Püschel et al., 1992 - Sequence and expression pattern of pax-6 are highly conserved between zebrafish and mice. Development (Cambridge, England)   114:643-651

Fig. 1

Structure and expression of pax-6. (A) Schematic representation of the pax-6 cDNAs. The box indicates the coding region, the darkly stippled regions the paired domain, the lightly stippled regions the homeodomain and the black region the 14 amino acid insert in the paired domain of zf pax-6b. Lines indicate the two classes of isolated cDNAs (I: n9, nl6, n27, nlO8, nl30; II: n8, nl5). The 5′ ends of class II clones were near position 500 of the sequence shown in Fig. 2. Clone nlO8 contains an additional sequence 5′ of the insert which most likely represents an intron (data not shown) which is not present in the other partially sequenced cDNA′s. Brackets indicate probes used for Northern blot hybridization and in situ hybridization. (A) a BamHl - EcoRI fragment, (B) a cloned oligonucleotide containing the 42 bp insert of zf pax-6b, (C) a Hindlll - Ndel fragment. (B) Northern blot of 36 h embryonic mRNA hybridized with a pax-6 probe. A Northern blot with 5 ng of poly(A)+ RNA was hybridized with probe A. A message of approximately 2.9 kb was detected. The same result was obtained when using probe C. (B) BamHI, (C) ClaI, (H) HindIII, (K) KpnI, (N) NdeI, (P) PstI, (R) EcoRI.

Anatomical Term:
Stage: Prim-25

Fig. 4 pax-6 is expressed in zebrafish during neurulation. Whole embryos were hybridized with probes A and C, which are specific for pax-6. Hybridization with each probe alone gave identical results. (A, B) Dorsal view of the prospective brain region at 10 h. Two expression domains are discernible. The domain in the prospective forebrain appears earlier (A) than the one in the prospective hindbrain (B). The embryos differ slightly in age and show the gradual appearance of the hindbrain expression domain. Younger embryos show only the forebrain stripe (not shown). (C) Dorsal and (D) lateral view of a 10 h embryo, showing the two expression domains (h, hindbrain; f, forebrain). No expression is seen at the midline of the hindbrain (A, C and data not shown). (E, F) Lateral views of 14 h embryos. Expression is seen in the prospective forebrain (f), hindbrain (h) and the optic vesicle (ov). Anterior is to the left in A - C and up and to the left in D - F. Scale bar is 150 μm in A, B, C and 125 μm in D, E, F.

Fig. 5 pax-6 is expressed in limited regions of the neural keel. Paraffin sections of embryos were hybridized with 35S-labelled RNA probes (probe A, probe C gave the same results). (A,B) Parasagittal sections of a 14 h embryo. Expression is seen in the optic vesicle (A, B), the prospective forebrain (B) and the prospective hindbrain and spinal cord (A, B). Lines in B indicate the plane of section in panels C and D. (C) Cross-section of the prospective forebrain at 14 h. Expression is seen in the dorsal half, excluding the dorsal-most cells of the forebrain. (D) Cross-section of the neural keel at 14 h. Expression is seen in the ventral half. (E) Parasagittal section of the optic vesicle (ov) at 14 h. Expression is seen in the ventral and lateral part of the vesicle. Little or no expression is detectable in the dorsal part. Expression is also seen in the ectoderm (ect) overlying the optic vesicle. (F) Horizontal section of an 18 h embryo. Expression is seen in the diencephalon (di) and the myelencephalon (my). (G) Cross-section through the trunk of a 24 h fish. Expression is detectable in the ventral half of the neural tube, excluding the floorplate and cells adjacent to it as was confirmed by inspecting the corresponding bright-field images (not shown). Anterior is to the left in A, B, E and F and dorsal to the top in C, D and G. Scale bar is 200 μm in A, B, 160 μm in C, D, G and 120 μm in E, F. ce: cerebellum.

Fig. 6 pax-6 is expressed in the brain and spinal cord. (A) 24 h embryo. Expression is seen in the olfactory bulb (ob), the diencephalon (di), the eye and the myelencephalon (my). (B) Expression in the hindbrain starts at the level of the first rhomobomere (rol). The line indicates the level of the cross-section in C. (C) A double-exposure of the bright-field (blue) and dark-field (red) images of the same cross-section of the hindbrain at the level of the otocyst (oc). The domain of pax-6 expression is seen as a red signal. Expression in the hindbrain is restricted to the ventral half excluding the floorplate. Anterior is to the left in A and B and dorsal is up. Scale bar is 100 μm in A; 200 μm in B; and 50 μm in C.

Fig. 7 pax-6 is expressed in distinct regions at 32 and 36 h. Parasagittal sections of 32 h (A, B) and 36 h (C - H) fish were hybridized with a pax-6 probe (probe A, probe C gave identical results). Double-exposures of brightfield (blue) and dark-field (red) images (A, C, E) and dark-field images (B, D, F) of the same sections. Expression is detectable in the myelencephalon up to the border between the myelencephalon and the cerebellum (A - F, H). The density of grains over the cerebellum and the mesencephalon is the same as that seen throughout the slide and do not represent specific hybridization to pax-6 transcripts, pax-6 is expressed in the diencephalon and the telencephalon (A - F, G) and specific subareas within these regions (C, D: arrow, G). Abbreviations: ce, cerebellum; di, diencephalon; ms, mesencephalon; my: myelencephalon; ot: optic tectum; p, pituitary gland; te, telencephalon. Anterior is to the left, dorsal up. Scale bar is 100 μn in A - F and 40 μm in G, H.

Anatomical Terms:
Stage Range: Prim-15 to Prim-25

Fig. 8 pax-6 is still expressed in the head at hatching (72 h). Cross-sections of 3-day fish were hybridized with pax-6 specific probes. Dorsal is up. The sketch in the upper part indicates approximate levels of the sections. Expression is apparent in the olfactory bulb (A, ob), the ganglion cell layer (gl) and the inner nuclear layer (inl) of the eye (A - D). Specific parts of the diencephalon express pax-6 (C - D). The signal in the pigment epithelium (pe) of the eye is due to pigment and does not represent a hybridization signal. Scale bar is 200 μm in A - D and 290 μm in drawing.

Fig. 9 pax-6 and eng-genes are expressed in adjacent regions. Adjacent horizontal sections of 14 h embryos were hybridized with probes specific for pax-6 or eng-1 separately or with pax-6 and eng-2 (A) or pax-6 and eng-1 (B, C) together. Anterior is to the left. Only sections with the double-hybridization are shown. Arrows delineate the limits of eng-1/2 expression. The signals to the left and to the right of eng-1 expression are specific for pax-6. The eng genes are expressed in the gap of pax-6 activity in the mes- and metencephalon. C is a higher magnification view of B. The eng-1 expression domain is separated from that of pax-6 by about 5 to 10 cells which show no activity of either gene. (D) Schematic summary of the superimposed expression domains. Stippled areas express pax-6, the dark areas express only eng-1 and the lightly stippled area expresses both eng-1 and eng-2. The broken line indicates the edge of the yolk. Scale bar is 200 μm in A, B, D and 80 μm in C.

ZFIN wishes to thank the journal Development (Cambridge, England) for permission to reproduce figures from this article. Please note that this material may be protected by copyright.