What is the Himalayan gene?
The Himalayan gene is a mutation on the C locus on chromosome A1. This genetic trait is also characterised by its heat sensitivity, which presents as darkened points (face, ears, legs and tail) and a pale body, known as ‘pointed’. In addition to the characteristic coat, the Himalayan gene also contributes to the blue eye colour seen in these cats.
Siamese cats are the most recognised pointed breed. However, the Himalayan gene is also found in the Ragdoll, Birman (another ancient breed believed to have originated from matings between Siamese and longhaired cats), and Himalayan (pointed Persian). There are a number of additional breeds that allow colourpoint in the breed standard, and the Himalayan gene can even show up in random-bred cats. Cats who carry this gene are referred to as pointed, or in some cases, colourpoint. The most well-recognised pointed colour is the ‘seal point’. This colour consists of dark brown to black points on the face, ears, lower legs and tail. Genetically, the seal point is a black cat, but the Himalayan gene inhibits the colour on warmer parts of the body.
Tyrosinase is an enzyme essential for melanin production, the key pigment responsible for colour in a cat’s skin, hair, and eyes. In cats with two copies of the Himalayan, tyrosinase fails to operate effectively at normal body temperatures. It only manifests in the cooler areas of the body, like the nose, ears, paws, and tail, leading to their distinctive colour points. The Himalayan gene is denoted as c^s or c^h, resulting from a mutation of the original gene c. The mutation makes the enzyme tyrosinase thermosensitive—active and capable of producing melanin at lower temperatures, but inactive at higher temperatures.
This gene is similar to the one found in guinea pigs, rabbits, mice and rats and has two different but similar alleles on the C locus, which are c^s and c^b, contributing to the colourpoint features in Siamese.
History
The Himalayan gene gained prominence with the Siamese breed. The Siamese cat, originally from Thailand (formerly Siam), is one of the oldest and most recognisable cat breeds. Historical records and artwork suggest that pointed cats resembling Siamese were present in Siam several centuries ago, but it wasn’t until the late 19th and early 20th centuries that they were introduced to the Western world and became popular in cat shows.
The spread of the Himalayan gene in other cat breeds began with intentional breeding programs. Breeders sought to combine the striking pointed coat pattern of the Siamese with the features of other breeds. One notable example is the Himalayan cat, which originated from crossing Siamese cats with Persian cats to blend the colourpoints of the former with the long, luxurious fur of the latter.
Throughout the 20th century, as the understanding of genetics advanced, the mechanisms behind the Himalayan gene became clearer. Geneticists were able to identify the specific mutation responsible for the temperature-sensitive pigment production, shedding light on how this unique coat pattern is inherited and expressed in cats.
Today, the Himalayan gene is not only a subject of interest in the world of cat breeding but also serves as an important model in genetic studies, helping scientists understand how genes can influence physical traits and how these traits can vary between different species. The beauty and uniqueness of the Himalayan pattern continue to captivate cat enthusiasts and contribute to the diversity and appeal of the feline world.
The gene itself is named after the Himalayan rabbit, which was one of the first animals in which this colour pattern was scientifically described.
Understanding cat genetics
DNA, or deoxyribonucleic acid, is a molecule that carries the genetic instructions for the growth, development, functioning, and reproduction of cats (and all living organisms). Within the feline genome, specific genes determine coat colour, and the interplay of genes gives us a wide spectrum of coat colours and patterns.
One important player in cat colouration is the C locus, which is a specific location on a chromosome where genes related to pigment production are located. Genes on the C locus are primarily responsible for the production and distribution of melanin, the pigment that gives colour to a cat’s fur, skin and eyes.
The C locus includes several alleles, or different forms of a gene, that can result in a wide range of colours and patterns. These alleles can be dominant or recessive, and it is the combination of these alleles inherited from both parents that determines the colouration of the cat. For instance, an allele for black fur might be dominant over one for red fur, resulting in a predominantly black-coated cat. The Himalayan gene is recessive, which means the cat must inherit a copy of the gene from each parent for the cat to exhibit the trait.
The Himalayan gene
Unlike full albinism, which is characterised by a complete lack of pigment resulting in all-white fur and pink eyes. Partial albinism caused by the Himalayan gene allows for some colour to appear in the fur. This particular gene is a variation within the series of alleles found at the C locus, which is influential in determining the presence and intensity of melanin—the pigment responsible for colouration in animals.
The Himalayan ‘mutation’ is a point mutation. A point mutation means there is a change in a single nucleotide base in the DNA sequence. This mutation alters the structure of the tyrosinase enzyme in such a way that it becomes temperature-sensitive and only functions properly at lower temperatures. This is why cats with this mutation have darker fur on the cooler parts of their bodies and lighter fur elsewhere.
Genetic impact on health
The Himalayan gene is not directly associated with specific health issues. However, Siamese and related breeds can be prone to strabismus (cross-eyes) and nystagmus (involuntary eye movements). Pleiotropy occurs when a single gene affects multiple physical traits. In the case of Siamese and related cats, the gene responsible for their colour-point pattern might also influence the development of neural pathways related to eye positioning.
Burmese cb gene
The “cb” gene in Burmese cats is part of the albino series of genes, which includes C (full colour), c (albino), ca (caramel albino), and cs (Himalayan gene). The Burmese gene, denoted as cb, is responsible for the distinct coat colouration seen in the Burmese breed.
The cb gene causes a reduction in pigment, resulting in the characteristic sable or dark brown colour of Burmese cats. Unlike the Himalayan or cs gene, which leads to a pointed pattern, the cb gene produces a more uniform colour distribution across the body.
This gene does not make the tyrosinase enzyme temperature-sensitive. This means that the enzyme can function at normal body temperatures, allowing for more consistent pigment production throughout the body.
Genetically, the cb gene is considered an intermediate form between the C (full colour) and cs (Himalayan) genes. When a cat inherits one copy of the cb gene and one of the cs gene (cb/cs), it displays the colouration known as the Tonkinese pattern, which is intermediate between Burmese and Siamese – darker than Siamese but with some colour gradation.
Which cat breeds have the Himalayan gene?
While the Siamese is the most well-known cat, many other breeds also carry the Himalayan gene. This includes the Ragdoll, Birman and Himalayan. These breeds can only display the Himalayan colouration. Other breeds within the cat fancy are permitted to be pointed include:
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