TEKT3-mutant spermatozoa show small thin acrosomes. (A–C) Microscopic analyses were used to assess the differences in spermatozoa from normal control and proband samples harboring TEKT3 mutations. Spermatozoa were analyzed by light microscopy following H&E staining (A) or SEM (C). Sperm exhibiting acrosomal abnormalities are denoted with asterisks. (B) The frequencies of morphologically normal acrosomes in spermatozoa in the indicated individuals are shown by light microscopy. (D and E) Confocal laser scanning microscopy was used to image spermatozoa following acrosomal and nuclear staining with PNA and DAPI, respectively. (F) Immunofluorescent staining of ACTL7A in spermatozoa from a normal donor and probands harboring TEKT3 mutations. (G and H) Ultrastructural characteristics of spermatozoa in samples from a fertile donor and probands harboring TEKT3 mutations. AC, acrosome; N, nucleus; PT, perinuclear theca.