Scientists Identify Dyslexia Gene
ROBERT SIEGEL, host:
Scientists said today that they have found a gene for dyslexia. Yale University researchers hope that the gene will let them test children for a predisposition to reading difficulties and to get them help sooner. Even though researchers think they have the right gene, NPR's Joe Palca reports that proving it is another matter.
JOE PALCA reporting:
It's pretty clear that reading disorders are inherited.
Mr. JEFFREY GRUEN (Yale University): If you search in just about any family that has at least one family member with dyslexia, you'll frequently find several family members with dyslexia.
PALCA: Jeffrey Gruen heads the team at Yale University that's been searching for a dyslexia gene. Gruen now thinks he's found one. It's a gene on chromosome six called DCDC2. Gruen has several lines of evidence for his gene. First, there's animal data. Rat brains don't develop normally without it. Then there's human evidence. Gruen says DCDC2 is switched on or, as geneticists say it, expressed in brain tissue.
Mr. GRUEN: And interestingly enough, yes, it's expressed in the brain but it's particularly expressed in the temporal lobe, the prefrontal region and the posterior cingulate gyrus.
PALCA: The temporal lobe, the prefrontal region and the posterior cingulate gyrus are all parts of the brain scientists believe are involved in reading. The final piece of evidence is genetic. Gruen says DCDC2 shows an inheritance pattern that coincides with the inheritance pattern of dyslexia in families. Gruen has shared his data with colleagues in Finland and Germany who are also studying families with dyslexia and they, too, see a genetic association with DCDC2.
Mr. GRUEN: So we feel really confident about this, that our data is being reproduced elsewhere and that's really wonderful.
PALCA: Gruen's evidence will appear in the proceedings of the National Academy of Sciences. And to hear Gruen tell it, it all sounds quite convincing, ut...
Mr. CLYDE FRANCKS (University of Oxford): It's a very interesting gene, for sure, but the proof of whether it's actually involved in dyslexia is fairly shaky still or at least is preliminary still.
PALCA: Clyde Francks is another dyslexia gene hunter. He's with the University of Oxford in England. He's looked for an association with DCDC2 in the families he studies and he doesn't see one.
Mr. FRANCKS: There's another gene on chromosome six that's fairly close to this one and matching that horrible name, KIAA0319, and nobody really knows what it does. But the genetic data implications are considerably stronger, I would say, than DCDC2.
PALCA: So is the evidence for KIAA0319 really stronger than the evidence for DCDC2? Ellen Wijsman is a statistical geneticist from the University of Washington in Seattle.
Ms. ELLEN WIJSMAN (University of Washington): No, I don't think it's any better. I think it also has some holes in it.
PALCA: Wijsman's also hunting for a dyslexia gene. She says there may be a gene on chromosome six, as Francks and Gruen both think, or there may not be. Studies from Finland have implicated genes on chromosome 15 and chromosome 3. She says even though human genetics has made great strides in the past decades, tracking down the genes for something like a reading disorder is at the outer limits of what's possible.
Ms. WIJSMAN: These complex traits are really hard to sort out. I think this is one of the, you know, million-dollar questions in this field is how do we really go about doing this and knowing we've got something interesting in the end?
PALCA: Wijsman agrees it will be useful to know a gene associated with reading disorders because a genetic test would show which children needed special help early on. She just doesn't think we have one yet. Joe Palca, NPR News, Washington.