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Fig. 3. Whole-mount in situ hybridization of the middle and long variants of type XVIII collagen using probe 2, detecting both variants (A–C) and probe 3, specific to the long variant (D). Stages 28 (A), 29/30 (B,D) and 32 (C) are shown. Due to low expression of the long variant, probe 2 detects mainly the middle variant, signals being seen in the peripheral nervous systems, particularly in the fifth, seventh and ninth cranial ganglia (gV, gVII and gIX). In addition, the middle variant is found in the pronephros and pronephric duct, in narrow stripes between somites (arrowhead), in the ventral parts of the branchial arches and in the head mesenchyme underneath the olfactory placode (thick arrow). The long variant is expressed in minor amounts around the otic vesicle (vOt), in the pronephros/pronephric duct (open arrowhead) and in the head mesenchyme. |
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Fig. 4. Location of the middle and long variants of type XVIII collagen RNAs in sections of stage 28 and 37/38 embryos. Due to differences in the expression levels of the middle and long variants, probe 2 mainly detects the middle variant mRNA. (A) Lateral sagittal section of a stage 28 tail bud embryo. Signals are seen in the branchial arch mesoderm (thin arrow) and underneath the olfactory placodes in the head mesenchyme (thick arrow). (B,C) Horizontal sections of stage 37–38 embryos show signals in the sub-epidermal mesenchyme of the head, in the branchial arch mesoderm and in the pronephros (open arrowhead). Strong signals are seen between the somites in the intersomitic arteries (black arrowhead). e, eye; cg, cement gland. |
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Fig. 2. Whole-mount in situ hybridization of type XVIII collagen using probe 1, detecting all variants. (A) Stage 20 embryos show signals in the eye anlagen (ea), in the midbrain (mb) and at boundaries between somites (arrowheads). (B) At stage 29 signals are seen in the heart (he), pronephros (pn), eye (e) and the mesenchyme underneath the olfactory placode (pOl), at the midbrain–hindbrain boundary (mhb), around the otic vesicle (vOt) and in the branchial arches. |
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Fig. 5. Location of the long type XVIII collagen variant RNA in sections of stage 40 embryos as shown with probe 3. (A) A sagittal section of a stage 40 embryo shows signals in the head mesenchyme (thick arrow) and branchial arches (thin arrow). (B) A transverse section of a stage 40 tadpole shows signals in the head mesenchyme/mesoderm of the branchial arches (thin arrow). cg, cement gland; fb, forebrain; ph, pharynx. |