Behavioural Brain Research 219 (2011) 175–180 Contents lists available at ScienceDirect Behavioural Brain Research journal homepage: www.elsevier.com/locate/bbr Research report Sensorimotor and cognitive function of a NEFL P22S mutant model of Charcot–Marie–Tooth disease type 2E Mohammed Filali a,∗ , Florence Dequen a , Robert Lalonde b,c , Jean-Pierre Julien a a CHUL Research Center (CHUQ) and Department of Molecular Medicine, Laval University, 2705 Laurier boul., Québec G1V 4G2, Canada b Centre Hospitalier de l’Université de Montréal/St-Luc, Unité de Recherche en Sciences Neurologiques, Montréal H2X 3J4, Canada c Université de Rouen, Faculté des Sciences, France article info Article history: Received 8 November 2010 Received in revised form 8 December 2010 Accepted 10 December 2010 Available online 17 December 2010 Keywords: Charcot–Marie–Tooth disease NEFLP22S transgenic mice Peripheral neuropathy Sensorimotor deficits Spatial memory abstract Charcot–Marie–Tooth (CMT) disease is the most frequently encountered hereditary disease causing sen- sorimotor neuropathies and slowly progressive muscle weakness and atrophy. The P22S mutation of the NEFL gene encoding the light polypeptide neurofilament (NFL) is associated with CMT. To under- stand more clearly the pathogenesis of sensorimotor dysfunction in CMT, we generated transgenic mice with the NEFL P22S mutation under the tet-off tetracycline regulated system with involvement of the Thy1 neuron-specific promoter. NEFL P22S transgenic mice exhibited extended duration of the hindlimb clasping response and gait anomalies, as well as sensorimotor deficits in stationary beam and suspended bar tests. In addition, the NEFL P22S mice were deficient in the reversal phase of left–right discrimination learning in a water maze. This model mimics some aspects of human CMT pathology and provides an opportunity of ameliorating CMT symptoms with experimental therapies. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Charcot–Marie–Tooth (CMT) is the most frequently encoun- tered hereditary disease causing sensorimotor neuropathies with slowly progressive muscle weakness and atrophy. There are two main types: CMT1, with demyelination and slowed nerve conduc- tion speed, and CMT2, with axonopathy but normal or slightly reduced conduction speed [8]. Mutations of NEFL, encoding neu- rofilament of light molecular weight (NFL), are associated with CMT2E, predicted to interfere with the proper assembly of NFs and causing accumulation and axonal swelling [2,5]. In a Slovenian fam- ily with CMT2E, a NEFL P22S mutation was discovered [6], located in the N-terminal of NFL, critical for NF assembly. In vitro studies indicate that the abnormal protein fails to interact with neurofila- ments of medium and heavy molecular weight, causing aggregation in SW13 cells and cortical neurons [24]. These aggregations likely trap proteins and organelles inside the cytoplasm, causing defective axonal transport [20]. In the present study, we describe the behavioral phenotypes of a CMT mouse model with the NEFL P22S mutation that was recently reported [3]. In the previous study, we reported that this CMT mouse model exhibits abnormal hindlimb posture as well as sen- sorimotor deficits in pole-climbing and rotorod tests. We extended ∗ Corresponding author. Tel.: +1 418 654 2296; fax: +1 418 654 2761. E-mail address: Mohammed.Filali@crchul.ulaval.ca (M. Filali). these analyses with stationary beam and suspended bar tests [11], as well as footprint patterns, sensitive to the functional efficiency of the sciatic nerve innervating the hindlimbs [13]. Moreover, sensory thresholds and pain perception were determined. We completed analyses with T-maze left–right discrimination learning and rever- sal, to determine whether spatial functions are affected. By picking them by the tail, we noticed an abnormal flexion reflex, in contrast to the normal extension response of normal mice [3,14]. 2. Methods 2.1. Animals NEFL P22S mutants are double transgenic mice with controlled expression of the human gene under the Tet-off tetracycline-regulated system [12]. Tetracycline tran- scriptional activator (tTa) expression is driven by the Thy1 neuron-specific promoter [3]. Mutant mice (n = 26) and control littermates (n = 29) on the C57BL/6 genetic background were evaluated at 9 months of age, housed 1–5 per cage under a 12-h light/dark cycle (on at 7:00 a.m.) with access to food and water at all times. A separate series of mice was evaluated in T-maze discrimination (n = 12 in each group). General health was regularly checked with a modified SHIRPA screen [22]. The animals were tested during the light phase by an experimenter blind to genotype, confirmed by DNA analysis of tail biopsies. The mice were never treated with doxycycline. Guide- lines of the Canadian Council on Animal Care were followed in a protocol approved by the Animal Welfare Committee at the University of Laval. 2.2. Behavioral analyses 2.2.1. Hindpaw clasping NEFL P22S mutant mice appeared normal during the first few months of life but signs of neurological dysfunction appeared at approximately 6 months of age in the 0166-4328/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.bbr.2010.12.022