"We've made the very first mouse model of human EEC syndrome," notes Emma Vernersson Lindahl, Ph.D., a postdoctoral researcher and lead author of a paper appearing today in the American Journal of Medical Genetics that announces the team's results. "These mice, like babies born with EEC, showed a range of birth defects, fully recapitulating the range of defects that one sees in the human syndrome," she says.
To solve the mystery of variable pathology, the CSHL team tested the idea that the p63 protein itself controlled or "modified" EEC's manifestation in different individuals. The scenario they tested and which proved successful was this: mice with the EEC-causing p63 mutation were crossed to mice engineered to lack TAp63, one of the two major classes of p63 proteins. Those with both genetic changes consistently had features of EEC.
Most genes generate instructions for manufacturing proteins; precisely how the gene is turned on or its message edited affects which versions of structurally distinct proteins are manufactured. All healthy people generate both major classes of p63 proteins. TAp63 proved to be the class of p63 protein that modifies EEC features. Mice lacking TAp63 did not have any pathology, which means that TAp63 loss alone is not responsible for the syndrome. But when mice lacking TAp63 also possess the EEC-causing p63 gene mutation, pathology always occurs.
This work suggests that levels of the TAp63 protein determines whether children that have inherited one copy of the EEC-causing mutation from one of their parents are born with birth defects. Mills speculates that when levels of TAp63 drop beneath a certain threshold, it is no longer
|Contact: Peter Tarr|
Cold Spring Harbor Laboratory