Mice survival, neurological scores, and motor studies

The behavioral scores of the SOD1-G93A and FUS mice were assessed to monitor the progression of the disease. The assessments began at 70 and 25 days of age, respectively, for the SOD1-G93A and FUS mice. A rating scale ranging from 5 (representing a healthy mouse without symptoms of paralysis) to 1 (indicating full paralysis of the hind limbs, with the inability to straighten up within 30 ​s after being turned on their back) was used [25]. Once a mouse reached a score of 1, it was euthanised following preclinical testing guidelines [26].

To evaluate neuromuscular deficits, the mice underwent hanging wire tests twice a week, starting at 70 (SOD1-G93A) or 25 (FUS) days of age. The test involved placing the mouse on a wire grid (with a wire thickness of 2 ​mm) and gently shaking the grid to prompt the mouse to hold onto it. The grid was then turned upside down, and the latency for the mouse to release the grid was recorded within three attempts. The maximum recording time was 90 ​s for SOD1-G93A mice or 60 ​s for FUS mice [27,28]. Whenever a mouse dropped from the grid in three consecutive trials, it was considered symptomatic. For SOD1-G93A mice, motor performance was assessed twice a week using a rotarod apparatus (Ugo Basile 7650 model) set at a constant speed of 15 rotations per minute. The testing started at 11 weeks of age and continued until the mice could no longer remain on the rotarod. Following a three-day training period, the latency to fall off the rotarod was recorded as a measure of motor function. Each test day included three trials, and the best performance was recorded and included in the data analysis [29].