engleski

Development of the caudal part of the mouse embryo in brachyury, splotch and truncate mutants

The caudal part of the vertebrate embryo develops from the undifferentiated blastema located in the tip of the embryonic tail referred as the tail bud. The formation of the tail structures: the neural tube, the notochord and the tail gut does not involve folding of epithelial sheets and cell migration characteristic for gastrulation. The tail structures arise by rearrangement of mesenchymal cells of the tail bud without formation of the germ layers, i.e. by secondary body formation. In order to investigate mechanisms of tail formation and the role of T and Pax3 genes in this process, we analyzed three mouse mutants with tail malformations: brachyury, splotch and truncate. The normal and mutant embryos were analyzed by serial semithin sections, scanning and transmission electron microscopy. All three mutants showed aberrant tail bud differentiation. Brachyury heterozygous embryos develop the duplication of the tail tip containing two tail buds. Splotch homozygotes show proper formation of the notochord and the tail gut, but the caudal part of the secondary neural tube lacks the lumen and it is represented by in irregular group of cells. In the lumbosacral region the neural tube is opened. In the truncate homozygous embryos the tail notochord is partially missing. In contrast to the normal embryos, where the notochord develops together with the tail gut, in truncate it detaches from the wall of the neural tube. The observed malformations indicate that the proper differentiation of the tail bud is necessary for the development of the caudal part of the embryo.

brachyury; splotch; truncate; embryo; mouse

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