Abstract
BackgroundThe arginine vasopressin V1a receptor (V1aR) modulates social cognition and behavior in a wide variety of species. Variation in a repetitive microsatellite element in the 5' flanking region of the V1aR gene (AVPR1A) in rodents has been associated with variation in brain V1aR expression and in social behavior. In humans, the 5' flanking region of AVPR1A contains a tandem duplication of two ~350 bp, microsatellite-containing elements located approximately 3.5 kb upstream of the transcription start site. The first block, referred to as DupA, contains a polymorphic (GT)25 microsatellite; the second block, DupB, has a complex (CT)4-(TT)-(CT)8-(GT)24 polymorphic motif, known as RS3. Polymorphisms in RS3 have been associated with variation in sociobehavioral traits in humans, including autism spectrum disorders. Thus, evolution of these regions may have contributed to variation in social behavior in primates. We examined the structure of these regions in six ape, six monkey, and one prosimian species.ResultsBoth tandem repeat blocks are present upstream of the AVPR1A coding region in five of the ape species we investigated, while monkeys have only one copy of this region. As in humans, the microsatellites within DupA and DupB are polymorphic in many primate species. Furthermore, both single (lacking DupB) and duplicated alleles (containing both DupA and DupB) are present in chimpanzee (Pan troglodytes) populations with allele frequencies of 0.795 and 0.205 for the single and duplicated alleles, respectively, based on the analysis of 47 wild-caught individuals. Finally, a phylogenetic reconstruction suggests two alternate evolutionary histories for this locus.ConclusionThere is no obvious relationship between the presence of the RS3 duplication and social organization in primates. However, polymorphisms identified in some species may be useful in future genetic association studies. In particular, the presence of both single and duplicated alleles in chimpanzees provides a unique opportunity to assess the functional role of this duplication in contributing to variation in social behavior in primates. While our initial studies show no signs of directional selection on this locus in chimps, pharmacological and genetic association studies support a potential role for this region in influencing V1aR expression and social behavior.
Highlights
The arginine vasopressin V1a receptor (V1aR) modulates social cognition and behavior in a wide variety of species
Comparative studies in monogamous and non-monogamous vole species have suggested that variability in the 5' flanking region of the AVPR1A gene contributes to both variation in V1aR distribution patterns in the brain and in sociobehavioral traits
The galago, the only prosimian species examined here, has a conserved region that corresponds with a portion of the DupA/B region but the sequences surrounding this area are highly diverged from the other primate species that we investigated, indicating that either this region is not fully represented prior to Simiiforms or we failed to identify a truly orthologous sequence
Summary
The arginine vasopressin V1a receptor (V1aR) modulates social cognition and behavior in a wide variety of species. The composition of a microsatellite region located 626 base pairs (bp) upstream of the AVPR1A transcription start site (TSS) exhibits striking species differences in length and subtler individual length variation within species [3,5,6]. This inter- and intra-specific length variation is sufficient to drive differences in gene expression in vitro in a cell-type specific manner [3,7]. Individual variation in the length of this region in prairie voles is associated with differences in central V1aR patterns and variation in maletypical social behaviors [2,3]
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