What the Nose Knows

Dyson Professor Jack Horne, PhD, and his students use a state-of-the-art confocal microscope to study how genes affect the development of the brain and olfactory system in zebrafish.

Image of zebrafish embryo axons taken with Pace’s confocal microscope.

“There are olfactory neurons, the ones that actually sense the smells, that synapse first in the olfactory bulb, which is the first step in smelling for zebrafish and humans, and from the olfactory bulb they send that smell information to a bunch of other parts of the brain,” explains Dyson Professor Jack Horne, PhD. “We’re working on that second step, where the neurons in the olfactory bulb send out axons to wire-up to several different parts of the brain, and we can actually view that wiring-up in live embryos of zebrafish.”

Horne and his team of Pace undergraduates use zebrafish in their research for two main reasons: the first being that they are a vertebrate model system, which means that the basic brain structure and organizational parts are very similar to humans, unlike other model organisms such as the fruit fly. Second, the embryos of zebrafish are essentially transparent, which makes them perfect for doing microscopy work.

“The cerebral cortex of the mouse is more similar to ours than the fish is, but it’s difficult to watch the brain development of the embryo because not only is the brain inside a skull, but also inside the mom mouse,” says Horne.

In zebrafish, Horne is able to incorporate a fluorescent protein in the early developing neurons and watch them grown in real time thanks to the use of Pace’s newly acquired confocal microscope. Horne’s basic experimental approach is to look at how genes affect the pattern of axons growing back into the brain. “We found a couple of genes that if we disrupt their functions we no longer see the normal pattern of nerves growing to other parts of the brain,” he says.  “That tells us that those genes are important to the normal process of how the brain wires up.”

“The genes that we’ve identified to be involved in the development of the zebrafish olfactory system are likely to be involved in how the human olfactory system wires up,” Horne says.

In 2011, Horne and colleagues at Pace were awarded $335,000 by the National Science Foundation for the acquisition of the confocal microscope that he and his student researchers are using in the labs. The microscope allows for 3D imaging (much like a medical doctor’s use of MRI) of the developing brain in the still living zebrafish embryo. The images can be taken intermittently over time to loop together in the creation of a time lapse video of brain development.

“It’s the microscope that makes it possible. Without the microscope, our students wouldn’t be able to do their projects. Before we got our own at Pace, we would have to go to the Albert Einstein Medical School to use theirs,” says Horne. “It’s a big boon to what we’re doing in our lab.”