Identification and characterization of a tandem repeat in exon III of the dopamine receptor D4 (DRD4) gene in cetaceans

• Published in: Journal of Heredity
• Main Authors: Mogensen, Line, Kinze, Carl Christian, Werge, Thomas, Rasmussen, Henrik Berg
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2006
• Subjects: Balaenoptera acutorostrata; Lagenorhynchus albirostris; minke whale; Phocoena phocoena; Physeter macrocephalus; Sperm whale; White-beaked dolphin
• Online Access: https://curis.ku.dk/portal/da/publications/identification-and-characterization-of-a-tandem-repeat-in-exon-iii-of-the-dopamine-receptor-d4-drd4-gene-in-cetaceans(e80a4214-bcb7-4209-aec6-7469f38d97fe).html; https://doi.org/10.1093/jhered/esj024

A large number of mammalian species harbor a tandem repeat in exon III of the gene encoding dopamine receptor D4 (DRD4), a receptor associated with cognitive functions. In this study, a DRD4 gene exon III tandem repeat from the order Cetacea was identified and characterized. Included in our study were samples from 10 white-beaked dolphins (Lagenorhynchus albirostris), 10 harbor porpoises (Phocoena phocoena), eight sperm whales (Physeter macrocephalus), and five minke whales (Balaenoptera acutorostrata). Using enzymatic amplification followed by sequencing of amplified fragments, a tandem repeat composed of 18-bp basic units was detected in all of these species. The tandem repeats in white-beaked dolphin and harbor porpoise were both monomorphic and consisted of 11 and 12 basic units, respectively. In contrast, the sperm whale harbored a polymorphic tandem repeat with size variants composed of three, four, and five basic units. Also the tandem repeat in minke whale was polymorphic; size variants composed of 6 or 11 basic units were found in this species. The consensus sequences of the basic units were identical in the closely related white-beaked dolphin and harbor porpoise, and these sequences differed by a maximum of two changes when compared to the remaining species. There was a high degree of similarity between the cetacean basic unit consensus sequences and those from members of the horse family and domestic cow, which also harbor a tandem repeat composed of 18-bp basic units in exon III of their DRD4 gene. Consequently, the 18-bp tandem repeat appears to have originated prior to the differentiation of hoofed mammals into odd-toed and even-toed ungulates. The composition of the tandem repeat in cetaceans differed markedly from that in primates, which is composed of 48-bp repeat basic units.