Exercise damages muscle, which the body subsequently repairs. In the repair process, satellite cells (also called muscle stem cells) that are normally at rest, get switched on to replicate, and fuse to, existing muscle fibers. As few as seven satellite cells can generate over 100 new muscle fibers to replace damaged tissue. Consequently, these cells are ideal candidates for treating severe muscle degenerative diseases such as Duchenne muscular dystrophy (the most common form of MD), which cause rapidly progressive muscle weakness and atrophy, and is eventually fatal. Leslie So is assessing the role of a protein called CD34 in muscle regeneration. A short form of CD34 is present on resting satellite cells. Once the cells are activated and recruited for muscle repair, a longer form of CD34 quickly replaces the short form. During the last steps in muscle regeneration, CD34 is no longer present. Leslie is investigating whether the protein maintains satellite cells in their resting state, or helps these cells switch on. To date, efforts to grow and inject satellite cells to treat damaged muscle have been disappointing. In previous work, she developed methods to isolate satellite cells, and therefore hopes that further research will enable scientists to grow cells able to repair damaged muscles, providing a new treatment, and possibly a cure, for muscle degenerative diseases.