Synaptonemal complex alterations in X-irradiated and in oestrogen-treated mice: a comparative study

Area of Science:

• Reproductive biology
• Radiation biology
• Cytogenetics

Background:

• Synaptonemal complexes (SCs) are crucial for homologous chromosome pairing during meiosis.
• Understanding SC responses to environmental stressors like radiation and hormones is vital for reproductive health.
• NMRI mice serve as a model organism for studying meiotic aberrations.

Purpose of the Study:

• To investigate and compare the effects of X-irradiation and oestradiol benzoate (E2B) on synaptonemal complex (SC) structures in male mice.
• To identify specific types of SC alterations induced by each treatment.
• To elucidate the mechanisms underlying these radiation- and hormone-induced SC lesions.

Main Methods:

• Male NMRI mice were exposed to single X-ray doses (5, 7.5, 10 Gy) or daily E2B injections at different life stages (adult, neonatal).
• SC analysis was performed at various time points post-exposure/treatment (24 h to 16 weeks).
• Morphological assessment of SCs, including asynapsis, fragmentation, and multivalent formations, was conducted.

Main Results:

• Both X-irradiation and E2B treatment induced SC alterations, but with distinct patterns.
• Asynapsis was more prevalent in E2B-treated mice, whereas SC fragmentation was more frequent in X-irradiated mice.
• X-irradiation uniquely resulted in quadrivalents, bridges, rings, and loops, while E2B-associated heterotelomeric associations were observed.

Conclusions:

• X-irradiation and E2B exert differential effects on SC formation and stability.
• The observed SC lesions provide insights into the distinct genotoxic and hormonal mechanisms affecting male meiosis.
• Further research into the precise mechanisms of these SC alterations is warranted.