Rex mutation


The rex mutation is a genetic variation in mammals that results in soft curly fur. These effects are due
to changes in the structure of groups of hairs and cross-section of individual hairs. The Rexed coats are unusual but occur in cats, rats, rabbits, horses, and dogs. The mutations, infrequent and spontaneous, occur in a variety of genes and genetic regulatory structures. The diversity of genetic factors results in variable coat thickness/density and fur length.

Rex rabbits

A great variety exists within rex rabbits. They vary from very dense and short-haired varieties to long-haired curly-haired breeds.
The rex rabbit was introduced in 1919 by Abbe Gillet from a spontaneous mutation. The next rex rabbit was discovered in the hutches of a breeder in Lübeck, Germany in 1926. This breed was originally called Deutsch-Kurzhaar and is due to the r2 gene. In 1927, yet another short-hair rabbit was discovered in the hutches of the French breeder Madame Du Bary, a fancier of Himalayan rabbits. This breed was called Normannen-Kurzhaar and is due to the r3 gene.
Of the 3 genetic sources of rex rabbits, the one due to the gene r1 is the most popular with fanciers and has the simple Mendelian inheritance pattern of autosomal recessive. It was not linked with any other genes known at the time although it was eventually found to be in the same linkage group as r2.
The phenotype of r1 and r2 is a completely normal coat but r1 or r2 alone produces a short coat with curly whiskers. Although the phenotypes are identical for each gene, the linkage distance was eventually worked out.

The gene r3 is independent of r1 and r2 in breeding tests so they fall on different chromosomes.
The mutation associated with r1 was recently studied using modern genetic tools. A deletion of a single nucleotide was found in LIPH of rex rabbits. In humans, this gene is associated with alopecia. This mutation results in a frameshift that causes the mRNA transcription machinery to sense the end of the gene prematurely. The stop codon generated by the deletion may be shortening the protein by 19 amino acids. The exact mechanism was not determined but the deletion is necessary and sufficient for the rex phenotype.
See more information about Oryctolagus cuniculis genetics here.

Rex cats

There are four main internationally recognised rex breeds: Cornish Rex, Devon Rex, LaPerm, and Selkirk Rex.
There are also a number of rarer, less well known or developing rex-coated breeds, including the German Rex, Ural Rex, Tennessee Rex, Tasman Rex group and Skookum. Spontaneous rexed variants have also been observed in breeds such as the Maine Coon and Persian as well as in random-bred cats such as the Ohio Rex, Oregon Rex and California Rex, however there has been no significant attempt to develop or seek recognition for these varieties and most have died out. A number of experimental breeds have been developed from the main 4 rex breeds, such as the German-bred Pudelkatze, now believed to be extinct. The Tennessee Rex is a natural mutation breed of cat dating back to 2004. It was discovered by Franklin Whittenburg.
Rex breeds vary considerably in appearance, from the elegant slender build of the Cornish Rex to the larger, cobby and heavy-boned Selkirk Rex. Each results from a separate mutation rather than being bred from a common ancestor. Each mutation causes the hair follicles to be oval in shape, instead of the normal regular round form, which results in hairs curling round as they grow instead of growing straight. Many of the other spontaneously occurring rex mutations have occurred and some have proven to be the same gene as the main four breeds. Some of those mutations, such as the Dutch Rex, were found to have unmanageable or unattractive fur and were not pursued as breeds.
The name Rex was taken from the Rabbit Fancy because the first rex cat breed to be developed, the Cornish Rex, has a coat similar to that of a rex rabbit, in that it comprises only the undercoat with no topcoat or guard hairs.

Named mutations

Rex Syrian Hamsters first appeared in the 1970s, it's characterised by Curly Whiskers and a Curly Coat, the curls in the coat are easily visible in Short Coated Hamsters but more difficult to see in Long Coated Hamsters.
Rex in Campbell Dwarf Hamsters isn't recorded as to when it first appeared. Unlike with Syrian Hamsters, the Rex Coat in Campbell is commonly very sparse and gives a bald appearance to it. The whiskers are curled.

Guinea pig