Fig. 1

(A, B) Differential interference contrast (DIC) images of WT and tti^s450 larvae at 120 hpf. (A) The black arrows indicate, from left to right, the 3 regions of the intestine: the intestinal bulb, mid-intestine and posterior intestine. (B) The intestinal epithelium in WT larvae is extensively folded (upper panel) and is thinner and unfolded in tti^s450 larvae (bottom panel). In tti^s450, yolk resorption is incomplete and the swim bladder does not inflate. Microphthalmia is evident and the head is slightly smaller and misshapen. (C, D) Transverse (C) and sagittal (D) histological sections of WT and tti^s450 larvae at 120 hpf stained with alcian blue periodic acid-Schiff reagent. The anterior part of the intestine (intestinal bulb) is expanded and the epithelium is elaborated into folds in WT larvae (C, left panel). In tti^s450 the intestinal bulb, liver and pancreas are smaller than in WT and the epithelium is relatively thin and flat (C, right panel). (D) The intestinal epithelial cells of the entire intestinal tract are columnar in shape in WT larvae (left panels) and are cuboidal in tti^s450 (right panels). Goblet cells containing acidic mucins (turquoise staining) are present in approximately equal numbers (white arrows) in the WT and tti^s450 mid-intestine. sb, swim bladder; b, brain; ib, intestinal bulb; y, yolk; e, eye; s, somite; P, pancreas; L, liver; (E) The average apicobasal length of the IECs in the intestinal bulb region of tti^s450 larvae at 120 hpf is approximately half that of WT IECs. Measurements were performed on 10 cells in 3 independent sections. (F) Fluorescent activated cell sorting analysis of the cell cycle in cells derived from the GFP-positive, endoderm derived organs (liver, pancreas, intestine) of tti^s450 and WT larvae on the gutGFP background at 96 hpf. Data are represented as the mean +/ SD (n = 3), *p<0.05.