nuclear morphology and the amount of heterochromatin. The morphology of spermatid acrosomes and nuclei was used to determine the stages of seminiferous tubules and distinguish among various types of germ cells. The stage of each seminiferous tubule is shown as roman numerals in the center. LIN28-positive spermatogonia are indicated by arrows. Note that strong signal in interstitial cells (Leydig cells) is due to autofluorescence. Pa, pachytene spermatocyte; Lp, leptotene spermatocyte; RS, round spermatid; ES, elongating spermatid. Scale bar, 50 μm. (B) Frequency of LIN28-positive spermatogonia during spermatogenesis. A total of 177 seminiferous tubule cross-sections were examined for LIN28-positive spermatogonia. The count of tubule sections examined is shown above each stage (I-XII). The number of LIN28-positive cells per tubule section (mean ± SE) is plotted.