This gene is located within a D4Z4 repeat array in the subtelomeric region of chromosome 4q35. The D4Z4 repeat is polymorphic in length; a similar D4Z4 repeat array has been identified on chromosome 10. Each D4Z4 repeat unit has an open reading frame (named DUX4) that contains two homeoboxes; the repeat-array and ORF is conserved in other mammals. There was no evidence for transcription from standard cDNA libraries however RTPCR and in-vitro expression experiments indicate that the ORF is transcribed.
^Gabriëls J, Beckers MC, Ding H, De Vriese A, Plaisance S, van der Maarel SM, Padberg GW, Frants RR, Hewitt JE, Collen D, Belayew A (August 1999). "Nucleotide sequence of the partially deleted D4Z4 locus in a patient with FSHD identifies a putative gene within each 3.3 kb element". Gene. 236 (1): 25–32. doi:10.1016/S0378-1119(99)00267-X. PMID10433963.