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glow in the dark fish

> Date: Thu, 6 Dec 2001 18:11:46 -0500
> From: vrondi at mailandnews_com
> Subject: glow-in the dark fish
> http://www.wired.com/news/photo/0,1860,46678,00.html
> umm, gee.  This link goes to a headline at the WIRED website about
> some new glow-in-the-dark fish.  M3 has linked to it on their main
> page.  They're "genetically modified".  I read about several other
> sorts of critters earlier this year they did this with.  They use a gene
> form a certain Jelly-fish, I believe it is, and splice it in, to make a
> glowy critter.  I think it requires black light or similar to actually see
> this quality.

Fascinating.  I am surprised that it was taken this long for
such a critter to appear in aquarium stores as i and some other
colleagues joked about this very idea seven years ago.

These appear to be zebra danios (Brachydanio species) that have had
the green fluorescent protein from jellyfish cloned into a ubiquitous
gene (that is, a gene expressed in every cell).

In the last 10-15 years zebrafish have been used as a model organism
for vertebrate developmental genetics, to the point where they are
now considered one the the best model organisms for development
right up there with the fruit fly and nematode worm. Mice are used
for developmental genetics as well, but they are very costly and have
some limitations that make the zebrafish worthwhile.

I bet this will not be the first example of danio varieties produced in
the laboratory ending up in fishkeeper's tanks, there are pigmentation
and finnage mutants that truly boggle the mind.  A recent cover of the
journal _Development_ was covered with different pigmentation and
patterning mutants.

About 8-10 years ago (maybe longer) biologists started tagging proteins
with this jellyfish protein (green fluorescent protein, or GFP) because
it allowed you to track cell development or the precise locations of
subcellular structures in living and unpreturbed cells.

Coupled with high-resolution light microscopy, this has caused
an avalanche of innovation and experimentation. There are now
many different color varieties of GFP and any number of methods
and applications within biology. I've used it myself to image
cellular membranes, chromosmes, and even individual genes on
the chromosomes themselves.

You were right in that it requires backlight to make the fish glow,
the proteins (unlike luciferase from fireflies) require an external
light source to excite the protein enough to cause fluorescence.

I'm surprised this is the only application of GFP to consumer
items, another joke we had was to market a beer where the yeast
used to produce it would secrete a stable form of GFP so the
beer would glow in blacklight.

>    Intriguing idea.  What do ya'll think of this?  cool? objections?  I
> bet it'll go over big with the kiddies.

I have some concerns. blacklite is in the ultraviolent range and
may harm the fish.  What's more when imaging live cells we have
to be careful not to illuminate too long or with too much intensity
or the oxygen radicals and heat produced will kill the cell.

It's possible the danios are fine with extended illumination,
but i have my doubts.  This would go double if the strain used
to make the glowing fish were albino to begin with.

My final concern is that if we allow transgenic zebrafish into
the hobby, what will happen if the fish escapes into the wild and
this transgene interacts with local fish populations?  This
isn't very likely unless the fish are released into a habitat
that supports zebrafish, but it is worth considering.

- Brian Harmon