Isolated spermatozoa as indicators of mutations transmitted to progeny
Norris, Michelle Beth
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We used transgenic medaka to evaluate whether analysis of mutations directly in isolated spermatozoa is a reliable alternative to using progeny to assess genetic health risks. Mutant frequencies of cII targets (MF) in spermatozoa exposed to ethylnitrosurea (ENU) at either post-meiotic or pre-meiotic germ-cell stages of spermatogenesis were compared. The MFs of exposed pre-meiotic stem cell spermatogonia showed a significant 9-fold induction in MF, consistent with progeny analyses. By contrast, significantly elevated MFs were detected in progeny derived from ENU-treated post-meiotic germ cells, but not in isolated spermatozoa. DNA damage not fixed as a cII mutation in spermatozoa will not be detected. However, damage in spermatozoa that persists to or after fertilization can be fixed as a mutation and is detected in the embryo. Consequently, using isolated spermatozoa can provide a reliable alternative to using progeny providing the spermatozoa sampled correspond to pre-meiotic germ-cell stages exposed to the mutagen.