SATIN, GLITTER AND GRIZZLE IN CATS
I am indebted to Frank Whittenburg for his investigation into the satin-on-solid gene manifested by his Tennessee Rex cats and the use of his photographs..
In 1986, Wright and Walters noted in their "Book of the Cat" that satin was a highly sought after mutation in cats. This mutation, seen in mice and other rodents, gave a pearly sheen to the coat. Until recently, the closest breeders had to a satin effect was found in Siamese and Oriental cats. Their close-lying fur had a silky light-reflective sheen, though far less pronounced than the satin gene in rodents and probably due to polygenes rather than a single gene mutation.
In the Russian Blue, each hair should have a silvery tip, giving a sheen to the coat. In the 1990s, there was correspondence in cat magazines as to whether this was due to translucent "hollow" tips to the fur. The hollow hair-tip was declared undesirable in the breed.
In the 1990s, a sparkling white coat was developed on a short-lived British breed known as the Suqutranese by crossing Somalis with white shorthairs. The effect was due to translucent banding of the white hair-shaft. The breed's demise appeared due to the description of the cats as "white Somali-type," leading to antipathy from Somali breeders and a narrow-minded cat fancy in Britain (who released a statement condemning the cats). Hair from the Suqutranese was not microscopically examined, but was described as white with translucent banding. It could be recreated by crossing white shorthairs with Somalis and the fur examined.
With no confirmed glitter gene mutations in cats, even the cat breeders' bible "Robinson's genetics for Cat Breeds (4th Ed)! Has nothing to say on the matter.
Chausie breeders also noticed a form of glitter which they termed "grizzle". Silver-tipped black is found in melanistic Jungle Cats (F chaus) and in the Chausie breed derived from Jungle Cat hybrids. This affects the hair tip and not the entire hair shaft. The Grizzle gene has not been fully investigated, but appears to have been introduced from melanistic Jungle Cats. Silver tipped black is seen in Jungle Cats.
Bengal breeders had noted an effect called "glitter" on some of their cats. This became desirable within the Bengal breed. On the brown Bengals, the effect was of "gold dust" (termed "golden glitter") while on silver Bengals it had a pearly effect. Although solid black Bengals sometimes occur due to recessive genes, the glitter effect seemed confined to the patterned Bengals and has been traced to an Indian cat used in the foundation stock. Two different types of glitter were posited - "mica" (affecting the tips only) and "satin" (affecting the whole shaft).
In August 2004, cat lover Franklin Whittenburg in the Tennessee Valley in the Chattanooga area took in a straight-coated feral female and her 3 kittens, of which 2 had curly fur. In addition to their rex coats, the 2 kittens exhibited the coveted "satin" mutation. When the fur was viewed closely in direct sunlight, there appeared to be tiny little prisms along the length refracting the light into a rainbow spectrum. This effect is currently termed "satin-on-solid" to differentiate it from the satin associated with patterned Bengals although Whittenburg prefers the term "satin-on-rex" as the satin gene currently appears inseparable from the curled fur. Because data on satin-coated cats is lacking, Frank Whittenburg investigated the cause of the satin effect and likely manifestations through discourse with rodent breeders. He found two degrees of satinization: satin and radical satin (the latter being analogous to the double-satinization in rodents).
Tennessee Rex photos courtesy F Whittenburg
Once a satin-on-solid mutation had been described and photographed, other cat breeders were more aware of what to look for. In England, Anthony Nichols reported a solid black 7 year old neutered male (Jasper) as having a satin coat. The possibility of a glittered black Bengal was ruled out and there was no way to reproduce the trait as the cat was neutered. Even if the parents could be mated again, there was no guarantee that this was not a mutation in Jasper himself. Hair from Jasper has not been investigated microscopically. It is possible that satin has turned up and been overlooked in other random-bred cats because the cats' owners didn't realise what they were looking at or because the cats (and their parents and siblings) had already been neutered by a cat rescue group, preventing the gene from being perpetuated.
TYPES OF GLITTER AND SATIN
In the Bengal, breeders have identified 2 apparent types of glitter: glitter and mica. Initially it was thought to be a single recessive glitter gene termed "gl", but microscopic studies of hair types suggest there are 2 different types of glitter which are currently termed "Mica" and "Satin" by Bengal breeders. Mica glitter (recessive) affects the tips of hairs and results in reflective hair-tips with what appear to be small flecks of mica (a highly reflective silicate crystal) embedded in the tip and visible under a microscope. Unlike the satin mutation (which affects the length of the hair shaft), mica only affects the hair-tip. This type of glitter was present in a domestic cat used in Jean Mill's original hybrids between Asian Leopard Cats and domestics.
Above is a New Zealand Satin Rex mutation. A neutered household pet with a single patch of rexed/shiny fur on the shoulders. This effect has been observed in one other neutered pet cat. Below are photos of two satin rexes born in Mackay, Queensland, Australia in 2016. The curls have decreased with age and the satin has increased. These came from a litter of 4 kittens that came into Kim Gale's pet shop. Their parents are unknown. All 4 kittens were rexed. Two were 2 desexed immediately and Kim decided to invesigate the rex and satin with the other two as they had been compared to the Tennessee rex. Golden Gale is a short hair rex female with pronounced attin/glitter in her coat. Her sister, Twisted Gale, is a longhair rex girl and the satin is best seen on her legs. Both have had curly-haired kittens and it remains to be seen if these kittens lose the curl and inherit the satin fur.
Satin, or satin glitter, (recessive) affects the whole of the hair shaft. This type of mutation is found in fancy rodents (in some species, homozygous satin results in balding). The hair shaft contains air pockets along its length. These refract light and give the coat a pearlised effect also termed "oyster". The hair is soft, smooth and silky as a result of the air pockets in the hair shaft. The longer the air pockets, the softer and silkier the fur. Found in Bengals, Oriental-type cats and, to a limited degree, in straight-coat variants of Tennessee Rexes.
Left: Cream Satin. Right: Red Satin. Tennessee Rex photos courtesy F Whittenburg
In the Tennessee Rex, the satin (which appears to behave as a recessive) on the original rex-coated males males is manifesting as a reflective coating material similar to oyster shell on the hair-shaft. It isn’t yet known whether a single gene mutation produces both effects, or whether there are 2 mutated genes situated close to each other, that have so far been inherited together. At first, these were thought to be "air pockets" in the hair shaft that that refracted light rather than simply reflecting it. Closer examination of the satin on the original Tennessee Rex males showed a reflective coating material similar to oyster shell on the hair shaft along with triangular ridges. Straight haired offspring showed some air-pockets. Normal cat hair has a relatively solid core of pigment. Satin Tennessee Rex hair has looser, irregular bands of pigment while glittered Bengal hair has more tightly packed pigment granules forming a narrower core. Hairs from crosses of satin Tennessee Rex x glittered Bengal more closely resemble those of the Bengal than the Tennessee Rex.
At first, it was thought that Tennessee Rex Satin was related to the recessive Bengal “Glitter” mutation. A satin-coated Tennesse Rex test-mated to a high glitter Bengal female had a normal shiny coat, but did not exhibit either Glitter or Satin. This proved the mutations were different. The kittens were all neutered and not used in either breed. An outcross of Tennessee Rex female to a domestic shorthair male also produced shiny-coated – but not Satin-coated – straight-haired offspring. Carriers of the gene appear to exhibit a degree of shine while the "radical satin" effect has appears restricted to the rex-coated individuals. The satin mutation may be linked to the rex mutation in the same way that Bengal glitter appears linked to the Bengal patterns. This is similar to the expression of Satin in mice where homozygous mice (2 copies of the recessive gene) are satin-coated, and heterozygous mice (1 copy of the gene) may show a lesser degree of satin. However, if all heterozygotes have a degree of satin then this is also the behaviour of a dominant gene with an additive effect - mild satin in heterozygotes and "radical satin" in homzygotes.
Tennessee Rex satinization can make creams appear brownish, pinkish or even bluish. Orange cats can have a blue cast, while agouti blacks can look silver. This is due to the way the light is reflected from the hairs. A more recently reported satin mutation, in Oregon, USA, produces a more prominent frosting, and blueing effect, with some kittens looking fever coated at birth.
INHERITANCE OF GLITTER AND SATIN
In the Bengal, the 2 posited types of glitter (satin glitter and mica) both show a recessive pattern of inheritance are seen only on patterned cats. Solid black Bengals are few and far between, but those that exist apparently lack either type of glitter (there may simply be too few of them to confirm this).
In the Tennessee Rex, satin appears linked to the rex mutation which is a recessive gene. At the time of writing, the Tennessee Rex cats are 2.5 years old and the satin-on-solid effect have mostly been seen on red cats, plus one straight-coated blue (grey) cat which had a "frosted" appearance. If this rainbow effect mutation were to occur in a white Tennessee Rex it would produce "oyster shell" or "pearl" colour that would be unique to the breed.
The mode of inheritance on Jasper, the 7 year old black cat, is unknown and, because the cat is neutered, cannot be determined. It is not possible to test-mate Jasper to a Tennessee Rex. It is also not known (at least at the present time) whether either parent was satin-coated; whether they were normal-coated but able to produce satin-coated offspring (a recessive satin mutation) or whether the mutation occurred within Jasper himself and not his parents (in which case probably a dominant mutation).
In the Suqutranese, the sparkling effect appeared due to the interaction of epistatic white and agouti banding. This could be recreated, but there appears to be prejudice against the breed/type.
It is not known what the future holds for the satin-on-solid gene or the Tennessee Rex. The mutation itself is stunning and the new breed is extremely attractive. Conceivably some breeders may wish to explore satin in straight-coated cats derived from Tennessee Rexes and in all colours and fur lengths. There is the possibility that some breeders may want to create "satinized" versions established breeds in the same way that some envisaged short-legged versions of those breeds. At present there are only a few satin-coated cats in existence and more breeders required to perpetuate the trait in the Tennessee Rex breed before even considering its possible introduction into other breeds.