Additional file 9: Movie S1. 18-month old N390D/+ mouse (#108). Note the 18-month old N390D/+ mice (Additional file 9: Movie S1 and Additional file 10: Movie S2) but not +/+ littermate (Additional file 11: Movie S3) exhibit spastic and tremble gait. Some of them show difficult movement due to paralysis of the hind limbs (Additional file 10: Movie S2).