Fig. S1

Sexually Dimorphic dkk1b:EGFP Expression Patterns

(A) Whole-mount images of male and female dkk1b:EGFP trunks. Males have many dkk1b:EGFP+ scale features, although posterior scales have much less. Both sexes show dkk1b:EGFP expression affiliated with bone. (B) Whole-mount images of dkk1b:EGFP dorsal, anal, and pelvic fins. dkk1b:EGFP+ ET are present on distal fin regions in males, but not females. Male caudal fins do not have detectable dkk1b:EGFP+ ET. Insets show higher magnification views of ET in male fins. Note that the exterior of the anterior fin ray in dorsal, anal, and pelvic fins expresses dkk1b:EGFP, as well as the most dorsal and ventral rays of the caudal fin. (C) (Left) Whole-mount images of pectoral fins from 4-6-month-old AB, Wik and Tuebingen (Tu) strain males. All tested male strains had pectoral fin ET. (Right) Quantification of average numbers of ET per fin. n = 6 fins for each strain. Data are mean ± s.d.*P < 0.05, **P < 0.001 by two-tailed Student’s t-test. (D) dkk1b:EGFP expression patterns at 4 weeks post-fertilization (wpf). At 4 wpf, dkk1b:EGFP+ cells are located near bone in the trunk (Top) and pectoral fins (Bottom). (E) dkk1b:EGFP+ pectoral fins at 6 and 8 weeks post-fertilization (wpf), when malespecific ET begin to become prominent. Insets are high magnification views of boxes. (F) dkk1b:EGFP+ ET are detectable in the head and scales of male zebrafish at 8 wpf. Insets are high magnification views of boxes. (G) Quantification of the average number of ET per ray segment, from 4 quantified segments per fish. ET were counted from two segments located just proximal to the bifurcation point on the 3rd and 4th fin rays (from the anterior). (H) Quantification of mean dkk1b:EGFP fluorescence in ET (see Materials and Methods). n = 6. Data are mean ± s.d. *P < 0.05, **P < 0.001 by two-tailed Student’s t-test. Scale bars = 1 mm (A, B, D, E); 500 μm (F)