ORIGINAL PAPER Altered fast- and slow-twitch muscle fibre characteristics in female mice with a (S248F) knock-in mutation of the brain neuronal nicotinic acetylcholine receptor David J. Cannata Æ David I. Finkelstein Æ Ilse Gantois Æ Yaroslav Teper Æ John Drago Æ Jan M. West Received: 5 January 2009 / Accepted: 15 April 2009 / Published online: 29 April 2009 Ó Springer Science+Business Media B.V. 2009 Abstract We generated a mouse line with a missense mutation (S248F) in the gene (CHRNA4) encoding the a4 subunit of neuronal nicotinic acetylcholine receptor (nAChR). Mutant mice demonstrate brief nicotine induced dystonia that resembles the clinical events seen in patients with the same mutation. Drug-induced dystonia is more pronounced in female mice, thus our aim was to determine if the S248F mutation changed the properties of fast- and slow-twitch muscle fibres from female mutant mice. Reverse transcriptase-PCR confirmed CHRNA4 gene expression in the brain but not skeletal muscles in normal and mutant mice. Ca 2? and Sr 2? force activation curves were obtained using skinned muscle fibres prepared from slow-twitch (soleus) and fast-twitch (EDL) muscles. Two significant results were found: (1) the (pCa 50 - pSr 50 ) value from EDL fibres was smaller in mutant mice than in wild type (1.01 vs. 1.30), (2) the percentage force produced at pSr 5.5 was larger in mutants than in wild type (5.76 vs. 0.24%). Both results indicate a shift to slow-twitch char- acteristics in the mutant. This conclusion is supported by the identification of the myosin heavy chain (MHC) iso- forms. Mutant EDL fibres expressed MHC I (usually only found in slow-twitch fibres) as well as MHC IIa. Despite the lack of spontaneous dystonic events, our findings sug- gest that mutant mice may be having subclinical events or the mutation results in a chronic alteration to muscle neural input. Keywords Ca 2? /Sr 2? -activation Á Dystonia Á Nicotinic acetylcholine receptor Á S248F mutation Á Skinned muscle fibre Introduction We have generated a mouse model of autosomal dominant nocturnal frontal lobe epilepsy [ADNFLE] (Scheffer et al. 1995) originally described to be due to a missense mutation (S248F) in the gene (CHRNA4) encoding the a4 subunit of neuronal nicotinic acetylcholine receptor [nAChR] (Stein- lein et al. 1995). Although spontaneous seizures are not observed in these knock-in mice, they do exhibit nicotine- induced behaviours that mimic the brief dystonic events reported in ADNFLE (Teper et al. 2007). Brain nAChRs are ligand-gated ion channels which can be divided into muscle and neuronal receptor types. These receptors are involved in fast synaptic transmission and are located in both the peripheral and central nervous system (Hogg et al. 2003). The receptors are composed of five subunits surrounding a central pore and are made up of different combinations of the acetylcholine binding sub- units (a2–a10 and b2–b4; Hogg et al. 2003). The nAChRs Electronic supplementary material The online version of this article (doi:10.1007/s10974-009-9177-x) contains supplementary material, which is available to authorized users. D. J. Cannata (&) Á J. M. West School of Life and Environmental Sciences, Deakin University, 221 Burwood Highway, Melbourne, VIC 3125, Australia e-mail: djcan@deakin.edu.au D. I. Finkelstein The Mental Health Research Institute of Victoria, Melbourne, VIC 3052, Australia I. Gantois Laboratory of Biological Psychology, Katholieke Universiteit Leuven, Tiensestraat 102, 3000 Leuven, Belgium Y. Teper Á J. Drago Howard Florey Institute, The University of Melbourne, Melbourne, VIC 3010, Australia 123 J Muscle Res Cell Motil (2009) 30:73–83 DOI 10.1007/s10974-009-9177-x