Abstract
A growing number of studies have explored the oxytocin system in humans and non-human animals, and some have found important genetic polymorphisms in the oxytocin receptor gene (OXTR) associated with the bonding system, social behaviors, and personality in several species. Although single nucleotide polymorphisms in OXTR have been well-examined in various species, microsatellites (or short tandem repeats) adjacent to OXTR have rarely been studied, despite some suggestions that microsatellite polymorphisms near genes might play a role in genetic transcription and translation. In this study, we surveyed microsatellites in the upstream, intron, and downstream regions of OXTR in domestic cats (Felis catus). We succeeded in amplifying 5 out of 10 regions, and recognized these five regions as polymorphic. We compared allele frequencies in these five regions between mongrel cats in Japan (n = 100) and cats of 10 pure breeds (n = 40). There were significant differences in allele frequencies between the two populations in all microsatellite regions. Additionally, the owners of mongrel cats answered a comprehensive personality questionnaire, and factor analysis extracted four factors (Openness, Friendliness, Roughness, and Neuroticism). We examined the association between the microsatellite genotypes, age, sex, neutering status, and personality scores. Compared to their counterparts, younger cats tended to score higher on Openness, male cats scored higher on Friendliness, and female and neutered cats scored higher on Roughness. When we divided the sample into three groups depending on the length of alleles, we found a marginally significant association between Friendliness and MS3. Additionally, we found a sex-mediated effect of genotypes in MS4 on Friendliness, resulting in different effects on females and males. Our findings that mongrel cats had longer alleles in MS3 and MS4 than purebred cats, and that those cats tended to score higher on Friendliness, supported the previous findings. However, future studies such as comparison between purebred cats with apparently different origin or personality are required to determine the association of genetic variants in the OXTR with personality.
Highlights
Many studies focusing on the oxytocin system in humans have revealed that some genetic polymorphisms are associated with a large variety of individual differences in, for example, empathy (e.g., Rodrigues et al, 2009; Wu et al, 2012; Laursen et al, 2014), attachment anxiety (e.g., Chen and Johnson, 2012), prosociality (e.g., Shang et al, 2017), and pair-bonding behavior (e.g., Walum et al, 2012)
We considered oxytocin receptor gene (OXTR) genotypes and the effects of age, sex, and neutering on cat personality, and sex-mediated effects connected with OXTR, as suggested in human studies (e.g., Stankova et al, 2012)
Linkage Disequilibrium among Five Microsatellite Loci All five regions were polymorphic in both cat groups
Summary
Many studies focusing on the oxytocin system in humans have revealed that some genetic polymorphisms are associated with a large variety of individual differences in, for example, empathy (e.g., Rodrigues et al, 2009; Wu et al, 2012; Laursen et al, 2014), attachment anxiety (e.g., Chen and Johnson, 2012), prosociality (e.g., Shang et al, 2017), and pair-bonding behavior (e.g., Walum et al, 2012). For OXTR in non-human primates, Staes et al (2014) tried to find genetic differences between chimpanzees and bonobos at the locus of rs53576 in the intron 3 region of OXTR, which had been shown to be involved in many associations in humans (e.g., Rodrigues et al, 2009; Laursen et al, 2014); they expected this locus would contribute to species differences in empathy between chimpanzees and bonobos They did not find polymorphism at this locus, they found novel polymorphisms near rs53576 in these two species.
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