Figure 2.

Low levels of SigD reduce plasma membrane PIP₂. (A–F) Phase-contrast (phase) and (A′–F′) corresponding fluorescence images of live squashed preparations of male germ cells expressing PLCδ-PH-GFP (A′, B′, D′, and E′) or -RFP (C′ and F′), which bind PIP₂. Arrowheads, early round spermatids; arrows, growing ends of spermatid cysts. SigD-low cysts lack a growing end (see text). PIP₂ is found at the plasma membrane of wild-type early round spermatids (A′) and elongating spermatids (D′). Low levels of SigD reduce PIP₂ at the plasma membrane (B′) and cause accumulation of PLCδ-PH-GFP in the cytoplasm (B′ and E′). Coexpression of Sktl with SigD-low partially restores plasma membrane PIP₂ in early (arrowhead, C′) and elongating (F′) spermatids. Scale bars, 10 μm.