Laboratory of Molecular Biology, University of Mons-Hainaut, 6, Mons, Belgium.
PLoS One. 2009 Oct 15;4(10):e7482. doi: 10.1371/journal.pone.0007482.
Facioscapulohumeral muscular dystrophy (FSHD) is a dominant disease linked to contractions of the D4Z4 repeat array in 4q35. We have previously identified a double homeobox gene (DUX4) within each D4Z4 unit that encodes a transcription factor expressed in FSHD but not control myoblasts. DUX4 and its target genes contribute to the global dysregulation of gene expression observed in FSHD. We have now characterized the homologous DUX4c gene mapped 42 kb centromeric of the D4Z4 repeat array. It encodes a 47-kDa protein with a double homeodomain identical to DUX4 but divergent in the carboxyl-terminal region. DUX4c was detected in primary myoblast extracts by Western blot with a specific antiserum, and was induced upon differentiation. The protein was increased about 2-fold in FSHD versus control myotubes but reached 2-10-fold induction in FSHD muscle biopsies. We have shown by Western blot and by a DNA-binding assay that DUX4c over-expression induced the MYF5 myogenic regulator and its DNA-binding activity. DUX4c might stabilize the MYF5 protein as we detected their interaction by co-immunoprecipitation. In keeping with the known role of Myf5 in myoblast accumulation during mouse muscle regeneration DUX4c over-expression activated proliferation of human primary myoblasts and inhibited their differentiation. Altogether, these results suggested that DUX4c could be involved in muscle regeneration and that changes in its expression could contribute to the FSHD pathology.
面肩肱型肌营养不良症（FSHD）是一种显性疾病，与 4q35 处的 D4Z4 重复阵列收缩有关。我们之前在每个 D4Z4 单元中鉴定了一个双同源盒基因（DUX4），它编码一种在 FSHD 中表达但不在对照成肌细胞中表达的转录因子。DUX4 及其靶基因有助于 FSHD 中观察到的基因表达的全局失调。我们现在已经描述了位于 D4Z4 重复阵列中心体侧 42kb 处的同源 DUX4c 基因。它编码一个 47kDa 的蛋白质，具有与 DUX4 相同的双同源结构域，但在羧基末端区域存在差异。通过 Western blot 用特异性抗血清在原代成肌细胞提取物中检测到 DUX4c，并且在分化时被诱导。与对照肌管相比，FSHD 中的蛋白质增加了约 2 倍，但在 FSHD 肌肉活检中达到了 2-10 倍的诱导。我们通过 Western blot 和 DNA 结合测定表明，DUX4c 过表达诱导了 MYF5 成肌调节因子及其 DNA 结合活性。我们通过共免疫沉淀检测到 DUX4c 可能稳定 MYF5 蛋白，因为我们检测到它们的相互作用。与 Myf5 在小鼠肌肉再生过程中成肌细胞积累中的已知作用一致，DUX4c 过表达激活了人原代成肌细胞的增殖并抑制了其分化。总之，这些结果表明 DUX4c 可能参与肌肉再生，其表达变化可能导致 FSHD 病理学。
