A polydactyl cat is a cat with a congenital physical anomaly called polydactyly (also known as polydactylism or hyperdactyly), which causes the cat to be born with more than the usual number of toes on one or more of its paws. Cats with this genetically inherited trait are most commonly found along the East Coast of North America (in the United States and Canada) and in South West England and Wales.
Polydactyly is a congenital abnormality that can be inherited in an autosomal dominant manner. Some cases of polydactyly are caused by mutations in the ZRS, a genetic enhancer that regulates expression of the sonic hedgehog (SHH) gene in the limb. [1] The SHH protein is an important signalling molecule involved in patterning of many body elements, including limbs and digits.
Normal cats have a total of 18 toes, with five toes on each fore paw, and four toes on each hind paw; polydactyl cats may have as many as nine digits on their front or hind paws. Both Jake, a Canadian polydactyl cat, and Paws, an American polydactyl cat, were recognised by Guinness World Records as having the highest number of toes on a cat, 28. [2] Various combinations of anywhere from four to seven toes per paw are common. [3] Polydactyly is most commonly found on the front paws only; it is rare for a cat to have polydactyl hind paws only, and polydactyly of all four paws is even less common. [4]
The condition seems to be most commonly found in cats along the East Coast of North America (in the United States and Canada) [5] and in Western England and Wales. [4] Polydactyl cats have been extremely popular as ship's cats. [5] Although there is some controversy over whether the most common variant of the trait originated as a mutation in New England or was brought there from Britain, there seems to be agreement that it spread widely as a result of cats carried on ships originating in Boston, Massachusetts, and the prevalence of polydactyly among the cat population of various ports correlates with the dates when they first established trade with Boston. [5] Contributing to the spread of polydactyl cats by this means, sailors were long known to value polydactyl cats especially for their extraordinary climbing and hunting abilities as an aid in controlling shipboard rodents. [5] Some sailors thought they bring good luck at sea. [5] The rarity of polydactyl cats in Europe may be because they were hunted and killed based on superstitions about witchcraft. [5]
Genetic work studying the DNA basis of the condition indicates that many different mutations in the same ZRS area can all lead to polydactyly. [1]
Author Ernest Hemingway became a famous aficionado of polydactyl cats after a ship captain gave him a six-toed cat that he named Snow White. [6] [7] [8] Upon Hemingway's death in 1961, his former home in Key West, Florida, became a museum and a home for his cats, and it currently houses approximately 50 descendants of his cats (about half of which are polydactyl). [8] Because of his love for these animals, polydactyl cats are sometimes referred to as "Hemingway cats". [8] [9]
Nicknames for polydactyl cats include Hemingway cats, [8] [9] mitten cats, [8] conch cats, boxing cats, mitten-foot cats, snowshoe cats, boston-toed cats, thumb cats, six-fingered cats, and Cardi-cats. Two specific breeds recognized by some cat fancier clubs are the American Polydactyl and Maine Coon Polydactyl.
American Polydactyl cats are bred as a specific cat breed, with specific physical and behavioral characteristics in addition to extra digits. [10]
The American Polydactyl is not to be confused with the pedigree Maine Coon Polydactyl. The polydactyl form of the Maine Coon is being reinstated by some breeders. [11] [ self-published source? ]
 | This section is missing information about patterns of inheritance.(January 2021) |
In the case of preaxial polydactyly of the Maine Coon cat (Hemingway mutant) a mutation of the cis-regulatory element ZRS (ZPA regulator sequence) is associated. ZRS is a noncoding element, 800 kilobasepairs (kb) remote to the target gene SHH. An ectopic expression of SHH is seen on the anterior side of the limb. Normally SHH is expressed in an organiser region, called the zone of polarizing activity (ZPA) on the posterior limb side. From there it diffuses anteriorly, laterally to the growth direction of the limb. In the mutant mirroring smaller ectopic expression in a new organiser region is seen on the posterior side of the limb. This ectopic expression causes cell proliferation delivering the raw material for one or more new digits. [12] [13] An identical sequence at this position serves the same function in human and mice and cause similar symptoms when mutated. Different mutations have different specific effects: for example, while the Hemingway (Hw) mutant tends to mostly induce extra fingers in the fore limbs, many other mutations affect the posterior limbs too. [1]
Polydactyly is a spontaneous complex phenotypic variation, developed in one generation. In the concrete preaxial form of the Hemingway (Hw) mutant the variation is induced by a single point mutation in a noncoding cis-regulatory element for SHH. In an extensive phenotypic variation like this, one or more complete digits at each single limb are developed including nerves, blood vessels, muscles and ligaments. The physiology of the digits can be perfect. This complex phenotypic result cannot be explained by the mutation alone. The mutation can only induce the variation. In the consequence of the mutation, thousands of events, each different from the wildtype, occur on different organisation layers, such as expression changes of other genes, cell-cell signal exchange, cell differentiation, cell and tissue growth. The summarized small random changes on all layers build the raw material and the process steps for the generation of the plastic variation. [3] The mentioned form of polydactyly of the Hemingway mutant shows a biased variation. In a recent empirical study first the number of extra toes of 375 mutant Maine Coon cats were variable (polyphenism) and second, the number of extra toes followed a discontinuous statistical distribution. They were not equally distributed as one might expect of an identical single point mutation. The example demonstrates that the variation is not explained completely by the mutation alone. [3]
The Maine Coon is a large domesticated cat breed. One of the oldest natural breeds in North America, the breed originated in the U.S. state of Maine, where it is the official state cat.
Polydactyly or polydactylism, also known as hyperdactyly, is an anomaly in humans and non-human animals resulting in supernumerary fingers and/or toes. Polydactyly is the opposite of oligodactyly.
In biology, dactyly is the arrangement of digits on the hands, feet, or sometimes wings of a tetrapod animal. The term is derived from the Greek word δακτυλος meaning "finger."
Sonic hedgehog protein (SHH) is encoded for by the SHH gene. The protein is named after the video game character Sonic the Hedgehog.
A paw is the soft foot-like part of a mammal, generally a quadruped, that has claws.
The Silkie is a Chinese breed of chicken named for its atypically fluffy plumage, which is said to feel like silk and satin. The breed has several other unusual qualities, such as black skin and bones, blue earlobes, and five toes on each foot, whereas most chickens have only four. They are often exhibited in poultry shows, and also appear in various colors. In addition to their distinctive physical characteristics, Silkies are well known for their calm and friendly temperament. It is among the most docile of poultry. Hens are also exceptionally broody, and care for young well. Although they are fair layers themselves, laying only about three eggs a week, they are commonly used to hatch eggs from other breeds and bird species due to their broody nature. Silkie chickens have been bred to have a wide variety of colors which include but are not limited to: Black, Blue, Buff, Partridge, Splash, White, Lavender, Paint and Porcelain.
A squitten is a cat with a genetic deformity which causes a partial formation or complete absence of the radius bone making it resemble a squirrel. These cats should be kept indoors and seen to by specialist veterinarians, as long term management of the condition is essential for quality of life in these cats. It is an example of a cat body type genetic mutation. The word is a portmanteau of squirrel and kitten.
In genetics, expressivity is the degree to which a phenotype is expressed by individuals having a particular genotype. Alternatively, it may refer to the expression of a particular gene by individuals having a certain phenotype. Expressivity is related to the intensity of a given phenotype; it differs from penetrance, which refers to the proportion of individuals with a particular genotype that share the same phenotype.
Zinc finger protein GLI3 is a protein that in humans is encoded by the GLI3 gene.
Greig cephalopolysyndactyly syndrome is a disorder that affects development of the limbs, head, and face. The features of this syndrome are highly variable, ranging from very mild to severe. People with this condition typically have one or more extra fingers or toes (polydactyly) or an abnormally wide thumb or big toe (hallux).
The apical ectodermal ridge (AER) is a structure that forms from the ectodermal cells at the distal end of each limb bud and acts as a major signaling center to ensure proper development of a limb. After the limb bud induces AER formation, the AER and limb mesenchyme—including the zone of polarizing activity (ZPA)—continue to communicate with each other to direct further limb development.
Limb development in vertebrates is an area of active research in both developmental and evolutionary biology, with much of the latter work focused on the transition from fin to limb.
Limb region 1 protein homolog is a protein that in humans is encoded by the LMBR1 gene.
Diplopodia is a congenital anomaly in tetrapods that involves duplication of elements of the foot on the hind limb. It comes from the Greek roots diplo = "double" and pod = "foot". Diplopodia is often found in conjunction with other structural abnormalities and can be lethal. It is more extreme than polydactyly, the presence of extra digits.
Acropectoral syndrome is an autosomal dominant skeletal dysplasia syndrome affecting the hands, feet, sternum, and lumbosacral spine. A recently proposed candidate gene for preaxial polydactyly is LMBR1, encoding a novel transmembrane receptor, which may be an upstream regulator of SHH. The LMBR1 gene is on human chromosome 7q36.
Polydactyly in stem-tetrapods should here be understood as having more than five digits to the finger or foot, a condition that was the natural state of affairs in the earliest stegocephalians during the evolution of terrestriality. The polydactyly in these largely aquatic animals is not to be confused with polydactyly in the medical sense, i.e. it was not an anomaly in the sense it was not a congenital condition of having more than the typical number of digits for a given taxon. Rather, it appears to be a result of the early evolution from a limb with a fin rather than digits.
Polysyndactyly is a congenital anomaly, combining polydactyly and syndactyly, in which affected individuals have an extra finger or toe that is connected, via fusing or webbing, to an adjacent digit.
In evolutionary biology, developmental bias refers to the production against or towards certain ontogenetic trajectories which ultimately influence the direction and outcome of evolutionary change by affecting the rates, magnitudes, directions and limits of trait evolution. Historically, the term was synonymous with developmental constraint, however, the latter has been more recently interpreted as referring solely to the negative role of development in evolution.
Familial opposable triphalangeal thumb duplication is a limb malformation syndrome and a type of pre-axial polydactyly, characterized by having duplicated opposable triphalangeal thumbs. This condition can be a symptom of other genetic disorders, such as Holt–Oram syndrome and Fanconi anemia. This trait is autosomal dominant and often runs in families. Sometimes big toe duplication, post-axial polydactyly, and syndactyly of the hand and feet can occur alongside this malformation Approximately 20 families with the condition have been described in medical literature.
Several sources I checked recounted the story you told, that ships' captains carried them onboard because they were considered lucky (and better mousers, one source said). An article from Cornell University's Cat Watch (1998) looked at studies done on polydactyl cats from the 1940s to the 1970s, and tentatively concluded that the trait probably initially occurred in cats who came over from England to the Boston area with the Puritans in the mid 1600s. There was also speculation in the article that the mutation might have developed in cats already in the Boston area [...] In Europe, polydactyl cats are rare because they were practically wiped out during medieval times due to superstitions about witchcraft (Kelly, Larson, 1993).
In fact, polydactyl cats are often referred to as 'Hemingway Cats'.
