[Minibrain/DYRK1A gene: candidate gene for mental retardation in Down's syndrome?].

DYRK1A is the first member of a novel subfamily of protein kinases with dual specificity. The human gene for DYRK1A is located in the "Down syndrome critical region" (21q22.2). Due to its relationship to the Drosophila gene minibrain (Mnb), whose mutation results in specific defects in neurogenesis, and based on functional experiments on transgenic mice, DYRK1A is discussed as a candidate gene for mental retardation in Down syndrome. The kinase is characterized by its ability to catalyze tyrosine-directed autophosphorylation as well as phosphorylation of serine/threonine residues in substrates. Its exact cellular function is yet unknown. DYRK1A is, however, known to be translocated into the nucleus and supposed to be involved in the control of cell growth and development. The pathogenetic impact of DYRK1A on Down syndrome needs further elucidation.