APO-DYSTROPHIN-3 - A 2.2KB TRANSCRIPT FROM THE DMD LOCUS ENCODING THEDYSTROPHIN GLYCOPROTEIN BINDING-SITE

The molecular defect in Duchenne muscular dystrophy is well establishe d as being due to mutations at Xp21 which disrupt the normal synthesis of the 14kb dystrophin mRNA. More recently, several groups have ident ified a 4.8kb transcript from this locus which shares exons with the c arboxy-terminal region of the dystrophin gene. In this paper we presen t evidence for an additional 2.2kb mRNA transcript. The 5' untranslate d region and first 7 amino acids are identical to that published for t he 4.8kb transcript. The position of the translational stop codon and 3' untranslated region is similar to that previously described as the truncated fetal dystrophin isoform. This 2.2kb mRNA has a similar tiss ue distribution to that described for the 4.8kb mRNA but unlike the ot her transcripts from the DMD locus, the 2.2kb mRNA is expressed in ear ly development. The relevance of this transcript in the clinical expre ssion of muscular dystrophy and developmental delay is discussed.