Functional studies of an eyestalk molt inhibiting hormone (MIH-1) in black tiger shrimp Penaeus monodon by RNA interference

Functional studies of an eyestalk molt inhibiting hormone (MIH-1) in black tiger shrimp Penaeus monodon by RNA interference

Frontiers in Neuroendocrinology Frontiers in Neuroendocrinology 27 (2006) 23–26 www.elsevier.com/locate/yfrne ICN 2006 Conference Abstracts Comparat...

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Frontiers in Neuroendocrinology Frontiers in Neuroendocrinology 27 (2006) 23–26 www.elsevier.com/locate/yfrne

ICN 2006 Conference Abstracts

Comparative neuroendocrinology Comparative effects of estrogenic, androgenic endocrine disruptors, and atrazine on behavior and neuroendocrine systems in quail Mary Ann Ottinger, Emma Lavoie, Nichola Thompson, Kasen Whitehouse, Meredith Barton, Mahmoud Abdelnabi, Moira McKernan, Sara Pollack, Michael Quinn Jr. Department of Animal and Avian Sciences, University of Maryland College Park, MD 20742, USA Endocrine disrupting chemicals (EDCs) exert weakly hormonal effects, however there are also unexpected effects due to ancillary toxic actions. Therefore, it is important to distinguish specific neuroendocrine impacts of EDCs and the risk that field relevant exposures have for wild populations. The Japanese quail provides a precocial avian model, which is sexually differentiated prior to hatch. Of particular concern are potential effects of EDCs on neural targets from embryonic exposure and subsequent impact on reproductive function in adults. Because birds maternally deposit EDCs into their eggs, we compared the effects of early embryonic injection of estradiol, androgenic compounds, or atrazine, a highly utilized herbicide on hypothalamic neuroendocrine systems and behavior. Fertile quail eggs (n = 85–95/group) were injected with 20 ll sesame oil (control), 17b estradiol, trenbolone, or DDE into the yolk at embryonic day 4. Atrazine (0, 0.5, 5, or 50 lg/egg) was injected prior to incubation. Quail that had been dosed were sampled at hatch or raised to maturity. Birds were behaviorally tested at 1 week of age on an adapted runway and adult males were tested at maturity to assess male sexual behavior. Hypothalamic aromatase (AROM), catecholamines, and GnRH-I were measured. Behavior proved to be a sensitive index of exposure, with trenbolone exposure impaired vocalization in week old chicks. Male sexual behavior was impaired by estradiol, androgenic EDCs, and atrazine treatment, especially mount latency. GnRH-I was sexually dimorphic in adult controls; atrazine affected hypothalamic GnRH-I in hatchlings and adults; other EDCs had variable effects. Atrazine decreased dopamine in the medium dose in both hatchlings and adults. Hypothalamic neurotransmitters that modulate reproductive function may provide valuable indices of endocrine disruption associated with later con-

doi:10.1016/j.yfrne.2006.03.047

sequences of embryonic exposure to EDCs. (Supported by EPA R826134010 (Star Grant), NSF 9817024, and EPA R-2877801 (MAO).) doi:10.1016/j.yfrne.2006.03.048

Functional studies of an eyestalk molt inhibiting hormone (MIH-1) in black tiger shrimp Penaeus monodon by RNA interference C.Y. Mak, S.-M. Chan Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong Molting in crustacean is negatively regulated by an eyestalk neuropeptide known as molt inhibiting hormone (MIH). In black tiger shrimp Penaeus monodon, the molt inhibiting hormone 1 (Pem-MIH1) has recently been characterized. Its amino acid sequence shows 95 and 99% homology to the MIHs of Marsupenaeus japonicus (Pej-SGP-IV) and Litopenaeus vannamei (Lv-SGP-1), respectively. To elucidate the physiological role of Pem-MIH1, RNA interference was used. Shrimp at intermolt stage were injected with 3 lg of Pem-MIH1 double-stranded RNA (dsRNA) in vivo. Injection was made at the arthropodial membrane of the fifth pereiopod using a microsyringe. As compared to the non-specific Tiger Frog Virus dsRNA or PBS controls, Pem-MIH1 expression was suppressed at 48 h after injection but restored to normal level at 72 h. In normal shrimp, the expression of cathepsin L is up-regulated during the premolt stage in the hepatopancreas. Stimulation of cathepsin expression after Pem-MIH1 dsRNA treatment suggests that these shrimp were induced from the intermolt to premolt stage. However, the expression of farnesoic acid O-methyltransferase did not show any significant change. Further injection studies will be performed to investigate the change in molt cycle duration of shrimp after treatment with Pem-MIH1 dsRNA. (Supported by a RGC grant (HKU#7482/05M) from the Hong Kong SAR Government.) doi:10.1016/j.yfrne.2006.03.049