Seminar Speaker – Denise Garcia, Ph.D.

Astrocytes encompass a broad class of cells whose diverse roles in CNS function are only beginning to be understood. We identified a subpopulation of astrocytes in the adult mammalian forebrain that expresses the transcription factor, Gli1, indicating active Sonic hedgehog (Shh) signaling. Interestingly, Shh is expressed in neurons, identifying Shh signaling as a mediator of neuron-astrocyte communication. Our work is focused on understanding the role of Shh signaling in astrocyte function. Recent studies have revealed that Shh activity in astrocytes is required for establishing and maintaining synaptic organization of cortical neurons. Targeted loss of Shh signaling selectively in astrocytes produces aberrant synapse number that emerges during development and persists into adulthood. Moreover, neurons in these mutant mice exhibit perturbations in neuronal activity. These data identify a critical role for neuron-astrocyte communication mediated by Shh signaling in sculpting local cortical circuits.