Fish genes work in human cells
Understanding how mammal splicing enhancers differ from fish makes Fugu more
useful
By Cathy Holding

Researchers based in the United States have discovered significant
differences in the regulation of gene splicing between mammals and fish.
Their findings, reported in PNAS this week, could help scientists develop
transgenic techniques using pufferfish DNA sequences in mouse and human
cells.

The genome of the pufferfish-or Fugu-contains all the alternative promoters
and splice exons and introns that are present in mammalian genomes, but
because the introns are so much smaller, genes are about an eighth the size,
said lead author Christopher B. Burge, at Massachusetts Institute of
Technology (MIT).

This makes the Fugu genome a potentially powerful tool for functional gene
analysis, Burge said, but scientists have until now been frustrated in their
attempts to use the resource because mammalian cells do not correctly splice
the fish genes.

Burge's team developed a variant of a previously devised method for
predicting splicing enhancer sequences. The new technique-dubbed
RESCUE-ISE-predicts intronic splicing enhancers (ISEs), and by comparing
human, mouse, zebrafish, and Fugu genomes, Burge's group discovered that
this class of splicing regulatory element appears to differ substantially
between mammals and fish.

Burge told The Scientist that "89 to 96% of all the hexamers that we
predicted as ISEs in mammals fall into one of two clusters-they're either
G-rich or C-rich. But when we applied the same method to Fugu introns, we
just got a completely different spectrum of motifs."

Burge proposes that by applying a scoring method to individual intron
sequences, Fugu genes can be tested for problem motifs and modified for
transgenic experiments in mice-a method he has successfully piloted. "You
have to do a bit of extra cloning or site-directed mutagenesis," he said.
"But these Fugu genes would be much easier to manipulate and that much more
genetically tractable."

Full Text at The Scientist
http://www.biomedcentral.com/news/20041026/02

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