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Archive - Jul 26, 2015

DNA Studies Show That Inbreeding Is Likely Not the Cause of Decline in Bighorn Sheep Population in Colorado’s Rocky Mountain National Park

The health of Colorado's bighorn sheep population remains as precarious as the steep alpine terrain the animals inhabit, but a new study led by researchers at the University of Colorado Boulder (CU-Boulder) has found that inbreeding--a common hypothesis for a recent population decline--likely is not to blame. Bighorn herds tend to be small and isolated in their mountain ecosystems, putting the animals at high risk for a genetic "bottleneck," said Catherine Driscoll, a graduate student in the Department of Ecology and Evolutionary Biology at CU-Boulder and lead author of the study. Previous research has shown that inbreeding can weaken a population's immunity to disease across subsequent generations. However, after using mitochondrial DNA data to analyze a diverse set of hereditary markers, researchers found that all five native herds in Colorado’s Rocky Mountain National Park (RMNP) are maintaining healthy levels of genetic variation compared to other bighorn populations across the western United States. "There's been enough gene flow between the herds, primarily due to high ram migration, that the population has been genetically rescued," Ms. Driscoll said. The new findings, which were published in the July 2015 issue of the Journal of Wildlife Management, suggest that other factors, such as nutritional deficiencies, habitat fragmentation, and competition from encroaching mountain goats may play a more significant role in depressing bighorn population growth. The article is titled “A Tale of Two Markers: Population Genetics of Colorado Rocky Mountain Bighorn Sheep Estimated from Microsatellite and Mitochondrial Data.” The researchers used DNA testing to examine genetic diversity across five separate RMNP herds.

Researchers Unravel How TOPLESS Co-Repressor in Plants Interacts with Other Molecules to Turn Genes Off; Work Provides a General Model for Type of Gene Silencing

Scientists at Van Andel Research Institute (VARI), in Grand Rapids, Michigan, have revealed an important molecular mechanism in plants that has significant similarities to certain signaling mechanisms in humans, which are closely linked to early embryonic development and to diseases such as cancer. In plants, as in animals and humans, intricate molecular networks regulate key biological functions, such as development and stress responses. The system can be likened to a massive switchboard--when the wrong switches are flipped, genes can be inappropriately turned on or off, leading to the onset of diseases. Now, VARI scientists have unraveled how an important plant protein, known as TOPLESS, interacts with other molecules responsible for turning genes off. The findings in plants provide a general model across species for this type of gene silencing, which is linked to several vital biological functions in humans. The discovery was published in the July 3, 2015 issue of Science Advances. The article is titled "Structural Basis for Recognition of Diverse Transcriptional Repressors by the TOPLESS Family of Corepressors." This is really a fundamental discovery--our structure shows the co-repressor TOPLESS interacting with key repressor motifs, which constitutes a major component of gene silencing in plants," said Van Andel Research Institute's Karsten Melcher, Ph.D., one of the study's corresponding authors. "Understanding this interaction in plants gives us unique insight into similar pathways in humans that involve these proteins, which are notoriously tough to investigate." Using X-ray crystallography, the team determined the three-dimensional structure of TOPLESS, both on its own and when linked with other molecules responsible for turning genes off, thereby regulating gene expression.