DYRK1A and Alzheimer disease: By phosphorylating ASF at Ser227, Ser234 and Ser238, DYRK1A transforms its nuclear distribution, making it unavailable to the tau transcript and favoring the production of the 3R-Tau isoform (characteristic for AD and other tauopathies) over the 4R-Tau isoform, creating a strong disequilibrium and therefore neurofibrillary degeneration [43].