Research Interests

We are interested in understanding the molecules and mechanisms underlying the formation, function, and plasticity of synapses – from the cues that prompt neurons to form synaptic connections to the molecules that orchestrate their organization and determine their functional properties. We conduct our studies primarily in Drosophila, where we employ the rich array of genetic tools and a well-characterized model synapse that is accessible to physiological, imaging, and behavioral studies. Because of the remarkable conservation of synaptic genes, we can make generalizable insights, as has been demonstrated repeatedly through the fundamental discoveries made studying model synapses in a variety of organisms. In parallel, we have focused on developing new genome engineering tools to overcome barriers to the study of synapses in vivo.
1. Identification of new regulators of synapse formation, function and plasticity. In our ongoing screens for new synaptic proteins, we are combining CRISPR with bioinformatic approaches for identifying evolutionarily conserved candidate synaptic genes. We are currently characterizing several recently identified genes that encode poorly understood, conserved neuronal proteins associated with human disease.
We previously identified Fife, the Drosophila homolog of Piccolo, in a behavioral screen. Fife mutants exhibit locomotor deficits and severely decreased neurotransmitter release (Bruckner, Gratz et al., 2012). Prior to this identification, it was believed that Piccolo was a vertebrate-specific component of the otherwise highly conserved complex of presynaptic scaffolding proteins known as the active zone cytomatrix. Piccolo is linked to major depression and bipolar disorder, but has been difficult to study in mammals due to genetic redundancy. Through loss-of-function studies in Drosophila, we determined that Fife promotes high-probability neurotransmitter release by organizing active zone structure to spatially couple Ca2+ channel clusters and release-ready synaptic vesicles in nanometer proximity. In addition to its role in determining baseline release probability, Fife is essential for presynaptic homeostatic potentiation (Bruckner et al., 2017). These studies help explain how synaptic strength is established and modified locally at active zones to tune communication in neural circuits.
2. Determining how neurotransmitter release properties are established and modulated at individual synapses. To predictably control behavior while remaining responsive to an ever-changing environment, neural circuits must balance reliability and plasticity. Intrinsic variability in presynaptic neurotransmitter release properties may facilitate this balance. To bridge the gap between synaptic function and structure, we are conducting electron tomographic studies of synapse ultrastructure (Bruckner et al., 2017; Zhan et al., 2016) and combining functional imaging at single synapses with CRISPR-mediated endogenous tagging of synaptic proteins. By combining genetic and multi-level imaging approaches, we aim to gain a comprehensive view of synapse structure and its molecular determinants to significantly advance our understanding of how active zones are organized to achieve precise release properties -- and reorganized to modulate circuit function in the face of changing inputs.
3. Genome engineering. Genetic and molecular techniques to manipulate the genomes of organisms are invaluable tools for understanding gene function. In collaboration with the Wildonger and Harrison labs, we demonstrated that the bacterially derived CRISPR RNA-guided Cas9 nuclease can be employed to delete and replace genes in Drosophila, and that these genome modifications can be efficiently transmitted through the germline. We have since optimized tools and techniques for CRISPR-catalyzed homologous recombination and developed an online tool for identifying highly specific CRISPR target sites. More recently, we have focused on developing high-throughput approaches for following endogenous synaptic proteins in vivo, including in subsets of their endogenous patterns, and for identifying, labeling and controlling specific subpopulations of neurons in the intact brain. The ability to follow endogenous synaptic proteins in sparse subsets of neurons will greatly facilitate in vivo studies in the synapse-dense central nervous system. For more information visit the flyCRISPR website and discussion board.