Genomic Differences Between Dog Breeds

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Genomic Differences Between Dog Breeds

http://www.medicalnewstoday.com/medicalnews.php?newsid=34697

As any dog lover knows, no two breeds are identical. Some dogs are

perfect for sloppy kisses. Others make fierce guardians. Still others

resemble tiny, fluffy toys. Now, two new studies by scientists at The

Institute for Genomic Research (TIGR) and collaborators reveal the

genomic differences beneath such canine characteristics.

In the December issue of Genome Research--a special issue devoted to

dog genomes--TIGR researchers Ewen Kirkness and Wei Wang compared the

genome sequences of two dogs, a standard poodle and a boxer. Finding

key genetic differences between the two dogs, the researchers went on

to compare those telltale genetic variations in the genomes from nine

additional dog breeds--beagle, Labrador retriever, German shepherd,

Italian greyhound, English shepherd, Bedlington terrier, Portuguese

water dog, Alaskan malamute, and rottweiler--and five genomes of wild

canids (four types of wolves and a coyote).

" This work demonstrates a significant amount of variation that you

can see between individual dogs at the genomic level, " says Kirkness,

lead investigator of the project, funded by TIGR. " That variation can

now be exploited to study the differences between dogs, their

diseases, development and behaviors. " More broadly, Kirkness adds,

the comparisons illustrate evolutionary influences that can shape

mammalian genomes.

In the study, the scientists first compared the two most complete

canine genomes available. Those genomes belong to Shadow, a standard

poodle whose genome was published by TIGR in 2003, and Tasha, a boxer

sequenced by the Broad Institute of Cambridge, Massachusetts, in

2004.

To compare Shadow's and Tasha's genomes, the researchers tracked

short interspersed elements (SINEs)--stretches of DNA that occur

randomly in the genomes of many organisms. SINEs are inserted near or

within genes, often turning the expression of those genes up, down or

even off. The scientists found that the poodle and boxer differed in

their content of SINEs at 10,562 locations in their genomes.

Broadening the study to compare SINEs among the additional nine dog

breeds and five wild canids, the scientists estimated that the

overall dog population contains at least 20,000 SINE differences.

To genomics researchers, variable SINEs can act as signposts for

specific genes linked to disease or traits. The dog is a unique

genomics model. Through selective breeding of dogs, humans have

created the highest degree of physical and behavioral differences

seen within a species. Roughly 400 dog breeds exist, with specific

breeds predisposed to heart disease, cancer, blindness, deafness and

other common disorders. Identifying genes responsible for diseases or

physical traits may be easier to do in dogs that have been

genetically selected.

In a second study, published in the December 8 issue of Nature,

researchers from 15 institutions describe a high-resolution draft of

the boxer genome. This work includes a high resolution map of canine

single nucleotide polymorphisms (SNPs), based largely on a comparison

of the boxer and poodle sequences. Eventually, Kirkness predicts,

efforts to document genetic differences between dogs will lead to

major health gains for the animals. And perhaps us, too: A dog genome

is estimated to include some 19,300 genes--nearly all corresponding

to similar human genes.

The Institute for Genomic Research is a not-for-profit center

dedicated to deciphering and analyzing genomes. Since 1992, TIGR,

based in Rockville, Md., has been a genomics leader, conducting

research critical to medicine, agriculture, energy, the environment

and biodefense.

The Institute for Genomic Research

http://www.tigr.org