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2006-05-20 - Colloque/Présentation - poster - Anglais - 1 page(s)

Ansseau Eugénie , Coppée Frédérique , Belayew Alexandra , "Fonctional characterization of the DUX4 et DUX4c genes located within repeated elements at the FSHD locus" in Bioforum, Liège, Belgique, 2006

  • Codes CREF : Biologie moléculaire (DI3111), Pathologies particulières (DI3370)
  • Unités de recherche UMONS : Biologie moléculaire (M122)
  • Instituts UMONS : Institut des Sciences et Technologies de la Santé (Santé)

Abstract(s) :

(Anglais) Facioscapulohumeral muscular dystrophy (FSHD) is a dominant disease linked to partial deletions in a stretch of 3.3-kb repeated elements named D4Z4 in the 4q35 subtelomeric region. These deletions are thought to alter local chromatin structure and allow transcriptional activation of neighbouring genes 1. We previously identified a putative double homeobox (DUX4) gene within the D4Z4 unit itself 2. DUX4 was considered as a pseudogene because its TATA box was mutated to TACAA and lacked introns and a polyadenylation signal. However, it could express a 424-residue protein. We have now characterized the homologous DUX4c gene in an isolated D4Z4 unit mapping 42 kb centromeric of the D4Z4 repeat array. DUX4c differed from DUX4 in the promoter region, and by the presence of a putative polyadenylation signal. The open reading frame (ORF) encoded a 374-residue protein highly similar to DUX4 except in its shorter carboxyl-terminal domain 3. The DUX4 and DUX4c promoters drove transient expression of a linked luciferase gene in transfected muscle cells (C2C12 mouse myoblasts and TE671 human rhabdomyosarcoma cells). Their mRNA’s were studied in cells transfected with chromosomal fragments comprising the DUX4 or DUX4c natural genes and in human primary myoblasts derived from muscle biopsies of controls and FSHD patients. We performed 5’ RACE experiments and found one major transcription initiation site for DUX4 mapping 47 bp downstream from a TACAA box. In contrast, multiple transcription start sites mapped around a CATAA box and two GC boxes for the DUX4c gene. All of these sites are located upstream of the translation start codon. For both genes, alternative splicings were detected by 3’RACE downstream from the stop codon. RT-PCR products including the full DUX4 or DUX4c ORF could be amplified from cells transfected with the natural genes and from human primary myoblasts. In conclusion, our data demonstrated that the DUX4 and DUX4c genes were functional and expressed mRNA’s encoding the full length protein in control and FSHD myoblasts. Although these genes belong to repeated element considered as “junk DNA”, they should be evaluated as candidate genes for FSHD. We acknowledge funding by the ABMM (Belgium), AFM (France), MDA and NHI (USA), the Frenzel (Germany) and Shaw-Fischer (USA) families. E.A. held a pre-doctoral fellowship from the FRIA (Belgium). 1. van der Maarel,S.M., Frants,R.R. The D4Z4 repeat-mediated pathogenesis of facioscapulohumeral muscular dystrophy. Am. J. Hum. Genet. (2005), 76, 375-386. 2. Gabriels,J., Beckers,M.C., Ding,H., De Vriese,A., Plaisance,S., van der Maarel,S.M., Padberg,G.W., Frants,R.R., Hewitt,J.E., Collen,D., Belayew,A. Nucleotide sequence of the partially deleted D4Z4 locus in a patient with FSHD identifies a putative gene within each 3.3 kb element. Gene (1999), 236, 25-32. 3. Coppée,F., Mattéotti,C., Ansseau,E., Sauvage,S., Leclercq,I., Leroy,A., Marcowycz,A., Figlewicz,D., Ding,H., Belayew,A. The DUX gene family and FSHD. In Cooper,D., Upadhyaya,M. (eds.), Facioscapulohumeral Muscular Dystrophy (FSHD): Clinical Medicine and Molecular Cell Biology. Bios Scientific Publisher Ltd, Oxford (2004).