- The evolutionary distribution and structural organization of the homeobox-containing repeat D4Z4 indicates a functional role for the ancestral copy in the FSHD region. Winokur, S.T., Bengtsson, U., Vargas, J.C., Wasmuth, J.J., Altherr, M.R., Weiffenbach, B., Jacobsen, S.J. Hum. Mol. Genet. (1996)