A collaborative study led by UNL’s Jay Storz and his colleagues at Aarhus University in Denmark has been selected as The Journal of Experimental Biology Outstanding Paper of 2013.
In this paper, the UNL-Danish team reported that the blood of high-altitude ground squirrels has unusual respiratory properties that enable these animals to survive and function under low-oxygen conditions.
First-authorship of the prize-winning paper was shared by two graduate students, Inge Revsbech of Aarhus University — co-advised by Storz and his Danish collaborator, Angela Fago — and Danielle Tufts of UNL.
“This year’s winner stands out because it integrates mechanistic molecular understanding of a physiological process…and relates this understanding to an ecological context,” said Hans Hoppeler, the journal’s editor-in-chief.
Whether climbing to the tops of mountain peaks, running through subterranean burrow systems or taking a long winter’s nap, ground squirrels face serious challenges to respiratory gas transport due to the reduced availability of oxygen. These animals are therefore compelling subjects for studies of respiratory adaptations to low-oxygen conditions.
The research is important because it identified the specific mutations that are responsible for modifying the respiratory properties of hemoglobin, the protein in red blood cells that is responsible for transporting oxygen from the lungs to all the cells of the body.
The research also revealed the mechanisms that are responsible for altering blood biochemistry during winter hibernation. These changes help ground squirrels survive a period of suspended animation that is characterized by severely depressed ventilation — hibernating ground squirrels experience an extreme form of apnea where they take a single breath every 45 minutes. Having hemoglobin with an especially high oxygen-binding affinity helps maximize oxygen uptake during periods of apneic breathing.
“The hemoglobins have evolved some really unique properties,” Storz said. “The increased oxygen-binding affinity of their hemoglobin is an evolved property that is caused by a specific set of mutations.”
The surprise findings came when researchers cross-referenced the mutations to the hemoglobins of other species.
“One of the interesting things is that some of these mutations’ functional effects were completely unexpected, based on what we know about human hemoglobin,” Storz said. “The same mutations that produce beneficial effects in ground squirrel hemoglobins produce pathological effects in human hemoglobin.”
Mutations in human hemoglobin have been the subject of very detailed studies because they often cause disease, with sickle-cell anemia being one of the most well known.
Other UNL authors on the prize-winning paper include Hideaki Moriyama, associate professor; and Joana Projecto-Garcia, a postdoc in Storz’s lab.