XB-ART-7058Mech Dev July 1, 2002; 115 (1-2): 113-6.
cDNA cloning, sequence comparison, and developmental expression of Xenopus rac1.
The Rho family of small GTP-binding proteins are important signaling molecules that regulate the dynamics of the actin cytoskeleton and mediate changes in cell morphology and motility. Here, we describe the temporal and spatial patterns of expression of the Rho family member, rac, during the development of the amphibian, Xenopus laevis. We also present the deduced amino acid sequence of Xenopus rac (Xrac). At the amino acid level, Xrac is highly conserved relative to previously characterized rac homologs, and is nearly identical to human rac1. RNase protection assays and Western blot analysis indicate that Xrac mRNA and protein are present from fertilization through tailbud stages of development. Whole-mount in situ hybridizations show that Xrac transcripts are especially abundant in cells of the involuting marginal zone, and later, in the cranial neural crest, the developing central nervous system, and in the somites. The remarkable degree of evolutionary conservation observed in the Xrac primary structure together with its high level of expression in cells and structures critical to morphogenesis suggest a functionally important role for this Rho family member in early vertebrate development.
PubMed ID: 12049773
Article link: Mech Dev
Species referenced: Xenopus laevis
Genes referenced: actl6a akt1 rac1 rho tbxt
Article Images: [+] show captions
|Fig. 4. Localization of rac mRNA by whole-mount in situ hybridization. Xrac mRNA is detected in cells of the marginal zone during early and late gastrulation (A,B, stage 10.5, vegetal view; C, stage 12, lateral view). ‘d’ indicates the position of the dorsal blastopore lip, and ‘y’ indicates the yolk plug of the blastopore. The embryo in (A) is uncleared. Xbra expression in an early gastrula-stage embryo indicates the location of presumptive mesodermal cells for comparison (D). Sagittal paraffin sections of hybridized gastrula-stage embryos (F,G). At stage 10.5, rac mRNA is abundant in the presumptive ectoderm and is also detected at elevated levels in cells of the dorsal involuting marginal zone (F). ‘d’ marks the dorsal blastopore groove. In (G), a sagittal section of the stage 12 embryo shown in whole-mount in (C) reveals rac transcripts specifically in cells of the dorsal (dim) and ventral (vim) involuting mesoderm, the prechordal plate (p), and the sensorial layer of the neuroectoderm (n). The archenteron (a) and blastocoel (b) are indicated. In late neurula-stage embryos, Xrac is expressed in the anterior neural plate (anp) and the notochord (nc) (H,I). At stage 25, Xrac is expressed in the cement gland (cg), the eye (e), the brain (the rhombencephalon (rh) is indicated), the notochord (nc), and somites (so), and is also expressed in the cranial neural crest (cnc), including cells of the hyoid (hy), and anterior (ab) and posterior (pb) branchial streams (J,K). At tailbud stage 33/34, Xrac expression persists in the eye and central nervous system, and is evident in the branchial arches (ba), the otic vesicle (ov), and in the trigeminal (t), facial (f), glossopharyngeal (g), and vagus (v) cranial nerves (M,N). Gastrula-, hatching-, and tailbud-stage embryos were incubated with Xrac sense probe to control for nonspecific hybridization (E,L,O). Scale bar equals 0.5 mm in (A–E,H–J,L,M,O), and 0.2 mm in (F,G,K,N).|
|rac1 (Rac family small GTPase 1 ) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 10.5, vegetal view, dorsal up.|
|rac1 (Rac family small GTPase 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 25, lateral view, anterior left, dorsal up.|
|rac1 (Rac family small GTPase 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 34 & 35, lateral view, anterior left, dorsal up.|
|rac1 (Rac family small GTPase 1) gene expression in Xenopus laevis embryo, assayed via in situ hybridization, NF stage 12, sagittal section, dorsal up.|