Homozygosity for Mobile Element Insertions Associated with WBSCR17 Could Predict Success in Assistance Dog Training Programs

Abstract

Assistance dog training programs can see as many as 60% of their trainees dismissed. Many training programs utilize behavioral assays prior to admittance to identify likely successful candidates, yet such assays can be insconsistent. Recently, four canine retrotransposon mobile element insertions (MEIs) in or near genes WBSCR17 (Cfa6.6 and Cfa6.7), GTF2I (Cfa6.66) and POM121 (Cfa6.83) were identified in domestic dogs and gray wolves. Variations in these MEIs were significantly associated with a heightened propensity to initiate prolonged social contact or hypersociability. Using our dataset of 837 dogs, 228 of which had paired survey-based behavioral data, we discovered that one of the insertions in WBSCR17 is the most important predictor of dog sociable behaviors related to human proximity, measured by the Canine Behavioral Assessment Research Questionnaire (C-BARQ©). We found a positive correlation between insertions at Cfa6.6 and dog separation distress in the form of restlessness when about to be left alone by the owner. Lastly, assistance dogs showed significant heterozygosity deficiency at locus Cfa6.6 and higher frequency of insertions at Cfa6.6 and Cfa6.7. We suggest that training programs could utilize this genetic survey to screen for MEIs at WBSCR17 to identify dogs with sociable traits compatible with successful assistance dog performance.

Keywords: Canis; domestication; genetics; hypersociability; transposons.

Figure 1

The variable importance measures (VARIMP) for dogs of age 1–5 years for (A) loci Cfa6.6, Cfa6.7, and Cfa6.83 for separation distress; (B) loci Cfa6.6, Cfa6.7, and Cfa6.83 for attachment and attention-seeking; (C) all four loci for separation distress; and (D) all four loci for attachment and attention-seeking. VARIMP measures were computed using conditional random forests with 20,000 bootstrap samples.

Figure 2

Heat map depicting beta values for associations between Cfa6.6, Cfa6.7, Cfa6.66, and Cfa6.83 MEI copy number and C-BARQ© scores assessing lower social interest in strangers (Q3, Q9, Q13, Q15), higher hypersociability (Q22, Q23, Q24, Q25, Q26), and lower attentional bias (Q29 and Q32) for (A) all dogs of 1–5 years of age (n = 117); (B) pet dogs of 1–5 years of age (n = 69); (C) pet dogs >5 years of age (n = 95); (D) all dogs owned for >1–5 years (n = 115); (E) pet dogs owned from 1–5 years (n = 65); and (F) pet dogs owned >5 years (n = 96). Significant beta values (p < 0.05) are marked with an asterisk (*). See Table S2 for more details on each insertion. C-BARQ©: Canine Behavioral Assessment Research Questionnaire; MEI: mobile element insertion.

Figure 3

Mean and variation of C-BARQ© scores of behavioral types for assistance (n = 49) and pet (n = 69) dogs for (A) stranger-directed aggression; (B) dog-directed fear; and (C) energy. Bar graphs display the frequency of the inserted allele at each locus: (D) Cfa6.6; (E) Cfa6.7; (F) Cfa6.66; and (G) Cfa6.83.

Figure 4

Frequency of the inserted allele within the divergent and recent-radiation breed groups, respectively, at each locus: (A) Cfa6.6; (B) Cfa6.7; (C) Cfa6.66; and (D) Cfa6.83.