Fig. 1

A Mesothelium in human versus zebrafish embryo. Transverse schematic of zebrafish embryo showing liver, gut, and budding swim bladder with associated mesothelium and smooth muscle at 3 dpf. B Tracing LPM using drl:creERT2 × hsp70l:Switch, 4-OHT administered at shield stage and washed off before 24 hpf. drl>EGFP indicates LPM lineage labeling. C Trunk section of drl lineage-traced 3 dpf embryo co-stained for smooth muscle (Tagln). Boxed regions show details of EGFP lineage-labeling and smooth muscle-labeling around gut (box I), swim bladder (box II), and liver ducts (box III). Arrows depict Tagln-negative;EGFP-positive cells, arrowheads depict Tagln;EGFP double-positive cells. D, E EGFP-based LPM labeling in the peritoneum around liver (D) and pancreas (E). F Rostral transverse section, lineage labeling of pericardium, ventricle (endocardium, myocardium, potentially epicardium (asterisk), blood), and LPM-derived and endoderm-derived organs in the head (head cartilage, vasculature, pharynx). G, H Sections of two regions along the anterior-posterior axis, G at yolk, H at yolk extension, showing drl-based LPM lineage labeling of parietal peritoneum forming body wall together with skin layer (boxed region). Pronephric duct (pd), liver (li), gut (g), swim bladder (sb), pancreas (pa), heart (h), blood vessel (bv), spinal cord (sc), pharynx (ph), and red blood cells (rbc). Nuclei in blue (DAPI). Scale bars C–H 50 μm and 25 μm (boxed regions).