"Most genetic mutations reduce the production of a protein, or a mutated gene might produce a detrimental protein," Miller said. "FSHD is unusual because it is most often caused by genetic deletions that paradoxically result in the production of DUX4 in the wrong tissue at the wrong time. "
Scientists have previously shown that the genetic deletions in FSHD somehow caused an epigenetic change an alteration in one of the mechanisms that control a gene's activity. The relaxation of the tightly wound chromatin structure allowed the otherwise sealed code in the gene to be read and the toxic DUX4 to be produced in skeletal muscle.
"Our study builds on this model and identifies a new mechanism that allows this relaxation and DUX4 production to occur. Production of DUX4 in muscle cells can be viewed as a molecular switch. We've discovered that the switch that turns on DUX4 expression can be activated in different ways but the mechanism of muscle destruction by DUX4 remains the same. Identifying different ways the switch can be activated is a crucial step toward therapy development because it allows us to apply multiple and different strategies to prevent activation of the switch." Miller said.
Five percent of FSHD-affected individuals have array lengths, longer than 10 copies (the threshold for chromatin relaxation) of the DNA sequence in question making them appear to lack the genetic mutation that normally causes FSHD.
However, these unusual individuals lacked repression of DUX4 code-reading in their skeletal muscle cells because of a mechanism other than copy number.
"Breakthroughs in scientific discovery are often achieved by studying individuals with unusual disease presentations," Miller said. The researchers identified individuals withou
|Contact: Leila Gray|
University of Washington