DYRK1A (Dual-specificity tyrosine phosphorylation-regulated kinase 1A)(OMIM 600855) is a kinase whose gene is located at 21q22.13 and is highly conserved.It is composed of a nuclear targeting sequence, a protein kinase domain, a leucine zipper motif and a 13-consecutive-histidine repeat. The gene is located in the so-called "Down syndrome critical region" (DSCR), a region on chromosome 21 thought responsible for most phenotypic manifestations of Down syndrome. DYRK1A is involved in signaling pathways regulating cell proliferation in brain development. Amongst others, haploinsufficiency of DYRK1A, DYRK1A overexpression and interactions with alpha-synuclein are thought to be the main factors for the clinical phenotype.