Figure 2. Impaired spermatogenesis in Parl-/- testis is associated with early mitochondrial morphological abnormalities and progressive degeneration of arrested spermatocytes.
(A) Toluidine blue-stained semithin sections of testis from 5-week-old WT and Parl-/- mice. Seminiferous tubules from Parl-/- mice show extensive degenerative changes in arrested spermatocytes including tortuous membrane infoldings, cytoplasmic vacuolation (arrows), irregular chromatin clumping, nuclear fragmentation (arrowheads), and absence of mature germ cells such as adluminal spermatids and spermatozoa (n = 3 for each genotype). A WT seminiferous tubule with normal germ cell maturation is shown for comparison (left panel). Scale bars, 20 µm. (B) Electron microscopy examination shows multifocal cisternae distention, disruption of the endoplasmic reticulum and Golgi apparatus, and abundant accumulation of damaged membranous material and organelles (asterisks) in Parl-/- spermatocytes. The nuclear envelope is diffusely distended (arrowheads) outlining a convoluted fragmented nucleus (N) with dense irregular clumps of chromatin. A WT spermatocyte at the end of pachytene is shown for comparison (left panel). Scale bars, 1 µm. (C) Electron microscopy analysis shows that mitochondria in Parl-/- primary spermatocytes are swollen with few thin irregular cristae and loss of normal matrix density (right panel, arrowheads) compared to WT (left panel, arrowheads). The thin arrows indicate the intermitochondrial cement (nuage) typically associated with mitochondria in primary spermatocytes. The large arrows indicate fully assembled synaptonemal complexes, structures that are only detectable during the zygotene and pachytene stages of meiotic prophase I (n = 3 for each genotype). Scale bars, 0.5 µm.
Figure 2—figure supplement 1. Ultrastructural abnormalities of mitochondria and other cell compartments are restricted to arrested spermatocytes and absent in other testis cell types.
