Socialization and genetic variability as a driver of domestication (by the example of dog breeds)

Social activity is the basis of interaction between different species in the process of common niche forming, including animal domestication. The increased social activity is universal characteristic of the “domestication syndrome” for different species (M.A. Zeder, 2017). It is assumed that some elements of this increase are due to a certain neotenization of a number of brain metabolic pathways (M. Somel et al., 2009). This is in good agreement with the data on the association of "domestication syndrome" with the slowing of neural crest cell proliferation (M.A. Zeder, 2015). The syndrome of hypersocialization (Williams-Behren Syndrome - WBS) in humans has been described, associated with hemideletion/hemiduplication of the 7q11.23 region, which includes 25-28 genes whose products are critical for the activity of various aspects of the central nervous system (A. Antonell et al., 2010). It was found that the complex of such genes is located on chromosome 6 in canids, and the domestic dog, considered in recent years as the main model object for studying the genetic mechanisms of domestication (E.A. Ostrander et al., 2019), differs from wolves in the presence of transposon insertions, increased methylation, and reduced gene expression in this region (B.M. von Holdt et al., 2017, 2018; D. Tandon et al., 2019). The aim of this work was to analyze such insertions in the region of the key gene for increased social activity in dogs WBSCR17 (Cfa6.6 and Cfa6.7) in representatives of different breeds and interspecific hybrids with jackals, as well as finding out the presence of mobile genetic elements in these areas. The detected sequences have high homology to the non-autonomous dispersed nuclear element SINEC2A1_CF (94 % homology) and to two regions of endogenous retrovirus 3 the sequences of which are described in humans and cattle (approximately 80 % homology). Data were obtained on the increased variability of the presence and number of insertions into these areas in dogs of different breeds and hybrids, on the presence of homology sites to endogenous human and bovine retroviruses, as well as a short dispersed nuclear element, species-specific for domestic dogs, SINEC2A1_CF, carrying the hexanucleotide AATAAA which contributes to the completion of transcription. These finding suggest the involvement of retroviruses in the formation of an aggregate niche in the domestication process, which leads to increased variability that contributes to the selection of animals with hypersocialization.