Dilute Gen: Color Dilution Alopecia (CDA) beim Hund | Blue Line

Dilute Gen: Color Dilution Alopecia (CDA) beim Hund | Blue Line

In this article we would like to explain about the dilute gene and color dilution alopecia (CDA for short). In cooperation with Dr. Patrick Hensel from Tierdermatologie Basel, we have summarized the most important questions in the form of an interview and would like to provide you with the right information with the help of an animal dermatology expert.


What is the dilute gene?

Dog skin and coat color is determined by 2 types of melanin. That Eumelanin produces a black to dark brown color while Pheomelanin causes a red/yellow coloration. There are also other genes in different areas, called loci, that determine the distribution of melanin. There is e.g. B. S-Locus (white patches in the coat), M-Locus (merle coat), K-Locus (dominant black), D-Locus (dilution), etc. The dilute gene is therefore a gene that has been around for a very long time and represents a color variation. The dilute is often incorrectly labeled as a "genetic defect", which is completely wrong. Like Merle and Co., Dilute is a color variation. To be honest, it has to be said that science cannot yet provide definitive insights into the dilute gene. Many geneticists and veterinarians are therefore working intensively on research. It is currently believed to be the gene responsible for the production of melanophilin (MLPH). The task of MLPH is to advance the transport and distribution of the color pigment melanin. However, other genes are probably also involved, about which it has not yet been possible to gain sufficient knowledge.

How does the dilute gene come about?

We don't want to go that deep into genetics, but a little school knowledge from biology class is needed 🙂

If we look at a chromosome pair, it consists of two alleles. In doing so, he Locus represents the physical location where a particular gene resides, sort of the location of the gene. Let's think back to the M for a momentendel Laws, then, let's remember that it is related to color, for example recessive or dominant colors exist. This means that dominant colors are more likely to be passed on than recessive colors. So if the seeds of a red rose (R / dominant) are mixed with those of a white rose (r / recessive), the following color variations can result:

  • Genotype: RR and the rose turns red,
  • as well as in the genetic combination of Rr, because in this case too the rose will be phenotypically red, since red is the dominant gene,
  • only with the rr genotype does the rose become phenotypically white. 
The genotype is what is stored genetically and the phenotype is what is externally recognizable. Why we took this little excursion into school biology is quite simple: It's the same process that determines coat color in dogs.



Which animals are affected? 

This color dilution occurs in many different animal species and also occurs in a whole range of dog breeds. A classic example would be this Weimaraner and Slovak Pointer, the it only  with dilute colors there. Then there are dog breeds where it is relatively common (Italian Greyhounds, Whippets, Tibetan Mastiffs and Neapolitan Mastiffs). Then there is a whole range of dogs in which the dilute gene is rare, but has recently become more popular as a result of the trend (e.g. American Staffordshire Terrier, Great Dane, Shar Pei, Labrador, French Bulldog , Etc.)

Dilute gene and the disease of CDA

Dilute is no genetic defect, as it is always popular, but wrongly spread, but a color variation, which usually does not lead to any further problems. Due to the increased demand in recent years, a disease associated with the Dilute gene has emerged and goes by the name Color Dilution Alopecia (short: CDA) is known. With CDA, the dogs suffer from severe skin problems, shedding and itching. The skin becomes crusted and the dog's quality of life decreases. The reasons that lead to the development of CDA are not yet known.  In fact, not all dogs with color dilution (that is, the dilute gene) develop problems. For the most part, the dilute gene does not lead to CDA, but in Dobermans and some other breeds it is known that there is a particularly common link between CDA and the dilute gene.

In fact, there are many breeds that are bred exclusively in the Dilute colors and have not had any proven problems for generations (for example the Weimeraner). However, more and more gray or isabella/lilac dogs are developing CDA. The reasons are not yet entirely clear. The issue should be taken seriously, mainly the breeding and choice of the dog should be considered. Breeding itself can be an important indication. Especially in the last few years, the demand for gray dogs has increased enormously and there are many questionable dog sellers on eBay classifieds who offer almost exclusively gray dogs. Most providers have no idea about genetic processes and experiment around at the expense of the dog's health. Dogs from unreliable sources and from incomprehensible breeding can then develop CDA more frequently.

The fact that dilute colors pose minimal to no health concern in only a few seriously bred dogs suggests other, as yet unexplored, causes. Research currently assumes that CDA only occurs with a large number of various other mutations. With a selected breed, the probability that the puppies will develop CDA is very low.

    There are now some scientific texts dealing with CDA and Dilute. If you are interested in reading more, have a look here:

    • Polymorphisms within the canine MLPH gene are associated with dilute coat color in dogs: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1183202/
    • Color dilution alopecia in a blue Doberman pinscher crossbreed: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2671874/
    • Color–dilution alopecia in dogs: https://www.ncbi.nlm.nih.gov/pubmed/16131833
    • A Noncoding Melanophilin Gene (MLPH) SNP at the Splice Donor of Exon 1 Represents a Candidate Causal Mutation for Coat Color Dilution in Dogs: https://academic.oup.com/jhered/article/98/5/468/2187775
    • Chromosomal Assignment of the Canine Melanophilin Gene (MLPH): A Candidate Gene for Coat Color Dilution in Pinschers: https://academic.oup.com/jhered/article/96/7/774/2187651