GSK3β and cdk5 are two major tau kinases whose activity is increased and prolonged in Alzheimer’s disease, however, it is also known that cdk5 is a negative regulator of GSK3β and inhibits its activity by increasing its phosphorylation on serine-9 [4, 60, 74, 192]. The gene discussed is GSK3B; the disease is early-onset autosomal dominant Alzheimer disease.