title: Perchlorate Exposure Reduces Primordial Germ Cell Number in Female Threespine Stickleback.
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.
authors.affiliation: Institute of Ecology and Evolution, Department of Biology, University of Oregon, Eugene, Oregon, 97403, United States of America.|Department of Integrative Biology, Oregon State University Cascades, Bend, Oregon 97703, United States of America.
authors.forename: Ann M
authors.initials: AM
authors.lastname: Petersen
authors.affiliation: Institute of Ecology and Evolution, Department of Biology, University of Oregon, Eugene, Oregon, 97403, United States of America.
authors.forename: Nathanial C
authors.initials: NC
authors.lastname: Earp
authors.affiliation: Institute of Ecology and Evolution, Department of Biology, University of Oregon, Eugene, Oregon, 97403, United States of America.
authors.forename: Mandy E
authors.initials: ME
authors.lastname: Redmond
authors.affiliation: Institute of Neuroscience, Department of Biology, University of Oregon, Eugene, Oregon, 97403, United States of America.
authors.forename: John H
authors.initials: JH
authors.lastname: Postlethwait
authors.affiliation: Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona, 86001, United States of America.
authors.forename: Frank A
authors.initials: FA
authors.lastname: von Hippel
authors.affiliation: Department of Biological Sciences & Center for Bioengineering Innovation, Northern Arizona University, Flagstaff, Arizona, 86001, United States of America.
authors.forename: C Loren
authors.initials: CL
authors.lastname: Buck
authors.affiliation: Institute of Ecology and Evolution, Department of Biology, University of Oregon, Eugene, Oregon, 97403, United States of America.
authors.forename: William A
authors.initials: WA
authors.lastname: Cresko
mesh_terms: D000818:Animals; D005260:Female; D005306:Fertilization; D005838:Genotype; D005854:Germ Cells / Q000166:cytology*; D006066:Gonads / Q000254:growth & development*; D008297:Male; D008540:Meiosis; D010472:Perchlorates / Q000009:adverse effects*; D012733:Sex Differentiation; D012737:Sex Factors; D023701:Smegmamorpha / Q000254:growth & development*; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000009:adverse effects*
chemical_list: D010472:Perchlorates; D014874:Water Pollutants, Chemical