GTPases of the Rho family are molecular switches that play important roles in converting and amplifying external signals into cellular effects. Originally demonstrated to control the dynamics of the F-actin cytoskeleton, Rho GTPases have been implicated in many basic cellular processes that influence cell proliferation, differentiation, motility, adhesion, survival, or secretion. To elucidate the evolutionary history of the Rho family, we have analyzed over 20 species covering major eukaryotic clades from unicellular organisms to mammals, including platypus and opossum, and have reconstructed the ontogeny and the chronology of emergence of the different subfamilies. Our data establish that the 20 mammalian Rho members are structured into 8 subfamilies, among which Rac is the founder of the whole family. Rho, Cdc42, RhoUV, and RhoBTB subfamilies appeared before Coelomates and RhoJQ, Cdc42 isoforms, RhoDF, and Rnd emerged in chordates. In vertebrates, gene duplications and retrotranspositions increased the size of each chordate Rho subfamily, whereas RhoH, the last subfamily, arose probably by horizontal gene transfer. Rac1b, a Rac1 isoform generated by alternative splicing, emerged in amniotes, and RhoD, only in therians. Analysis of Rho mRNA expression patterns in mouse tissues shows that recent subfamilies have tissue-specific and low-level expression that supports their implication only in narrow time windows or in differentiated metabolic functions. These findings give a comprehensive view of the evolutionary canvas of the Rho family and provide guides for future structure and evolution studies of other components of Rho signaling pathways, in particular regulators of the RhoGEF family.
Bone morphogenetic proteins (BMPs) are members of the transforming growth factor beta superfamily signaling molecules that play important roles in a wide variety of developmental processes. In this study, we have used an antibody specific for the phosphorylated and activated form of Smad1 to examine endogenous patterns of BMP signaling in chick embryos during early development. We find complex spatial and temporal distributions of BMP signaling that elucidate how BMPs may function in multiple patterning events in the early chick embryo. In the pregastrula embryo, we find that BMP signaling is initially ubiquitous and is extinguished in the epiblast at the onset of primitive streak formation. At the head process stage, BMP signaling is inactivated in prospective neural plate, while it is strongly activated at the neural plate border, a region which is populated by cells that will give rise to neural crest. During later development, we find a dynamic spatiotemporal activation of BMP signaling along the rostrocaudal axis, in the dorsal neural tube, in the notochord, and in the somites during their maturation process. We discuss the implication of our results for endogenous functions of BMP signaling during chick development.
Gastrointestinal (GI) development is highly conserved across vertebrates. Although several transcription factors and morphogenic proteins are involved in the molecular controls of GI development, the interplay between these factors is not fully understood. We report herein the expression pattern of Sox9 during GI development, and provide evidence that it functions,in part, to define the pyloric sphincter epithelium. SOX9 is expressed in the endoderm of the GI tract (with the exclusion of the gizzard) and its derivate organs, the lung and pancreas. Moreover, SOX9 is also expressed at the mesoderm of the pyloric sphincter, a structure that demarcates the gizzard from the duodenum. Using retroviral misexpression technique, we show that Sox9 expression in the pyloric sphincter is under the control of the BMP signaling pathway, known to play a key role in the development of this structure. By misexpressing SOX9 in the mesoderm of the gizzard, we show that SOX9 is able to transdifferentiate the adjacent gizzard epithelium into pyloric sphincter-like epithelium through the control of mesodermal-epithelial signals mediated in part by Gremlin (a modulator of the BMP pathway). Our results suggest that SOX9 is necessary and sufficient to specify the pyloric sphincter epithelial properties.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with đź’™ for researchers
Part of the Research Solutions Family.