Fig. 1

Identification of cis-regulatory elements in the zebrafish eng2a gene. (A) Schematic representation of the eng2a:eGFP BAC transgene, its deletion derivatives and the enhancers that they identify; the activity of each construct in the MHB, MP cells and MFF is indicated by a + or - sign (+ indicates low-level expression). The dotted box indicates the limits of the 2 kb fragment referred to throughout as the ME. (B-D) Whole-mount lateral views (anterior to left, dorsal up) of: a 30 hour Tg(eng2a:eGFP)ⁱ²³³ embryo showing eGFP expression in the MHB and MP/MFF population (B); a 30 hour Tg(eng2a:eGFP)ⁱ²⁴³ embryo showing eGFP expression restricted to the MHB (C); a 30 hour Tg(eng2a:eGFP)ⁱ²³⁶ embryo showing eGFP expression restricted to the MP/MFF population (D). Note that in D the levels of eGFP expression are relatively low, such that only the MP expression is clearly visible at low magnification. (E) Parasagittal optical section of anterior trunk region of a 14 ss Tg(eng2a:eGFP)ⁱ²³³ embryo showing myotomal expression restricted to a subset of the slow fibres revealed by staining with the mAb F59 antibody. (F,G) Similar preparations of F, a 14 ss Tg(eng2a:eGFP)ⁱ²³³ embryo stained with mAb 4D9 showing coincidence of expression (lower merged image) of the transgene (middle image) and the endogenous Eng proteins (upper image), and G, a 36 hour Tg(eng2a:eGFP)ⁱ²³³ stained with mAb 4D9; the transgene is now expressed in both MPs and multinucleate MFFs. UCNE/DCNE: upstream/downstream conserved non-coding element (conserved from fish to mammals).