A female Abyssinian named Cinnamon who currently resides on campus at the University of Missouri in Columbia, USA, has helped make scientific history in the world of feline genetics.
Researchers have largely decoded the playful cat's DNA, a step that may aid the search for treatments for both feline and human diseases.
The new work is reported in the November issue of the journal Genome Research by a research team led by Stephen O'Brien and Joan Pontius, both of the Laboratory of Genomic Diversity (LGD) at the National Cancer Institute in Maryland, USA.
Decoding The Genome
The full complement of an organism's DNA is called its genome. In cats, as in people, it's made up of nearly 3 billion building blocks. The sequence of those blocks spells out the hereditary information, just as strings of letters spell out sentences. Decoding a genome, which is called sequencing, means identifying the order of the building blocks.
The new work identified 20,285 genes in the cat, probably about 95 percent of the animal's full complement. That's similar to the 20,000-25,000 genes estimated for humans.
Light Genome Sequencing
Cinnamon's genome was decoded used the so-called "shotgun" technique. The cat's DNA was extracted, chopped into overlapping fragments, each piece was sequenced and then reassembled into continuous stretches.
The process must be repeated several times to get the sequence correct, and the number of repetitions determines how complete the genome will be. For example, the dog genome was done with 7.5 repetitions making it almost 99 per cent complete. By contrast, Cinnamon's "light" genome sequence was produced with just 1.9 passes, covering just 65% of the gene-coding regions. The team filled in the blanks using extensive gene marker maps and analogous regions from the more complete dog and human genomes.
Having the cat genome is an exciting resource, says Leslie Lyons at the University of California, Davis, US, who studies breeding, hereditary blindness, and heart and kidney disease in cats. However, light coverage does have drawbacks, she says. "With a two times sequence it's very limited. We are certainly not complaining, but it is frustrating to think that maybe only 60 to 80% of the gene you are looking for will be there."
A team at the Washington University Genome Sequencing Center in St. Louis
is planning to increase the cat genome to a six-fold draft
Cinnamon was chosen for the project because she is highly inbred, and so has fewer differences between her two sets of chromosomes. That makes assembling the sequence easier. The team tested many cats "and Cinnamon won the lottery", says O'Brien.
Cats May Benefit People
The information learned from decoding the feline DNA may eventually be of benefit to humankind. Cats can contract more than 200 diseases that resemble human illnesses. Knowing the specifics of feline genetic makeup may help in the search for vaccines and treatments that may be extrapolated to help combat human diseases. Stephen J. O'Brien of the National Cancer Institute says the list of possible cat diseases that can be used as a model in investigating human health problems includes a cat version of AIDS, SARS, diabetes, influenza, retinal diseases and spina bifida.
Decoding Mammalian DNA
Scientists have unraveled the DNA of more than two dozen different species of mammals so far. The list includes dogs, chimps, rats, mice, cows and of course, people.
Cats are among the 26 mammals selected by the National Human Genome Research Institute in the US for less complete or "light" genome sequencing