The characteristic acrosome organelle fails to develop properly in <i>Rfx2</i>^-/- mice.

<p>(A-H) Periodic acid shiff (PAS) / light green stained segments of testis sections from <i>Rfx2</i>^<i>+/+</i> mice (A-D) and comparable sections from <i>Rfx2</i>^<i>-/-</i> mice (E-H). Developmental stages of the seminiferous tubules are noted on each panel. Insets show a 3-fold magnification of a spermatid from the respective section (box). Insets show in: (A, E) step 2 spermatids, (B, F) step 5 spermatids, (C, G) step 7 spermatids. (I-P) High power views of individual cells with the acrosomes stained by fluorescently-tagged peanut agglutinin. For <i>Rfx2</i>^<i>+/+</i> sections, different step of acrosome development are shown (I: step 2, J-L: step 6–7 spermatids). For <i>Rfx2</i>^<i>-/-</i> sections, variations in acrosome morphology are shown for spermatids that are about to arrest (M-P). In the majority of cases the acrosome fails to spread normally over the anterior end of the nucleus and frequently occurs as unattached vesicles (arrows).