Sonic hedgehog induces Motor Neuron Differentiation in P19

Sonic hedgehog (Shh) is a member of the hedgehog family of signalling molecules and secreted from two signalling centers, the notochord and the floor plate, where it functions as a morphogen to induce early dorso-ventral patterning of the cenral nervous system (CNS). More recently, multiple actions of Shh during CNS development have been discovered in additional sites, where it specifies the fates of oligodendrocytes and motor neurons as well as proliferation of neural precursors and control of axon outgrowth. To explore the roles of Shh in neuronal differentiation, we utilized embryonal carcinomal P19 cells as an in vitro model system. We overexpressed Shh in P19 cells and investigated it’s effects on proliferation and differentiation of P19 cells., P19/Shh, P19 cells overexpressing Shh, proliferated at higher rates than normal P19 cells even when normal P19 cells stopped growth and underwent differentiation. Ironically, P19/Shh also differentiated into neurons at higher rates than normal P19 cells. Upregulation of both proliferation and neuronal differentiation P19/Shh suggests that Shh may induce neuronal fates from uncommitted P19 cells and concomitantly promote the proliferation of the resulting neuronal precursor cells. As expected motor neuron markers (Hb9, ii ChAT) as well as a dopaminergic neuron marker (TH) were upregulated in neuronal cells derived from P19/Shh. Collectively, these results suggest that Shh may have multiple functions in neural induction of uncommitted stem cells, proliferation of neural precursors, and dorso-ventral patterning of the CNS