X-Message-Number: 15673
From: "Jan Coetzee" <>
Subject: 'Super Gene' May Hold Brain Secrets
Date: Sat, 17 Feb 2001 19:22:22 -0500

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'Super Gene' May Hold Brain Secrets

      [By Nicolle Charbonneau in HealthScout.]
dailynews.yahoo.com/h/hsn/20010216/hl/_super_gene_may_hold_brain_secrets_1.h
tml

      When scientists print out a paper copy of the chemical instructions
for an average gene, it's roughly the size of an open newspaper.
      But when geneticists at the Hospital for Sick Children in Toronto
printed out the codes for a new gene they'd discovered, the printout
stretched down an entire corridor of the building.
      The new gene, called CNTNAP2, is between 50 and 100 times larger than
the average gene, but its tremendous size may be more than just an
interesting piece of trivia. Its discoverers think it may hold the genetic
blueprints that dictate how the brain develops in a growing fetus.
      Not only do these findings advance our basic knowledge of the brain,
they say, but they also raise hopes of future treatments for neurological
disorders that begin in the womb.
      The gene was discovered last summer by Stephen Scherer and Kazuhiko
Nakabayashi as part of a project to map all genes on the human chromosome 7.
Each cell in the body contains 23 pairs of chromosomes. Each of the 46
chromosomes is made up of a coiled strand of DNA, which contains the genetic
information that makes us who we are.
      The researchers say they immediately noticed they were dealing with a
larger-than-normal gene. The average gene contains 20,000 to 50,000 base
pairs of nucleotides, which contain the instructions for that gene's
proteins, but this new gene contains at least 2.3 million base pairs.
      "The human genome has diversity," says Nakabayashi. Thanks to the
Human Genome Project, the U.S. government-coordinated effort to map the
genetic makeup of people, the study was completed in a matter of months,
rather than years, he says. Details appear in this month's issue of the
journal Genomics.
      Research by a different laboratory found that the protein produced by
this gene is limited to the brain, but the Toronto team found that the gene
requires more than 16 hours to produce that protein, Nakabayashi says.
      "That is a long one," says Roger Reeves, a professor of physiology and
affiliate member of the Center for Genetics at Johns Hopkins University in
Baltimore. "That would be directly a function of its size. It requires more
work to make it."
"In order to make a protein,.that means transcribing the entire gene,"
Reeves says. "Most genes would be under 10,000 base pairs, so you can see
that the time required to make a gene that was 200 times bigger than that is
probably going to be longer."
According to the researchers, the long period of time required to make the
protein points to a process that also occurs over a long period of time --
like a pregnancy.
      The gene would not be the first that's expressed in the early brain.
"There are quite a few that are known to be involved in brain development
from the very earliest time points in embryogenesis until much later on, up
to specific things that would trigger important processes in development and
maturation of neurons," Reeves says.
      And this newly discovered "super gene" already might have potential
implications for those with certain hereditary disorders.
      "This gene is a candidate gene for hearing loss," Nakabayashi says.
The researchers already suspect that it may play a role in a type of
deafness that occurs when children are born without hearing in either ear.
      Together with French researchers, the Toronto scientists are launching
a study of people with this rare inherited hearing disorder, hoping to find
the mutation on the gene that leads to this condition.
* * *

Genes, Behavior, and Buddha

http://www.the-scientist.com/yr2001/feb/multiple_p16_010219.html


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