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Fig. 1. Expression of the FRG1 protein during development. (A) Stage 36 whole-mount immunostaining shows the ubiquitous appearance of the FRG1 protein. FRG1-immunostained tadpoles were then sectioned either sagitally (B) or transversally (C) in the regions depicted in A. (D) Diagram of the minimal frg1 regulatory element (FRE) construct that was used to examine tissues with active transcription. EGFP expression was observed in stage 32 transgenic animals by both whole-mount fluorescence (E) and egfp in situ hybridization (F). By stage 36, transgenic egfp expression becomes restricted to muscle and vascular cell lineages (G), and by stage 42 it is observed almost exclusively within the vasculature (H). In adult X. laevis, immunostaining of FRG1 [green (I,K)] is observed in the gastrocnemius muscle, where it colocalizes precisely with rhodamine-labled lectin [red (J,K)], a marker for capillaries. Antibody specificity for the FRG1 peptide in these immunohistology experiments was confirmed by immunostaining with (M), or without (L), FRG1 peptide competition. (N) Strong FRG1 staining (red) was observed in arteries and veins in gastrocnemious sections co-stained with wheat germ agglutinin (green) and DAPI (blue). Abbreviations: ps, pronephric sinus; pd, pronephric duct; pcv, posterior cardinal vein; pda, paired dorsal arteries; nc, notochord; nt, neural tube; aa, aortic arches; ov, ophthalmic vessel; da, dorsal artery; dlav, dorsal lateral vein. Bars, 1 mm (A,E–H); 30 μm (B,C); 50 μm (K–N). |
