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Mech Dev
2002 Jun 01;1141-2:109-13. doi: 10.1016/s0925-4773(02)00014-x.
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Cloning of three variants of type XVIII collagen and their expression patterns during Xenopus laevis development.
Elamaa H
,
Peterson J
,
Pihlajaniemi T
,
Destrée O
.
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Xenopus laevis type XVIII collagen occurs in three variants, 22 + 1285 amino acid residues (signal peptide + mature protein), 23 + 1581 residues and 23 + 1886 residues in length, differing in their N-terminal non-collagenous domains. The region showing highest homology to mammalian counterparts is the C-terminal endostatin domain. All three variants are expressed, at different levels, during early and late stages of development, as demonstrated by reverse transcription-polymerase chain reaction. Whole-mount in situ hybridization shows that the short variant is expressed at high levels in the developing eye, the central nervous system, the otic vesicle, the headmesenchyme, the branchial arches and the pronephros, and at the boundaries between somites. The middle variant is expressed in the headmesenchyme, the branchial arches, the peripheral nervous system, the pronephros and the pronephric duct, and at the somite boundaries. The longest variant is weakly expressed in the headmesenchyme and branchial arches.
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12175494
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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.
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 headmesenchyme 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 headmesenchyme.
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 headmesenchyme (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.
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 headmesenchyme (thick arrow) and branchial arches (thin arrow). (B) A transverse section of a stage 40 tadpole shows signals in the headmesenchyme/mesoderm of the branchial arches (thin arrow). cg, cement gland; fb, forebrain; ph, pharynx.
