DNA in macaques,
mice and chimps but
missing in humans
510
segments
210
segments
Duplicated DNA in
humans compared
with other primates
Computer chips wired with wetware
Experiments could lead to ways of melding mind and machine
By Rachel Ehrenberg
Nerve cell tendrils readily thread their
way through tiny semiconductor tubes,
forming a crisscrossed network like vines
twining toward the sun, scientists have
found. Understanding how offshoots
from nascent mouse nerve cells explore
the specially designed tubes could lead
to tricks for studying nervous system
diseases or testing the effects of potential drugs. Such a system may even bring
researchers closer to brain-computer
interfaces that seamlessly integrate artificial limbs or other prosthetic devices.
“This is quite innovative and interest-
ing,” says nanomaterials expert Nicholas
Kotov of the University of Michigan in
Ann Arbor. “There is a great need for
interfaces between electronic and neu-
ronal tissues.”
To lay the groundwork for a nerve-
electronic hybrid, graduate student
Minrui Yu of the University of Wisconsin–
Madison and his colleagues created tubes
of layered silicon and germanium, materi-
als that can insulate a nerve cell’s electric
signals. The tubes were various sizes and
shapes and were big enough for a nerve
cell’s extensions to crawl through, but too
small for the cell’s main body to get inside.
Mouse nerve cells (purple) extend
projections through specially designed
semiconductor tubes in this illustration.
that nerve cells are game for exploring
the tiny tubes, which seem to be biologically friendly, and that the cell extensions
will follow the network to link up physically. But it isn’t clear if the nerves are
talking to each other, sending signals the
way they do in the body. Future work
aims to get voltage sensors and other
devices into the tubes so researchers can
eavesdrop on the cells.
DNA lost to evolution created
some traits in the naked ape
missing from Neandertals, suggest-
ing that the pieces were lost sometime
between 500,000 and 6 million years ago.
Only one of the missing bits contained
an actual gene. The rest of the absent
genetic instructions may be important
switches for turning on genes. Such
switches, known as enhancers, can be
located far from a gene but still govern
when and where the gene is flipped on
during development.
Defining humans
by what’s lacking
Humans and chimps have roughly the
same set of genes, yet have clear physical
and behavioral differences. Some scientists have reasoned that changing the way
genes are used — by turning a gene on or
off in a particular tissue or during a phase
of development — may be a way to evolve
new characteristics, such as the bigger
brains possessed by people.
Because most of the missing chunks of
DNA don’t contain genes, it is difficult to
say exactly what the pieces are supposed
to do. The Stanford team used “a very
clever computational analysis” to tease
out a couple of pieces of DNA that might
By Tina Hesman Saey
In evolution as on reality TV, sometimes
the biggest loser is a winner.
Losing chunks of DNA may have
enabled humans to develop bigger brains
and other distinctive traits, Stanford
researchers David Kingsley, Gill Bejerano
and their colleagues report in the March
10 Nature. The study is the latest attempt
to find genetic factors that make humans
human. Previous work focused on searching for genes unique to humans, but the
new study turns that approach on its head
by looking for pages redacted from the
human genetic instruction book.
Humans lack at least 510 chunks
of DNA that chimps, macaques and
mice all seem to share. Most are also
have clear-cut functions, says David
Haussler, a Howard Hughes Medical
Institute investigator at the University
of California, Santa Cruz.
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April 9, 2011 | science news | 15
