摘要
Fragile X syndrome （FXS） is the most common monogenic cause of intellectual disability and a cause for autism. FXS females report milder phenotypes and a lower rate of cognitive problems compared to males. This is most likely because most females are heterozygous, while males are hemizygous for the disease. Thus, most preclinical studies have been completed in males. As there is major interest in testing experimental drugs for FXS, it is imperative to determine whether females in animal models used for research, present behavioral alterations that might translate to humans in order to confirm that experimental drugs have an effect on both genders. In our study we describe behavioral phenotypes in homozygous FXS female mice developed on the FVB.129 background. We focused on detection of hippocampal-mediated cognitive abilities and other behaviors described for FXS. Our research shows that, while female FVB.129-Fmrl knockout mice present normal learning, they have impaired memory, as well as susceptibility to audiogenic seizures. In agreement with previous reports in rodents and humans, significant levels of the small GTPase Racl were found in FXS female mice. Because Racl is involved in neuronal development, plasticity and behavior, we additionally aimed to pharmacologically inhibit Racl and determine whether observed phenotypes are rescued. Treatment of female FVB.129-Fmrl knockout with a Racl inhibitor abolished behavioral deficits, bringing phenotypes to control levels. Our results suggest that female FVB.129-Fmrl knockout mice display behavioral impairments that resemble FXS in humans. Moreover, those behavioral shortfalls might be associated with alteration of plasticity involving excessive Racl function, since pharmacological reduction of Racl normalizes previously altered phenotypes to control levels.
Fragile X syndrome （FXS） is the most common monogenic cause of intellectual disability and a cause for autism. FXS females report milder phenotypes and a lower rate of cognitive problems compared to males. This is most likely because most females are heterozygous, while males are hemizygous for the disease. Thus, most preclinical studies have been completed in males. As there is major interest in testing experimental drugs for FXS, it is imperative to determine whether females in animal models used for research, present behavioral alterations that might translate to humans in order to confirm that experimental drugs have an effect on both genders. In our study we describe behavioral phenotypes in homozygous FXS female mice developed on the FVB.129 background. We focused on detection of hippocampal-mediated cognitive abilities and other behaviors described for FXS. Our research shows that, while female FVB.129-Fmrl knockout mice present normal learning, they have impaired memory, as well as susceptibility to audiogenic seizures. In agreement with previous reports in rodents and humans, significant levels of the small GTPase Racl were found in FXS female mice. Because Racl is involved in neuronal development, plasticity and behavior, we additionally aimed to pharmacologically inhibit Racl and determine whether observed phenotypes are rescued. Treatment of female FVB.129-Fmrl knockout with a Racl inhibitor abolished behavioral deficits, bringing phenotypes to control levels. Our results suggest that female FVB.129-Fmrl knockout mice display behavioral impairments that resemble FXS in humans. Moreover, those behavioral shortfalls might be associated with alteration of plasticity involving excessive Racl function, since pharmacological reduction of Racl normalizes previously altered phenotypes to control levels.
