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Fig. 1. Hybridization of a non-tissue-specific clone to sections of stage-42 embryos.
(A) Photomicrograph of a transverse section through the gut region of an embryo,
hybridized with probe G17. Sections were stained with methylene blue. Scale bar
equals 100 \ivs\. (B) Same section as in A, darkfield illumination. Note the high density
of labelling over all tissue types: e.g. spinal cord, somite and epidermis. Cells of the
notochord do not survive the histological procedures. (C) Control section, at a level
similar to that shown in A and B, hybridized with labelled plasmid pBR322 DNA not
containing a cDNA insert. Note the reflectance of melanocytes in the epidermis and
dorsal to the spinal cord and in the coelomic wall. Cells of the gut are not present in this
particular section. No non-specific hybridization of plasmid sequences to embryonic
tissue is seen. (D,E) Bright- and darkfield photomicrographs of a section through the
embryonic head region, hybridized with probe G17. Scale bar equals 100 jum.
Abbreviations: di, diencephalon; e, epidermis; g, gut; n, notochord; oc, optic cup; ph,
pharynx; s, somite; sc, spinal cord.
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Fig. 2. Photomicrographs of embryonic sections hybridized with probe A4 (A-D) or
pBR322 DNA (E-H). (A,B) Section through the cloacal region of a stage-42 embryo,
hybridized with A4. Scale bar equals 100 (im. Note hybridization, apparent with
darkfield illumination, to the epidermis. (E,F) Control section, hybridized with
pBR322 DNA. The presence of melanocytes in the epidermis gives rise to patches of
reflectance, unlike the even reflectance due to silver grains overlying the epidermis
after hybridization with probe A4 (A,B). (C) Transverse section through the gut
region of a stage-42 embryo, hybridized with A4. Compare with control section,
hybridized with pBR322 DNA, in Fig. 2G. (D,H) Adjacent sections through the gut
region of a stage-35/36 albino embryo. Albino embryos were used because they have
less pigment. The epidermal localization of probe A4 is clearly visible (compare D,
hybridized with A4, with H, hybridized with pBR322 DNA). Abbreviations: c, cloaca;
e, epidermis; n, notochord; sc, spinal cord.
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Fig. 3. Hybridization of probe D8 to cells of the nervous system of stage-42 embryos.
(A,B) Section through the head region at the level of the eyes. Hybridization to cells of
the central nervous system and neural retina is apparent. Scale bar equals 100 jum.
(C,D) Section through the head region at the level of the otic vesicles. Hybridization to
cells of the metencephalon and to cranial nerve ganglia 8 (acoustic-vestibular) and 9
(vagal-lateralis) is apparent. Scale bar equals 100 jan. (E,F) Hybridization to cells of
the ganglion of cranial nerve 7 (facial). Scale bar equals 20jian. Abbreviations: di,
diencephalon; mes, mesencephalon; met, metencephalon; n, notochord; ov, otic
vesicle; ph, pharynx; 7, 8, 9, ganglia of cranial nerves 7, 8, 9.
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Fig. 4. Hybridization of muscle-specific probes Dl and A2 to sections of stage-42 embryos. (A,B) Probe Dl hybridizes intensely to tail
muscle in the caudal end of the embryo. Note the lack of hybridization to neural tissue (spinal cord) and epidermis. Scale bar equals 100 jum.
(C,D) More anteriorly, Dl hybridizes to the somites which are largely myogenic at this point. Scale bar equals 100 jum. (E) Hybridization of
probe A2 to smooth muscle beneath the epithelium overlying the gut. Pigment granules in the epidermis are visible. Scale bar equals 20 jum.
(F) Control hybridization of an adjacent section with pBR322. Abbreviations: e, epidermis; g, gut; n, notochord;/?, pigment granules; s,
somite; sc, spinal cord; sm, smooth muscle; tm, tail muscle.
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Fig. 5. Hybridization of muscle-specific probes A2, Dl and H2 to skeletal and myocardial muscle. All probes hybridize to skeletal muscle
but differ in hybridization to myocardium. Panels D,E,F are higher magnifications of panels A,B>Q respectively. Corresponding regions of
the sections are marked with V. Scale bar equals (A), 100 [an; (D), 2O.jUm. (A,D) Hybridization of probe A2 to a section ihrough the
heart at the level of the otic vesicles. Hybridization to somitic and branchiomeric muscles can be seen. However, as is indicated in the
higher magnification photomicrograph (D) hybridization to heart muscle does not exceed background. (B,E) Hybridization of probe Dl to
somites, laryngeal muscle and heart. Dl hybridizes at above background levels to heart muscle but less intensely than to somitic
musculature. (C,F) Hybridization of probe H2 (a-cardiac actin) to somites and heart. H2 hybridizes intensely to heart muscle.
Abbreviations: bm, branchiomeric muscle; /, laryngeal muscle; me, myocardial muscle; n, notochord; s, somite.
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Fig. 6. Hybridization of tissue-specific cloned sequences to genomic DNA. Genomic
DNA was digested with Eco RI (E) or Hind III (H), separated on 0-8 % agarose gels,
transferred to nitrocellulose and hybridized with nick-translated plasmid DNA as
indicated above each set of lanes. Marker sizes are in kilobase pairs and are derived
from Eco RI+Hind III digested phage A DNA.
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