[
Nature,
2002]
The genomes of animals, plants and fungi seem to be relatively disorganized. Genes appear to be randomly distributed, with only a few exceptions: repeats of similar sequences caused by gene duplications, for example, and a limited number of ancient gene clusters containing functionally related genes (such as the Hox genes that are involved in control of animal development). Apart from these, the average gene is generally assumed to be independent of its neighbours, and genomes are constantly rearranged and shuffled. However, in one group of animals the nematodes (small, unsegmented worms) neighboring genes are occasionally assembled into regulatory units called operons. On page 851 of this issue, Blumenthal et al. now report the first whole-genome characterization of such operons in a mulicellular organism, an raise intriguing questions as to how (and why) they have evolved.
[
Worm,
2016]
Dorsal intercalation is a coordinated cell migration event that rearranges hypodermal cells during C. elegans embryogenesis, and that resembles cell intercalation in many systems from flies to mice. Despite its conservation, the molecular mechanisms that govern dorsal intercalation in worms have remained elusive. Here, we comment on our recent publication, Walck-Shannon etal.,(1) which begins to spatially map the molecular requirements for intercalation. First, we provide a historical perspective on the factors that have previously hampered the study of dorsal intercalation. Next, we provide a summary of the molecular pathways identified in Walck-Shannon etal.,(1) pointing out surprises along the way. Finally, we consider the potential conservation of the molecular pathway we described and discuss future questions surrounding dorsal intercalation. Despite the challenges, dorsal intercalation is a process poised to advance our understanding of cell intercalation during morphogenesis throughout the animal kingdom.