Herzog et al., 2003 - Adenohypophysis formation in the zebrafish and its dependence on sonic hedgehog. Developmental Biology   254(1):36-49 Full text @ Dev. Biol.

Fig. 2 Zebrafish prl, pomc, tsh, and gh show a differential temporal expression profile. RT-PCR analyses at indicates stages (h, hours after fertilization), with ef1α as loading control. prl and pomc are already expressed at 24 h, while tsh and gh transcripts are first detectable from 42 h onwards.

EXPRESSION / LABELING:
Genes:
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Anatomical Term:
Stage Range: Prim-5 to Pec-fin

Fig. 3 Zebrafish prl and pomc are expressed in the stomodeal-hypophyseal placode. Single (A, E) and double (B–D, F–H) whole-mount in situ hybridizations with probes indicated in corresponding colors in top right corner. The age of stained embryos is indicated in bottom right corner (hpf, hours after fertilization). (D) A lateral view on the anterior region of the head; all other panels show frontal views. (B–D, F–H) are at a threefold higher magnification than (A) and (E). Frames in (A) and (E) mark magnified region. prl- and pomc-positive cells are intermingled and located in lateral (24 hpf; B, F) or anterior regions (26 hpf; D) of the lim3 domain. At 24 hpf, the number of prl-positive cells is significantly higher than the number of pomc-positive cells (compare F with B). During further development, the number of pomc-positive cells increases, while the number of prl-positive cells remains largely unchanged, so that at 32 hpf, the two cell types are present at similar numbers (H). Also, both prl- and pomc-positive cells converge from lateral regions of the pituitary anlage toward the midline, while lim3-positive cells initially located medially move posteriorly (compare B–D; see also Fig. 7 for schematic illustration; domains I, II, and III are indicated).

EXPRESSION / LABELING:
Genes:
Fish:
Anatomical Term:
Stage Range: Prim-5 to Prim-15

Fig. 4 The pituitary anlage moves into the head via a common invagination of the hypophyseal-stomodeal placode. (A–G, I, J) pomc expression. (H) gh expression. Embryos in (B) and (G) are counterstained for nk2.1 in red. Ages of embryos are indicated in bottom-right corner (hpf, hours after fertilization). (A–G) Lateral views. (H) Transverse section through pituitary (compare with histological sections of larvae at 72 and 120 hpf at http://zfin.org/zf_info/anatomy/dev_atlas.html). (I, J) Frontal views (with magnification of pituitary region in insets). (D) Magnified pituitary region of embryo shown in (C). Putative hypothalamic pomc-positive cells in (A, C, E, G, J) are indicated by arrows. Note the progressive spreading of pomc-positive cells along the anteroposterior axis in (A–E), leading to two distinct pomc domains at the anterior and posterior ends of the pituitary anlage (F, G). Abbreviations: oc, oral cavity; fg, foregut; ca, cartilage.

Fig. 5 Patterning of the zebrafish pituitary at 120 hpf. (A–F) Double in situ hybridizations, with probes indicated in top right corner in the corresponding colors. (A–E) Ventral view. (F) Sagittal section. (G, H) Schematic drawing of the pituitary composition in zebrafish larvae at 120 hpf (G; ventral view) and in adult teleost, modified from Norris (1997) (H; lateral view). A, corticotropes; M, melanotropes (both stained by pomc); P, lactotropes (prl); S, somatotropes (gh); T, thyrotropes (tsh); HN, endorphin-expressing hypothalamic neurons; in (H), the rudimentary neurohypophyis (infundibulum) is marked in gray.

Fig. 6 Shh is required for pituitary induction, growth, and patterning. (A–C) shh is expressed adjacent to the pituitary anlage. (A) At 22 hpf, lateral view, showing shh (blue) in the hypothalamus (hyp), and lim3 (red) in the primordium of the adenohypophysis (pit). (B) At 26 hpf, frontal view, showing shh (red) in the hypothalamus (hyp), and prl in lactotropes (blue). Note that shh expression is strongest in the midline, adjacent to prl-negative medial cells of the pituitary placode. (C) At 45 hpf, lateral view, showing shh (blue) in hypothalamus (hyp), oral ectoderm (oe), and foregut (fg), and pomc in corticotropes and hypothalamic neurons (red). (D–J) shh is involved in pituitary induction and/or pituitary growth; (D–F) prl (blue) and lim3 (red), 26 hpf, frontal view, (D) control; (E) shh mRNA-injected embryo, with many extra prl- and lim3-positive cells in lateral placodal regions; (F) syu mutant, with reduced number of prl-positive cells (two cells indicated by arrows). (G, H) lim3 (blue), 22 hpf, frontal view; (G) control; (H) syu mutant, with moderately reduced number of lim3-positive cells, suggesting that pituitary induction is only slightly impaired. (I, J) prl (blue) and lim3 (red), 32 hpf, lateral view; (I) control; (J) syu mutant. The mutant pituitary is significantly thinner along its dorsoventral axis, with fewer prl- and lim3-positive cells (indicated in I, J by arrowheads and arrows, respectively), pointing to reduced proliferation and/or maintenance of pituitary cells. (K–N) syu mutants display defective pituitary patterning. (K, L) prl (blue) and pomc (red), 72 hpf, ventral view; (K) control; (L) syu mutant, with reduced numbers of lactotropes and corticotropes. (M, N) gh (blue); 72 hpf, ventral view; (M) control; (N) syu mutant, lacking somatotropes.

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Reprinted from Developmental Biology, 254(1), Herzog, W., Zeng, X., Lele, Z., Sonntag, C., Ting, J.W., Chang, C.Y., and Hammerschmidt, M., Adenohypophysis formation in the zebrafish and its dependence on sonic hedgehog, 36-49, Copyright (2003) with permission from Elsevier. Full text @ Dev. Biol.