Fragile X Syndrome (FXS) is a leading cause of inherited mental disability and autism spectrum disorders. An increased number of CGG repeats (>200) in the fmr1gene results in a loss of the gene’s protein product, Fragile X Mental Retardation Protein (FMRP), resulting in neural deficits and impaired learning and social behaviors. Our goal was to use RNA interference (RNAi) to inhibit fmr1 expression in adult Acheta domesticus crickets and to analyze how the subsequent loss of FMRP can impact cricket agonistic behavior. The cricket is an excellent model for this study since cricket agonistic, or aggressive, behavior hasbeen well characterized and the cricket is also highly susceptible to RNAi. During RNAi, small segments of double-stranded RNA (dsRNA) are injected into the animal and the dsRNA will then inhibit, or knockdown, expression of a gene of interest. To measure RNAi knockdown of the fmr1 gene, male crickets were injected with 2.5μg of dsRNA for Fmr1 (experimental) or for DsRed2, a gene not expressed in insects (negative control), on day 1 of adulthood. The relative expression of fmr1 was 40% lower in the brains of Fmr1 males compared to control males at 8 days after dsRNA injection. Agonistic trials between two age-matched adult male crickets were performed 20 days after injection. Trials consisted of (1) control fights between two DsRed2 injected males and (2) experimental fights between a DsRed2 and Fmr1 injected male. Fmr1 males were as aggressive and as likely to win a fight as control males. However, Fmr1 males were less likely to initiate a fight suggestive of a reduced motivation to fight. Since FXS in humans is a developmental disorder, we have begun to use parental RNAi to inhibit fmr1 expression in the cricket from birth and into adulthood. Such studies will allow us to also examine the role of FMRP in the development of social behavior.
References
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Authors: Emily G. Wyatt, Bao Huy Pham, Mollie R. Sorrell
Faculty Advisor: Dr. Kathleen A. Killian, Department of Biology
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