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DLA-CHARACTERIZATION AND ITS IMPORTANCE TO THE BEARDED COLLIE

DLA-CHARACTERIZATION AND ITS IMPORTANCE TO THE BEARDED COLLIE

Researchers have recently started to study a genomic region called MHC (major histocompatibility complex) to understand canine diseases known or suspected to be genetically inheritable. In canines, the MHC region is called DLA and in humans it is called HLA. The genes in the region are known to participate in immune responses and immune-mediated diseases. The MHC region is known to favour diversity, unlike most of the rest of the genome that prefers to remain unchanged. Individuals have different forms of genes, called alleles, in the genomic region.

Many immunological diseases have been shown to be related to the genes of MHC-region. Polymorphism and diversity are needed in the region, and thus there should be as many different variants of MHC genes as possible within a breed. Other immunological problems, such as allergies, may also occur more frequently if polymorphism has decreased. When the MHC region is more polymorphic, the body is likely to be more resistant to bacteria and viruses. Some alleles have already been shown to be associated with specific autoimmune diseases; in humans e.g. rheumatism, SLE and MS-disease.

A haplotype is a combination of several alleles which is inherited as a unit. In DLA-tests, a combination of three genes from the MHC region is studied, namely DRB1, DQA1 and DQB1. This haplotype is the most polymorphic in its region. Each dog has two of these haplotypes in its genotype, one inherited from the sire and the other from the dame. If the two haplotypes are different, the individual is heterozygote, and if they are the same, then the individual is homozygote. Homozygote dogs are thus less polymorphic. A dog can pass on only those haplotypes that it has in its genotype.

Several combinations can be built from haplotypes. Haplotype frequencies are typically expressed as percentages of the portion of the haplotype in the studied population. The more variation in the breed genome, the more haplotypes there are. The number of haplotypes is not enough for good diversity, the haplotypes should also distribute evenly in population. If some haplotype is rarely expressed, it is in danger of disappearing. If some haplotype is expressed frequently, there are likely more homozygous dogs. If the number of dogs used in breeding is large and they are used evenly, the disappearance of alleles is slower.

In 2009 the Finnish Bearded Collie Club co-operated with a research group in Helsinki University to undertake a study of genetic diversity of the Bearded Collie. In the study, 77 dogs were selected for analysis, representing as many bloodlines as possible. Some relatedness was unavoidable due to the known breed history of registered Bearded Collies in U.K. This analysis has been reported already and is found in http://www.suomenpartacolliet.info/DLA_raporttiEnglish.pdf.

More testing has been done since the initial study, and the number of tested dogs is 156 as of 3.1.2011. The DLA status of additional 9 dogs has been derived from the results of their parents and offspring. This makes a total of 165 dogs, most of them residing in Finland and registered in the Finnish Kennel Club register. The results are listed in http://kesannon.fi/files/App1_030111.pdf. Analysis reveals seven different haplotypes, named Parta1-Parta7 for brevity. This is a reasonable number of haplotypes, but the genetic diversity is less than one might expect since the frequency of the two most common haplotypes is approximately 75%. The frequencies of the haplotypes in the studied population are presented in http://kesannon.fi/files/App2_030111.pdf..

The low variation in polymorphism is also seen as a high number of homozygote dogs, approximately 30% of the studied population. Except for one dog, the homozygotes are Parta1 or Parta2 dogs. The exception is Parta3 type. Table 1 (below) gives in detail the seven haplotypes found in the studies Bearded Collie population. The numbers given refer to the alleles of genes, for example DQA1-gene has three different alleles; 00101, 00601 and 00901.

Table 1. Haplotypes found among the studied registered Bearded Collie population.
Haplotype DRB1 DQA1 DQB1
Parta1 01801 00101 00201
Parta2 01801 00101 00802
Parta3 00901 00101 00802
Parta4 01501 00601 00301
Parta5 01501 00601 02301
Parta6 00201 00901 00101
Parta7 01501 00601 02201

Although the analysis has been mainly done of the Bearded Collie population residing in Finland, it is very likely that knowing the background and ancestors of the studied dogs, the situation may be quite similar in other countries as well. A short overview shows that:
- only 18% of the studied dogs are bred from Finnish parents,
- of tested and analysed dogs, 27% were not born in Finland,
- of tested and analysed dogs born in Finland, 44% has one of the parents imported to Finland
- of tested and analysed dogs born in Finland 111% has both of the parents imported to Finland

Thus, altogether 82% of the population was either imported or the parents were imported to Finland. This makes it possible that the distribution of the haplotypes in many other counties is similar.

In addition to the registered Bearded Collies that have been tested, Dr Lynne Sharpe of Brambledale kennel has tested haplotypes of three of her dogs. Of these, B. Breeze has two generations of working Beardie sires, B. Blodyn’s dame is B. Breeze and a third working Beardie sire. The third tested dog is Briery Glen, a working Bearded Collie, who is not closely related to the previous ones. These three dogs have been added in the tables linked above. In short, the Brambledale-born mother and daughter possess less common haplotypes. Especially interesting is that both haplotypes of Briery Glen have not been previously found among registered, tested Bearded Collies (haplotypes described in http://kesannon.fi/files/App1_030111.pdf). This gives us hope that by using Bearded Collies from working lines and using the individuals in a sensible way in breeding, the diversity of the genome could be increased.
For those interested in the health records of Brambledale-dogs, refer to http://www.spanglefish.com/brambledalebeardedcollies/index.asp?pageid=15...

References:
http://www.suomenpartacolliet.info/DLA_raporttiEnglish.pdf
http://www.koiranjalostus.fi/ENG_articles.html
http://www.suomenpartacolliet.info/DLA_KOONTI2010paivitetty12_2010.pdf
http://jalostus.kennelliitto.fi/frmEtusivu.aspx