Alterations in chromosomal synapses and DNA repair in apoptotic spermatocytes of Mus m. domesticus

Area of Science:

• Reproductive biology
• Cell biology
• Genetics

Background:

• Meiosis is crucial for sexual reproduction, involving precise chromosomal pairing and DNA repair.
• Apoptosis, or programmed cell death, eliminates damaged cells, including those with meiotic errors.
• Understanding meiotic errors in apoptotic cells can reveal critical regulatory mechanisms.

Purpose of the Study:

• To investigate chromosomal synapse and DNA repair alterations in apoptotic spermatocytes of Mus m. domesticus.
• To identify the stage-specific distribution of these apoptotic cells within spermatogenesis.
• To explore the potential role of these alterations in triggering meiotic checkpoints.

Main Methods:

• Induction of apoptosis in spermatocytes via heat shock (42°C).
• Identification of apoptotic spermatocytes using activated Caspase-9.
• Assessment of chromosomal synapses using SYCP1 and SYCP3.
• Evaluation of DNA repair and chromatin remodeling using Rad51 and γH2AX.

Main Results:

• Apoptotic spermatocytes were predominantly found in spermatogenic stages III-IV and XI-XII, mainly in middle pachytene and metaphase.
• Significant structural anomalies were observed in autosomal bivalents, including splitting of axes and partial asynapses.
• Atypical distribution of γH2AX and Rad51 was associated with asynaptic chromatin and discontinuous axes, with 50% showing alterations in both synapses and DNA repair.

Conclusions:

• Apoptotic spermatocytes exhibit a high frequency of defects in chromosomal synapsis and DNA repair protein recruitment.
• These meiotic errors, including asynapsis and aberrant DNA repair protein localization, are likely recognized by meiotic checkpoints.
• The study suggests that these detected alterations contribute to the induction of apoptosis during male meiosis.