A meiotic linkage map of the silver fox, aligned and compared to the canine genome

Abstract

A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogenetic homologies between the dog and fox, and by the availability of high resolution canine genome maps and sequence data. Furthermore, the high genomic sequence identity between dog and fox allows adaptation of canine microsatellites for genotyping and meiotic mapping in foxes. Using 320 such markers, we have constructed the first meiotic linkage map of the fox genome. The resulting sex-averaged map covers 16 fox autosomes and the X chromosome with an average inter-marker distance of 7.5 cM. The total map length corresponds to 1480.2 cM. From comparison of sex-averaged meiotic linkage maps of the fox and dog genomes, suppression of recombination in pericentromeric regions of the metacentric fox chromosomes was apparent, relative to the corresponding segments of acrocentric dog chromosomes. Alignment of the fox meiotic map against the 7.6x canine genome sequence revealed high conservation of marker order between homologous regions of the two species. The fox meiotic map provides a critical tool for genetic studies in foxes and identification of genetic loci and genes implicated in fox domestication.[Supplemental material is available online at www.genome.org.]The silver fox is a coat color variant of the red fox (Vulpes vulpes) (Nes et al. 1988). In nature, the red fox has a wider geographical distribution than any other Carnivora species, inhabiting ecological zones ranging from tundra to desert, and demonstrates remarkable variation in size and morphology (Nowak 1991;Sheldon 1992;MacDonald and Reynolds 2004). Multiple genetically determined coat color phenotypes have been maintained in farm-raised foxes since the early twentieth century (Nes et al. 1988;Vage et al. 1997). Although bred in captivity, farm-bred foxes normally exhibit a pattern of aggressive, fear-aggressive, and avoidance behavior toward humans. At the Institute of Cytology and Genetics of the Russian Academy of Sciences (ICG) the silver fox was chosen as a model for experimental domestication. Starting with a large commercial population, foxes were selected for tame behavior for over 45 generations to produce a strain with behavioral responses to humans like those of domestic dogs (Belyaev 1969(Belyaev , 1979Trut 1980Trut , 1999Trut , 2001Trut et al. 2004). In parallel, selection for aggressive behavior produced extremely aggressive and difficult-to-handle animals (see http:// cbsu.tc.cornell.edu/ccgr/behaviour/index.html). Domesticated foxes are eager to establish human contact from a very early age (Trut 1999). Like dogs, they develop a close attachment to...

A Comprehensive Linkage Map of the Dog Genome

“…Genetic map-based estimates of recombination rate are available for two additional carnivore species, house cat ($1.1 cM/Mb; Menotti-Raymond et al 1999) and silver fox ($0.6 cM/Mb; Kukekova et al 2007). While large differences in map quality and coverage preclude detailed comparisons, the rate of recombination in dog is clearly not an outlier among carnivores.…”

Genomic responses to selection for tame/aggressive behaviors in the silver fox (Vulpes vulpes)

“…The 45 heritability of these behavioral traits has been confirmed in multiple experiments (14)(15)(16)(17), 46 making these fox strains a promising model for the identification of the genetic basis of tame and aggressive behaviors. 48 To identify the genetic basis of the behavioral differences between tame and 49 aggressive fox strains we developed the fox meiotic linkage map, experimental cross-50 bred pedigrees, and mapped eight significant and suggestive quantitative trait loci (QTL) 51 for behavioral traits (17)(18)(19)(20). Although QTL mapping is a promising strategy for the 52 identification of genomic regions implicated in complex traits, this approach alone 53 usually does not allow identification of the causative genes and mutations.…”

Comparative Genomics of 3 Farm Canids in Relation to the Dog

“…Some groups were assigned to specific chromosomes (VVU14, ALA4 and ALA10). A meiotic linkage map of the red fox, including 320 microsatellite markers, was constructed by Kukekova et al [2007]. The map covered all 16 autosomes and chromosome X and the total length of the mapped genome was 1,480 cM with an average distance between the loci of 7.5 cM.…”