Filamin isogene expression during mouse myogenesis

The developmental pattern of filamin gene expression has been studied in mo use embryos by using in situ hybridization. The probes used were isoform sp ecific, S-35-labeled antisense complementary ribonucleic acids (cRNAs) to t he 3' untranslated region (3' UTR) of muscle-specific and nonmuscle-specifi c filamin genes. Northern blot and in situ hybridization results showed tha t nonmuscle-specific filamin transcripts had a size of 9.5 kb and were expr essed in all nonmuscle tissues. Labeling was most intense in tissues contai ning a substantial proportion of epithelial and smooth muscle cells. Muscle -specific filamin transcripts had a size of 10 kb and mere expressed primar ily in cardiac and skeletal muscle. The expression of muscle-specific filam in messenger ribonucleic acids (mRNAs) was detected in heart at 8.0 days af ter coitum, whereas that in the myotomes of somites was not detected until 10.5 days after coitum. The expression of muscle-specific filamin mRNAs in heart and in skeletal muscle continued through the subsequent days of myoge nesis. The results showed that muscle-specific filamin gene transcripts are detected before the formation of myotubes in vivo. This is the first study of filamin gene expression at the early stages of skeletal muscle developm ent. (C) 2000 Wiley-Liss, Inc.