Fig. 6.

Brca2^wt/mut testicular germ cells exhibit accumulation of DNA double-strand break and increased apoptosis. (a, b, c, d) Representative immunohistochemical images and quantitative analysis of γH2AX in spermatogonia and spermatocytes classified in type A spermatogonia (stage IX-XIV), type B spermatogonia (stage IV-VI), resting form (stage VIII), leptotene (stage IX-XIII), zygotene (stage XIV), transition form (stage I-V), early pachytene (stage VI-VIII) and late pachytene (stage IX-XIII) (n = 5, with at least 10 fields taken randomly with x20 magnification were analyzed per individual, bar = 30 μm, ). In spermatogonia and spermatocyte of Brca2^wt/mut rats at 11 weeks and 8 months, accumulation of DNA double strand breaks is observed throughout the differentiation stages. R, resting spermatocytes; L, leptotene; T, transition form; P, pachytene; DI, diplotene and diakinesis; M, metaphase. (e) Representative images of TUNEL-staining in seminiferous tubules. Brca2^wt/wt seminiferous tubules contained scarce TUNEL-positive cells (bar = 100 μm). On the other hand, Brca2^wt/mut seminiferous tubules contained higher population of TUNEL-positive cells, especially in seminiferous tubules classified as JS-7 or lower. (f, g, h) Analysis of TUNEL-positive rate of germ cells within seminiferous tubules at each stage, excluding seminiferous tubules classified as JS-7 or lower. This analysis revealed that, compared to Brca2^wt/wt, Brca2^wt/mut exhibited increased apoptosis in spermatogonia, spermatocytes, and spermatids at all stages of seminiferous tubules.