An Emory team of researchers has found that Emery-Dreifuss muscular dystrophy (EMD) is caused by deletion of the gene encoding emerin, which lies on the X chromosome. Stephen Warren and colleagues at the School of Medicine have concluded that misalignment of two long, similar motifs that flank the emerin gene result in its deletion.
After analyzing the DNA of a patient with EMD, the team reasoned that such repeats might also be capable of mediating a straightforward inversion of chromosomal material. They analyzed the order of chromosome markers on normal X chromosomes and found them to be inverted in 33 percent of women and 19 percent of men. The research is outlined in the May issue of Nature Genetics.
"This study shows how the genome project allows one to uncover the cause of a disease, here a muscular dystrophy, as well as to uncover unique properties of the human DNA," said Warren, Timmie Professor of Human Genetics in biochemistry, as well as a Howard Hughes Medical Institute investigator. "In this case we found that in this region of the genome, the order of genes can be completely reversed in some people without causing a disease but slightly altering behavior of the chromosomes."
The inversion provides an neat answer to one puzzle-why this region of the X chromosome has a lower rate of genetic exchange than would be expected from its length-and provides a lesson for geneticists faced with similar discrepancies in other parts of the genome.