Fibronectins (FNs) are major extracellular proteins in blood plasma and many tissues of vertebrates, and play important roles in adhesion, migration and differentiation of cells. We have identified a novel variant (FN...Fibronectins (FNs) are major extracellular proteins in blood plasma and many tissues of vertebrates, and play important roles in adhesion, migration and differentiation of cells. We have identified a novel variant (FN3) of fibronectin in zebrafish. FN3 mRNA is abundant, as detected by whole-mount in situ hybridization, in the presomitic mesoderm and the newly formed somites, but less abundant in mature somites. Ectopic expression of Sonic Hedgehog (SHH) results in a decrease of FN3 expression, whereas the expression level of FN3 increases in the flhi mutants that lack the notochord. Our results suggest that FN3 may be involved in the formation of somites, but during somite differentiation its expression needs to be downregulated by signals derived from the axial tissues.展开更多
Mesp family proteins comprise two members named mesodermal posterior 1 （Mespl） and mesodermal pos- terior 2 （Mesp2）. Both Mespl and Mesp2 are transcrilption factors and they share an almost identical basic helix-l...Mesp family proteins comprise two members named mesodermal posterior 1 （Mespl） and mesodermal pos- terior 2 （Mesp2）. Both Mespl and Mesp2 are transcrilption factors and they share an almost identical basic helix-loop-helix motif. They have been shown to play critical regulating roles in mammalian heart and somite development. Mespl sits in the core of the complicated regulatory network for generation of cardiovascular progenitors while Mesp2 is central for somitogenesis. Here we summarize the similarities and differences in their molecular functions during mammalian early mesodermal development and discuss possible future research directions for further study of the functions of Mespl and Mesp2. A comprehensive knowledge of molecular functions of Mesp family proteins will even- tually help us better understand mammalian heart development and somitogenesis as well as improve the production of specific ceil types from pluripotent stem cells for future regenerative therapies.展开更多
During vertebrate somitogenesis,somites bud off from the anterior end of the presomitic mesoderm(PSM).Meso-dermal posterior(Mesp)-related genes play essential roles in somitogenesis,particularly in the definition of t...During vertebrate somitogenesis,somites bud off from the anterior end of the presomitic mesoderm(PSM).Meso-dermal posterior(Mesp)-related genes play essential roles in somitogenesis,particularly in the definition of the somite boundary position.Among vertebrates,two types of Mesp-related genes have been identified:Mesp1 and Mesp2 in the mouse;Meso-1 and Meso-2 in the chicken;Xl-mespa and Xl-mespb(also known as Thylacine1)in the African clawed frog(Xenopus laevis);and mesp-a and mesp-b in the zebrafish.However,the functional differences between two Mesp-related genes remain unknown.In the present study,we carried out comparative analyses of the Xl-mespa and Xl-mespb genes.The amino acid sequences of the Xl-mespa and Xl-mespb proteins showed a high level of similarity.The expression of Xl-mespa started broadly in the ventrolateral mesoderm and gradually shifted to a striped pattern of expression.In contrast,Xl-mespb showed a striped pattern of expression from the start.These expression profiles completely overlapped at the PSM during somitogenesis.To investigate the functional differ-ences between Xl-mespa and Xl-mespb in terms of target gene regulation,we carried out a luciferase assay using the murine Lunatic fringe(L-fng)promoter.Transcription of the L-fng promoter was activated more strongly by Xl-mespb than by Xl-mespa.This same pattern was observed for the murine Mesp-related proteins.These results suggest that the functional differences between the two types of Mesp-related genes are evolutionally conserved in vertebrates.展开更多
基金the National Natural Science Foundation ofChina (Grant Nos. 30025020 and 39970360), TRAPOYT of MOE, and the "863" Program (Grant No. 2001AA221241).
文摘Fibronectins (FNs) are major extracellular proteins in blood plasma and many tissues of vertebrates, and play important roles in adhesion, migration and differentiation of cells. We have identified a novel variant (FN3) of fibronectin in zebrafish. FN3 mRNA is abundant, as detected by whole-mount in situ hybridization, in the presomitic mesoderm and the newly formed somites, but less abundant in mature somites. Ectopic expression of Sonic Hedgehog (SHH) results in a decrease of FN3 expression, whereas the expression level of FN3 increases in the flhi mutants that lack the notochord. Our results suggest that FN3 may be involved in the formation of somites, but during somite differentiation its expression needs to be downregulated by signals derived from the axial tissues.
文摘Mesp family proteins comprise two members named mesodermal posterior 1 （Mespl） and mesodermal pos- terior 2 （Mesp2）. Both Mespl and Mesp2 are transcrilption factors and they share an almost identical basic helix-loop-helix motif. They have been shown to play critical regulating roles in mammalian heart and somite development. Mespl sits in the core of the complicated regulatory network for generation of cardiovascular progenitors while Mesp2 is central for somitogenesis. Here we summarize the similarities and differences in their molecular functions during mammalian early mesodermal development and discuss possible future research directions for further study of the functions of Mespl and Mesp2. A comprehensive knowledge of molecular functions of Mesp family proteins will even- tually help us better understand mammalian heart development and somitogenesis as well as improve the production of specific ceil types from pluripotent stem cells for future regenerative therapies.
文摘During vertebrate somitogenesis,somites bud off from the anterior end of the presomitic mesoderm(PSM).Meso-dermal posterior(Mesp)-related genes play essential roles in somitogenesis,particularly in the definition of the somite boundary position.Among vertebrates,two types of Mesp-related genes have been identified:Mesp1 and Mesp2 in the mouse;Meso-1 and Meso-2 in the chicken;Xl-mespa and Xl-mespb(also known as Thylacine1)in the African clawed frog(Xenopus laevis);and mesp-a and mesp-b in the zebrafish.However,the functional differences between two Mesp-related genes remain unknown.In the present study,we carried out comparative analyses of the Xl-mespa and Xl-mespb genes.The amino acid sequences of the Xl-mespa and Xl-mespb proteins showed a high level of similarity.The expression of Xl-mespa started broadly in the ventrolateral mesoderm and gradually shifted to a striped pattern of expression.In contrast,Xl-mespb showed a striped pattern of expression from the start.These expression profiles completely overlapped at the PSM during somitogenesis.To investigate the functional differ-ences between Xl-mespa and Xl-mespb in terms of target gene regulation,we carried out a luciferase assay using the murine Lunatic fringe(L-fng)promoter.Transcription of the L-fng promoter was activated more strongly by Xl-mespb than by Xl-mespa.This same pattern was observed for the murine Mesp-related proteins.These results suggest that the functional differences between the two types of Mesp-related genes are evolutionally conserved in vertebrates.
