Identification and Characterization of a Tandem Repeat in Exon III of the Dopamine Receptor D4 (DRD4) Gene
A large number ofmammalian species harbor a tandem repeat in exon III of the geneencodingdopamine receptorD4 (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 s...
| Main Authors: | , , , , , |
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.492.9714 http://jhered.oxfordjournals.org/content/97/3/279.full.pdf |
| Summary: | A large number ofmammalian species harbor a tandem repeat in exon III of the geneencodingdopamine receptorD4 (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 albir-ostris), 10 harbor porpoises (Phocoena phocoena), eight sperm whales (Physeter macrocephalus), and fiveminkewhales (Balae-noptera acutorostrata). Using enzymatic amplification followed by sequencing of amplified fragments, a tandem repeat com-posed of 18-bp basic units was detected in all of these species. The tandem repeats in white-beaked dolphin and harbor por-poisewerebothmonomorphic and consistedof 11 and12basic 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 unitswere identical in the closely related white-beaked dolphin and harbor porpoise, and these se-quences differed by a maximum of two changes when com-pared to the remaining species. There was a high degree of similarity between the cetaceanbasic 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. |
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