MAPT and Dravet syndrome: Increased Dual Specificity Tyrosine Phosphorylation Regulated Kinase 1A (DYRK1A) gene dosage due to Chr21 trisomy may also contribute to the early onset of neurofibrillary degeneration in DS (Figure 2), through the phosphorylation of alternative splicing factors, that alters the relative abundance of tau protein with three or four microtubule-binding domains [66].