Abstract
The secreted protein Noggin1 was the first discovered natural embryonic inducer produced by cells of the Spemann organizer. Thereafter, it was shown that vertebrates have a whole family of Noggin genes with different expression patterns and functional properties. For example, Noggin1 and Noggin2 inhibit the activity of BMP, Nodal/Activin and Wnt-beta-catenin signalling, while Noggin4 cannot suppress BMP but specifically modulates Wnt signalling. In this work, we described and investigated phylogeny and expression patterns of four Noggin genes in lampreys, which represent the most basally divergent group of extant vertebrates, the cyclostomes, belonging to the superclass Agnatha. Assuming that lampreys have Noggin homologues in all representatives of another superclass of vertebrates, the Gnathostomata, we propose a model for Noggin family evolution in vertebrates. This model is in agreement with the hypotheses suggesting two rounds of genome duplication in the ancestor of vertebrates before the divergence of Agnatha and Gnathostomata.
Highlights
The secreted protein Noggin[1] was the first discovered natural embryonic inducer produced by cells of the Spemann organizer
We were able to simplify the screening because the lamprey Noggin coding sequences presumably should not contain introns, since the absence of introns was previously shown for all known Noggin genes in both invertebrates and vertebrates
We revealed in the L. camtschaticum and the P. marinus genomes the following four genes, which had no introns, with protein products that demonstrated homology with the Noggin[1], Noggin[2] and Noggin[4] described in gnathostomes[9,17,18]
Summary
The secreted protein Noggin[1] was the first discovered natural embryonic inducer produced by cells of the Spemann organizer. We described and investigated phylogeny and expression patterns of four Noggin genes in lampreys, which represent the most basally divergent group of extant vertebrates, the cyclostomes, belonging to the superclass Agnatha. The divergence of Agnatha (jawless fishes) and Gnathostomata (gnathostomes) occurred ~535–462 MYA, i.e., at the earliest stages of the evolution of vertebrates in the Palaeozoic Era[1,2,3] These data allow one to consider jawless fishes, including extant lampreys and hagfishes, as the most basally divergent group of vertebrates. This early separation of cyclostomes from other vertebrates makes them a recognized model for studying the genetic innovations that led to the evolutionary emergence and development of unique traits of the vertebrates, such as the telencephalon, neural crest cells, the epimorphic regeneration ability of the body appendages, and adaptive immunity[4,5,6]. The obtained results incline us to the hypothesis suggesting two rounds of genome duplication in the common ancestor of vertebrates before divergence of jawless and gnathostomes
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