PRINCE, V.E.*; HURLEY, I; STOCKERT, J; HALE, M; University of Chicago; University of Chicago; University of Chicago; University of Chicago: Vertebrate axial patterning and the consequences of duplication events

It has been proposed that genome duplications can provide genetic raw material for evolutionary transitions. Support for this hypothesis has come from studies of teleosts, which suggest that a duplication of the whole genome occurred more than 110 million years ago in the ray-finned fish lineage. This duplication event may have provided the genetic material that fueled the explosive teleost radiation. Classical models predict that the most likely outcome of duplication is loss of one gene (non-functionalization), while the other gene continues to fulfill the ancestral role. More rarely, one gene may take on a new beneficial role, which is positively selected (neo-functionalization). Recently, a third model (sub-functionalizaton) has been proposed, where the two genes undergo complementary degenerative mutations to partition the functions of the ancestral gene. Our analysis of zebrafish Hoxb1 duplicates hoxb1a and hoxb1b suggests that functions of the single ancestral gene, in patterning the segmented hindbrain, were indeed partitioned between the duplicates through sub-functionalization mechanisms. We are now extending this analysis to a broader range of teleosts, to investigate variation in frequency and mechanism of duplicate gene preservation. Our analysis of the functions of zebrafish hoxb1 genes further suggests that duplicated neural circuits, like duplicated genes, can offer a substrate for evolution. We suggest that redundant neural circuits, like redundant gene pairs, offer possibilities for neo-functionalization or sub-functionalization, potentially allowing novel circuitry to evolve.