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Gene Expr Patterns
2004 May 01;43:303-8. doi: 10.1016/j.modgep.2003.10.006.
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Regulated gene expression of hyaluronan synthases during Xenopus laevis development.
Nardini M
,
Ori M
,
Vigetti D
,
Gornati R
,
Nardi I
,
Perris R
.
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Here reported is the developmental gene expression pattern of the three known vertebrate hyaluronan synthases (XHas1, XHas2 and XHas3) and a comparative analysis of their mRNAs spatio-temporal distribution during Xenopus laevis development. We found that while XHas2 shows a steady-state expression from gastrula to late tailbud stage, XHas1 is mainly present in the early phases of development while XHas3 is predominantly transcribed in tailbud embryos. XHas1, XHas2 and XHas3 show distinct tissue expression patterns. In particular, XHas1 is localized in ectodermal derivatives and in cranial neural crest cells, whereas XHas2 is mainly found in mesoderm-derived structures and in trunk neural crest cells. Moreover, the expression pattern of XHas2 overlaps that of MyoD in cells committed to a muscle fate. Unlike the other hyaluronan synthases, XHas3 mRNA distribution is very restricted. In particular, XHas3 is expressed in the otic vesicles and closely follows the inner ear development. In conclusion, XHas1, XHas2 and XHas3 mRNAs have distinct and never overlapping spatial expression domains, which would suggest that these three enzymes may play different roles during embryogenesis.
Fig. 1. Upper panel: temporal expression of XHas1, XHas2 and XHas3 by RT-PCR from total RNA at different stages of Xenopus development. RT-PCR with ODC primers was used as a loading control. RT−: RNA sample without reverse transcriptase was used as a negative control for PCR. Lower panel: whole-mount in situ hybridization analysis of XHas1 (A,B,B′) and XHas2 (C,D,D′) at blastula and gastrula stages. (A) XHas1 is distributed in the animal pole of the embryo at stage 9. (B) XHas1 expression covers the entire ectoderm at stage 11, as even shown in the corresponding histological section (B′). (C) XHas2 expression at stage 9 with a faint signal in the animal pole and a higher labelling in the marginal zone. (D) At stage 11, XHas2 is distributed as a ring with a dorso-ventral gradient of expression around the closing blastopore. (D′) A histological section of the embryo shown in D. The arrowhead indicates the dorsal blastopore lip.
Fig. 2. Whole-mount in situ hybridization analysis of XHas1 (A,B,B′,E,F,F′) and XHas2 (C,D,D′,G,H,G′) at neurula and early tailbud stages. (A) At stage 13, XHas1 is present in non-neural ectoderm. (B) At stage 17, XHas1 appears in the neural crest cells (NCC), red arrow. (B′) A stage 17, dissected embryo shows the XHas1 expression in the cephalic NCC. (B′) XFoxD3 mRNA expression in the cephalic NCC at stage 17. (C) At stage 13, XHas2 is expressed in paraxial mesoderm. (D,D′) At stage 18, XHas2 expression is confined in the pre-somitic mesoderm as shown in whole and dissected embryo. (E) At stage 21, XHas1 is down-regulated in the ectoderm and in the NCC. (F,F′) XHas1 expression in stage 24 whole embryo and in the corresponding histological section. (G,H) XHas2 distribution in stage 21 and stage 24 embryos. Yellow arrowhead: heartprimordium. Black arrowhead: pronephric anlage. Red arrowhead: trunk neural crest cells. (G′) Frontal view of stage 21 embryo showing XHas2 expression in the head region. The arrow indicates the expression in a region containing the pituitary anlage. The pituitary anlage is revealed by the expression of Xlim-3 reported in the inset.
Fig. 3. Whole-mount in situ hybridization analysis of XHas1 and XHas2 at tailbud stages. (A) XHas2 expression at stage 28. White arrow: the heart, white arrowhead: branchial arches. (A′) Frontal view of a stage 28 embryo showing the XHas2 expression in the eye (red arrowhead) and in an anteriorhead region containing the pituitary (yellow arrow). (A′) Histological section of a stage 28 embryo at the eye level showing XHas2 expression in the lens. (B) XMyoD expression in a stage 28 embryo. (C and C′) Horizontal sections of stage 27 embryos hybridized with XSox9 and XHas2 probes, respectively. Red arrows: migrated NCCs. Black arrows: endodermal part of the pharyngeal pouch.
Fig. 4. Whole-mount in situ hybridization analysis of XHas3 expression pattern during Xenopus development. (A) At stage 18, XHas3 is exclusively detectable in the otic placodes. (B) A lateral view of a stage 23 embryo. (C) A stage 26 embryo. XHas3 is expressed in the otic vesicle and in the posterior half of the cement gland (arrow). (D) Stage 37/38 embryo. XHas3 is still present in the otic vesicle (red arrowhead) and appears in the pronephric glomerula (yellow arrowhead). Time course expression analysis of XHas3 in the early inner ear development. (B′) Stage 23, (C′) stage 26: XHas3 labelling signal is higher at the dorsal and ventral sides of the otic vesicle. (E,F,D′) Stage 30, 33/34 and 37/38: XHas3 mRNA gradually disappears from the ventral part of the otic vesicle walls, remaining localized at the dorsal side.
