DUX4 and facioscapulohumeral muscular dystrophy: These antisense agents target both DUX4 transcript variants: (i) the full-length DUX4 mRNA (fl-DUX4) produced from the last D4Z4 unit in FSHD and extended to the flanking pLAM region that provides a polyadenylation signal [8], [11]; (ii) the shorter DUX4 mRNA (s-DUX4) that ends at the same pLAM polyadenylation site and uses a cryptic splice donor site within the DUX4 ORF that would limit a putative expressed protein to its double homeodomain [11].