The image shows a mouse's naval cavity. The green structure is the olfactory epithelium, a sheet of tissue, found in all animals, that hosts millions of odor-sensing neurons. Photo by Lu Yang/Washington University School of Medicine
Aug. 10 (UPI) -- Why did some mammals, like dogs, develop such a powerful sense of smell, while others, like humans, get stuck with a relatively puny olfactory system?
The discovery of a new stem cell could help scientists better understand how and why sense of smell varies widely across the animal kingdom.
Scientists know the olfactory epithelium, a sheet of tissue in the nasal cavity, is essential to an animal's sense of smell. The sheet hosts special neurons that receive and bind with odor molecules. When activated, the neurons send signals to the brain -- signals interpreted as smells.
In humans, the sheet is relatively small and simple, but in dogs, the olfactory epithelium structure is complex, stretching across protrusions in the naval cavity called turbinates. These structural intricacies create more surface area, which allows a dog's olfactory epithelium to host hundreds of millions more odor-binding neurons.
"We think the surface area of the sheet matters in how well animals smell and in the types of smells they can detect," Dr. David M. Ornitz, a professor of developmental biology at the Washington University School of Medicine, said in a news release. "One reason we think this stems from differences in the complexity of these turbinates. Animals that we think of as having a great sense of smell have really complex turbinate systems."
Until now, scientists have struggled to test their theories about olfactory epitheliums and turbinate complexity.
While conducting research in Ornitz's lab, graduate student Lu M. Yang discovered a stem cell linked with both olfactory epithelium development and turbinate growth. They dubbed the stem cell FEP. The discovery confirmed what scientists had theorized, a link between sophisticated turbinate structures and powerful olfactory systems.
Researchers described their discovery this week in the journal Developmental Cell.
In followup studies, scientists hope to compare the development of turbinates and olfactory epitheliums in normal mice and in mice that had FEP activity blocked during embryonic development.
"Before our study, we didn't know how the epithelium expands from a tiny patch of cells to a large sheet that develops in conjunction with complex turbinates," Yang said. "We can use this to help understand why dogs, for example, have such a good sense of smell. They have extremely complex turbinate structures, and now we know some of the details about how those structures develop."