MCB NOTES
OCTOBER 2010
Who Calls the Tune when
Chromosomes Dance?
Chromosomes in dividing cells perform an elaborate
dance. After each makes a copy of itself, the pairs separate,
one copy gliding to each newly forming cell. These
molecular dancers are drawn to their destinations by an
intricate network of spindle fibers that connect to each new
chromosome at sites called centromeres. How do these
spindle fibers find the centromeres so that they can guide
the chromosomes away from one another? MCB Assistant
Professor Barbara Mellone uses sophisticated microscopy to
find that out, by studying how cells from fruit flies orchestrate
these cellular performances.
Mellone
was
awarded
$776,420
from
the
National
Science
Inside MCB Notes:
Foundation for a 4-year project to examine the roles of a key
Papke wants to know,
centromere-associated protein called CID that directs spindle fibers to
would a microbial species
centromeres. CID, along with other proteins Mellone will study, forms a
by any other name still
structure called a kinetochore that links the centromere to the spindle
smell as sweet?
fibers. Mellone attaches fluorescent tags onto CID and other proteins in
♦ MCB undergraduate
cells so she can watch them perform their intracellular dance using a
2
3
researchers do MCB
fluorescence microscope. She will create mutants with defects that
proud in Australia
stop the cell division process at different stages to better understand
♦ Alder explores protein
trafficking in
mitochondria
♦ Trout disease resistance
enhanced through
Chen’s efforts
when each protein plays its part.
Mellone uses fruit flies for her studies because she can make
hypotheses about the function of CID and other centromere proteins
by examining chromosome movement in isolated fly cells and then test
those hypotheses by analyzing mutations affecting those proteins in
flies. “The fly is a simple and genetically defined organism,”
said Mellone, “that provides a way to look at tissues and
animals” Frequently, such mutations cause an incorrect
number of chromosomes to appear in cells. When similar
mutations occur in humans, they can cause serious birth
defects, including some forms of Down syndrome.
Dividing cells with red spindles pulling green
chromosomes to the ends of the new cells.
As part of the NSF mission to enhance science
education, Mellone will work with students to create videos of cell division and chromosome separation in
normal and mutant cells. These videos will be posted on-line for use by other educators around the country.
The Natural Scheme of Things Microbial Intrigues Asst. Prof. Papke
"When I see a bird that walks like a duck and swims like a duck and quacks
like a duck, I call that bird a duck." James Whitcomb Riley (1849–1916)
Were it so easy to classify bacteria and archaea. The definition
of a species is a contentious topic in microbiology. Assistant
Professor R. Thane Papke has waded into the thick of this
controversy aided by a $479,660 National Science Foundation
grant.
"Things may not conform to our preconceived notions of what
should be a species," Papke says. All agree that any classification
system should reflect natural divisions shaped by evolutionary
history. Which characteristics of microbes one should use to define
those divisions, and whether natural divisions exist, are two areas of contention.
To identify more natural divisions between species, Papke examines organisms called halophiles,
microbes that live in salty places. Papke collects his halophiles from salt ponds in Spain and measures their
genetic differences in his lab. Though they would constitute a single species by traditional criteria, he finds
that their gene sequences tell a different story. From these he learns of their evolution and their true
relationship to one another.
Even though his halophiles reproduce by making copies of themselves, the members of this "species" are
not genetically identical. He finds subsets of genetically distinguishable clusters of organisms, that is, true
species. There appear to be rules that keep these clusters from homogenizing into a genetically
“Sometimes
the only way to
make progress
is to develop
new ideas and
compare them
with the old.”
indistinguishable mob and Papke has set out to discover those rules.
“Science is conservative in nature and sometimes the only way to make progress is
to develop new ideas and compare them with the old," Papke noted. Now he has to
convince the traditionalists that the methods he uses with the halophiles can be used
to classify all microbes. A traditional taxonomist would call James Whitcomb Riley's
bird a duck, but an evolutionary taxonomist like Papke would call it a small dinosaur.
It’s the genes of both ducks and halophiles that tell who their true relatives are.
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MCB NOTES October 2010
MORE NOTES
TWO MCB UNDERGRADS TRAVEL DOWN UNDER Two MCB University Scholars
represented UConn at Universitas 21 in Melbourne, Australia this summer.
Universitas 21 is a network of 23 research universities from 15 countries that
facilitates collaborations among member institutions. UConn is a new
member of Universitas 21 and will participate in educational and research
projects with this international team of universities. Professor Michael Lynes
accompanied MCB seniors Stephanie Davis and Charles Mackin who were
selected to present posters of their work that was conducted in Lynes' and
Assistant Professor R. Thane Papke's labs.
ALDER SNAGS NSF FUNDING FOR MITOCHONDRIA RESEARCH Examining the
activity of a protein inside a cell in real time is challenging enough, but to
examine a protein inside an intracellular organelle, the mitochondria, is not
for the faint of heart. MCB Assistant Professor Nathan Alder has taken on this
challenge to examine the mitochondrial machinery involved in moving
proteins manufactured outside the mitochondrion through its membrane to
the inside. Alder received a $788,000 grant from the National Science
Foundation to study the mitochondrial proteins responsible for this transport
using fluorescently-labeled membrane proteins. He will view transport in real
time as he exposes mitochondria to transport activators and inhibitors.
GENETICALLY ENGINEERED TROUT SUBJECT OF CHEN AWARD Aquaculture is a
rapidly growing industry that provides fish without harvesting them from
natural environments. When raised in enclosed areas, fish are generally more
prone to disease and can produce less nutritious food. Professor Thomas
Chen's laboratory has engineered trout that are more disease-resistant and
that produce more of the natural antioxidant, astaxanthin. He recently
received a 5-year $2.1 million grant from the US Dept. of Agriculture to
identify the genes responsible for disease resistance and to genetically
enhance astaxanthin production in trout. His work will bolster future efforts to
breed healthier and more nutritious fish to help meet the growing demand
Written and edited by Prof. Kenneth Noll, MCB; [email protected]
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MCB NOTES October 2010