Noggin4 expression during chick embryonic development.

We describe here the expression pattern of Noggin4 during the early development of the chick embryo (Gallus gallus). The expression of this gene starts with the onset of gastrulation (stage HH4), in two bilateral bands along the primitive streak, with a local maximum around Hensen's node. By the end of gastrulation, Noggin4 transcripts are distributed diffusely throughout the epiblast, with the highest concentration in the head ectoderm. Interestingly, the expression of Noggin4 during the first half of gastrulation demonstrates a clear left-right asymmetry in Hensen's node, being much more intensive in its right anterior portion. During neurulation, Noggin4 is expressed mainly in the neuroectoderm, with the most intensive expression in the head and lateral neural folds. In mesoderm derivatives, expression is seen in somites but not in the notochord. In general, primarily ectodermal and diffusive expression of Noggin4 in chick embryo, with a maximum in the anterior neurectoderm, resembles that of its ortholog in Xenopus, which indicates a conservative function of this gene in evolution.