|Horse Genome Assembled
Data on Equine Genome Freely Available to Researchers
Bethesda, Md.— The first draft of the horse genome sequence
has been deposited in public databases and is freely available
for use by biomedical and veterinary researchers around the globe,
leaders of the international Horse Genome Sequencing Project announced
The $15 million effort to sequence the approximately 2.7 billion
DNA base pairs in the genome of the horse (Equus caballus)
was funded by the National Human Genome Research Institute (NHGRI),
one of the National Institutes of Health (NIH). A team led by Kerstin
Lindblad-Toh, Ph.D., at the Eli and Edythe L. Broad Institute of
the Massachusetts Institute of Technology and Harvard University,
in Cambridge, Mass., carried out the sequencing and assembly of
the horse genome.
Approximately 300,000 Bacterial Artificial Chromosome (BAC) end
sequences, which provide continuity when assembling a large genome
sequence, were contributed to the horse sequencing project by Ottmar
Distl, D.V.M., Ph.D. and Tosso Leeb, Ph.D., from the University
of Veterinary Medicine, in Hanover, Germany and Helmut BlŲcker,
Ph.D., from the Helmholtz Centre for Infection Research in Braunschweig,
Germany. Production of the BAC end sequences was funded by the
Volkswagen Foundation and the State of Lower Saxony.
Sequencing of the domestic horse genome began in 2006, building
upon a 10-year collaborative effort among an international group
of scientists to use genomics to address important health issues
for equines, known as the Horse Genome Project (www.uky.edu/Ag/Horsemap/).
The horse whose DNA was used in the sequencing effort is a Thoroughbred
mare named Twilight from Cornell University in Ithaca, N.Y. Researchers
obtained the DNA from a small sample of the animalís blood. To
download a high-resolution photo of Twilight, go to http://www.genome.gov/pressDisplay.cfm?photoID=20008.
Twilight is stabled at the McConville Barn, Baker Institute for
Animal Health, College of Veterinary Medicine, at Cornell University,
with a small herd of horses that have been selected and bred for
more than 25 years to study the mechanisms that prevent maternal
immunological recognition and destruction of the developing fetus
during mammalian pregnancy. The research, conducted by Cornell
professor Doug Antczak, V.M.D, Ph.D., and funded by the National
Institute of Child Health and Human Development, has implications
in reproduction, clinical organ transplantation and immune regulation.
In addition to sequencing the horse genome, researchers produced
a map of horse genetic variation using DNA samples from a variety
of modern and ancestral breeds, including the Akel Teke, Andalusian,
Arabian, Icelandic, Quarter, Standardbred and Thoroughbred. This
map, comprised of 1 million signposts of variation called single
nucleotide polymorphisms, or SNPs, will provide scientists with
a genome-wide view of genetic variability in horses and help them
identify the genetic contributions to physical and behavioral differences,
as well as to disease susceptibility. There are more than 80 known
genetic conditions in horses that are genetically similar to disorders
seen in humans, including musculoskeletal, neuromuscular, cardiovascular
and respiratory diseases. The SNPs are available at the Broad Institute
web site (www.broad.mit.edu/mammals/horse/snp)
and will be available shortly from NCBIís Single Nucleotide Polymorphism
database, dbSNP (www.ncbi.nlm.nih.gov/SNP).
The initial sequencing assembly is based on 6.8-fold coverage
of the horse genome, which means, on average, each base pair has
been sequenced almost seven times over. Researchers can access
the horse genome sequence data through the following public databases:
at NIH's National Center for Biotechnology Information (NCBI);
NCBI's Map Viewer (www.ncbi.nlm.nih.gov);
UCSC Genome Browser (www.genome.ucsc.edu) at the University of California
at Santa Cruz; and the Ensembl Genome Browser (www.ensembl.org)
at the Wellcome Trust Sanger Institute in Cambridge, England. The
data is also available from the Broad Institute Web site (www.broad.mit.edu/ftp/pub/assemblies/mammals/horse/).
Over the next several months, researchers plan to further improve
the accuracy of the horse genome sequence and expect to deposit
an even higher resolution assembly in public databases. Comparing
the horse and human genomes will help medical researchers learn
more about the human genome and will also serve as a tool for veterinary
researchers to better understand the diseases that affect equines.
A publication analyzing the horse genome sequence and its implications
for horse population genetics is being planned for the future.
To learn more about the expanding field of comparative genomics,
go to http://www.genome.gov/11509542.
A complete list of organisms and their sequencing status can be
viewed at www.genome.gov/10002154.
NHGRI is one of the 27 institutes and centers at the National
Institutes of Health, an agency of the Department of Health and
Human Services (DHHS). Additional information about NHGRI can be
found at its Web site, www.genome.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.