Selkirk Rex: morphological and genetic characterization of a new cat breed

Abstract

Rexoid, curly hair mutations have been selected to develop new domestic cat breeds. The Selkirk Rex is the most recently established curly-coated cat breed originating from a spontaneous mutation that was discovered in the United States in 1987. Unlike the earlier and well-established Cornish and Devon Rex breeds with curly-coat mutations, the Selkirk Rex mutation is suggested as autosomal dominant and has a different curl phenotype. This study provides a genetic analysis of the Selkirk Rex breed. An informal segregation analysis of genetically proven matings supported an autosomal, incomplete dominant expression of the curly trait in the Selkirk Rex. Homozygous curl cats can be distinguished from heterozygous cats by head and body type, as well as the presentation of the hair curl. Bayesian clustering of short tandem repeat (STR) genotypes from 31 cats that represent the future breeding stock supported the close relationship of the Selkirk Rex to the British Shorthair, Scottish Fold, Persian, and Exotic Shorthair, suggesting the Selkirk as part of the Persian breed family. The high heterozygosity of 0.630 and the low mean inbreeding coefficient of 0.057 suggest that Selkirk Rex has a diverse genetic foundation. A new locus for Selkirk autosomal dominant Rex, SADRE, is suggested for the curly trait.

Figure 1.

Phenotypes of the Selkirk Rex. (a) Adult heterozygous Selkirk Rex male, short-haired variety. The head morphology and ear type of the heterozygous cat are more desired. (b) Adult homozygous Selkirk Rex. The head morphology and bigger ears of a homozygous curled cat are not desired by the breed standard. (c) Desired curly coat of a heterozygous curled cat. (d) Not desired curly coat of a homozygous cat is more similar to Cornish Rex marcel wave.

Figure 2.

Pedigree of Selkirk Rex cats segregating for curled hair type. Cats with filled symbols are heterozygous curled; cats with stippled symbols are homozygous curled. Cats in parentheses did not have their DNA sampled and have unconfirmed parentage, however completed the represented litters.

Figure 3.

Population genetics assessment of the Selkirk Rex breed. (a) Bayesian clustering of 30 recognized cat breeds at K = 3. The Selkirk Rex clusters within the Western I group. Sokoke and Turkish Van, denoted by * and ** respectively, are breeds that group within Western II at K = 3 but form their distinct groups at higher K values. (b) Bayesian clustering of 19 Western breeds at K = 15. Selkirk Rex clusters with breeds that belong to the Persian family. (c) Principal component analysis of the Persian family breeds. (d) Principal component analysis of the Selkirk Rex breed, which shows the geographic distribution of the breed (BSH: British Shorthair, PER: Persian, ESH: Exotic Short Hair, S. Fold: Scottish Fold, S. Rex: Selkirk Rex).