Medicine at Michigan-

Sean Morrison
Photo: D.C. Goings

Most scientists find it difficult enough to study just one type of stem cell. Sean Morrison works with two. He studies neural crest stem cells — which develop into the peripheral nervous system, connective tissue and other types of cells — as well as hematopoietic stem cells, which form the blood and immune systems.

“The interdisciplinary focus in my lab is fundamentally important to what we’re trying to accomplish,” says Morrison. “We want to test our hypotheses by integrating data from two stem cell systems.

We use hematopoietic and neural crest stem cells, because scientists know the most about them and have developed powerful tools to study them.”

By examining similarities and differences between stem cells, Morrison hopes to answer some of the most basic questions in stem cell biology. Questions like: how do stem cells reproduce themselves in a process called self-renewal? Do all stem cells have a master regulatory gene or are there many different genes involved? Can adult stem cells be reprogrammed or induced to change from one type of cell to another?

Unlike his U-M colleagues, Morrison isn’t interested in working with human embryonic stem cells, although he agrees they have great potential for use in medicine. “The scientific questions that interest me can best be answered with somatic or adult stem cells from mice and rats,” he says.

In recent research, Morrison discovered that undifferentiated neural crest stem cells can be found in sciatic nerves of rats for several days after birth — long after the formation of the nervous system is complete. The discovery that stem cells remain in animals much longer than scientists previously believed supports the intriguing possibility that adult stem cells could be harvested and reprogrammed for use in another organ system.

While he recognizes the importance of clinical applications for stem cell research, Morrison is still most intrigued by basic science. “People who have the biggest impact clinically are people who learn fundamentally important new things at a basic scientific level,” Morrison says. “The most exciting thing for me is to discover things no one has ever seen before and link them together to understand how nature works. A scientist is like a storyteller. It’s exciting to discover a good story and be able to tell people about it.”

__________________________________

Mark Kiel Photo: D.C. Goings

Mark Kiel, from Grand Rapids, has spent a year working as a research assistant in Sean Morrison’s laboratory to see if he wants to devote his career to biomedical research. In this photo, he’s using a technology called Fluorescent Activated Cell Sorting, or FACS, to separate stem cells quickly and efficiently from millions of other cells in a cell sample.

When Kiel sorts cell samples with FACS, he relies on years of work by other scientists who have already identified the unique pattern of receptor proteins on the stem cell’s surface. Since each type of cell has its own combination of receptor proteins, Kiel can program the computer to sort for the surface receptor patterns of stem cells he wants to study. Before he begins the FACS procedure, Kiel treats the cell sample with a special technique that attaches a fluorescent molecule or “tag” to the specific surface receptors he’s looking for.

Like a half-million-dollar vacuum cleaner, FACS then sucks the cells in Kiel’s sample one at a time through a narrow high-pressure nozzle and a laser beam. When the laser strikes a cell with a fluorescent tag, it becomes negatively charged. Cells without the fluorescent tag are positively charged. An electric field inside the device pulls all the negatively charged cells into a separate sample.

Kiel studies the role of hematopoietic stem cells during early embryo development in mice. He has applied to the M.D./Ph.D. program in the U-M Medical School and hopes to begin work on his dual degrees in the fall.

Also:

Unlocking the Secrets of Stem Cells

A Stem Cell Glossary