microRNA-19b regulates proliferation & patterning in the avian forebrain

Unlike the six-layered organization of neurons in the mammalian neocortex, the avian pallium features spatially-segregated neuronal clusters with partially conserved gene expression. While efforts to uncover similarities between the avian pallium and mammalian neocortex have persisted, the mechanisms of pallial development in birds have not been comprehensively explored. Here, we have established the role of a highly conserved microRNA, miR-19b, in controlling proliferation in the embryonic avian forebrain, by regulating the expression of E2f8, a cell-cycle inhibitor and NeuroD1, a neuronal differentiation factor. Further, investigation revealed that there exists a proliferation-dependent specification of pallial neurons in birds, similar to that in mammals. In summary, these findings suggest a profound role of miR-19b in shaping the avian pallium and indicate a closer resemblance of developmental mechanisms between the avian pallium and the mammalian neocortex.