Fig. 3

FOXN3 Drives Increased Hepatic Glucose Production

(A) Human FOXN3 and zebrafish Foxn3 orthologs are shown with the central DNA-binding Forkhead box (nearly invariant aminoacyl residues 112-204) and length marked (to the right). The percent identity of the zebrafish amino-terminus, Forkhead box, and C terminus relative to human FOXN3 is shown. The conserved Sin3-binding signature (EAA within the C terminus) is marked. Putative phosphorylation sites found in five or more published phospho-proteomic surveys are shown as well: the significance of these residues’ phosphorylation has not been established in any organism.

(B) A non-transgenic (wild-type [WT]) 7 days post-fertilization (dpf) larva and two transgenic larvae were photographed in light- and green fluorescent channels in the left-lateral view. The Tg(fabp10a:foxn3,EGFP)^z106 transgenic line overexpresses zebrafish foxn3 and EGFP, and the Tg(fabp10a:FOXN3,EGFP)^z107 transgenic line overexpresses human FOXN3 and EGFP (transcript variant -T003). The encoded EGFP protein is translated as a free (not as a fusion) protein ( Provost et al., 2007). The scale bar represents 500 µm.

(C and D) pck1 promoter activity (bioluminescence derived from assay of luciferase) in lysates prepared from 5 and 6 days post-fertilization (dpf), never-fed Tg(pck1:Luc2,cryaa:mCherry)^s952, Tg(fabp10a:foxn3,EGFP)^z106; Tg(pck1:Luc2,cryaa:mCherry)^s952 and Tg(fabp10a:FOXN3,EGFP)^z107; and Tg(pck1:Luc2,cryaa:mCherry)^s952 larvae. p < 0.02; two-tailed Student’s t test. n = 5-7.

(E and F) Whole-body glucose levels in 6 dpf WT, Tg(fabp10a: foxn3,EGFP)^z106, and Tg(fabp10a:FOXN3,EGFP)^z107 larval extracts. p < 0.02; two-tailed Student’s t test. n = 4-5 pooled samples of ten larvae each. All values are mean ± SEM.

(G and H) Fasting blood glucose levels in WT, Tg(fabp10a: foxn3,EGFP)^z106, and Tg(fabp10a:FOXN3,EGFP)^z107 transgenic adult animals of both sexes after an overnight fast.*p = 0.01; two-tailed t Student’s t test. n = 9-13.