The origin of chordates and the consequent genesis of vertebrates were major events in natural history. The amphioxus (lancelet) is now recognised as the closest extant relative to the stem chordate and is the only living invertebrate that retains a vertebrate‐like development and body plan through its lifespan, despite more than 500 million years of independent evolution from the stem vertebrate. The inspiring data coming from its recently sequenced genome confirms that amphioxus has a prototypical chordate genome with respect to (...) gene content and structure, and even chromosomal organisation. Pushed by joint efforts of amphioxus researchers, amphioxus is now entering a new era, namely its maturation as a laboratory model, through the availability of a large amount of molecular data and the advent of experimental manipulation of the embryo. These two facts may well serve to illuminate the hidden secrets of the genetic changes that generated, among other vertebrates, ourselves. (shrink)

Understanding how the chordate body plan originated and evolved is still controversial. The discovery by Spemann and Mangold in 1924 of the vertebrate organizer and its inductive properties in patterning the AP and DV axis was followed by a long gap until the 1960s when scientists started characterizing the molecular events responsible for such inductions. However, the evolutionary origin of the organizer itself remained obscure until very recently; did it appear together with the origin and radiation of vertebrates, or was (...) it a chordate affair? A recent study by Yu and collaborators,1 which analyses the expression of several organizer‐specific genes in amphioxus together with recent phylogenetic data that reversed the position of invertebrate extant chordates (e.g. urochordates and cephalochordates), indicates that the organizer probably appeared in early chordates. It likely had separate signalling centres generating BMP and Wnt signalling gradients along the DV and AP axis. The organizer was then lost in the urochordate lineage, most probably as an adaptation to a rapid and determinate development. BioEssays 29:619–624, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Alternative splicing (AS) is a widespread mechanism with an important role in increasing transcriptome and proteome diversity by generating multiple different products from the same gene. Evolutionary studies of AS have focused primarily on the conservation of alternatively spliced sequences or of the AS pattern of those sequences itself. Less is known about the evolution of the regulation of AS, but several studies, working from different perspectives, have recently made significant progress. Here, we categorize the different levels of AS evolution, (...) and summarize the studies on evolution of AS regulation, which point to a high level of evolutionary conservation of the regulation of AS events conserved between related species. This suggests that the quantitative regulation of AS is an intrinsic part of AS function. We discuss the potential role of changes in developmental regulation of AS as an additional layer in complex gene regulatory networks and in the emergence of genetic novelties. (shrink)