SYN1 and Cognitive impairment: These novel substrates, such as synapsin 1 (SYN1), also found in the phosphoproteomic analyses of Ts65Dn, the most used DS model, bring new insight into the role of DYRK1A, and allow us to propose some dysregulated biological processes related to axonal organization and synaptic response which are responsible for cognitive deficits associated with DS.