Neurodegeneration in SCA14 is associated with increased PKCγ kinase activity, mislocalization and aggregation

Area of Science:

• Neuroscience
• Genetics
• Molecular Biology

Background:

• Spinocerebellar ataxia type 14 (SCA14) is a progressive neurodegenerative disorder.
• SCA14 results from mutations in the PRKCG gene, encoding protein kinase C gamma (PKCγ).
• The precise pathological mechanisms of SCA14 remain unclear despite numerous identified mutations.

Purpose of the Study:

• To investigate the molecular neuropathology of SCA14.
• To characterize the effects of specific PRKCG mutations (H36R, H101Q) in the C1 domain.
• To evaluate patient-derived induced pluripotent stem cells (iPSCs) as disease models.

Main Methods:

• Analysis of post-mortem cerebellum tissue from SCA14 patients.
• Generation and analysis of human patient-derived iPSCs carrying SCA14 mutations.
• Immunofluorescence microscopy to detect PKCγ localization and aggregation.
• Biochemical assays to assess PKCγ activity and substrate phosphorylation.

Main Results:

• Mutant PKCγ exhibited cytoplasmic mislocalization and aggregation in both patient iPSCs and cerebellum.
• PKCγ aggregates were resistant to degradation.
• Mutant PKCγ showed hyper-activation, leading to increased substrate phosphorylation.
• Patient iPSCs accurately recapitulated neuropathological features seen in post-mortem tissue.

Conclusions:

• SCA14 pathogenesis involves a combination of loss-of-function and gain-of-function mechanisms due to C1 domain mutations in PKCγ.
• Patient-derived iPSCs serve as valuable models for SCA14.
• These iPSCs show promise as tools for future drug discovery in SCA14.