DLA diversity

DLA diversity test - following the immunogenetic diversity of the MHC locus in breeds and lines

Much of the genetic diversity of dogs is dimished or lost in many breeds due to aggressive breeding programs and closed inbred populations. Loss of genetic diversity threatens the welfare and vitality of dogs and may predispose them to various diseases.

An important part of this genetic diversity is related to genes, which are responsible for the effective and functional immune defense against viruses, parasites and other foreign pathogens in dogs. There are probaly hundreds if not thousands of genes involved in the functionality of the immune system in mammalian genome. One of the most important such gene cluster is called major histocompatibility complex (MHC) in the dog’s genome. MHC complex includes a large number of genes and lies in canine chromosome 6.

This MHC complex includes genes that are responsible for the recognition of the species own tissues from foreign material. Recognition is related to the genetic diversity and some of the genes in this region contain particulary hypervariable areas in their coding regions to maintain them as diverse as possible. The loss of diversity in the MHC region or inheritce of particular allele combinations may result in increased susceptibility to autoimmune diseases such as diabetes, atopia, hypothyroiditis and different forms of inflammatory disorders. Many canine autoimmune disorders have been already associated with risk haplotypes in the MHC locus and homozygosity to risk alleles or haplotypes seems to increase the disease risk. Heterozygosity is preferred in the MHC locus in wild population too.

We have now tools to type your dog’s MHC II genes (DLA typing) so that you can follow the diversity of your dogs and lines and use this important information while planning new breedings. It is useful to have a DLA-profile from your breed in differnet countries since the frequency of the alleles in the MHC genes may vary a lot between populations. Once the DLA-profile is established you could compare your dog's profile for the overall breed' or line's profile and take it into account while planning new breedings.

As a geenral rule it may be wise to avoid increasing homozygosity in the MHC locus containing a large number of important genes. There is a growing body of evidence that homozygosity in the MHC locus increases the risk for autoimmune disorders. It may be wise to choose a breeding partner that has different haplotypes to maintain heterozygosity and diversity in your litters and lines.

Since MHC locus is functionally important it is not neutral and lies under a selective pressure. Certain MHC haplotypes may not be allowed at all or may lead to inviablity. DLA typing tests sonly the MHC locus in one chromosome and although it provides important data that may also reflect the overall diversity of the breed it is recommened to test also other more neutral markers in other chromosomes for comparison. Due to selective pressure to maintain diversity the MHC locus may turn out to be more heterozygous than other part of the dog's genome.

Here is an example how to use the DLA diversity test:

1. Test and determines the three DLA genes (haplotypes) from your breeding

bitch and from the proposed 2-3 candidate sires.

2. Comapre bitch’s haplotypes wth each of the sires. Select the sire that has the most

different DLA haplotypes compared with the bitch for mating to enable different DLA combination in the litter. If the bitch and the stud have the same haplotypes, the litter will

inherit also the same genotypes increasing the risk for homozygosity.

DLA test can be only made from blood sample due to the complexity of the analysis that requires high quality DNA.

DLA profiling service for Breed Clubs

Before typing individual dog's it would be useful to have a public DLA-profile from the breed. We provide DLA-profiling services for Breed Clubs. We suggest to type about 50-100 unrelated dogs provided by the owners or the Club. We can also utilize samples collected in the Finnish Dog DNA bank in the University of Helsinki. After the analysis, the Breed Club will get haplotype profiles and frequencies. This information can be used to advise better and healthier breeding habits. The DLA-profile service takes usually at least 2-3 months to complete.

If your Club is interested in this service, please contact our Customer service. Several Clubs have already successully profiled their breeds with us.

Starting at 1.6.2010 we offer basically as follows: 5-30 dogs120 €/dog, 31-50 dogs 115 €/dog and 51-> dogs 110 €/dog (incl. VAT). Old offers are valid until 31.5.2010 and has to be confirmed hitherto.