Overground Locomotion of Spiny Mice With Variations in the Lumbosacral Vertebral Formula

Intraspecies variability of lumbosacral vertebrae is a known phenomenon in mammals, yet its association with motor function remains poorly understood, particularly in novel laboratory models. The spiny mouse has become a promising model organism for investigating central nervous system regeneration. This study provides an analysis of overground locomotion features in adult spiny mice with different lumbosacral vertebral formulae (VC7-VT13-VL5-VS5 vs. VC7-VT13-VL6-VS4--VL5 and VL6 groups, respectively). General features of locomotor kinematics, their dependence on speed, locomotor gait types, and several anatomical parameters were compared. Multiple locomotor gaits were observed in spiny mice; the most frequently used were trot, canter, and gallop. A decrease in step cycle duration, stance duration, limb step width, perineum oscillation amplitude, and toe-heel angle, together with an increase in relative and absolute swing duration with increasing speed, was revealed. Animals from the VL6-group showed significantly lower perineum oscillation amplitude in trot. No intergroup differences in hindlimb length and pelvic metrics were observed; however, a higher lumbar region length was found in the VL6-group. We suggest that the observed differences in stepping parameters during locomotion in spiny mice with the VL6-group formula may be related to spine biomechanics, or linked to differences in the neuronal control of locomotion, which requires further investigation.