Slβ expression pattern during embryogenesis. WT zebrafish embryos at 23 hpf (A,B), 29 hpf (D,E), 30 hpf (C), 35 hpf (F–H) and 48 hpf (I–K). (A,C,H,J,K) lateral view, anterior to the left; (B,F,G,I) frontal view, dorsal to the top; (D,E) lateral view, ventral to the top, anterior to the left; corresponding to the orientation in supplementary material S1. The scale bars in each picture correspond to 40 μm. Picture (B) corresponds to an assembly of two pictures: the same embryo focused in the medial part on prl and slβ signals, assembled with a picture of a more anterior plane with eyes in focus to be able to spot the morphology in comparison with the red and blue label. The arrows point at the slβ label. Prl (in red) is expressed anterior to slβ (in blue) at 23 hpf (A), in several cells (B), while slβ is detected only in one cell located on the left side of the embryo (B). At 30 hpf, slβ- and prl-expressing cells are intermingled (C). (D) Prl and slβ are expressed in different cells. Merger of red and green fluorescence in confocal microscopy: A 29 hpf embryo was labeled by combined fluorescent in situ hybridization: red fluorescence for slβ and green for prl. (E) classical microscopy picture showing the orientation of the embryo represented in (D) and in supplementary material S1, lateral view, ventral to the top, anterior to the left. Note the red slβ label. The square outlines the enlarged portion in (D) and S1. (F–K) The blue label corresponds to slβ, the red label to prl. Slβ expression increases at 35 hpf (F–H) through 48 hpf (I–K) and the expressing cells move posterior relative to the prl domain.

Slβ expression pattern during embryogenesis. WT zebrafish embryos at 30 hpf (A–C) and 48 hpf (D–F). (A–D) Lateral view, anterior to the left. (E,F) ventral view, anterior to the top. Scale bars represent 40 μm. (A–C) Slβ is expressed in several cells also expressing pit1. The blue label corresponds to slβ, red to pit1. (B) same emryo as in (A) after the red label was washed out. (D–F) Gh and slβ are expressed in different cells. (D,E) slβ label is in blue and Gh was revealed by using Fast Red, for visualization by classical microscopy (D) and by fluorescence (E). Gh (in red) is expressed anterior to slβ (in blue) (F) The same embryos were analyzed by combined fluorescent in situ hybridization: red fluorescence for slβ and green for gh. Gh-expressing cells are clearly anterior to slβ-expressing ones.

Expression of slβ requires Pit1 and Aal. in situ hybridization of wt and mutant 35 hpf embryos. The red label corresponds to prl and blue to slβ. The scale bar in (A) represents 40 μm (A) wt sibling expressing prl and slβ; (B) Aal homozygous mutant expressing only prl; (C) and (D) the same embryos as in (A) and (B) are shown, after the red label was washed out; (E) wt sibling; and (F) Pit-1 mutant deficient in prl and slβ. (A–F) Lateral view, anterior to the left.

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