Tragedy and a DNA puzzle

Lincoln's DNA sample was the key to homing in on areas of three chromosomes where the mutation may exist, center director Hakon Hakonarson said.

That's still a vast expanse of DNA to comb through - like looking for a single typo in the many chapters of three big books. Even so, Hakonarson said he was optimistic that the mutation could be found within a year with tissue samples from a few more ACD families. Toward that end, he hopes to collaborate with researchers at Baylor - something that Langston said she was open to, and that Snyder is eager to arrange.

Even if they find the mutation, many questions will remain: Are there other ACD-causing gene defects that are recessive? Does the dominant form always cause disease, or is its activity sometimes masked, as it apparently is in Snyder? How much does the severity of ACD vary? Could some people with chronic pulmonary problems have mild ACD?

The 3 Angels foundation is assembling the funding, awareness campaigns, and research agenda to find answers. Snyder obtained a $250,000 congressional appropriation that the U.S. Centers for Disease Control and Prevention will use to educate neonatologists about ACD - an important step toward collecting more tissue samples and figuring out the true incidence of the disease. Robinson has lined up a friend, Tony Award-winning singer and West Wing cast mate Kristin Chenoweth, to do two fund-raising concerts.

This is not just about ACD, experts agree, but about understanding the primitive molecular origins of pulmonary vascular development.

"That could be important for other diseases and for repair mechanisms that could benefit many more people," Langston said.

Snyder and Robinson would love to have another child if research yielded a prenatal test for ACD, so speeding up the glacial pace of scientific discovery is in their interest. But like the very decision to conceive, their motivation is manifold.

"It's our way to honor these three children, and also protect our Shirley in case she carries the gene," Snyder said. "And maybe do something good for the world."