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LUKE GROSKIN: This is Sam.
He's a pretty special monkey.
You see, unlike all other male squirrel monkeys,
Sam can see the color red and happily proves it
in exchange for a sugar pellet.
MAUREEN NEITZ: In squirrel monkeys,
all the males have color vision deficiency.
So they're all colorblind.
LUKE GROSKIN: But not Sam here, whose ability
to smoosh his face against the pink dots on a touch screen
represents a culmination of color vision research
by Jay and Maureen Neitz.
JAY NEITZ: Maureen is a geneticist and genetic engineer
and I'm a neuroscientist and so we put together our expertise.
LUKE GROSKIN: Not to bring male squirrel monkeys up
to par with females.
JAY NEITZ: Our whole goal was eventually
be able to do this in people.
LUKE GROSKIN: Colorblind people, many of whom
might be green with envy watching a monkey see red.
There are a lot of misperceptions
about color blindness.
JAY NEITZ: Oh, you must see only in black and white,
like a black and white television,
but almost everybody who is colorblind
is not completely colorblind.
LUKE GROSKIN: 99% of colorblind people
have the red-green variety.
This doesn't mean they can't see red or green.
They just experience red or green
differently from normal people and this small gap
in the color spectrum can taint even
the most basic experiences.
JAY NEITZ: A red pepper and a green pepper almost
look identical.
A green banana and a yellow banana, again,
very, very hard to tell.
LUKE GROSKIN: A similar frustration
can occur at the butcher's counter.
JAY NEITZ: A colorblind person is pretty lost
at being able to tell the nice, bright red meats using
their color vision.
As a matter of fact, you can't be a USDA meat inspector
unless you have perfect color vision.
LUKE GROSKIN: Other jobs are difficult or impossible.
JAY NEITZ: People want to be a pilot
or they want to be a nurse.
A nurse cannot really be colorblind.
There's all those pills that are all those different colors.
If the patient's turning blue or if they're flushed
and they're red.
LUKE GROSKIN: Or if you're a colorblind videographer trying
to make a video about color vision.
JAY NEITZ: It just makes your life extremely different.
LUKE GROSKIN: Preach on, Dr. Neitz.
JAY NEITZ: Oh honey, let's take a vacation to Vermont
and see the beautiful autumn colors, the sunset.
Oh sweetheart, isn't it so romantic?
Yeah, the color of the sky looks pretty much the same.
LUKE GROSKIN: You can start to see
why one in 12 men or one in 200 women affected by the disorder
might be interested in a cure.
MAUREEN NEITZ: So in 1999, we decided
that we would give it a shot and try
to see if we could do the cure.
LUKE GROSKIN: Easier said than done.
Colorblind isn't an illness.
It's 100% genetic.
BOTH: Right.
JAY NEITZ: So that-- Well, that--
LUKE GROSKIN: Let's back up for a second.
At the back of your eye is your retina and inside
that are three types of photoreceptor cells called
cones.
JAY NEITZ: There's one most sensitive to red,
one most sensitive to blue, and one most sensitive to green.
LUKE GROSKIN: And each of these cones
and their corresponding pigments are encoded by specific genes.
MAUREEN NEITZ: So humans and other Old World primates
have two genes on the X chromosome
that encode visual pigments.
One encodes the red cone pigment and the other one
encodes the green cone pigment.
LUKE GROSKIN: But if you're colorblind.
MAUREEN NEITZ: Only one type-- red or green-- is expressed.
LUKE GROSKIN: Finding that faulty gene
was relatively simple.
Replacing those genes inside the cone cells
with the right genes, well, that's a bit trickier.
MAUREEN NEITZ: You have to have some way of delivering
a gene to the cells that you're trying to treat and not
into other cells.
LUKE GROSKIN: Fortunately, nature
has crafted a really powerful method of forcing DNA
into a very specific cell.
A virus.
MAUREEN NEITZ: The virus that we use
is called Adeno Associated Virus and people call it AAV.
Its main advantage is that you don't get an immune response
against the virus.
LUKE GROSKIN: So while researching
how to load the therapeutic gene into the virus,
the Neitzes trained a pair of colorblind male squirrel
monkeys-- Sam and Dalton-- to take a color blindness test.
JAY NEITZ: Every single morning, the monkeys wake up
and before they have breakfast, they
go OK, it's time to have our color vision
tested, and the monkey is trained to touch
the place where they see that color blob
and then they get a treat.
They can be most efficient and gets the most rewards
if they're-- just touch with their nose and then they get
down and get their little treat.
LUKE GROSKIN: And just to be thorough.
JAY NEITZ: We also ran untreated animals.
Occasionally, they might just by chance touch the right spot
but over trials you know that they can only really get it
right all the time if they have normal color vision.
LUKE GROSKIN: Once the monkeys were trained
and the virus was ready, Sam and Dalton
underwent a fairly elaborate procedure.
JAY NEITZ: A vitro retinal surgeon slipped the needle
underneath the retina.
Then the fluid is infused in order
to treat the whole entire back of the eye.
LUKE GROSKIN: It wasn't immediately obvious
that it worked.
MAUREEN NEITZ: And we didn't know
how long it was going to take for them
to change their behavior after the pigment was expressed
robustly.
JAY NEITZ: Now when you look back
and you see the difference between the animals,
it's so dramatic.
It's an amazing thing and it amazed us.
LUKE GROSKIN: Although the FDA has yet
to approve the procedure for human trials,
recently the Neitzes have developed a one shot
version of the cure.
JAY NEITZ: It's like a every day shot
that would take one second.
Just a shot right into the eye.
LUKE GROSKIN: And while getting a shot in your eye
sounds terrifying to some, it's a small price
to pay for living out a dream or getting
to see a sunset in all its glory or maybe just
not leaving your house dressed like this.
For Science Friday, I'm Luke Groskin.
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