RESUMO
The leucine zipper transcription factor TSC-22 (TGF-beta1 Stimulated Clone-22) was first isolated from a mouse osteoblast cell line as an immediate-early target gene of TGF-beta1. However, work with other cell lines, as well as with a Drosophila homolog, bunched, suggests that it is an effector gene of various growth factors and potentially involved in the integration of multiple extracellular signals. Throughout mouse embryogenesis TSC-22 is expressed in a dynamic pattern. Although early TSC-22 expression is ubiquitous in 6.5 day embryos, as development proceeds TSC-22 expression is upregulated at sites of epithelial-mesenchymal interactions such as the limb bud, tooth primordiurn, hair follicle, kidney, lung, and pancreas. TSC-22 is also expressed in many neural crest-derived tissues including the mesenchyme of the branchial arches, the cranial, dorsal root, and sympathetic ganglia, as well as the facial cartilage and bone. Other areas of expression are the otic and optic vesicles, the heart, and cartilage and bone forming regions throughout the embryo.
Assuntos
Regulação da Expressão Gênica no Desenvolvimento , Mesoderma/metabolismo , Proteínas Repressoras , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Animais , Encéfalo/embriologia , Encéfalo/metabolismo , Epitélio/embriologia , Epitélio/metabolismo , Olho/embriologia , Olho/metabolismo , Gânglios/embriologia , Gânglios/metabolismo , Hibridização In Situ/métodos , Zíper de Leucina/genética , Botões de Extremidades/metabolismo , Camundongos , Reação em Cadeia da Polimerase Via Transcriptase ReversaRESUMO
The anteroposterior axis of the developing embryo becomes morphologically apparent at the onset of gastrulation with the formation of the primitive streak. This structure, where the first mesodermal cells arise, marks the posterior aspect of the embryo. To examine the potential role of non-mesodermal signals in specifying posterior (hematopoietic and endothelial) cell fates in the mouse embryo, we have devised a transgenic explant culture system. We show that interactions between primitive endoderm and adjacent embryonic ectoderm or nascent mesoderm are required early in gastrulation for initiation of hematopoiesis and vasculogenesis. Surprisingly, primitive endoderm signals can respecify anterior (prospective neural) ectoderm to a posterior mesodermal fate, resulting in formation of blood and activation of endothelial markers. Reprogramming of anterior ectoderm does not require cell contact and is effected by stage-dependent, short-range, diffusible signal(s). Therefore, primitive endoderm signaling is a critical early determinant of hematopoietic and vascular development and plays a decisive role in anterior-posterior patterning during mouse embryogenesis.
Assuntos
Desenvolvimento Embrionário e Fetal , Endoderma/metabolismo , Hematopoese/fisiologia , Transdução de Sinais/fisiologia , Animais , Divisão Celular , Regulação da Expressão Gênica no Desenvolvimento/genética , Genes Reporter/genética , Globinas/genética , Histocitoquímica , Camundongos , Camundongos Transgênicos , Técnicas de Cultura de Órgãos , RNA Mensageiro/análiseRESUMO
The visceral yolk sac plays a critical role in normal embryogenesis, yet little is known about the specific molecules that regulate its development. We show here that four winged-helix genes (HNF-3alpha, HNF-3beta, HNF-3gamma and HFH-4) are restricted to visceral endoderm. In the absence of HNF-3beta, visceral endoderm forms but the morphogenetic movements by which the embryo becomes enclosed within its yolk sac are disrupted and serum protein gene transcription is greatly reduced. Hedgehog and Bmp genes, which encode signaling molecules known to play multiple roles in embryonic development, are also differentially expressed in the closely apposed yolk sac mesoderm and endoderm layers. Our results suggest that similar mechanisms may be utilized to mediate inductive interactions in both extraembryonic and embryonic tissues.
