Abstract :
[en] In amphipods, growth, development and reproduction are mediated by the molt, which is a hormonally controlled
process and which, therefore, could be impacted by endocrine disruption compounds (EDC). The molt
process is controlled by both X-organ (XO) and Y-organ (YO) through a variety of hormones and receptors
including the molt-inhibiting hormone (MIH) and the ecdysteroid receptor (EcR). However, although many
studies were devoted to characterize MIH and EcR in crustaceans, only few works evaluated their variations
under EDCs exposures. Consequently, the present work aimed to characterize MIH and EcR genes of the amphipod
Gammarus pulex, as well as to study their relative expression variations after exposure to four EDCs,
proved in vertebrates: ethinylestradiol (estrogen), 4-hydroxytamoxifen (anti-estrogen), 17α-methyltestosterone
(androgen) and cyproterone acetate (anti-androgen).
PCR amplification allowed to obtain 204 bp length and 255 bp length fragments, encoding for partial sequences
of 68 amino acids and 85 amino acids, which correspond to EcR and MIH, respectively, and which are
highly conserved in crustacean species. Results highlighted MIH and EcR expressions mainly in G. pulex head,
which is the localization of XO and YO. Moreover, irrespective of the EDC exposure, increases of MIH and EcR
relative expressions were observed, as it was observed after the exposure to 20-hydroxyecdysone (20HE), the
natural molt hormone, used as positive control. Therefore, it appeared that tested EDCs behaved like 20HE,
suggesting that their effects could occur through the ecdysteroids pathways, and so impact the molt process of G.
pulex on the long term. Finally, the present study is a first step in the possibility of using MIH and EcR relative
expressions as biomarkers of exposure for EDCs risk assessment. However additional studies must first be carried
out to better characterize and understand their variations, and also better predicted consequences for the exposed
amphipods.
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