Impaired motor coordination correlates with persistent multiple climbing fiber innervation in PKC gamma mutant mice

Area of Science:

• Neuroscience
• Motor Control Research
• Cellular Mechanisms of Learning

Background:

• Motor coordination relies on learning component movements and refining the overall motor program.
• Protein kinase C gamma (PKC gamma) plays a role in motor control.
• PKC gamma mutant mice exhibit impaired motor coordination.

Purpose of the Study:

• To investigate the specific motor learning deficits in PKC gamma mutant mice.
• To determine the cellular and circuit-level basis for the impaired motor coordination in these mice.
• To elucidate the role of climbing fiber innervation in motor program refinement.

Main Methods:

• Behavioral analysis of motor coordination and eyeblink conditioning in PKC gamma mutant mice.
• Assessment of cerebellar long-term depression (LTD) as a cellular correlate of motor learning.
• Histological examination of climbing fiber innervation onto Purkinje cells in adult mutant mice.

Main Results:

• PKC gamma mutant mice displayed impaired motor coordination but normal eyeblink conditioning, indicating intact component movement learning.
• Cerebellar long-term depression (LTD) was unimpaired in mutant mice, suggesting normal cellular learning mechanisms.
• Mutant mice showed persistent innervation of multiple climbing fibers onto Purkinje cells in adulthood, unlike wild-type mice.
• This defective elimination of surplus climbing fibers was identified as the likely cause of motor discoordination.

Conclusions:

• PKC gamma is crucial for the experience-based refinement of motor programs, not for basic component movement learning.
• The persistence of supernumerary climbing fibers in the cerebellum of PKC gamma mutant mice underlies their motor coordination deficits.
• Targeting climbing fiber elimination pathways may offer therapeutic strategies for motor discoordination disorders.