FRG1 and facioscapulohumeral muscular dystrophy: In this regard, the array contraction might cause proximal or distal changes in chromatin structure, with the consequent up-regulation of one or more 4qter genes [8], and it is known that transgenic mice over-expressing the FRG1 gene (located 125 kb from the D4Z4 array) develop a muscular dystrophy resembling human FSHD.