Fig. 4.

L1 expression in advanced germ cells. (A) L1 and HILI immunofluorescence in a GW16 human testis. Arrowheads indicate puncta of L1/HILI colocalization. (B) Expression of L1 and HIWI2 at GW17. Scale bars: 20 μm. Arrows indicate regions of mutually exclusive staining between L1 and HIWI2 puncta. (C) L1 expression at GW21 (top panel) and GW18 (bottom panel), co-stained with OCT4 or a pan-GC marker (OCT4 and VASA), respectively. (Top) Arrowheads indicate an L1⁺, OCT4⁺ germ cell; arrows highlight a L1⁺, OCT4⁻ cell. (Bottom) Arrows indicate L1⁺ and pan-GC negative cell. (D) L1⁺/HIWI2^low germ cells (arrows), a HIWI2^high/L1^low germ cell (arrowheads) and double-positive AGCs (stars) in human fetal testis at GW19 and GW22. (E) xy scatter plots of HIWI2 versus L1 fluorescence intensities (left panels) and HIWI2 versus VASA (right panels), with Pearson's correlation coefficients and corresponding P values. For GW19 (top), n=526 VASA⁺ objects, counted from three stitched xy sections. For GW22 (bottom), n=472 VASA⁺ objects, from two stitched xy sections. (F) L1^high/HSP90α^low cells (arrows), HSP90α^high/L1^low cells (arrowheads) and double-positive cells (stars) in human fetal testis at GW16-22. (G) xy scatter plots of HSP90α versus L1 fluorescence intensities (left) and HSP90α versus VASA fluorescence intensities (right). Pearson's correlation coefficients and corresponding P values are indicated. For GW16 (top), n=768 VASA⁺ objects, counted from three stitched xy sections. For GW19 (middle), n=1809 VASA⁺ objects, counted from four stitched xy sections. For GW22 (bottom), n=2098 VASA⁺ objects, counted from three stitched xy sections. Scale bars: 20 μm in A,B,D,F; 10 μm in C. Dashed red boxes in E and G indicate the ‘arms’ of single-positive cell populations.