In Science this week, a team of Swiss and German researchers report new details about the regulation of Hox genes, which are clustered together in the genome and control body shape and limb development. In the study, the researchers show that during mouse limb development, Hox genes are transcribed in two waves, the first controlling arm and forearm development and the second responsible for digit formation. To do so, the Hox genes interact with a telomeric domain when mouse limbs are just forming and later swing toward the centromeric chromosomal domain, establishing new contacts to specify digits. Notably, the centromeric domain is shut down at the right time in development even if the telomeric domain is deleted, suggesting that the two regions operate independently.
Also in Science, investigators from the Fred Hutchinson Cancer Research Center present their genetic analysis of the fruit fly that they conducted to help understand how relatively new genes evolve functions critical to life. The team traced the evolutionary steps of the Drosophila gene Umbrea, which is less than 15 million years old yet is essential for chromosome segregation and normal development. They found that a series of steps, including the loss of an ancestral heterochromatin-localizing domain followed by alterations that rewired its protein interaction network, led to the gene's acquisition of species-specific centromere localization activity. The work gives insights into how young genes gain essential functions.