Shp2 expression in embryonic Xenopus muscle. In situ hybridization assays for Shp2 mRNA were carried out with anti-sense (A) and control sense (B) probes using stage 22 (A and B, upper) and 28 (lower) Xenopus embryos. Specific labeling was observed with Shp2 mRNA anti-sense probe in myotomal muscle and brain. C. TX-100 total protein extracts of Xenopus tadpole tail muscle ("X") and cultured C2 myotubes ("C") were immunoblotted with an anti-Shp2 monoclonal antibody. A band of about 70 kD was observed in both samples. Positions of molecular weight markers are indicated on the left.