Evaluation of degenerating germ cells in normal juvenile mice

Absence of spermiogenesis in mice with meiotic defects complicates the staging of meiotic arrest using light microscopy. Consequently, new methodologies are required to establish accurate relationships among germ cells. In this study, we utilized a novel approach to analyze germ cell degeneration in juvenile mice. We used terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) in combination with meiosis-specific antibodies. Germ cell degeneration is a normal component of early spermatogenesis in juvenile mice. The incidence of germ cell death was monitored at various postnatal ages of mice using the TUNEL assay to quantify the incidence of apoptosis. Cell death occurred predominantly at 15.5 days after birth. It was found that groups of apoptotic cells were apparent in tubules containing two generations of spermatocytes that form in two progressive cohorts. Electron microscopic observations further illustrated that the majority of cells in the first cohort are in late pachytene, while groups of cells in the second cohort can degenerate in early pachytene. The methodology utilized in this study is significant because it allows one to accurately determine the point at which germ cells arrest. Consequently, we believe that these methods can be applied to study animals with meiotic defects that prevent spermiogenesis.