Categories: Integument (skin) phene

Mendelian trait/disorder: unknown

Disease-related: no

Species-specific description: As summarised by Whitaker and Ostrander (2019), "Double-coated dogs have two layers of hair: the courser primary or guard hairs which aid in the prevention of superficial injuries, repel excess moisture, and provide the primary coloration and texture patterns; and the more numerous secondary hairs or undercoat which are soft and downy in appearance and protect dogs from extreme temperatures. Wolves, the closest living ancestor to the modern domestic dog . . . , also have both a primary coat and undercoat, and this is assumed to be the ancestral trait. Single-coated dog breeds only have primary hairs and thus usually shed less because the undercoat is more prone to falling out with the change of season. There are roughly equal numbers of breeds with double- and single-coats distributed throughout the 161 breeds for which extensive phylogenetic studies have been done [Parker et al., 2017]. Some breed groups, such as those of Alpine origin, have predominantly one phenotype, in this case the double coat."

Mapping: Whitaker and Ostrander (2019) mapped this trait to a small region of chromosome CFA28 with the highest peak at 24,866,296. Subsequent WGS "identified a locus of 18.4 kilobases containing 62 significant variants within the intron of a long noncoding ribonucleic acid (lncRNA) upstream of ADRB1. Multiple lines of evidence highlight the locus as a potential cis-regulatory module. Specifically, two variants are found at high frequency in single-coated dogs and are rare in wolves, and both are predicted to affect transcription factor (TF) binding."