There has been much research into the genes which influence the coat type coat in dogs. Most of the research suggests there are three main genes involved: RSPO2, FGF5 and KRT71. These are responsible for:
Furnishings refer to the hair around the face resulting in a moustache and eyebrows. It's commonly seen in the Australian Cobberdog. The gene responsible is R-spondin-2 (RSPO2) on chromosome 13. This gene is involved in the pathway, which is essential in developing hair follicles.
Dogs with furnishings carry at least one copy of an allele containing an insertion after the coding region. It is believed the gene is dominant, as only one copy is needed to produce furnishings. It was probably originally from a mutation, as it hasn't been found in wild dogs.
The original function of the gene appears to be affected, which influences the stability of mRNA transcripts. These transcripts are what proteins are made from. Thus, going on to influence hair growth. There is a lot of research into the gene; it's believed to be responsible for more than just providing furnishings.
In the Australian Cobberdog, it is standard for the breed to have facial furnishings. Therefore, a lack of this gene, or more precisely, a lack of insertion after the coding region, results in incorrect furnishings or improper coat.
There is nothing wrong with the coat of the dog, despite the term, improper coat. It merely means the coat is not correct for the breed. Often these coats tend to shed, which is not suitable for people with asthma or allergies.
Curly hair is linked with the gene Keratin (KRT71). In dogs, only one mutation of this gene has been identified and linked to the amino acid R151W. The KRT171 gene produces a type II keratin, expressed in the inner root sheath.
It's important in forming straight filaments within the hair structure. Therefore a mutation in this gene will produce a curly coat.
Fibroblast Growth Factor-5 gene (FgF5) is responsible for the expression of long hair seen in the Australian Cobberdogs. The gene produces a protein responsible for regulating the hair cycle. In long-haired dogs, the mutation of this gene results in a change of the amino acid C95F.
This amino acid is believed to impair the function of the protein. FGF5 is found at the base of the hair follicle. The loss of function of this gene means the hair growth cycle is longer, resulting in longer hair.
There are various combinations of these genes which can produce differing results. All short-haired breeds carry the wild type alleles - short, straight coat, no furnishings.
Dogs with RSPO2 and KRT71 mutations have curly wire hair which is longer and curled with a similar wire feel as wire-haired dogs.
Dogs with FGF5 and RSPO2 mutations have long hair with furnishings, but the coat is soft rather than a wire coat. (I think most of ours fall into this category with some carrying one copy of below).
Dogs with FGF5 and KRT71 mutations have long curly hair.
Other genes of interest in the Australian Cobberdog are described below.
Black hair follicular dysplasia is an autosomal recessive trait which affects the hair. It is a type of hair loss (alopecia) which only affects black hair. Puppies are born with normal-looking black hair. However, it often begins to dull, becomes brittle and breaks easily over time.
The white hair is usually unaffected. Black hair fails to grow, and the skin can sometimes become scaly. Often the abnormal hair follicles can become infected. Black hairs will not grow back or be replaced with normal hairs.
The gene MC5R is responsible for the level of shedding and influencing coat length. The MC5R gene needs to be considered alongside the RSPO2 gene.
The wild type allele is responsible for producing:
The mutant allele is responsible for:
The combination of this gene and RSPO2 results in differing levels of shedding. In longer hair breeds, dogs are likely carrying:
The gene responsible for coat composition is CFA28. It's responsible for whether there is a single or double coat.
Primary or guard hairs:
Single coated dogs only have primary hairs and as such, tend to shed less. Double coated dogs often shed more. This is because the undercoat is more likely to fall out with the seasons.