Int J Dev Biol
January 1, 2008;
Identification and gene expression of versican during early development of Xenopus.
The chondroitin sulfate proteoglycan (PG) PG-M/versican
is known to be a primary component of the vertebrate embryonic extracellular matrix and, in the mouse, functional abrogation of the versican
gene leads to severe cardiovascular malformations and embryonic lethality. In order to provide a means for approaching the study of the role of versican
during embryogenesis, we have cloned the Xenopus versican
cDNA and we have performed in situ hybridization on embryos at different stages of development. We showed maternal Xversican
transcription, as well as a previously undocumented early expression of the PG during gastrulation and neurulation. At later stages of development, spatial transcription of Xversican
correlates with the patterns of migrating neural crest
) and it is expressed in embryonic regions representing the final sites of arrest of NCC
mRNA was also detected in a subpopulation of trunk NCC
migrating into the fin
, in tissues flanking the trunk NCC ventral
migratory pathway and in post-migratory cranial skeletogenic NCC
. Further embryonic sites expressing Xversican
were the pronephros
, pronephric ducts
anlage and branchial pouches. These findings constitute the basis for future studies aimed at clarifying unresolved aspects of versican
function during embryogenesis.
Int J Dev Biol
[+] show captions
Fig. 1. Spatial expression of Xversican mRNA in early Xenopus laevis embryos. (A) Xversican maternal transcript is distributed in the animal pole blastomeres of the blastula stage embryo (st. 6). (B,C) During gastrulation (st. 10.5 and 12.5 respectively) the mRNA is localized in the gastrulating dorsal axial mesoderm (arrows). (D) Dorsal view of a midneurula stage embryo (st. 16): the expression can be detected in the paraxial mesoderm (arrow) and in the midline of neural plate (arrowhead). (D Frontal view of the embryo shown in (D) exhibiting Xversican transcript in the eye field (e). (D) Vibratome transverse section of the embryo in (D) revealing the presence of Xversican mRNA in the notochord (arrow), in the medial ventral domain of the neural plate (np) and in the paraxial mesoderm (pm). (E) Dorsal view of late neurula stage embryo (st. 18). Xversican is detectable in the premigratory trunk NCC (arrowheads) and in the lateral plate mesoderm (arrow). (F, F At stage 22, Xversican transcript is still present in the trunk NCC (arrowheads) and appears in the cardiac field (cf), pronephrus (p) and pronephric ducts (pd). (F Vibratome sagittal section reveals the labelling in the floor plate of the neural tube (arrow) and the down regulation of Xversican in the forming somites (so).
Fig. 2. Spatial distribution of Xversican mRNA during branchial arches development. In each panel dashed lines indicate the level of the sections. (A) Lateral view of a tailbud stage embryo (st. 26) showing Xversican expression in the head region. (A Horizontal vibratome section highlighting Xversican transcript in the cranial mesenchyme (arrow). In brown, the immunolabelling for 12/101 antibody shows the head somites. (A) Horizontal vibratome section showing Xversican expression in the endoderm of the pouches. (B,BB) At stage 37 Xversican mRNA is expressed by the cranial NCC migrated into the branchial arches (B horizontal section) as confirmed by the expression of the NCC marker XSox9 in (B). (C,CC) Later in development (st. 41) Xversican transcript remains expressed in chondrogenic precursor cells as shown in the horizontal section in (C compared to the expression of XSox9 in (C). In each panel roman numbers indicate respectively the first, second and third/fourth branchial arches. nt, neural tube.
Fig. 3. Expression of Xversican mRNA in trunk neural crest cells and mesodermal derivatives in Xenopus embryos. Dashed lines indicate the level of the sections. (A) Diagram of the Xenopus trunk neural crest migration pathways, modified from Collazo et al., 1993. (B,C) Lateral views of stage 26 and 28 embryos respectively, showing Xversican transcript in trunk NCC migrating into the fin (compare arrows in (B,C), in the cardiac field (cf) (see also C, pronephrus (p) and pronephric ducts (pd). Xversican mRNA is localized in the caudal presomitic mesoderm of the tailbud (white arrow) and in branchial arches (see Fig. 3). (C Transverse vibratome section showing Xversican expression in the cardiac field (cf) and in the trunk NCC migrating, along the dorsal pathway, into the fin (arrowhead). A faint signal is still detectable in the ventral floor plate (arrow), while somites (so), labelled with the muscle cells specific marker 12/101 antibody, do not express Xversican. (C) Transverse vibratome section showing Xversican mRNA distribution at trunk level. NCC expressing Xversican are clearly detectable into the dorsal fin (arrowhead). Labelling signal appears in the ventro-medial portion of the somites (so), around the neural tube (nt) and the notochord (no) and in the ipochord (arrow), whereas no expression could be detected within the myotomes stained with the 12/101 specific antibody. (C Horizontal section showing somites stained with the 12/101 antibody and the metameric distribution of the Xversican transcript in the sclerotomic portion of the somites (arrow). (D,D At stage 41 Xversican expressing cells dispersed into the dorsal and ventral fin are still visible. D, dorsal trunk NCC pathway; V, ventral trunk NCC pathway.