Two skeletal α-tropomyosin transcripts with distinct 3′UTR have different temporal and spatial patterns of expression in the striated muscle lineages of Xenopus laevis

Abstract The Xenopus laevis α -tropomyosin (TM) gene, like its vertebrates counterparts, encodes muscle and non-muscle isoforms through two promoters and alternatively spliced exons. In the present study we describe a cDNA clone (XTM α 7) encoding a skeletal muscle isoform of the gene that differs from the previously described skeletal TM transcript (XTM α 2) by its 3′UTR sequence. The two skeletal α -TM encoding mRNAs are generated through distinct 3′end processing using different polyA signals and distinct patterns of exon splicing. Using RNAse protection and RNA in situ hybridization, we have analysed the developmental and spatial expression of the two transcripts. Both are expressed in the embryo, but XTM α 7 is by far the most prevalent of the two. In contrast, only XTM α 2 is expressed in adult striated muscle tissues. In the embryo, the spatial expression of XTM α 7 is restricted to the somites whereas XTM α 2 is expressed in both somites and embryonic heart.