Fig. 4.

The SUN4 N-terminal domain is located within the nucleoplasm of elongating spermatids. Representative electron micrographs of elongating spermatids in (A) pre-fixed and (B) native mouse testis cryo-sections with immunogold labeling (6 nm colloidal gold) of the SUN4 NTD. Gold particles (arrowheads) are mainly found along the inner surface of the INM (A) and the RNE (B). Higher magnifications of the areas indicated by black rectangles are depicted in A′,A″ and B′. Scale bars: 500 nm (B); 200 nm (A,A″,B′); 100 nm (A′). Cy, cytoplasm; Nu, nucleoplasm; NE, nuclear envelope; RNE, redundant nuclear envelope; Ac, acrosome; Bb, basal body. Images are representative of two experimental repeats.