Meeting Abstract

P1.66  Monday, Jan. 4  Boundary Integration Generates Brain Diversity SYLVESTER, JB*; RICH, CA; STREELMAN, JT; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology gth644s@mail.gatech.edu

The brain is the best-studied vertebrate organ and it has played an important role in the evolution of our own species. The rapid expansion of the cerebral cortex, or telencephalon, is a defining aspect of hominid evolution. The processes that control growth in the telencephalon have been well described in the ‘late equals large’ model, but little is known about the evolution of functional domains within the telencephalon. We investigate comparative telencephalon development in ecologically distinct cichlid fishes lineages from Lake Malawi (East Africa) to study diversity. The two dorso-ventral domains of the telencephalon, the pallium and subpallium, are patterned by wnt and shh signaling, respectively. Evolutionary variation in the deployment of these pathways and their downstream members changes the position of the pallial-subpallial boundary (PSB), which in turns modifies the size of each domain. Notably, rock vs. sand-dwelling Malawi species differ in the initial position of the PSB and early allocation of cells to the pallium and subpallium. We observe that this shift in the PSB is correlated with the relative position of an adjacent signaling boundary, also established in part by wnt and shh signaling, called the zona limitans intrathalamica (ZLI). The evolutionary correlation of PSB and ZLI suggests that diversity within the telencephalon results from the integrated patterning of boundaries across the developing forebrain.