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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 (Poodle Cat), 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.

Hamster

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.

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Rex Cats

Cats the animal most commonly associated with the Rex mutation. There are four main internationally recognised Rex breeds: Cornish Rex, Devon Rex, LaPerm, and Selkirk Rex. The name Rex was taken from a Rabbit named "Fancy" that was discovered to have this mutation. 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 (Poodle Cat), 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.

Devon Rex Genetics

The most documented rexoid cat breeds are known as the Cornish Rex and the Devon Rex, with the Cornish Rex represented by the symbol “r” and the Devon Rex represented by the symbol “re" . While they both have the genetic aspect of autosomal recessive loci, the Devon Rex’s gene expression can vary more . In terms of appearance, both breeds have short hair length and thickness, as well as a coat without protective guard hairs and a reduced undercoat . The Devon Rex coat is considered abnormal, and consists of blunt intact hair fibers, and other fibers that are distally broken . Little information currently exists on the specific genes involved in the occurrence of the curly rex coat. However, more information became available after studies utilizing genome-wide SNP (small nucleotide polymorphism) association implicated the gene KRT71 in the curly coat of Portuguese Water Dogs . An SNP in this gene codes for a protein involved in the hair follicle’s inner root sheath, causing a mutation. After this discovery, mutations of the sequence of KRT71 were identified in the Devon Rex breed. In the Devon Rex breed, this gene mutation occurs due to a splicing error induced by two deletions and two insertions into the genetic code. The allelic designation for the Devon Rex mutation was designated as KRT71^re. Originally, mutations involving the KRT71 sequence were not identified in other rexoid cat breeds, but its influence was not ruled out due to a lack of investigation on intronic and regulatory regions of the gene. The gene would later be determined to be involved in the coat of the Selkirk Rex. Cornish Rex Genetics

The investigation into the Cornish Rex genome involved a homozygosity analysis that discovered several genes also occurring in humans and coding for hair texture, with one being LPAR6. Located on the chromosome A1, the LPAR6 gene functions to maintain hair shaft integrity by encoding a G-protein coupled receptor. In Cornish Rex cats, expression of the shortened version of this gene leads to deletions of 4 trans-membrane domains, 2 intracellular domains, and 3 extracellular domains. Mutations to this gene also inhibit binding of LPAR6 to the fat lysophosphatidic acid (LPA) that functions to develop and protect the hair follicle.

Selkirk Rex Genetics

Like the Devon Rex and Cornish Rex, the Selkirk Rex exhibits the same curled fur from the Rex mutation. Studies show inheritance of this trait to be autosomal dominant. The influence of the KRT71 protein on the Selkirk Rex resumed after studies reexamined the impacts in the context of keratin. Mutations to this protein can disrupt the formation of keratin filaments, causing an abnormal coat. The allele designation representing this specific mutation is called KRT71^SADRE. Rex Hamsters

Rex Syrian hamsters first appeared in the 1970s. It was characterised by curly whiskers and a curly coat, with the curls in the coat easily visible in short-coated hamsters but more difficult to see in long-coated hamsters. The Rex mutation in Campbell Dwarf hamsters wasn't recorded as to when it first appeared. Unlike with Syrian hamsters, the Rex Coat in Campbell hamsters is commonly very sparse and gives a bald appearance to the animal. The whiskers are curled and short.

The Rex mutation was observed in hamsters after an event of inbreeding for the purpose of studying the “smoky cast” coat in hamsters yielded offspring with the Rex coat. Further breeding exploiting the mutation resulted in a 3:1 ratio of normal coats to Rex coats, prompting researchers to conclude the Rex mutation as autosomal recessive. The Rex mutation in hamsters was assigned the symbol “rx”.