Some features of learning in swimming Morris test in rats selected for behavior towards human

Some features of learning in Morris water test were studied in gray rats after a long-term selection for elimination (tame strain) and enhancement (aggressive strain) of aggressiveness towards human. The content of plasma corticosteroids was estimated at different stages of learning. It was shown that tame rats were better in performance of a special Morris task than aggressive ones. The time of search for invisible platform was increased in aggressive rats owing to the fact that they spent more time near the pool walls. Also, time of rearing at the platform was higher in tame rats compared to aggressive animals. In the retention test, rats of both strains spent significantly more time in the target quadrant than they did in other quadrants. Rats of both strains did not differ in time of search for invisible platform when it was replaced to the opposite quadrant. After the first day of learning, the corticosteroid plasma level was lower in tame rats than aggressive animals. During the following days of training, the content of the hormone increased in tame rats and did not differ from aggressive rats. It is supposed that, in tame rats, low emotionality and stress response facilitated learning in Morris water test.     

Genetic regulation of canine skeletal traits: trade-offs between the hind limbs and forelimbs in the fox and dog

Genetic variation in functionally integrated skeletal traitscan be maintained over 10 million years despite bottlenecksand stringent selection. Here, we describe an analysis of thegenetic architecture of the canid axial skeleton using populationsof the Portuguese Water Dog Canis familiaris) and silver fox(Vulpes vulpes). Twenty-one skeletal metrics taken from radiographsof the forelimbs and hind limbs of the fox and dog were usedto construct separate anatomical principal component (PC) matricesof the two species. In both species, 15 of the 21 PCs exhibitedsignificant heritability, ranging from 25% to 70%. The secondPC, in both species, represents a trade-off in which limb-bonewidth is inversely correlated with limb-bone length. PC2 accountsfor approximately 15% of the observed skeletal variation, 30%of the variation in shape. Many of the other significant PCsaffect very small amounts of variation (e.g., 0.2–2%)along trade-off axes that partition function between the forelimbsand hind limbs. These PCs represent shape axes in which an increasein size of an element of the forelimb is associated with a decreasein size of an element of the hind limb and vice versa. In mostcases, these trade-offs are heritable in both species and geneticloci have been identified in the Portuguese Water Dog for manyof these. These PCs, present in both the dog and the fox, includeones that affect lengths of the forelimb versus the hind limb,length of the forefoot versus that of the hind foot, musclemoment (i.e., lever) arms of the forelimb versus hind limb,and cortical thickness of the bones of the forelimb versus hindlimb. These inverse relationships suggest that genetic regulationof the axial skeleton results, in part, from the action of genesthat influence suites of functionally integrated traits. Theirpresence in both dogs and foxes suggests that the genes controllingthe regulation of these PCs of the forelimb versus hind limbmay be found in other tetrapod taxa.     

Genetic Architecture of Tameness in a Rat Model of Animal Domestication

A common feature of domestic animals is tameness—i.e., they tolerate and are unafraid of human presence and handling. To gain insight into the genetic basis of tameness and aggression, we studied an intercross between two lines of rats (Rattus norvegicus) selected over >60 generations for increased tameness and increased aggression against humans, respectively. We measured 45 traits, including tameness and aggression, anxiety-related traits, organ weights, and levels of serum components in >700 rats from an intercross population. Using 201 genetic markers, we identified two significant quantitative trait loci (QTL) for tameness. These loci overlap with QTL for adrenal gland weight and for anxiety-related traits and are part of a five-locus epistatic network influencing tameness. An additional QTL influences the occurrence of white coat spots, but shows no significant effect on tameness. The loci described here are important starting points for finding the genes that cause tameness in these rats and potentially in domestic animals in general.ANIMAL domestication marked a turning point in human prehistory (Diamond 2002), and domestic animals have been the subject of research for many years (Darwin 1868). Recently, genetic studies have shed light on when, where, and how often a range of animal species were domesticated (Troy et al. 2001; Vila et al. 2001; Savolainen et al. 2002; Larson et al. 2005; Driscoll et al. 2007; Eriksson et al. 2008; Naderi et al. 2008). With the exception of coat color (e.g., Pielberg et al. 2008) and skin pigmentation (Eriksson et al. 2008), little is known about what occurred genetically during animal domestication. At what genes were allelic variants selected for by would-be practitioners of animal husbandry? Although domestic animals differ from each other in many ways, they all share the trait of tameness—i.e., they tolerate and sometimes even seek human presence and handling. Almost nothing is currently known about the genetic basis of tameness.In a series of studies initiated by D. K. Belyaev, researchers at the Institute for Cytology and Genetics in Novosibirsk (Russia) have subjected several mammalian species to a process of experimental domestication (Trut 1999). These studies, some of them ongoing for several decades, involve selection for tame and aggressive behavior in lines of animals derived from wild populations. They include a fox population that has been “domesticated” to such an extent that the tame foxes are now similar to dogs in some respects (Hare et al. 2005). They also include a population of wild-caught rats (Rattus norvegicus) that was selected for either reduced or enhanced aggression toward humans over >60 generations (Belyaev and Borodin 1982). To select the animals, their response to an approaching human hand was observed, and the rats showing the least and the most aggressive behavior were allowed to mate within the two lines, respectively. The initial response to selection was rapid and then slowed, so that little change in behavior from generation to generation has been observed in the last 10–15 generations, although the selection regime has been continued to the present. Today, the “tame” rats are completely unafraid of humans, they tolerate handling and being picked up, and they sometimes approach a human in a nonaggressive manner. By contrast, the “aggressive” rats ferociously attack or flee from an approaching human hand.To study the genetic basis of tameness we have established populations of both rat lines in Leipzig. In their new environment, the rats maintained their behavioral differences in response to humans, and these differences were not influenced by postnatal maternal factors (Albert et al. 2008). In addition, the rat lines differ in a number of other behavioral, anatomical, and physiological traits, raising the question whether these traits are influenced by the same loci as tameness and aggression toward humans.Many domestic animals display conspicuous coat color variations not found in their wild relatives. Prominent examples include the white color variants in dogs, pigs, cows, horses, and chickens. In laboratory rats, it has been proposed that “coat color genes” may account for many of the differences associated with domestication (Keeler and King 1942). It is thus interesting that individuals with white spots appeared in both the tame foxes (Trut 1999) and the tame rats (Trut et al. 2000) at higher frequency than in the corresponding aggressive lines, although they were absent or rare in the founding fox and rat populations, and although they were not selected for. The rat populations studied here provide an excellent opportunity to examine whether tameness is influenced by the same loci as white coat spotting.In this study, we crossed the two rat lines and bred >700 intercross animals. A broad set of behavioral, anatomical, and physiological traits was measured, and a genomewide set of genetic markers was used to identify genomic regions (quantitative trait loci, QTL) that influence tameness as well as other traits that differ between the lines, including white spots.     

A marker set for construction of a genetic map of the silver fox (Vulpes vulpes)

The silver fox, a variant of the red fox (Vulpes vulpes), is a close relative of the dog (Canis familiaris). Cytogenetic differences and similarities between these species are well understood, but their genomic organizations have not been compared at higher resolution. Differences in their behavior also remain unexplained. Two silver fox strains demonstrating markedly different behavior have been generated at the Institute of Cytology and Genetics of the Russian Academy of Sciences. Foxes selected for tameness are friendly, like domestic dogs, while foxes selected for aggression resist human contact. To refine our understanding of the comparative genomic organization of dogs and foxes, and enable a study of the genetic basis of behavior in these fox strains, we need a meiotic linkage map of the fox. Towards this goal we generated a primary set of fox microsatellite markers. Four hundred canine microsatellites, evenly distributed throughout the canine genome, have been identified that amplify robustly from fox DNA. Polymorphism information content (PIC) values were calculated for a representative subset of these markers and population inbreeding coefficients were determined for tame and aggressive foxes. To begin to identify fox-specific single nucleotide polymorphisms (SNPs) in genes involved in the neurobiology of behavior, fox and dog orthologs of serotonin 5-HT1A and 5-HT1B receptor genes have been cloned. Sequence comparison of these genes from tame and aggressive foxes reveal several SNPs. The close relationship of the fox and dog enables canine genomic tools to be utilized in developing a fox meiotic map and mapping behavioral traits in the fox.     

Morphology of hair pigmentation in wild red foxes,silver foxes,and their hybrids

The effects of dominant allele Ar of locus Agouti on the morphology of hair pigmentation were described in foxes. The Ar allele was shown to determine the type of melanin and its content in hair with no effect on the morphology of pigment granules and their distribution throughout a hair. Using the method of electron spin resonance (ESR), the types of melanin (eumelanin and pheomelanin) and their content in the hair of red (ArArEE) and silver (aaEE) foxes and their hybrids (AraEE) were determined. In silver foxes, only one type of melanin (eumelanin) was found. In red foxes and their hybrids (which are phenotypically similar but darker than red foxes), both types of melanin (eu- and pheomelanin) were found. The highest melanin content was detected in the coat of silver foxes. In the hybrids, the total melanin content was lower than in silver foxes, but significantly higher than in red foxes. In red foxes, the contribution of pheomelanin to the total hair melanin content was twice as large as in the hybrids.     

A xyloglucan-specific endo-beta-1,4-glucanase from Aspergillus aculeatus: expression cloning in yeast, purification and characterization of the recombinant enzyme

A full-length c-DNA encoding a xyloglucan-specific endo -beta-1, 4- glucanase (XEG) has been isolated from the filamentous fungus Aspergillus aculeatus by expression cloning in yeast. The colonies expressing functional XEG were identified on agar plates containing azurine-dyed cross-linked xyloglucan. The cDNA encoding XEG was isolated, sequenced, cloned into an Aspergillus expression vector, and transformed into Aspergillus oryzae for heterologous expression. The recombinant enzyme was purified to apparent homogeneity by anion- exchange and gel permeation chromatography. The recombinant XEG has a molecular mass of 23,600, an isoelectric point of 3.4, and is optimally stable at a pH of 3.4 and temperature below 30 degreesC. The enzyme hydrolyzes structurally diverse xyloglucans from various sources, but hydrolyzes no other cell wall component and can therefore be considered a xyloglucan-specific endo -beta-1, 4-glucanohydrolase. XEG hydrolyzes its substrates with retention of the anomeric configuration. The Kmof the recombinant enzyme is 3.6 mg/ml, and its specific activity is 260 micromol/min per mg protein. The enzyme was tested for its ability to solubilize xyloglucan oligosaccharides from plant cell walls. It was shown that treatment of plant cell walls with XEG yields only xyloglucan oligosaccharides, indicating that this enzyme can be a powerful tool in the structural elucidation of xyloglucans.