Lineage Analysis of Pallial Subdivision-Derived Cells in the Developing Chick Pallium

The avian pallium is comprised of several nuclear regions (four main areas) and differs significantly from the mammalian telencephalon, which is a six-layered structure. Although it is known that cells with identical features at the gene expression level can exist in different regions, it remains unclear whether cells with identical features arise from the same region. In this study, we examined the cell lineages produced from each region by employing the recently developed integration-coupled gene expression On (iOn) switch and performing whole-brain imaging by light-sheet fluorescence microscopy (LSFM). We found that cells born in each area migrate across regions and, therefore, cells with identical characteristics are not always generated from the same progenitor regions. Furthermore, an examination of cell migration patterns in the dorsal ventricular ridge revealed that, as in mammals, cells preferably migrate along radial fibers in the early stages of migration, but radial fibers are not required for later migration. These results support the developmental convergence models recently proposed to describe cell lineage.