title: Motor hypertonia and lack of locomotor coordination in mutant mice lacking DSCAM.
abstract: Down syndrome cell adherence molecule (DSCAM) contributes to the normal establishment and maintenance of neural circuits. Whereas there is abundant literature regarding the role of DSCAM in the neural patterning of the mammalian retina, less is known about motor circuits. Recently, DSCAM mutation has been shown to impair bilateral motor coordination during respiration, thus causing death at birth. DSCAM mutants that survive through adulthood display a lack of locomotor endurance and coordination in the rotarod test, thus suggesting that the DSCAM mutation impairs motor control. We investigated the motor and locomotor functions of DSCAM(2J) mutant mice through a combination of anatomical, kinematic, force, and electromyographic recordings. With respect to wild-type mice, DSCAM(2J) mice displayed a longer swing phase with a limb hyperflexion at the expense of a shorter stance phase during locomotion. Furthermore, electromyographic activity in the flexor and extensor muscles was increased and coactivated over 20% of the step cycle over a wide range of walking speeds. In contrast to wild-type mice, which used lateral walk and trot at walking speed, DSCAM(2J) mice used preferentially less coordinated gaits, such as out-of-phase walk and pace. The neuromuscular junction and the contractile properties of muscles, as well as their muscle spindles, were normal, and no signs of motor rigidity or spasticity were observed during passive limb movements. Our study demonstrates that the DSCAM mutation induces dystonic hypertonia and a disruption of locomotor gaits.
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada;
authors.forename: Maxime
authors.initials: M
authors.lastname: Lemieux
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada;
authors.forename: Olivier D
authors.initials: OD
authors.lastname: Laflamme
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada;
authors.forename: Louise
authors.initials: L
authors.lastname: Thiry
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada;
authors.forename: Antoine
authors.initials: A
authors.lastname: Boulanger-Piette
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada; Faculty of Medicine, Department of Rehabilitation, Université Laval, Québec, Canada; and.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Frenette
authors.affiliation: Centre de Recherche du Centre Hospitalier Universitaire (CHU) de Québec-Centre Hospitalier de l'Université Laval (CHUL), Québec, Canada; Faculty of Medicine, Department of Psychiatry and Neurosciences, Université Laval, Québec, Canada frederic.bretzner.1@ulaval.ca.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bretzner
mesh_terms: D000818:Animals; D015815:Cell Adhesion Molecules / Q000172:deficiency / Q000235:genetics*; D005260:Female; D005684:Gait; D008297:Male; D051379:Mice; D009119:Muscle Contraction; D009123:Muscle Hypotonia / Q000378:metabolism* / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000502:physiology*; D009154:Mutation; D009469:Neuromuscular Junction / Q000378:metabolism / Q000502:physiology; D016138:Walking
chemical_list: D015815:Cell Adhesion Molecules; C491735:Dscam protein, mouse
keywords: DSCAM; EMG; locomotion; mutant; posture