PetersenPerchlorateExposureReduces.PDF

s Metrics Comments Related Content Abstract Introduction Methods Results Discussion Conclusions Supporting Information Acknowledgments Author Contributions References Reader Comments (0) Media Coverage (0) Figures Abstract Perchlorate is a common aquatic contaminant that has long been known to affect thyroid function in vertebrates, including humans. More recently perchlorate has been shown to affect primordial sexual differentiation in the aquatic model fishes zebrafish and threespine stickleback, but the mechanism has been unclear. Stickleback exposed to perchlorate from fertilization have increased androgen levels in the embryo and disrupted reproductive morphologies as adults, suggesting that perchlorate could disrupt the earliest stages of primordial sexual differentiation when primordial germ cells (PGCs) begin to form the gonad. Female stickleback have three to four times the number of PGCs as males during the first weeks of development. We hypothesized that perchlorate exposure affects primordial sexual differentiation by reducing the number of germ cells in the gonad during an important window of stickleback sex determination at 14–18 days post fertilization (dpf). We tested this hypothesis by quantifying the number of PGCs at 16 dpf in control and 100 mg/L perchlorate-treated male and female stickleback. Perchlorate exposure from the time of fertilization resulted in significantly reduced PGC number only in genotypic females, suggesting that the masculinizing effects of perchlorate observed in adult stickleback may result from early changes to the number of PGCs at a time critical for sex determination. To our knowledge, this is the first evidence of a connection between an endocrine disruptor and reduction in PGC number prior to the first meiosis during sex determination. These findings suggest that a mode of action of perchlorate on adult reproductive phenotypes in vertebrates, including humans, such as altered fecundity and sex reversal or intersex gonads, may stem from early changes to germ cell development

Hematoxylin and eosin staining of representative sagittal sections through the developing gonad in 16 dpf stickleback.

<p>Scale bars are 100 microns. White arrows denote location of PGCs within the gonad. At 16 dpf, number of PGCs in control male stickleback (A) were not different than in male stickleback raised in 100 mg/L perchlorate (B). At 16 dpf, however, control female stickleback (C) had more PGCs than females raised in 100 mg/L perchlorate (D).</p

Perchlorate Exposure Reduces Primordial Germ Cell Number in Female Threespine Stickleback - Fig 2

<p><b>Number of PGCs (+/-1SE) in 16 dpf genotypic male (solid lines) and female (dotted lines) stickleback, with interaction plots of the total number of PGCs (A), premeiotic PGCs (B), and meiotic cells (C).</b> Asterisk represents significantly different PGC counts (Two-Way ANOVA, Tukey's Post-Hoc Analysis, P< 0.05). n = 12–14.</p