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Fig. 1
drl transgene reporter expression in the early lateral plate mesoderm and cardiovascular development.
(a) The zebrafish draculin (drl) locus; blue depicts coding exons (with ATG and Stop codons), yellow are untranslated regions, a DANA retro-transposon is located in the upstream region, arrows and red bar indicate PCR product used for cloning the regulatory sequence. (b) drl:EGFP reporter expression during gastrulation (80% epiboly, inset shows the embryo in bright-field view), dorsal to the right; scale bar, 100 µm; note the scattered band of cells that form the precursors of the lateral plate mesoderm. (c,d) Bud stage embryos probed for endogenous drl (c, mRNA in situ hybridization, ISH) versus drl:EGFP (d, composite bright-field and EGFP confocal stack image) depicting the continuous lateral plate mesoderm; anterior to the top, posterior to the bottom and dorsal to the right; scale bar, 100 µm. (e) EGFP fluorescence from homozygous drl:EGFP transgenic zebrafish; 5–7 somite stage view of the converging lateral plate mesoderm; scale bar, 100 µm. (f–l) Genetic lineage tracing using drl:creERT2 × ubi:Switch (schematic on top), 4-OHT-induced at shield stage, labels the lateral plate mesoderm descendants at 36 h.p.f., including cardiac (outlined arrowhead in f; scale bar, 250 µm), pectoral fin mesoderm (solid arrowhead in f,g; scale bar, 50 µm), red blood cells (RBCs, h; scale bar, 50 µm), kidney (asterisks in i,j; scale bar, 50 µm), plus vasculature and scattered superficial trunk muscle cells (solid arrowheads in i). (k,l) 4-OHT induction at 12 somite stage and imaged at 36 h.p.f. refines tracing exclusively to the circulatory system and blood, note absence of kidney tracing (asterisks in k); scale bar, 50 µm.