Inside Salk - June 2008 - page 7

HUMAN EMBRYONIC STEM CELLS – FAMED FOR THEIR
capability to transform themselves into any type of specialized cell –
are a prissy bunch, as any scientist who has tried to grow them in
the lab can tell you. The slightest offense causes them to disavow
their almighty abilities, or pluripotency in science lingo, and start
differentiating into whatever cell type they feel like.
Travis Berggren knows this all too well. He spent five years
analyzing the needs of temperamental human embryonic stem cells
at WiCell, a private, non-profit stem cell institute headed by
scientific director James Thomson after the University of Wisconsin
researcher created the first human embryonic stem cell lines nearly
10 years ago.
“Pluripotent stem cells are balanced on a pinnacle and it doesn’t
take much to have them roll off on either side,” says Berggren, Salk’s
new staff scientist who joined the Institute in September to lead the
new stem cell core facility.
Just like any other cell type, stem cells are grown in plastic
laboratory culture dishes that contain a nutrient-rich broth known as
culture medium – with one important difference: The surface of the
dish is typically first coated with so-called feeder cells that provide
additional nutrients and signaling factors for the stem cells.
For some experiments and therapeutic applications, however, stem
cells need to be grown without the company of feeder cells, which
can skew results or contaminate the stem cell sample. Berggren
would later help solve this problem with a key discovery at WiCell.
A Different Breed of Cells
Berggren had just finished his doctorate degree in Chemistry at
the University of Wisconsin whenWiCell was looking for somebody
who could set up a mass spectrometry proteomics program for
human embryonic stem cells – his area of expertise. Mass
spectrometry is used to identify and, increasingly, to precisely
quantify thousands of proteins from complex samples.
“In the beginning I naively assumed that the stem cell work would
be done by others, but I quickly realized that if you need things to
get done, you needed to do it yourself,” Berggren remembers.
But that was easier said then done. While mouse stem cells had
been around for two decades and the technical details had been all
worked out, human embryonic stem cells turned out to be a different
breed altogether.
“The defined factors that allowedmouse stem cells to grow in
culture didn’t work for human cells,” says Berggren. “And, somewhat
ironically, the feeder cells that are used to growmouse embryonic
stem cells support both types of cells although they signal through
different pathways.”
So, the young stem cell researcher started by identifying the signal
molecules from feeder cells that are directly involved in allowing
human embryonic stem cells to grow. Aided by this research, WiCell
researchers successfully developed the first chemically defined
media for human embryonic stem cells. Other scientists have since
developed specially formulated culture media that allow them to grow
stem cells without the support provided by non-stem cells.
“While removing a lot of biological variability and inconsistencies,
growing cells without feeder cells makes it a lot more challenging.
But I have a lot of experience and I am looking forward to
establishing this expertise at the Salk,” says Berggren.
“On behalf of the Institute’s Stem Cell Committee, which includes
Salk researchers Fred H. Gage, Chris Kintner, Leanne Jones, Inder
Verma and Sam Pfaff, we are delighted to have Travis on board to
share his expertise in stem cells so that all of our scientists can take
this knowledge into new directions in research,” says Juan Carlos
Izpisúa Belmonte, chair of the committee.
A San Diego native, Berggren is no stranger to the Institute.
After finishing his undergraduate studies at UCSD and a short stint
as a commercial fisherman, he worked in professor Wylie Vale’s lab
at Salk.
“Originally, I wanted to do synthetic organic chemistry but it
sounded better on paper and I was glad to get a chance to work in a
lab with a biological focus,” says Berggren with a laugh.
For his graduate studies, he exchanged the eternal sunshine of
Southern California for icy winters along the shores of lake Michigan.
“I was just amazed howmuch your face can hurt,” he says, “but the
novelty factor wore off quickly and I am very happy to be back.”
Travis Berggren Returns to Salk to
Head Its Stem Cell Core Facility
7
Inside Salk June 2008
Travis Berggren
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