Rexoid and Sphynx Cats

Rexoid and Sphynx

The texture of most cats’ coat hairs is smooth and straight. However, certain cat breeds, such as the Selkirk and Devon Rex, are known for their unusual curly or woolly hair structure. The so-called “rexoid” distinctive of these cats is caused by a range of mutations to the gene for keratin 71 (KRT71). A related mutation, specific to the Sphynx cat, causes an almost total loss of hair instead.

The Selkirk Rex mutation, designated as SADRE or Re^S, results in tightly curled hair shafts, which form soft and woolly, unstructured curls in the fur. The Devon Rex mutation, designated as re, causes the coat to develop without guard hairs, resulting in a very short, soft and curly or wavy coat. The Sphynx hairlessness mutation, Re^hr, causes a total or near-total loss of body hair, as well as whiskers that tend to be short and broken. Please note that the hairlessness mutation of the Sphynx is the one occuring in the ‘regular’ or Canadian Sphynx, not the one causing hairlessness in the Russian Sphynx (Don Sphynx or Donskoy).

Another Rexoid coat, found in the Cornish Rex and German Rex, consists of only soft, short, wavy down hairs, lacking guard hairs and awn hairs. Unlike other examples here, it is not caused by a KRT71 mutation. Instead, the Cornish Rex coat is caused by a recessive mutation to the gene for the lysophosphatidic acid receptor 6 (LPAR6), designated as r.

Inheritance

The Re^S genotype (Selkirk Rex) is dominant over all other KRT71 alleles, and over the normal wild-type Re. Re^hr (Sphynx) and re (Devon Rex) are both recessive to the wild-type. Between these two, Re^hr is dominant over re.

It is unknown how the inheritance of LPAR6 (Cornish Rex) and KRT71 (Devon Rex, Selkirk Rex and Sphynx) mutations interact with each other.

Relevant tests

• K409
• K502
• K332