Images were captured with a Nikon Eclipse TE2000-U fluorescence microscope (Nikon Inc.). For immunofluoroscence, Mice were perfused with 4% paraformaldehyde and brains dissected and placed in PFA overnight. Tissue was then transferred to glucose for 48 h.

Following cryosectioning, slices were permeabilized (0.1% Tween-20 in PBS, 5 min), and non-specific binding of antibodies was blocked with PBS/5.0% BSA for 1 h. Slices were probed with primary antibodies and incubated overnight at 4 °C. The following antibodies were used: (1:500, Neuron Signaling, Danvers, MA, USA): Anti-GFAP, Anti-NeuN. After a washing step (PBS, 5 min), slices were counterstained with AlexaFluor-conjugated secondary antibodies (1:1000, 1 h, RT, PBS/5% BSA; Molecular Probes, Eugene, OR, USA), washed again and mounted onto slides with Prolong Gold Antifade reagent containing DAPI (molecular probes). Stained slides were visualized with a Nikon Eclipse R428 TE2000-U fluorescence microscope (Nikon Inc.). For MRI, experiments were conducted at the Research Imaging Institute using a horizontal 7T Biospec system (BrukerBioSpin, Ettlingen, Germany) and ParaVision 5 software. A small circular surface coil (ID = 1.1 cm) was placed on top of the head. Mice were imaged under 1.2% isoflurane with spontaneous breathing after placement

in a custom-made animal holder with ear and mouth bars. Respiration rate (80–130 bpm) and rectal temperature (37 ± 0.5 °C) were continuously monitored

and maintained within normal physiological ranges unless otherwise perturbed. PD98059 High-resolution (isotropic 100 μm), T1-weighted images were acquired using 3D FLASH sequence (scan parameters: with echo time (TE) 5.1 ms, repetition time (TR) 50 ms, flip angle of 30°, field of view (FOV) of 11 mm × 11 mm × 11 mm, matrix size 1024 × 1024 × 1024). Preprocessing consisted of removing non-brain tissues and global spatial normalization. The GM and WM were separated using FMRIB Software Library (FSL) packet (EPSRC, UK). The GM and WM volumes were determined using the Multi-Image Analysis GUI (MANGO) software (http://ric.uthscsa.edu/mango). Neuromuscular function was tested using Rotamex 4/8 (Columbus Instruments, Columbus, OH). Each mouse was trained for five consecutive days (six trails/day) where the speed of the rotor BCKDHB was accelerated from 4 to 40 rpm with an acceleration of 0.2 rpm/s. Twenty-four hours after the last training session, the mice were tested in a probe trial consisting of six trials as previously described. The latency to fall was then recorded. Forelimb muscle strength was determined by measuring peak force (in pounds) using the Digital Grip Strength meter equipped with a Hind Limb Pull Bar Assembly (Columbus Instruments, Columbus, OH). Mice are allowed to grip the metal grids of a grip meter with their forepaws, and gently pulled backwards by the tail until they could no longer hold the grids. The peak grip force observed in 10 trials was recorded [24].