Scanning of the dopamine D1 and D5 receptor genes by REF in neuropsychiatric patients reveals a novel missense change at a highly conserved amino acid.

In previous analyses of schizophrenic patients, multiple missense changes and one nonsense change were identified in the D5 dopamine receptor (DRD5) gene, but no sequence changes of likely functional significance were identified in the D1 dopamine receptor (DRD1) gene. In the present study, we examined these genes in patients with certain other neuropsychiatric disorders that may be related to dopaminergic dysregulation. The coding regions of the DRD1 and DRD5 genes were examined in 25 and 25 autistic patients, 25 and 28 attention deficit hyperactivity disorder patients, and 51 and 43 alcoholic patients, respectively. In addition, the DRD5 gene was examined in 75 schizophrenic patients to search for additional variants affecting protein structure or expression (VAPSEs). These patients were analyzed with REF (restriction endonuclease fingerprinting), a hybrid between SSCP and restriction endonuclease digestion, which allows the entire coding sequence to be screened in one lane of a gel. Approximately 800 kb of genomic sequence were examined. No sequence changes were identified in the DRD1 gene among the 101 patient samples analyzed. Two sequence changes were identified in the DRD5 gene among the 171 patient samples. These included one previously identified silent polymorphism at base pair 978 (P326P). The change was identified in patients from all disease categories and from different ethnic backgrounds. One novel missense change, L88F, occurred in transmembrane domain II at a highly conserved amino acid in all dopamine receptors as well as in alpha1- and beta-adrenergic receptors. The mutation was identified in a Caucasian male patient with autism. Further analysis is necessary to determine if this missense change is associated with a particular neuropsychiatric phenotype.