Audiogenic seizure susceptibility is reduced in fragile X knockout mice after introduction of FMR1 transgenes Sebastiano A. Musumeci a, ⁎ , Giuseppe Calabrese a , Carmela M. Bonaccorso e , Simona D'Antoni d , Judith R. Brouwer b , Cathy E. Bakker b , Maurizio Elia a , Raffaele Ferri a , David L. Nelson c , Ben A. Oostra b , Maria Vincenza Catania d,e a Department of Neurology, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy b Department of Clinical Genetics and Center for Biomedical Genetics, Erasmus University, Rotterdam, The Netherlands c Department of Molecular and Human Genetics, Baylor College of Medicine, Houston (TX), USA d Institute of Neurological Sciences, CNR, Catania, Italy e Laboratory of Molecular and Cellular Neurobiology, Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy Received 5 May 2006; revised 8 August 2006; accepted 10 August 2006 Available online 27 September 2006 Abstract The Fmr1 knockout (KO) mouse is characterized by an increased audiogenic seizure (AGS) susceptibility and is considered a good animal model for epilepsy and seizures in the human fragile-X (FRAX) syndrome. Here, we tested the hypothesis that the reintroduction of the FMR1 gene is able to revert the AGS susceptibility characterizing Fmr1 KO mice. To this aim, two groups of Fmr1 KO transgenic mice, which have additional copies of the human FMR1 gene (YAC) or FMR1 cDNA (G6) were used. AGS susceptibility of these mice was examined and compared to that of Fmr1 KO, wild type, and wild-type animals in whom the FMR1gene was also introduced (over-expressed). Mice were tested at different ages because AGS susceptibility is age dependent. The intensity of response was scored and the results were analyzed by means of 2-way analysis of variance to evaluate the effects of age and genetic condition. We found that AGS susceptibility rescue is complete in the G6 mice and partial in YAC mice. Our data indicate that the introduction of the human FMR1 gene in Fmr1 KO mice is able to revert the Fmr1 KO epileptic phenotype. © 2006 Elsevier Inc. All rights reserved. Keywords: Fragile X syndrome; FMR1; FMRP; Transgenic mice; Audiogenic seizures; Epilepsy Introduction Fragile X (FRAX) syndrome is one of the most common genetic causes of developmental disability, representing the most frequent form of inherited cognitive deficit and the second genetic cause of mental retardation after Down syndrome (Hagerman and Hagerman, 2002). FRAX syndrome is caused by the lack of fragile X mental retardation protein (FMRP) and affects approximately 1 in 4000 males and 1 in 8000 females, with a carrier prevalence of 1 in 813 males and 1 in 259 female (Rousseau et al., 1995; Dombrowski et al., 2002). The features of FRAX syndrome include mental retardation, seizures, autistic-like behaviors, attention-deficit hyperactivity disorder, behavioral problems, macroorchidism, facial abnormalities, and connective tissue dysfunction (Hagerman and Hagerman, 2002). Neurophysiological data suggest an increased cortical excitability in FRAX syndrome: FRAX patients are affected by epilepsy or seizures in 20-25% of cases and typical paroxysmal EEG abnormalities are present in about 50% of prepubertal boys (Musumeci et al., 1999; Berry-Kravis, 2002); in addition, giant middle-latency somatosensory evoked potentials and evoked EEG spikes have been found in FRAX patients (Ferri et al., 1994). Pathological examination of brains from FRAX patients have shown an increased density of long and tortuous dendritic spines suggesting a delay in spine maturation (Hinton et al., 1991; Irwin et al., 2001). The genetic defect underlying FRAX syndrome is an increased trinucleotide repetitive sequence (CGG) in the promoter region of FMR1 gene, which is located at Xq27.3. Experimental Neurology 203 (2007) 233 – 240 www.elsevier.com/locate/yexnr ⁎ Corresponding author. Oasi Institute for Research on Mental Retardation and Brain Aging, Via C. Ruggero, 73, I-94018 Troina (EN), Italy. Fax: +39 935 653327. E-mail address: samusumeci@oasi.en.it (S.A. Musumeci). 0014-4886/$ - see front matter © 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.expneurol.2006.08.007