Y-linked genes that may be of particular interest with respect to ADHD include the male-determining gene SRY (which is expressed in dopaminergic neuron-rich brain regions and is duplicated in cases of ADHD), and NLGN4Y and PCDH11Y, which encode cell membrane molecules important in maintaining synapse integrity and cell-cell interactions respectively, and both of which have been implicated as candidate genes for neurodevelopmental disorders [55]. The gene discussed is NLGN4Y; the disease is attention deficit-hyperactivity disorder.