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 (and have been preserved) 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.

A great variety exists within rex rabbits. They vary from very dense and short-haired varieties (Standard Rex) to long-haired curly-haired breeds (Astrex).

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 (dek) gene. In 1927, yet another short-hair rabbit was discovered in the hutches of the French breeder Madame Du Bary, a fancier of Himalayan (ch-) rabbits. This breed was called Normannen-Kurzhaar and is due to the r3 (nok) 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 mutation in the gene LIPH (Lipase Member H), a gene associated with alopecia, hair loss phenotypes, in humans. A deletion of a single nucleotide was found in LIPH of rex rabbits. 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 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.

There are four main internationally recognised rex breeds: Cornish Rex, Devon Rex, LaPerm, and Selkirk Rex.

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