Sex-specific disruptions in PKCγ signaling in a mouse model of spinocerebellar ataxia type 14.
Spinocerebellar ataxia type 14 (SCA14) is an autosomal dominant neurodegenerative disease caused by mutations in the gene encoding protein kinase C γ (PKCγ), a Ca2+- and diacylglycerol-dependent Ser/Thr kinase dominantly expressed in cerebellar Purkinje cells. These mutations impair autoinhibitory constraints to increase the basal activity of the kinase, resulting in deficits in the cerebellum that are not observed upon simple deletion of the gene, and severe ataxia. To better understand the impact of aberrant PKCγ signaling in disease pathology, we developed a knockin murine model of the SCA14 mutation ΔF48 in PKCγ. This fully penetrant mutation is severe in humans and is mechanistically informative, as it has high basal activity but is unresponsive to agonist stimulation. Genetic, behavioral, and molecular testing revealed that ΔF48 PKCγ mice have ataxia-related phenotypes and an altered cerebellar phosphoproteome driven primarily by enhanced Ca2+/calmodulin-dependent kinase 2 signaling, effects that were more severe in male mice. Analysis of existing human data revealed that SCA14 has a significantly earlier age of onset for males compared with females. Data from this clinically relevant mutation suggested that enhanced basal activity of PKCγ is sufficient to cause ataxia and that treatment strategies to modulate aberrant PKCγ may be particularly beneficial in males.