PAX7 and facioscapulohumeral muscular dystrophy: Moreover, the single-cell study found only 0.4% (23/5133) of FSHD cells expressing five or more DUX4 target genes (32), raising the question as to whether PAX7 target gene repression may more reliably discriminate DUX4 target gene-negative FSHD cells from controls, and hence represent a more efficient biomarker.