Shadowy Rodent Has Potential To Shed Light On Human Genetics And The Mysteries O

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Shadowy Rodent Has Potential To Shed Light On Human Genetics And The

Mysteries Of Evolution

http://www.medicalnewstoday.com/medicalnews.php?newsid=51906

Purdue University research has shown that the vole, a mouselike

rodent, is not only the fastest evolving mammal, but also harbors a

number of puzzling genetic traits that challenge current scientific

understanding.

" Nobody has posters of voles on their wall, " said J. DeWoody,

associate professor of genetics in the Department of Forestry and

Natural Resources, whose study appears this month in the journal

Genetica. " But when it comes down to it, voles deserve more

attention. "

Small rodents often confused for mice, except with shorter tails and

beady eyes, voles live throughout the Northern Hemisphere and are

often considered agricultural pests because they eat vegetation.

Nevertheless, voles are an " evolutionary enigma " with many bizarre

traits, DeWoody said. Understanding the basis for these traits could

lead to better understanding of the same phenomena in human genetics

and genetic disorders, and could have implications for gene therapy,

he said.

The study focuses on 60 species within the vole genus Microtus, which

has evolved in the last 500,000 to 2 million years. This means voles

are evolving 60-100 times faster than the average vertebrate in terms

of creating different species. Within the genus (the level of

taxonomic classification above species), the number of chromosomes in

voles ranges from 17-64. DeWoody said that this is an unusual

finding, since species within a single genus often have the same

chromosome number.

Among the vole's other bizarre genetic traits:

-- In one species, the X chromosome, one of the two sex-determining

chromosomes (the other being the Y), contains about 20 percent of the

entire genome. Sex chromosomes normally contain much less genetic

information.

-- In another species, females possess large portions of the Y (male)

chromosome.

-- In yet another species, males and females have different

chromosome numbers, which is uncommon in animals.

A final " counterintuitive oddity " is that despite genetic variation,

all voles look alike, said DeWoody's former graduate student and

study co-author Deb Triant.

" All voles look very similar, and many species are completely

indistinguishable, " DeWoody said.

In one particular instance, DeWoody was unable to differentiate

between two species even after close examination and analysis of

their cranial structure; only genetic tests could reveal the

difference.

Nevertheless, voles are perfectly adept at recognizing those of their

own species.

" I have seen absolutely no evidence of mating between different

species, " Triant said. " We don't know how they do this, but scent and

behavior probably play a role. "

DeWoody said, " The vole is a great a model system that could be used

to study lots of natural phenomena that could impact humans. "

His research focuses on the mitochondrial genome, the set of DNA

within the cellular compartment responsible for generating energy

(the mitochondria). Some of Triant's additional work explores the

unique ability of vole's mitochondrial DNA to insert itself within

DNA in the cell nucleus. The nuclear genome, as it is known, contains

the vast majority of a cell's DNA and is responsible for controlling

cellular function and development.

" Deb's work in this area could potentially have some basic science

impact on gene delivery mechanisms, such as those used in gene

therapy, " DeWoody said.

In this relatively new therapy, treatment involves the insertion of a

gene into human patients' cells in order to counter some illness or

disease like hemophilia. However, it is often difficult to insert the

desired gene in the " correct " location, or a location where it does

what it is supposed to do. A better understanding of the unusual

prevalence of this activity in voles, and the manner in which it

happens, could have important human implications.

DeWoody's research was funded by the National Science Foundation and

the U.S. Department of Agricultural. DeWoody hopes to continue his

work on vole genetics at some point in the future.